Title:
Hot-Dip Galvanized Sheet and Method for Manufacturing Same
Kind Code:
A1


Abstract:
The hot-dip galvanized steel sheet has: a steel sheet containing 0.1 to 3.0% of Si by mass; a hot-dip galvanizing layer; and a segregated layer, being placed between the steel sheet and the hot-dip galvanizing layer, having a thickness in a range from 0.01 to 100 μm; containing an oxide containing Si, and being composed of at least one component selected from the group consisting of S, C, Cl, Na, K, B, P, F, and N. The hot-dip galvanized steel sheet shows beautiful surface appearance without generating non-plating portion and provides excellent plating adhesion and sliding property in spite of using a base steel sheet containing a large quantity of Si. Furthermore, the alloy hot-dip galvanized steel sheet obtained by allying the hot-dip galvanized plating also has excellent anti-powdering property.



Inventors:
Suzuki, Yoshitsugu (Okayama, JP)
Fushiwaki, Yusuke (Okayama, JP)
Tada, Masahiko (Hiroshima, JP)
Tobiyama, Yoichi (Hiroshima, JP)
Ando, Hisanori (Kagawa, JP)
Kawano, Takashi (Hiroshima, JP)
Application Number:
11/664490
Publication Date:
03/20/2008
Filing Date:
10/07/2005
Assignee:
JFE STEEL CORPORATION (CHIYODA-KU TOKYO JAPAN, JP)
Primary Class:
Other Classes:
427/433
International Classes:
C23C2/02; C23C2/06
View Patent Images:
Related US Applications:
20090117386COMPOSITE COVERMay, 2009Vacanti et al.
20070272481Acoustic Elements And Their ProductionNovember, 2007Birch et al.
20020192399Open-face mezuzahDecember, 2002Richard III
20080206511SYNTHETIC MICROFIBER MATERIALAugust, 2008Treacy
200902086863D Bevel Sticky Note PadAugust, 2009Ho
20060083909Easy-open dough packages and related methods of manufactureApril, 2006Matthews et al.
20050106344Lamination adhesion of foil to thermoplastic polymersMay, 2005Morris et al.
20030138600Paper for producing panels and paper-making methodJuly, 2003Dohring et al.
20040224107Fiber-optic mouse padNovember, 2004Lewis
20090084424MULTILAYER ACID TERPOLYMER ENCAPSULANT LAYERS AND INTERLAYERS AND LAMINATES THEREFROMApril, 2009Hayes et al.
20080124519CLOTH AND SOLID PIECE ASSEMBLY AND PRODUCTION METHOD FOR CLOTH AND SOLID PIECE ASSEMBLYMay, 2008Arai



Primary Examiner:
AUSTIN, AARON
Attorney, Agent or Firm:
HOLTZ, HOLTZ & VOLEK PC (NEW YORK, NY, US)
Claims:
1. A hot-dip galvanized steel sheet comprising: a steel sheet containing 0.1 to 3.0% Si by mass; a hot-dip galvanizing layer; a segregated layer, being placed between the steel sheet and the hot-dip galvanizing layer, having a thickness in a range from 0.01 to 100 μm; containing an oxide containing Si, and being composed of at least one component selected from the group consisting of S, C, Cl, Na, K, B, P, F, and N.

2. The hot-dip galvanized steel sheet according to claim 1, wherein the concentration of the component in the segregated layer is higher than the concentration of the component in the steel sheet by 10% or more.

3. The hot-dip galvanized steel sheet according to claim 1, wherein the quantity of the oxide containing the Si in the segregated layer is in a range from 0.01 to 1 g/m2 as oxygen.

4. The hot-dip galvanized steel sheet according to claim 1, further comprising an Fe layer below the hot-dip galvanizing layer.

5. The hot-dip galvanized steel sheet according to claim 1, wherein the segregated layer is formed by a dispersed compound of the component and a component of the steel sheet.

6. The hot-dip galvanized steel sheet according to claim 5, wherein the component is S, the quantity of MnS in a particle shape having 50 nm or larger particle size as the compound is five or more particles per 20 μm of length on an arbitrary cross section in parallel with the interface between the hot-dip galvanizing layer and the steel sheet.

7. The hot-dip galvanized steel sheet according to claim 1, wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.

8. A method for manufacturing hot-dip galvanized steel sheet comprising the steps of: adhering at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof onto a surface of a steel sheet containing 0.1 to 3% Si by mass; heating the steel sheet after adhering the substance thereon to form an oxide film containing 70% by mass or less of hematite on the surface of the steel sheet; reducing the oxide film; and hot-dip galvanizing the reduced steel sheet.

9. The method for manufacturing hot-dip galvanized steel sheet according to claim 8, wherein the step of heating is conducted in an oxidizing atmosphere for Fe at above 500° C. of the ultimate temperature of the steel sheet.

10. The method for manufacturing hot-dip galvanized steel sheet according to claim 8, further comprising the step of alloying after the step of hot-dip galvanizing.

11. A method for manufacturing hot-dip galvanized steel sheet comprising the steps of: preparing a steel sheet containing 0.1 to 3% Si by mass as the base material; forming an oxide film containing 70% by mass or less of hematite on a surface of the base steel sheet before applying hot-dip galvanizing on the surface of the steel sheet; applying reducing treatment to the steel sheet; and applying hot-dip galvanizing thereto.

12. The method for manufacturing hot-dip galvanized steel sheet according to claim 9, further comprising the step of alloying after the step of hot-dip galvanizing.

13. The hot-dip galvanized steel sheet according to claim 2, wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.

14. The hot-dip galvanized steel sheet according to claim 3, wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.

15. The hot-dip galvanized steel sheet according to claim 4, wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.

16. The hot-dip galvanized steel sheet according to claim 5, wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.

17. The hot-dip galvanized steel sheet according to claim 6, wherein the hot-dip galvanizing layer is an alloyed hot-dip galvanizing layer.

Description:

TECHNICAL FIELD

The present invention relates to a hot-dip galvanized steel sheet suitable for the fields of automobile, building materials, household electric appliances, and the like, and to a method for manufacturing thereof, specifically relates to a hot-dip galvanized steel sheet having excellent plating adhesion and sliding property manufactured from a steel containing a large quantity of Si as the base material, and further relates to an alloyed hot-dip galvanizing prepared by alloying the hot-dip galvanized steel sheet.

BACKGROUND ART

In recent years, varieties of fields including automobile, building materials, and household electric appliances adopt surface-treated steel sheets prepared by providing a base material of steel sheet with rust-preventive property. As of these, there are specifically adopted hot-dip galvanized steel sheets which are manufactured at a low cost and which show excellent rust-preventive property, and alloyed hot-dip galvanized steel sheet prepared by alloying them.

Generally the hot-dip galvanized steel sheets are manufactured by the following process. That is, a slab is hot-rolled, and further is cold-rolled and heat-treated to form a thin steel sheet. The surface of thus prepared thin steel sheet is subjected to a pretreatment to apply degreasing and/or pickling to clean the surface thereof, or is supplied to a preheating furnace, without applying the pretreatment, to remove the oil on the surface of the thin steel sheet by combustion, and then is subjected to recrystallization annealing in a non-oxidizing atmosphere or in a reducing atmosphere, thereby obtaining a substrate steel sheet for plating. After that, the substrate steel sheet is cooled to a temperature suitable for the plating in a non-oxidizing atmosphere or a reducing atmosphere, followed by immersing the substrate steel sheet in a molten zinc bath containing a trace quantity of Al, (normally about 0.1 to about 0.2% by mass), without exposing to air, thereby obtaining the hot-dip galvanized steel sheet. The alloyed hot-dip galvanized steel sheet is manufactured by succeeding heat-treatment of the hot-dip galvanized steel sheet in an alloying furnace.

To attain both the decrease in thickness (decrease in weight) and the increase in strength of the steel sheets, the substrate steel sheets in recent years are designed to increase the strength. Accordingly, there is increasing the consumption of high strength hot-dip galvanized steel sheets which also have the rust-preventive property by applying hot-dip galvanizing to the substrate steel sheets.

As a means to increase the strength of the steel sheets, a solid solution strengthening element such as Si, Mn, and P is added to the steel. Specifically, since Si provides the steel with high strength without deteriorating the ductility, the Si-containing steel sheets are expected as the promised high strength steel sheets.

However, the hot-dip galvanized steel sheets and the alloyed hot-dip galvanized steel sheets prepared from the substrates of Si-containing high strength steel sheets have problems described below.

As described above, the substrate steel sheets for hot-dip galvanizing are subjected to annealing at temperatures in an approximate range from 600° C. to 900° C. in a reducing atmosphere, followed by hot-dip galvanizing. Since, however, the Si in the steel is an element of being readily oxidized, the Si is selectively oxidized on the surface of the steel sheet to form an oxide even in a commonly applied reducing atmosphere, thereby segregating the Si oxide to the surface of the substrate steel. That type of Si oxide deteriorates the wettability with the molten zinc during the plating treatment, thus inducing the generation of non-plating portions. Consequently, increase in the Si concentration in the steel aiming to increase the strength decreases the wettability, which induces the generation of many non-plating portions. Even when the non-plating portion does not appear, there is a problem of deteriorating the plating adhesion.

Furthermore, if the Si in the steel is selectively oxidized on the surface of the steel sheet, and if the oxidized Si segregates to the surface, the Si oxide hinders the alloying reaction between Zn and Fe, thereby significantly delaying the alloying in the alloying step after the hot-dip galvanizing. As a result, the productivity is significantly deteriorated. On the other hand, if the alloying treatment is given at further high temperatures to assure the productivity, powdering caused by the excess-alloying likely occurs. As a result, it is difficult to attain both the high productivity and the good anti-powdering property at a time in the related art.

To those problems, there are proposed several means.

For example, Japanese Patent No. 2587724 proposes a method for improving the wettability with molten zinc by heating a steel sheet in an oxidizing atmosphere to form an iron oxide on the surface of the steel sheet, in advance, then by conducting reduction-annealing.

The proposed technology is to suppress the surface segregation of Si in the reduction-annealing step by forming the iron oxide on the surface of the steel sheet. As widely known, however, the oxidation rate of iron on the surface of steel sheet significantly decreases with increase in the Si concentration in the steel. For example, for a steel sheet containing 0.1% by mass or more of Si, sole oxidizing means disclosed in the patent cannot fully progress the oxidation of the iron, and it is difficult to attain a necessary quantity of iron oxide to suppress the surface segregation of Si.

As a result, the occurrence of non-plating portion during the hot-dip galvanization cannot fully be suppressed. In addition, when that hot-dip galvanizing layer is alloyed, the problem of significant delay of alloying which is expected to occur in the alloying step cannot fully be solved.

If the alloying rate is small, the alloying temperature has to be increased to keep a specified productivity in a CGL which has a limited length of the alloying furnace. If, however, the alloying is conducted at elevated temperatures, the anti-powdering property is unavoidably deteriorated.

In addition, if the suppression of surface segregation of Si in the reduction-annealing step is insufficient, the homogeneity of alloying reaction of Zn and Fe is significantly deteriorated. Consequently, the plating surface gives significant irregularities on the Zn—Fe alloy layer caused by the non-homogeneous alloying reaction, which then significantly deteriorates the sliding property in the press-forming step.

For example, according to JP-A-11-50223, (the term “JP-A” referred to herein signifies the “Unexamined Japanese Patent Publication”), sulfur or a sulfur compound is adhered to the steel sheet in a quantity ranging from 0.1 to 1000 mg/m2 as S before the hot-dip plating step, then the preheating step is applied to the steel sheet in a weak oxidizing atmosphere, followed by annealing the steel sheet in a non-oxidizing atmosphere containing hydrogen.

Furthermore, JP-A-2001-279410 discloses a technology in which an ammonium salt containing S is adhered in a quantity from 0.1 to 1000 mg/m2 as S to the surface of a high tensile steel sheet containing Mn, P, and Si, followed by applying heat treatment, thus letting the S component diffuse into the ground metal of the steel sheet, thereby forming a sulfur compound such as MnS, which is the product of reaction with Mn in the steel. The method suppresses the surface segregation of Mn and shuts off the diffusion passage of Si to the surface of the steel sheet owing to the existence of the sulfur-segregated layer, thereby suppressing the surface segregation of Si.

Those technologies aim to improve the wettability with the molten zinc using a sulfide layer formed on the surface of steel sheet. However, the inventors of the present invention applied these technologies to steel sheets containing a large quantity of Si, and found that the sole effect of the sulfide layer cannot fully suppress the surface segregation of Si. Consequently, similar to the above-description, these technologies could not solve the problems of the performance of plating layer. Furthermore, the preheating step given in a weak oxidizing atmosphere could not solve the problems of anti-powdering property and sliding property, similar to above, when these technologies were applied to steel sheets containing a large quantity of Si.

In addition, since these technologies are to adhere sulfur or a sulfur compound onto the surface of steel sheet before the heat treatment, the succeeding heat treatment step emits large quantities of sulfur components as corrosive gases such as sulfur dioxide and hydrogen sulfide in the heating furnace. As a result, the corrosion damage of the heating furnace body and the intrafurnace apparatuses becomes significant, which requires frequent repair and renewal of deteriorated parts, and further requires to install a desulfurization apparatus in case of venting the furnace gas to atmosphere from the point of air pollution prevention. Therefore, practical application of these technologies in manufacturing lines needs further improvement.

The present invention has been perfected to cope with the above situations, and an object of the present invention is to provide a hot-dip galvanized steel sheet that has excellent plating adhesion and sliding property to sufficiently endure as the steel sheet for automobile that requests specifically severe plating characteristics even with a substrate steel sheet containing a large quantity of Si, and to provide a method for manufacturing the hot-dip galvanized steel sheet. Another object of the present invention is to provide an alloyed hot-dip galvanized steel sheet also having excellent anti-powdering property.

DISCLOSURE OF THE INVENTION

The present invention provides a hot-dip galvanized steel sheet having: a steel sheet containing 0.1 to 3.0% of Si by mass; a hot-dip galvanizing layer; and a segregated layer, being placed between the steel sheet and the hot-dip galvanizing layer, having a thickness in a range from 0.01 to 100 μm, containing an oxide containing Si, and being composed of at least one component selected from the group consisting of S, C, Cl, Na, K, B, P, F, and N.

For the hot-dip galvanized steel sheet, the concentration of the component in the segregated layer is preferably higher than the concentration of the component in the steel sheet by 10% or more.

For these hot-dip galvanized steel sheets, the quantity of the oxide containing the Si in the segregated layer is preferably in a range from 0.01 to 1 g/m as oxygen.

For any of these hot-dip galvanized steel sheets, an Fe layer preferably exists below the hot-dip galvanizing layer.

For any of these hot-dip galvanized steel sheets, the segregated layer is preferably formed by a dispersed compound of the component and a component of the steel sheet. In particular, it is more preferable that the component is S, and that the quantity of MnS in a particle shape, having 50 nm or larger particle size as the oxide is five particles or more per 20 μm of length on an arbitrary cross section in parallel with the interface between the hot-dip galvanizing layer and the steel sheet.

For any of these hot-dip galvanized steel sheets, the hot-dip galvanizing layer is preferably an alloyed hot-dip galvanizing layer.

Furthermore, the present invention provides a method for manufacturing hot-dip galvanized steel sheet having the steps of: adhering at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof onto a surface of a steel sheet containing 0.1 to 3% Si by mass; heating the steel sheet after adhering the substance thereon to form an oxide film containing 70% by mass or less of hematite; reducing the oxide film; and hot-dip galvanizing the reduced steel sheet.

For the method for manufacturing hot-dip galvanized steel sheet, the step of heating is preferably conducted in an oxidizing atmosphere for Fe at above 500° C. of the ultimate temperature of the steel sheet.

For any of the above methods for manufacturing hot-dip galvanized steel sheet, it is preferable to further apply the step of alloying after the step of hot-dip galvanizing.

The present invention provides a method for manufacturing hot-dip galvanized steel sheet having the steps of: preparing a steel sheet containing 0.1 to 3% Si by mass as the substrate; forming an oxide film containing 70% by mass or less of hematite on the surface of the substrate steel sheet before applying hot-dip galvanizing onto the surface of the steel sheet; applying reducing treatment to the steel sheet; and applying hot-dip galvanizing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating an example of depth profile of a cross section of an alloyed hot-dip galvanized steel sheet, drawn by the linear analysis of EPMA.

FIG. 2 is a graph illustrating an example of depth profile of a surface layer of an alloyed hot-dip galvanized steel sheet, drawn by GDS.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described in detail in the following.

To solve the above problems, the inventors of the present invention carried out detail studies, and found the following. To prevent the segregation of Si in the steel to the surface thereof, a segregated layer for a specified element is formed below the hot-dip galvanizing layer, and an oxide containing Si is formed in the segregated layer, thereby drastically improving the adhesion of the hot-dip galvanizing layer even with a steel sheet containing a large quantity of Si. Furthermore, by the existence of that oxide containing Si and of that segregated layer for the specified element, the homogeneous alloying is enhanced, and the formation of irregular plating layer is suppressed to attain a smooth plating surface, thereby significantly improving the sliding property.

For a means to suppress the generation of non-plating portion and to enhance the plating adhesion and the alloying on the steel sheet containing 0.1% or more of Si by mass, the inventors of the present invention conducted detail studies, and derived a conclusion that, for a steel sheet containing a large quantity of Si, simple enhancement of oxidation to form a sufficient quantity of iron oxide cannot fully improve the wettability with molten zinc, and cannot fully suppress the generation of non-plating portion.

To this point, the inventors of the present invention gave further studies, and found that it is important to form a sufficient quantity of iron oxide and further to specify the composition of the iron oxide. That is, for a steel sheet containing a large quantity of Si, it was found that the above objects are achieved by controlling the composition of the iron oxide being formed on the surface of the steel sheet when the sheet is oxidized, thus the present invention has been perfected.

That is, the inventors of the present invention provides a method for manufacturing hot-dip galvanized steel sheet having the steps of: adhering at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof onto a surface of a steel sheet containing 0.1 to 3% Si by mass; heating the steel-sheet after adhering the substance thereon to form an oxide film containing 70% by mass or less of hematite; reducing the oxide film; and hot-dip galvanizing the reduced steel sheet.

The description begins with the composition of the base sheet for plating, (substrate steel sheet), according to the present invention.

The present invention specifies the Si content in the substrate steel sheet to a range from 0.1 to 3.0% by mass because that level of Si quantity is necessary to increase the strength of the steel sheet, though a steel containing a large quantity of Si as the substrate steel sheet raises problems of plating adhesion and sliding property, and because the existence of Si in the substrate is necessary to form the above-described oxide containing Si. If the Si content in the steel is less than 0.1% by mass, the above-described oxide containing Si cannot fully be formed below the plating layer, which fails to attain the effect of the present invention.

According to the present invention, there is no specific limitation on the elements other than Si, and known component systems can be applied. Typical components are the following.

C, 0.5% by mass or less

Carbon is an element existing in steel, normally existing in a range from 0.0001 to 0.5% by mass. The present invention accepts that range of C content in the substrate steel sheet. Carbon is useful not only for the strengthening of steel but also for the structural control such as forming a residual austenite to improve the balance between strength and ductility. A preferred C content to realize these effects is 0.05% by mass or more. On the other hand, the C content of 0.25% by mass or less is preferred to also give superior weldability.

Mn: 5% by mass or less

Manganese is useful for strengthening steel, and the substrate steel sheet may contain Mn by 5% by mass or less. Specifically, the Mn content of 0.1% by mass or more, preferably 0.5% by mass or more, performs the effect significantly. Similar to Si, the Mn is an element to form an oxide film in the annealing step, and the Mn content of 3.0% by mass or less tends to improve the plating adhesion on forming the segregated layer for a specified element and on forming the oxide containing Si below the plating layer, and furthermore is preferable for assuring weldability and the balance between strength and ductility. Accordingly, the Mn content is preferably specified to 3.0% by mass or less, and more preferably in a range from 0.5 to 3.0% by mass.

Al: 5.0% by mass or less

Aluminum is an element added together with Si as a supplemental additive. A preferable content of Al is 0.01% by mass or more. On the other hand, 5.0% by mass or less of Al content tends to improve the plating adhesion on forming the segregated layer for a specified element and on forming the oxide containing Si below the plating layer, and furthermore is preferable for assuring weldability and the balance between strength and ductility. Accordingly, the Al content is preferably specified to 5.0% by mass or less, and more preferably in a range from 0.01 to 3.0% by mass.

Elements in steel other than those given above include Ti, Nb, V, Cr, S, Mo, Cu, Ni, B, Ca, N, P, and Sb. The confirmed content ranges of these elements to attain the effect of the present invention are: up to 1% by mass for Ti, up to 1% by mass for Nb, up to 1% by mass for V, up to 3% by mass for Cr, up to 0.1% by mass for S, up to 1% by mass for Mo, up to 3% by mass for Cu, up to 3% by mass for Ni, up to 0.1% by mass for B, up to 0.1% by mass for Ca, up to 0.1% by mass for N, up to 1% by mass for P, and up to 0.5% by mass for Sb.

One or more of the elements selected from the above group may be added within a range of 5% by mass or less as the sum of them. Balance is Fe and inevitable impurities.

According to the present invention, before the annealing step in the CGL (continuous galvanizing line), at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof is adhered to the surface of the above steel sheet (substrate steel sheet).

Examples of those substances are:

a compound containing P, such as phosphoric acid (H3PO4), potassium phosphate (K3PO4), ammonium phosphate ((NH4)3PO4), sodium phosphate (Na3PO4), sodium hydrogenphosphate (Na2HPO4), iron phosphate (FePO4), phosphonic acid (H3PO3), and phosphinic acid (H3PO2);

a compound containing Na, such as sodium hydroxide (NaOH), sodium sulfate (Na2SO4), sodium sulfide (Na2S), sodium thiosulfate (Na2S2O3), sodium chloride (NaCl), sodium carbonate (Na2CO3), sodium citrate (Na2C6H5O7), sodium cyanate (NaCNO), sodium acetate (CH3COONa), sodium hydrogenphosphate (Na2HPO4), sodium phosphate (Na3PO4), sodium fluoride (NaF), sodium hydrogencarbonate (NaHCO3), sodium nitrate (NaNO3), sodium oxalate ((COONa)2), sodium tetraborate (Na2B4O7), and sodium oxide (Na2O);

a compound containing K, such as potassium hydroxide (KOH), potassium acetate (CH3COOK), potassium borate (K2B4O7), potassium carbonate (K2CO3), potassium chloride (KCl), potassium cyanate (KCNO), potassium hydrogencitrate (KH2C6H5O7), potassium fluoride (KF), potassium molybdate (K2MoO4), potassium nitrate (KNO3); potassium permanganate (KMnO4), potassium phosphate (K3PO4), potassium sulfate (K2SO4), potassium thiocyanate (KSCN), and potassium oxalate ((COOK)2);

a compound containing Cl, such as hydrochloric acid (HCl), sodium chloride (NaCl), ammonium chloride (NH4Cl), antimony chloride (SbCl3), potassium chloride (KCl), iron chloride (FeCl2, FeCl3), titanium chloride (TiCl4), copper chloride (CuCl), barium chloride (BaCl2), molybdenum chloride (MoCl5), and sodium chlorate (NaClO3);

a compound containing S, such as sulfuric acid (H2SO4), sodium sulfate (Na2SO4), sodium sulfite (Na2SO3), sodium sulfide (Na2S), ammonium sulfate ((NH4)2SO4), ammonium sulfide ((NH4)2S), sodium thiosulfate (Na2S2O3), sodium hydrogensulfate (NaHSO4), ammonium hydrogensulfate (NH4HSQ4), potassium sulfate (K2SO4), iron sulfate (FeSO4, Fe2(SO4)3), ammonium ironsulfate (Fe(NH4)2(SO4)2, FeNH4(SO4)2), barium sulfate (BaSO4), antimony sulfate (Sb2S3), ironsulfate (FeS), thiourea (H2NCSNH2), thiourea dioxide ((NH4)2CSO2), a thiophenic acid salt having SCH group, and a thiocyanic acid salt having SCN group;

a compound containing F, such as antimony fluoride (SbF3), ammonium fluoride (NH4F), potassium fluoride (KF), ammonium hydrogenfluoride (NH4HF2), hydrofluoric acid (HF), sodium fluoride (NaF), barium fluoride (BaF), and cobalt fluoride (CoF3);

a compound containing B, such as boric acid (H3BO3), potassium borate (K2B4O7), sodium tetraborate (Na2B4O7), lead borate (Pb(BO2)2), and manganese borate (MnH4(BO3)2); and

a compound containing C and N, such as oxalic acid, an oxalic acid salt, citric acid, a citric acid salt, nitric acid, and a nitric acid salt.

The method to adhere the above substances to the steel sheet is not specifically limited, and a method of physical adhesion of them may be applied, such as a method of immersing the steel sheet in an aqueous or organic solvent solution or suspension of the substance, a method of spraying that solution or suspension, and a method of coating thereof using a roll coater and the like. Succeeding step of drying the adhered compound does not affect the effect of the present invention. Alternatively, direct coating of the compound also provides similar effect to above.

It is possible that, before adhering the above substance, conventional pretreatment such as electrolytic degreasing and pickling is applied, at need. Even when the pretreatment is given after adhering the above substance, the effect of the present invention is attained if only the substance is adhered to the steel sheet. Furthermore, a rolling oil containing the above compound may be used to adhere the compound to the steel sheet in the rolling step.

For any of above methods, it is important to adhere the above substance to the surface of the steel sheet during oxidizing the steel sheet.

A preferable range of the coating weight of the above substance is from 0.01 to 1000 mg/m2 as the sum of the substances, converted to the quantity of elements specified in the present invention, (hereinafter referred to also as the “quantity of specified element”), because that range is easy for controlling the hematite content to 70% by mass or less, and because the segregated layer is easily formed below the plating layer if the quantity of specified element is 0.01 mg/m2 or more. The quantity of specified element is specified to 1000 mg/m2 or less rather because of economical advantage than because of the effect of the present invention.

An applicable method for quantitatively determining the substance adhered to the steel sheet is a wet-system analysis. That is, the quantity of the adhered substance is readily determined by subtracting the quantity of specified element in the substrate steel sheet from the total amount of the specified element (including the substance) in the substrate steel sheet.

According to the present invention, an oxide film containing hematite in a quantity of 70% by mass or less is formed on the surface of the steel sheet by heating the steel sheet, on which steel sheet at least one substance selected from the group consisting of above S, C, Cl, Na, K, B, P, F, N, and a compound thereof is adhered, in advance.

For example, the oxide film is readily formed by heating the steel sheet with the adhered above substance. The difference in the oxidizing means does not affect the effect of the present invention, and any means can be adopted if only the means oxidizes the steel sheet.

The heating means is not specifically limited, and conventional heating means such as burner heating, induction heating, radiation heating, and electric heating may be applied. For example, the burner heating method can use a conventional heating furnace such as oxidizing furnace and non-oxidizing furnace.

For the case of non-oxidizing furnace, the steel sheet is readily oxidized by selecting the air-fuel ratio of the direct-firing burner to larger than 1.0, for example.

The oxidation is preferably conducted in an oxidizing atmosphere. For the cases of induction heating method, radiation heating method, and electric heating method, the steel sheet is readily oxidized by adjusting the atmosphere in the vicinity of the heating steel sheet to an oxidizing atmosphere. Although common oxidizing atmosphere is the one containing at least one of oxidizing gases such as oxygen, steam, and carbon dioxide, the atmosphere is not necessarily limited if only it oxidizes the steel sheet.

The above description gives typical examples, and any means may be applicable if only it oxidizes the steel sheet, thus the means is not specifically limited.

The description given below is the reason why the hematite content can be controlled to 70% by mass or less by adhering at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof to the surface of the steel sheet.

For a steel sheet in which the Si content is high, the conventional oxidation means allows the Si in the steel to segregate to the interface between the iron oxide and the substrate steel sheet, thereby forming a layered and dense film of Si oxide. Since the layered Si oxide hinders the Fe diffusion from the substrate, the oxidation of iron at surface of the steel sheet is significantly suppressed so that there is formed an iron oxide containing a large quantity of hematite (Fe2O3) which is an oxide of a type of excess metallic ion (n-type).

On the other hand, if the substance is adhered to the surface of the steel sheet, the formation of Si oxide at the interface between the iron oxide and the substrate steel sheet is hindered, thereby allowing easy Fe diffusion from the substrate. As a result, the iron is easily oxidized at surface of the steel sheet, thus allowing formation of an iron oxide containing a large quantity of magnetite (Fe3O4) and wuestite (FeO) which are the metallic ion deficient type (p-type), thereby allowing decreasing the hematite content.

According to the present invention, when oxidation is applied to the steel sheet to which at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof is adhered, the heating is preferably conducted in an oxidizing atmosphere giving an ultimate temperature of above 500° C. The ultimate temperature is determined by observing the surface of the steel sheet using, for example, a radiation thermometer or a contact thermometer. If the heating temperature is above 500° C., the hematite content in the oxide film is easily controlled to 70% by mass or smaller, and the surface segregation of Si is suppressed, thereby improving the wettability with molten zinc. Although the upper limit of the heating temperature is not specifically limited, there is an economical and practical upper limit, at or lower than the steel sheet temperature required to the succeeding reducing treatment, or, for example, in an approximate range from 750° C. to 800° C.

Generally, when the steel sheet is oxidized, an oxide film composed of wuestite (FeO), magnetite (Fe3O4), and hematite (Fe2O3) is formed. It is known that a steel sheet containing Si at or higher than 0.1% by mass results in increased content of hematite in the oxide film, (refer to, for example, Nisshin Seiko Technical Review No. 77, p. 1, (1998)). By adjusting the hematite content in the oxide film to 70% by mass or less, the wettability with molten zinc in the succeeding step is improved, and the generation of non-plating portion can be completely prevented. Furthermore, after plating, if the steel sheet and the hot-dip galvanizing layer are alloyed with each other, the alloying between the steel sheet and the zinc plating also becomes easy. If the hematite content exceeds 70% by mass, the wettability with molten zinc deteriorates, which fails to completely prevent the generation of non-plating portion. Since the quantity of hematite in the oxide film is preferably as small as possible, the hematite content of 0% by mass is naturally preferable. Ordinarily, however, a preferable range of hematite content is approximately from 10 to 70% by mass.

The mechanism of improvement in the wettability with molten zinc through the adjustment of hematite content in the oxide film on the steel sheet surface to 70% by mass or less is not fully analyzed. It is, however, presumed that the composition of the oxide film affects the behavior of segregation of Si on the surface of the steel sheet in the succeeding reducing step, and that the hematite content of 70% by mass or less results in complete prevention of surface segregation of Si, thus attaining excellent plating adhesion.

The term “oxide film” referred to herein does not limit to the above-described FeO, Fe3O4, and Fe2O3. Even when an oxide containing Si and the like which are the additives for steel exists, the effect of the present invention is not affected by the additives.

The determination of hematite content can be done by an X-ray diffractometry using a rotary vibration sample table, (Cu tube, 50 kV of tube voltage, and 250 mA of tube current). That is, the respective powder standard samples of hematite (Fe2O3), magnetite (Fe3O4), and wuestite (FeO) are prepared, and three kinds of samples each having different mixing rates (% by mass) are prepared for the X-ray diffractometry. There are determined the diffraction peak intensity (cps) of (104) plane for hematite (Fe2O3), (400) plane for magnetite (Fe3O4), and (200) plane for wuestite (FeO). From these determined diffraction peak intensities, the relation between the mixing rate (% by mass) and the diffraction peak intensity (cps) is derived to draw a working curve. Based on thus drawn working curve and from the obtained diffraction peak intensity, the hematite content (% by mass) can be determined.

The oxide film obtained by the above method is preferably an iron oxide of 0.01 to 5 g/m2 as oxygen quantity. The oxygen quantity of 0.01 g/m2 allows easy suppression of surface segregation of Si owing to the sufficient quantity of oxygen. On the other hand, the oxygen quantity of 5 g/m2 or less allows the succeeding step to be conducted easily, and the alloying step given after the hot-dip galvanizing proceeds with enhanced alloying.

An example of the method for determining the quantity of oxygen in the oxide film is the following. That is, the determination is readily done by subtracting the quantity of oxygen in the substrate steel sheet from the total quantity of oxygen in the hot-dip galvanized steel sheet according to the present invention, using the wet-system analysis. If a working curve is drawn in advance, a simplified determination method such as fluorescent X-ray and GDS are also applicable.

According to the method to prepare an oxide film containing 70% by mass or more of hematite by adhering at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof to the steel sheet, followed by oxidizing them, the substance is not emitted into the oxidizing atmosphere, thereby increasing the quantity of the substance entrapped in the oxide film or in the substrate steel sheet. Consequently, the method also provides an effect to suppress the entering of toxic gases into the heating furnace for oxidation treatment and the entering thereof from the heating furnace to the vent gas.

Then, according to the present invention, the oxide film thus formed on the surface of the steel sheet is reduced. The reducing method is not specifically limited, and a conventional method can be applied.

For example, it is a common practice that the reducing treatment is given in a reducing atmosphere containing hydrogen in an annealing furnace of radiation heating type at temperatures from about 600° C. to about 900° C. The method is, however, not specifically limited, and any method is applicable if only the method reduces the oxide layer at the surface of the steel sheet.

Furthermore, according to the present invention, the substrate steel sheet thus reduced is immersed in a plating bath to apply hot-dip galvanization. The hot-dip galvanization may be a conventional method. For example, the substrate steel sheet is cooled to a temperature suitable for the plating treatment, normally, a temperature near the temperature of the plating bath in a non-oxidizing or reducing atmosphere. The plating bath is normally prepared at approximate temperatures from 440° C. to 520° C. with the Al concentration of approximately from 0.1 to 0.2%.

Depending on the uses of the products, the plating conditions such as plating temperature and plating bath composition may be changed. The changes in the plating conditions, however, do not affect the effect of the present invention, thus these conditions are not specifically limited. For example, inclusion of elements such as Pb, Sb, Fe, Mg, Mn, Ni, Ca, Ti, V, Cr, Co, and Sn, other than Al, in the plating bath does not affect the effect of the present invention.

In addition, the method to adjust the thickness of the plating layer after plating is not specifically limited. Generally the gas-wiping method is applied. The thickness of the plating layer is adjusted by adjusting the gas pressure of gas-wiping, the distance between the wiping nozzle and the steel sheet, and the like. Although the thickness of the plating layer is not specifically limited, it is preferably adjusted to a range from about 3 to about 15 μm because 3 μm or larger thickness gives sufficient rust-preventive property, and because 15 μm or smaller thickness is advantageous in view of workability and economy.

Furthermore, according to the present invention, alloying treatment may be given after the above hot-dip galvanization treatment.

As described above, the present invention suppresses the surface segregation of Si in the annealing step, thus the present invention solves the problem of related art of significant delay of alloying even in a steel sheet containing a large quantity of Si. As a result, an alloyed hot-dip galvanized steel sheet having excellent anti-powdering property can be manufactured without deteriorating the productivity.

The alloying treatment may use any of conventional heating methods such as gas heating, induction heating, and electric heating, and the method is not specifically limited.

Consequently, the inventors of the present invention has developed a process of: adhering at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof onto the surface of a substrate steel sheet containing 0.1 to 3% Si by mass; forming an oxide film by oxidizing the steel sheet in, preferably, an annealing furnace of CGL; applying reduction-annealing to the steel sheet to reduce the oxide film; and then applying hot-dip plating to the steel sheet.

According to the present invention, by adhering the substance to the substrate steel sheet before annealing the substrate steel sheet, or before oxidation thereof, a larger quantity of iron oxide film is formed than in the related art in the oxidation step even on a steel sheet containing a large quantity of Si. Consequently, generation of surface segregation of Si is effectively suppressed, which Si segregation on the surface is occurred on the surface of substrate steel sheet after succeeding reduction-annealing step in the related art. As a result, when the substrate steel sheet after reduction-annealing processed by the method of the present invention is subjected to hot-dip galvanization, a plating layer giving good surface appearance free from non-plating portion thereon is attained, and a hot-dip galvanized steel sheet having both excellent plating adhesion and sliding property is obtained.

Furthermore, if the above oxidation suppresses the surface segregation of Si, the adhered substance can enter the surface layer of the steel sheet by the heat treatment such as oxidation treatment. As a result, after the hot-dip galvanization or after the succeeding alloying treatment, there becomes existence of segregated layer containing at least one component selected from the group consisting of S, C, Cl, Na, K, B, P, F, and N below the plating layer.

The term “segregated layer” referred to herein signifies a zone in which the concentration of at least one component (hereinafter referred to also the “segregated component”) selected from the group consisting of S, C, Cl, Na, K, B, P, F, and N is 10% or higher than the concentration of the component in the substrate steel sheet.

That segregated layer is represented as a zone where the peak intensity appeared in the vicinity of interface is higher by 10% or more than the component intensity in the substrate steel sheet, which peak intensity is determined by a depth profile of the segregated component (element) in the depth direction from the surface of the plated steel sheet using GDS, or determined by a depth profile derived from the linear analysis of EPMA on a cross section of the plated steel sheet, as given in the examples.

The segregated layer is specified to the zone where the peak intensity of the segregated component appeared in the vicinity of interface is higher by 10% or more than the component intensity in the substrate steel sheet because smaller than 10% of increase in the intensity cannot fully prevent the surface segregation of Si during the reduction annealing step.

The determination of the depth profile of the segregated layer may be done by the linear analysis of cross section using GDS or EPMA, which are described above. As described below, however, the segregated layer is preferably the one in which the compound of the segregated component and the component in the substrate steel sheet is dispersed, thus the linear analysis by EPMA needs a special caution. That is, if the compound with the component in the substrate steel sheet is dispersed, the linear analysis of cross section by EPMA may analyze a portion of absence of the component. Accordingly, the linear analysis by EPMA is conducted by the following procedure. The measurement is given on arbitrary five positions on a cross section of the steel sheet to determine the thickness of a zone where the intensity of the segregated component is higher by 10% or more than the intensity of the component in the substrate steel sheet, and then the average thickness of the five observed values is calculated as the thickness of the segregated layer.

When the substance according to the present invention is adhered to the steel sheet, and is subjected to oxidation treatment, the quantity of the formed iron oxide increases, and the Si oxide is formed at interface between the iron oxide and the ground metal and/or within the ground metal. After that, the succeeding reducing treatment reduces the iron oxide to iron, thus the Si oxide remains in the ground metal. As a result, after the succeeding hot-dip galvanizing, a (reduced) iron layer exists below the plating layer, and the segregated layer containing the oxide containing Si exists below the (reduced) iron layer.

The “oxide containing Si” referred to herein essentially needs the existence of Si and oxygen. Since, however, the oxide containing Si includes the case of containing an oxide of a steel component and the case of containing double salt, complex salt, and the like of the oxide, the oxide containing Si is not limited to the Si oxide, and the kind is not the limited one. Typical “oxide containing Si” includes SiO2, FeSiO3, Fe2SiO4, MnSiO3, and a mixture thereof.

That is, the hot-dip galvanized steel sheet according to the present invention has: a steel sheet containing 0.1 to 3.0% Si by mass; a hot-dip galvanizing layer; and a segregated layer between the steel sheet and the hot-dip galvanizing layer, containing an oxide containing Si, having a thickness in a range from 0.01 to 100 μm, and containing at least one component selected from the group consisting of S, C, Cl, Na, K, B, P, F, and N.

The mechanism that the hot-dip galvanized steel sheet according to the present invention provides excellent plating adhesion and sliding property is not fully analyzed. The inventors of the present invention, however, speculate the mechanism as follows.

As in the case of the present invention, when the segregated layer having the above component is formed on the surface of the substrate steel sheet, the compatibility between the Fe-Al intermetallic compound, formed at the interface between the zinc plating and the steel sheet, and the substrate steel sheet varies toward advantageous side for the adhesion in the hot-dip galvanizing step.

Furthermore, when the segregated layer of the component is formed on the surface of the substrate steel sheet, the component is unavoidably eluted into the plating layer in the hot-dip galvanizing step, and a part of the eluted component comes to exist in the plating layer in the vicinity of interface with the steel sheet. The mechanism presumably improves the sliding property compared with the ordinary hot-dip galvanized steel sheet which does not contain the segregated layer.

Furthermore, the mechanism of improving the plating adhesion and sliding property by the existence of an oxide containing Si in the segregated layer is speculated as follows.

When an oxide containing Si exists in the segregated layer, the shape of interface between the plating layer and the steel sheet becomes irregular to generate an anchor effect, which anchor effect improves the adhesion, and the sliding property in the working step also improves. The anchor effect is the same for both the hot-dip galvanized steel sheet and the alloyed hot-dip galvanized steel sheet.

Accordingly, when the segregated layer of the component is formed below the plating layer, and when the oxide containing Si is brought to exist in the segregated layer, the synergy effect of them drastically improves the adhesion, and also improves the sliding property.

The thickness of the segregated layer according to the present invention is required to be controlled in a range from 0.01 to 100 μm because the thickness of smaller than 0.01 μm cannot sufficiently attain the effect to improve the adhesion, and because the thickness of larger than 100 μm deteriorates the fatigue characteristics. Further preferable range of the thickness of the segregated layer is from larger than 1 μm to not larger than 50 μm.

According to the present invention, the concentration of the component in the segregated layer is preferably higher by 10% or more than the concentration of the component in the substrate steel sheet because that kind of segregated layer makes the surface segregation of Si sufficiently and easily suppress in the reduction annealing step.

That kind of segregated layer is represented as a zone where the peak intensity appeared in the vicinity of interface is higher by 10% or more than the intensity of the ground metal, determined by a depth profile drawn on a cross section of the plated steel sheet using GDS, or determined by a depth profile derived from the linear analysis of EPMA, as given in the examples.

The segregated layer is preferably formed by a dispersed compound of the segregated component and the component of the substrate steel sheet. The component in the substrate steel sheet is expected as, Fe naturally, and as Si, Mn, Ti, Nb, V, Cr, S, Mo, Cu, Ni, B, Ca, N, P, Sb, and the like. To form the segregated layer of a desired substance, the formation of a compound with the component of the substrate steel sheet is expected to more stably fix the segregated component. According to an analysis, most part of the compound exists at grain boundaries in the substrate steel sheet. Therefore, a presumable advantage of the dispersed state of the compound is that the compound plugs the passage of Si diffusion, thereby effectively suppressing the surface segregation of Si in the steel.

Furthermore, if the compound in the segregated layer is MnS, the effect of the present invention is more stably attained because, among the expected compounds, MnS is a very stable compound in the steel so that MnS is easily formed and easily controls the manufacturing conditions. To form MnS, when S is selected as the element to adhere to the steel sheet before the above-oxidation treatment, the S reacts with Mn in the steel in the surface layer of the steel sheet, (below the plating layer after the plating step), during oxidation treatment and reducing treatment, thereby segregates.

In that case, a favorable quantity of the formed compound is five or more of the MnS grains having a grain size of 50 μm or larger, in an arbitrary cross section, per 20 μm of length in parallel with the interface between the plating layer and the substrate steel sheet. The MnS referred to herein means that the main component is formed by Mn and S, and the inclusion of other element such as Fe raises no problem.

Determination and judgment of dispersion and the number of compound particles can be given by, adding to the SEM observation or the TEM observation of cross section of the plated steel sheet, using EDS, electron diffractometry (TED), and the like, at need.

The quantity of the oxide containing Si in the segregated layer is preferably adjusted in a range from 0.01 to 1 g/m2 as oxygen. If the quantity of the oxide containing Si is 0.01 g/m2 or more, the plating adhesion and the sliding property are significantly improved, and the quantity thereof at 1 g/m2 or less is economical.

On determining the oxide, the existence of Si in the oxide can be confirmed by the EDX analysis of a sample prepared by the TEM replica method.

By alloying the above-described hot-dip galvanized steel sheet according to the present invention, there is obtained an alloyed hot-dip galvanized steel sheet which can be alloyed at a low temperature, and which provides not only excellent, plating adhesion and sliding property but also excellent anti-powdering property.

When the conventional hot-dip galvanized steel sheet is alloyed, a Γ phase having higher hardness than that of the substrate steel sheet is formed at the interface between the zinc plating and the substrate steel sheet, and the deterioration of plating adhesion is unavoidably occurs caused by the difference in the hardness between the Γ phase and the steel sheet. When, however, the hot-dip galvanized steel sheet according to the present invention is alloyed, there is existed a segregated layer of the component below the plating layer so that the mechanical characteristics in the vicinity of interface between the zinc plating layer and the substrate steel sheet, specifically the hardness of the substrate steel sheet, become close to those of the Γ phase, thereby effectively decreasing the strain applied to the interface during the deformation of the substrate steel sheet. As a result, the plating adhesion presumably improves.

Since the hot-dip galvanized steel sheet according to the present invention suppresses the surface segregation of Si in the annealing step, the alloying is available at relatively low temperatures. As a result, there is attained a merit of suppressing the formation of Γ phase which is not favorable to the plating adhesion.

Generally, the sliding property of alloyed hot-dip galvanized layer appears depending on the variations of alloying behavior. That is, as described above, the material of Si-surface-segregated material appeared on the surface of the substrate steel sheet in the annealing step delays the alloying rate because the surface-segregated material which is segregated by the selective oxidation on the surface after annealing suppresses the alloying reaction between Zn and Fe. As a result, the plating layer after completing the alloying reaction becomes the one having significantly irregular surface resulted from the interference of homogeneous reaction of Zn and Fe. In addition, the alloy crystals of Zn and Fe become coarse. Owing to the irregular surface of plating layer and to the coarse crystal grains caused by the suppression of alloying, the sliding property of the plating layer deteriorates.

The hot-dip galvanized steel sheet according to the present invention, however, contains a segregated layer having the component below the plating layer, similar to the above case of adhesion. Thus, compared with the normal cases, the surface segregation of Si in the annealing step is suppressed, and the alloying is enhanced. As a result, the reaction between Zn and Fe proceeds homogeneously, and the plating layer becomes smooth. In addition, the crystal grains become fine, thereby providing good sliding property compared with the Si-containing steel manufactured by the conventional method.

It was described above that the hot-dip galvanized steel sheet according to the present invention contains a layer of (reduced) iron below the plating layer, and further contains the segregated layer containing an oxide containing Si below the (reduced) iron layer. When, however, the hot-dip galvanized steel sheet according to the present invention is subjected to alloying treatment, naturally the alloying between the zinc plating layer and the (reduced) iron proceeds. Consequently, the obtained alloyed hot-dip galvanized steel sheet may fail to identify the iron layer below the galvanized layer. That type of alloyed hot-dip galvanized steel sheet, however, is within the range of the present invention because the steel sheet has the “segregated layer of the component containing an oxide containing Si” below the plating layer.

EXAMPLES

Example A

Electrolytic degreasing was conducted on eight types of test specimens of cold-rolled steel sheets and hot-rolled steel sheets, given in Table 1, in a solution of 5% NaOH by mass, under the condition of 5 A/dm2, 80° C. for 5 seconds. Each of aqueous solutions containing the respective substances of (a) phosphoric acid (100 g/l), (b) hydrochloric acid (1 g/l), (c) sodium fluoride (2g/l), (d) sodium thiosulfate (20 g/l), (e) Potassium hydroxide (100 g/l), (f), ammonium thiocyanate (50 g/l), (g) sulfuric acid (50 g/l), (h) ammonium sulfate (30 g/l), (i) thiourea (20 g/l), (j) sodium sulfate (50 g/l), (k) iron sulfate (20 g/l), (l) sulfuric acid (10 g/l), (m) ammonium sulfate (5 g/l), (n) thiourea (1 g/l), and (o) ammonium sulfate (150 g/l), was applied onto the surface of the respective steel sheets using a bar-coater at the respective coating weights given in Table 2-1, Table 3-1, and Table 4-1. After that, the applied aqueous solution was dried in a drier.

Thus prepared test specimens were heated in a heating furnace in an oxidizing atmosphere. Once taken out specimens were treated by annealing, followed by plating in a hot-dip plating simulator. The oxidation condition and other conditions are given in Table 2-1, Table 3-1, and Table 4-1.

For comparison, annealing and plating were given to the specimen without applying heating treatment.

The heating was given in air while varying the ultimate temperature of the steel sheet. The holding time at the ultimate temperature was 1 second, and then rapid cooling was applied using nitrogen gas.

The annealing was given in an atmosphere of (10% by volume of hydrogen+nitrogen) of −35° C. of dew point, at 830° C. of the steel sheet temperature and 45 seconds of holding time.

The plating was done in a zinc plating bath containing 0.14% Al by mass (Fe-saturated) at 460° C., with an immersing sheet temperature of 460° C., and an immersing time of 1 second. The surface appearance after plating was evaluated. After the plating, the coating weight was adjusted to 45 g/m2 on one side using a nitrogen gas wiper.

For thus prepared hot-dip galvanized steel sheets, the following-given procedure was applied to determine the thickness of the segregated component, and the degree of segregation, and to determine the oxide containing Si below the plating layer, and further the following-given evaluation criterion was applied to evaluate the plating appearance and the plating adhesion. The properties of segregated layer are given in Table 2-2, Table 3-2, and Table 4-2.

Furthermore, some of the plated steel sheets were subjected to alloying treatment, after the plating, in an electric heating furnace at 40° C./s of temperature-rise rate with 10 seconds of holding time, thus evaluating the alloying rate based on the alloying temperature that gives 10±0.5% by mass of the Fe content in the plating layer. The evaluation criterion is given later. Using a sample having 10±0.5% by mass of the Fe content in the plating layer, a 90° bend test was given to evaluate the anti-powdering property based on the evaluation criterion given later. Furthermore, the sliding property was evaluated based on the criterion given later.

Those evaluation results are shown in Table 2-3, Table 3-3, and Table 4-3.

As seen in Tables 2-1 to 4-3, even for the case of using a substrate steel sheet containing a large quantity of Si, prepared by adhering a compound containing at least one substance selected from the group consisting of S, C, Cl, Na, K, B, P, F, N, and a compound thereof onto the surface of steel sheet, and prepared by oxidizing the adhered substance to form an oxide film containing 70% by mass or less of hematite, and then by annealing in a reducing atmosphere, there is obtained excellent anti-powdering property and sliding property without generating non-plating portion and without significant delay of alloying. The obtained hot-dip galvanized steel sheet or alloyed hot-dip galvanized steel sheet has a segregated layer below the plating layer, and the segregated layer contains an oxide containing Si. It was confirmed that the oxide film formed after the oxidation treatment has a structure of hematite and balance of mainly magnetite and wuestite.

Example B

The plated steel sheets were prepared under the same conditions to those in Example A except that the substance was each of (o) potassium chloride (50 g/l), (p) ammonium oxalate (100 g/l), (q) sulfuric acid (50 g/l), (r) sodium hydroxide (30 g/l), and (s) sodium tetraborate (3 g/l), at the respective coating weights given in Table 5-1, and the heating condition of (0.1% by volume of oxygen+nitrogen) atmosphere. Evaluation to them was given on the same criterion to that of Example A. The properties of the segregated layer are given in Table 5-2. The evaluation of thus prepared plated steel sheets is given in Table 5-3.

As seen in Tables 5-1 to 5-3, for the case of a substrate steel sheet containing a large quantity of Si, prepared by adhering the substance onto the surface of steel sheet, and by oxidizing the adhered substance to form an oxide film containing 70% by mass or less of hematite, and then by annealing in a reducing atmosphere, there was obtained excellent anti-powdering property and sliding property without generating non-plating portion and without significant delay of alloying. The obtained hot-dip galvanized steel sheet or alloyed hot-dip galvanized steel sheet has a segregated layer below the plating layer, and the segregated layer contains an oxide containing Si. It was confirmed that the oxide film formed after oxidation treatment has a structure of hematite and balance of mainly magnetite and wuestite.

Example C

The plated steel sheets were prepared under the same conditions to those in Example A except that the substance was each of (t) antimony chloride (20 g/l), (u) ammonium sulfate (30 g/l), (v) lead chloride (1 g/l), (w) thiourea (20 g/l), and (x) sodium chloride (25 g/l), at the respective coating weights given in Table 6-1, and the heating condition of direct-firing burner at 1.15 of air/fuel ratio. Evaluation to them was given on the same criterion to that of Example A. The properties of the segregated layer are given in Table 6-2, and the evaluation results for thus prepared steel sheets are given in Table 6-3.

As seen in Tables 6-1 to 6-3, for the case of a substrate steel sheet containing a large quantity of Si, prepared by adhering the substance onto the surface of steel sheet, and by oxidizing the adhered substance to form an oxide film containing 70% by mass or less of hematite, and then by annealing in a reducing atmosphere, there was obtained excellent anti-powdering property and sliding property without generating non-plating portion and without significant delay of alloying. The obtained hot-dip galvanized steel sheet or alloyed hot-dip galvanized steel sheet has a segregated layer below the plating layer, and the segregated layer contains an oxide containing Si. It was confirmed that the oxide film formed after oxidation treatment has a structure of hematite and balance of mainly magnetite and wuestite.

The criteria for evaluating the plating quality are the following.

<Determination of the Thickness of Segregated Component and of the Degree of Segregation>

To the hot-dip galvanized steel sheet and the alloyed hot-dip galvanized steel sheet, the linear analysis of EPMA and/or the GDS measurement were given on their cross sections. Based on the drawn depth profiles (for example, FIG. 1 and FIG. 2), the thickness of segregated layer was determined as the thickness of a zone where the peak intensity of the segregated component (element) appeared in the vicinity of interface is higher by 10% or more than the intensity of the component in the ground metal portion, at a ground metal side from the interface between the plating layer and the substrate steel sheet. In addition, the increase in the peak intensity A of the component in the segregated layer to the peak intensity B of the component in the ground metal is determined as the degree of segregation. That is, [the degree of segregation (%)={(the intensity A−the intensity B)/(the intensity B)}×100%]. For the case of the degree of segregation smaller than 10%, the thickness of the zone where the intensity of the segregated component in the depth profile becomes slightly higher than the intensity B of the segregated component in the ground metal is given in the table as the thickness of the segregated layer. For the linear analysis of EPMA, the measurement was given at five arbitrary positions on a cross section of the steel sheet, and the thickness of the zone where the intensity of the segregated component is higher than the intensity of the ground metal by 10% or more was determined. The thickness of the segregated layer and the degree of segregation were derived by determining the average thickness and the average peak intensity A for the five measured values. In the GDS measurement, conversion from the sputtering time into the thickness of segregated layer was calculated on the basis of 0.04 μm/sec of the iron sputtering rate under the following GDS condition.

(EPMA Measurement Condition)

Acceleration voltage: 20 kV

Beam current: 0.05 μA

(GDS Measurement Condition)

Tube current: 30 mA

Argon gas flow volume: 400 ml

<Method for Determining the Oxide Containing Si Below the Plating Layer>

To the hot-dip galvanized steel sheet and the alloyed hot-dip galvanized steel sheet, the plating layer was removed by dissolving in an alkali solution given below. The oxide quantity was determined from the difference in the oxygen analysis result between thus prepared steel sheet and a steel sheet which was mechanically polished to 100 μm of surface irregularity on both sides thereof. The existence of Si in the oxide was confirmed by the EDX analysis on a test specimen prepared by TEM replica method.

(Alkali Solution)

NaOH: 8.2%

Triethanolamine: 2.1%

H2O2: 1.2%<

Plating Appearance>

Appearance of thus prepared hot-dip galvanized steel sheet was observed visually and with a (×10) magnifier. The evaluation was given as “No non-plating portion exists” for the case of absence of non-plating portion, “Slight non-plating portion exists” for the case that the (×10) magnifier-recognized fine non-plating portion, and “Non-plating portion exists” for the case that visual observation recognized non-plating portion.

◯: No non-plating portion exists.

Δ: Slight non-plating portion exists.

X: Non-plating portion exists.

<Plating Adhesion>

A ball-impact test was given to thus prepared hot-dip galvanized steel sheet to evaluate the plating separation on tape-peeling test. The test was conducted by positioning a hot-dip galvanized steel sheet on a hemispherical protrusion (½ inch of diameter), and by dropping a 2.8 kg weight onto the steel sheet from 1 m of height. After that, the tape-peeling test was given on the convex side.

◯: No plating separation occurred.

X: Plating separation occurred.

<Alloying Rate>

◯: Alloying temperature: alloying completed at 500° C. or below.

X: Alloying temperature: alloying completed at above 500° C.

<Anti-Powdering Property>

A test specimen (25 mm in width and 40 mm in length) was cut from the alloy hot-dip galvanized steel sheet, and a scotch tape (24 mm in width, manufactured by NICHIBAN CO., LTD.) was attached to the test specimen at 20 mm position in the length thereof. After bending the taping side by 90° inward, the specimen was again straightened. The scotch tape was peeled, and the quantity of Zn grains adhered to the scotch tape was counted under fluorescent X-ray. The Zn count was converted into the count per unit length of the test specimen (1 m), and the evaluation was given on the basis of the following criterion.

◯: Good (count: 1 to 5000)

X: Bad (count: more than 5000)

<Sliding Property Test>

The sliding property test was given under the following condition using a tool having a shape described below. From the ratio of the drawing-out force F to the pressing load P, the friction factor μ was derived by the following formula. The evaluation was given on the basis of the criterion described below.
μ=2P/F

Face pressure of 9.8 MPa, sliding distance of 100 mm, sliding rate of 10 mm/s, specimen width of 20 mm, mold of flat tool (shoulder radius of 5 mm, polished to #1200), contact area with specimen of 10×20 mm, oil-applying condition of NOX-RUST 550KH, 1.0 g/m2.

◯: Good (μ: less than 0.12)

X: Bad (μ: 0.12 or more)

Example D

The plated steel sheet was prepared under the same condition to that of Example A. The evaluation method was almost the same to that of Example A. For the anti-powdering property, however, the evaluation criterion was changed to the following-given one for evaluating finer differences.

⊚: Excellent (count: less than 4000)

◯: Good (count: 4000 to 5000)

X: Bad (count: more than 5000)

For each of the test specimens, confirmation was given on the determination of segregated substance in the vicinity of interface with the plating layer and on the distribution thereof using SEM and TEM. The analytical samples were prepared from the test specimens by working the cross section using the focused ion beam (FIB). The SEM observation determined the size and the number of the generated compound particles of segregated component, and the TEM-EDS and the electron beam diffraction determined the compound. Regarding the evaluation of the number of compound particles, within a visual field of cross sectional observation by SEM, the number of compound particles having 50 nm or larger size existing in the vicinity of interface in a zone of 20 μm in width in parallel with the interface between the plating layer and the substrate steel sheet was counted at arbitrarily selected five positions. The average of the values of these five positions was adopted as the evaluation index.

The results are given in Table 7 together with adhered substance, oxidation treatment, and the properties of segregated layer.

As shown in Table 7, among the segregated layers formed adequately in the vicinity of the interface with the plating layer, further excellent characteristics are attained specifically bringing the segregated layer to establish a state of sufficiently dispersing the compound of the segregated component and the component in the substrate steel sheet.

TABLE 1
(mass %)
SteelSteel
typesheetCSiMnPSAlOther
ACold-rolled0.0020.151.50.070.0040.03
Bsteel sheet0.10.252.00.050.0020.70
C0.50.52.00.010.0030.04
D0.0020.751.50.060.0070.04
E0.11.03.50.010.0030.05
F0.0031.10.30.050.0080.02
G0.151.52.50.010.0030.03
H0.12.91.50.010.0030.03
IHot-rolled0.150.31.50.030.0050.05
Jsteel sheet0.12.01.00.100.0050.03
KCold-rolled0.150.52.00.010.0030.04Ti: 0.02
Lsteel sheet0.10.251.60.050.0020.30Nb: 0.03
M0.0020.251.50.070.0040.03V: 0.03
N0.080.52.00.010.010.02Cr: 0.1
O0.151.52.10.010.0030.03Mo: 0.2
P0.12.80.80.010.0030.03Cu: 0.2
Q0.070.31.50.090.0050.05Ni: 0.2
R0.181.52.50.010.0030.3B: 0.002
S0.0031.11.50.050.0080.02Ca: 0.02
T0.0030.81.90.010.0080.02N: 0.01
U0.11.04.50.010.0030.8Sb: 0.02
V0.21.91.20.100.0050.03Ti: 0.03,
Nb: 0.04
W0.080.352.20.020.0020.70Nb: 0.03,
Mo: 0.25
X0.12.92.50.060.0030.03Cu: 0.15

TABLE 2-1
Adhered substabceOxidation treatment
Quantity ofOxygen
specificUIltimatequantity inHematite
SteelConcentrtionelementApplied/temperatureoxide filmcontent
No.typeKind(g/l)(mg/m2)Not applied(° C.)(g/m2)(%)
Example 1APhosphoric10070Applied6500.6250
Example 2Bacid0.5850
Example 3C0.5955
Example 4D0.660
Example 5G0.5560
Example 6H0.5765
Example 7BHydrochloric10.1Applied5500.450
Example 8Cacid0.480
Example 9G0.525
Example 10H0.455
Example 11I0.4910
Example 12J0.510
Example 13ASodium21Applied7000.750
Example 14Bfluoride0.710
Example 15C0.680
Example 16E0.770
Example 17F0.690
Example 18H0.690
Example 19ASodium2070Applied6000.550
Example 20Bthiosulfate0.520
Example 21C0.540
Example 22D0.50
Example 23G0.525
Example 24H0.535
Example 25APotassium100100Applied6000.510
Example 26Bhydroxide0.490
Example 27C0.485
Example 28E0.455
Example 29F0.4510
Example 30H0.4520
Comparative Example 1BNoneNoneNoneApplied6000.1890
Comparative Example 2C0.1290
Comparative Example 3G0.0790
Comparative Example 4H0.0595
Comparative Example 5I0.290
Comparative Example 6J0.0895
Comparative Example 7ASodium21Not
Comparative Example 8Bfluorideapplied
Comparative Example 9C
Comparative Example 10E
Comparative Example 11F
Comparative Example 12H
Comparative Example 13ASodium2070Applied5000.0775
Comparative Example 14Bthiosulfate0.0780
Comparative Example 15C0.0780
Comparative Example 16D0.0585
Comparative Example 17G0.0685
Comparative Example 18H0.0585
Comparative Example 19AHydrochloric10.1Applied4000.00680
Comparative Example 20Bacid0.00780
Comparative Example 21C0.00675
Comparative Example 22D0.00680
Comparative Example 23G0.00580
Comparative Example 24H0.00275
Comparative Example 25APhosphoric10070Applied4000.0185
Comparative Example 26Bacic0.0285
Comparative Example 27C0.0285
Comparative Example 28D0.0185
Comparative Example 29G0.00590
Comparative Example 30H0.00590
Comparative Example 31AAmmonium5070Applied5000.0180
Comparative Example 32Bthiocyanate0.0280
Comparative Example 33C0.0280
Comparative Example 34D0.0180
Comparative Example 35G0.00590
Comparative Example 36H0.00590

TABLE 2-2
Properties of segregated layer
Segregated
componentThickenss of segregatedDegree ofQuantity of oxide
below platingcomponent (μm)segregation (%)containing Si
No.layerGDSEPMAGDSEPMA(g/m2)
Example 1P74000.1
Example 274000.1
Example 374000.15
Example 474000.12
Example 574000.5
Example 674000.7
Example 7Cl1.11000.05
Example 81.21000.05
Example 91.11000.05
Example 101.11000.05
Example 111.11000.05
Example 121.11000.04
Example 13F, NaF: 1.5, Na: 1.4F: 100, Na: 1000.12
Example 14F: 1.5, Na: 1.4F: 100, Na: 1000.13
Example 15F: 1.5, Na: 1.4F: 100, Na: 1000.12
Example 16F: 1.5, Na: 1.4F: 100, Na: 1000.12
Example 17F: 1.5, Na: 1.4F: 100, Na: 1000.14
Example 18F: 1.5, Na: 1.4F: 100, Na: 1000.13
Example 19S, NaS: 3.0, Na: 2.0S: 400, Na: 4000.1
Example 20S: 3.0, Na: 2.0S: 400, Na: 4000.15
Example 21S: 3.0, Na: 2.0S: 400, Na: 4000.1
Example 22S: 3.0, Na: 2.0S: 400, Na: 4000.11
Example 23S: 3.0, Na: 2.0S: 400, Na: 4000.12
Example 24S: 3.0, Na: 2.0S: 400, Na: 4000.1
Example 25K3.05000.12
Example 263.05000.13
Example 273.05000.11
Example 283.05000.1
Example 293.05000.12
Example 303.05000.13
Comparative Example 1None0.001
Comparative Example 20.001
Comparative Example 30.001
Comparative Example 40.001
Comparative Example 50.001
Comparative Example 60.001
Comparative Example 7F, Na(F: 0.004, Na: 0.003)F: 5, Na: 50.002
Comparative Example 8(F: 0.004, Na: 0.003)F: 5, Na: 50.003
Comparative Example 9(F: 0.004, Na: 0.003)F: 5, Na: 50.002
Comparative Example 10(F: 0.004, Na: 0.003)F: 5, Na: 50.002
Comparative Example 11(F: 0.004, Na: 0.003)F: 5, Na: 50.003
Comparative Example 12(F: 0.004, Na: 0.003)F: 5, Na: 50.002
Comparative Example 13S, Na(S: 0.004, Na: 0.004)S: 6, Na: 60.004
Comparative Example 14(S: 0.004, Na: 0.004)S: 6, Na: 60.005
Comparative Example 15(S: 0.004, Na: 0.004)S: 6, Na: 60.004
Comparative Example 16(S: 0.004, Na: 0.004)S: 6, Na: 60.003
Comparative Example 17(S: 0.004, Na: 0.004)S: 6, Na: 60.003
Comparative Example 18(S: 0.004, Na: 0.004)S: 6, Na: 60.003
Comparative Example 19Cl(0.003)50.002
Comparative Example 20(0.003)50.003
Comparative Example 21(0.003)50.004
Comparative Example 22(0.003)50.003
Comparative Example 23(0.003)50.003
Comparative Example 24(0.003)50.004
Comparative Example 25P(0.004)50.002
Comparative Example 26(0.004)50.004
Comparative Example 27(0.004)50.003
Comparative Example 28(0.004)50.002
Comparative Example 29(0.004)50.004
Comparative Example 30(0.004)50.003
Comparative Example 31S, C, N(S: 0.004, C: 0.003, N: 0.004)S: 5, N50.004
Comparative Example 32(S: 0.004, C: 0.003, N: 0.004)S: 5, N50.005
Comparative Example 33(S: 0.004, C: 0.003, N: 0.004)S: 5, N50.004
Comparative Example 34(S: 0.004, C: 0.003, N: 0.004)S: 5, N50.004
Comparative Example 35(S: 0.004, C: 0.003, N: 0.004)S: 5, N50.003
Comparative Example 36(S: 0.004, C: 0.003, N: 0.004)S: 5, N50.004

TABLE 2-3
Plating quality
Anti-
PlatingPlatingAlloyingpowderingSliding
No.appearanceadhesionratepropertyproperty
Example 1
Example 2
Example 3
Example 4
Example 5
Example 6
Example 7
Example 8
Example 9
Example 10
Example 11
Example 12
Example 13
Example 14
Example 15
Example 16
Example 17
Example 18
Example 19
Example 20
Example 21
Example 22
Example 23
Example 24
Example 25
Example 26
Example 27
Example 28
Example 29
Example 30
ComparativeΔXXXX
Example 1
ComparativeXXXXX
Example 2
ComparativeXXXXX
Example 3
ComparativeXXXXX
Example 4
ComparativeΔXXXX
Example 5
ComparativeXXXXX
Example 6
ComparativeXXXXX
Example 7
ComparativeXXXXX
Example 8
ComparativeXXXXX
Example 9
ComparativeXXXXX
Example 10
ComparativeXXXXX
Example 11
ComparativeXXXXX
Example 12
ComparativeΔXXXX
Example 13
ComparativeΔXXXX
Example 14
ComparativeXXXXX
Example 15
ComparativeXXXXX
Example 16
ComparativeXXXXX
Example 17
ComparativeXXXXX
Example 18
ComparativeXXXXX
Example 19
ComparativeXXXXX
Example 20
ComparativeXXXXX
Example 21
ComparativeXXXXX
Example 22
ComparativeXXXXX
Example 23
ComparativeXXXXX
Example 24
ComparativeXXXXX
Example 25
ComparativeXXXXX
Example 26
ComparativeXXXXX
Example 27
ComparativeXXXXX
Example 28
ComparativeXXXXX
Example 29
ComparativeXXXXX
Example 30
ComparativeXXXXX
Example 31
ComparativeXXXXX
Example 32
ComparativeXXXXX
Example 33
ComparativeXXXXX
Example 34
ComparativeXXXXX
Example 35
ComparativeXXXXX
Example 36

TABLE 3-1
Adhered substanceOxidation treatment
Quantity ofQuantity of
specificUltimateoxygen inHematite
SteelConcentrationelementApplied/temperatureoxide filmcontent
No.typeKind(g/l)(mg/m2)Not applied(° C.)(g/m2)(%)
Example 31ASulfuric5070Applied6000.550
Example 32Bacid0.550
Example 33C0.535
Example 34D0.525
Example 35G0.6110
Example 36H0.5110
Example 37BAmmonium30100Applied6500.560
Example 38Csulfate0.610
Example 39G0.525
Example 40H0.545
Example 41I0.5310
Example 42J0.5110
Example 43AThiourea2070Applied7000.640
Example 44B0.640
Example 45C0.625
Example 46E0.715
Example 47F0.6210
Example 48H0.5110
Example 49ASodium5070Applied6000.550
Example 50Bsulfide0.510
Example 51C0.585
Example 52D0.545
Example 53G0.5610
Example 54H0.5110
Example 55AIron2080Applied5500.410
Example 56Bsulfide0.340
Example 57C0.355
Example 58E0.415
Example 59F0.3810
Example 60H0.3610
Comparative Example 37BNoneNoneNoneApplied6000.2190
Comparative Example 38C0.2590
Comparative Example 39G0.1890
Comparative Example 40H0.2190
Comparative Example 41I0.2495
Comparative Example 42J0.1990
Comparative Example 43ASulfuric105Not
Comparative Example 44Bacidapplied
Comparative Example 45C
Comparative Example 46E
Comparative Example 47F
Comparative Example 48H
Comparative Example 49AAmmonium510Applied4000.00680
Comparative Example 50Bsulfate0.00884
Comparative Example 51C0.00486
Comparative Example 52D0.00682
Comparative Example 53G0.00480
Comparative Example 54H0.00386
Comparative Example 55AThio urea10.1Applied4000.00485
Comparative Example 56B0.00390
Comparative Example 57C0.00489
Comparative Example 58D0.00686
Comparative Example 59G0.00491
Comparative Example 60H0.00290
Comparative Example 61ANoneNoneNoneApplied8503.175
Comparative Example 62B2.972
Comparative Example 63C2.680
Comparative Example 64D2.885
Comparative Example 65E2.972
Comparative Example 66F2.871
Comparative Example 67G2.975
Comparative Example 68H2.586

TABLE 3-2
Properties of segregated layer
Segregated
componentThickness of segregatedDegree ofQuantity of oxide
below platingcomponent (μm)segregation (%)containing Si
No.layerGDSEPMAGDSEPMA(g/m2)
Example 31S4.553003000.1
Example 324.653003000.1
Example 335.153003000.9
Example 345.153003000.9
Example 354.953003000.7
Example 365.353003000.7
Example 37S10.5105005000.12
Example 3810.4105005000.12
Example 3910.2105005000.1
Example 4010.1105005000.1
Example 419.8105005000.9
Example 4210.0105005000.9
Example 43S3.134004000.08
Example 443.034004000.08
Example 453.034004000.07
Example 462.834004000.07
Example 473.534004000.06
Example 483.234004000.06
Example 49S15.1151001000.03
Example 5014.8151001000.03
Example 5115.0151001000.03
Example 5215.8151001000.02
Example 5315.3151001000.02
Example 5415.4151001000.02
Example 55S20.0206006000.2
Example 5620.1206006000.2
Example 5720.1206006000.18
Example 5820.4206006000.17
Example 5920.4206006000.15
Example 6019.9206006000.15
Comparative Example 37None0.001
Comparative Example 380.001
Comparative Example 390.001
Comparative Example 400.001
Comparative Example 410.001
Comparative Example 420.001
Comparative Example 43S(0.006)(0.006)880.006
Comparative Example 44(0.005)(0.005)880.005
Comparative Example 45(0.004)(0.004)880.004
Comparative Example 46(0.004)(0.004)880.004
Comparative Example 47(0.003)(0.003)880.003
Comparative Example 48(0.003)(0.003)880.003
Comparative Example 49S(0.005)(0.005)770.005
Comparative Example 50(0.005)(0.005)770.005
Comparative Example 51(0.004)(0.004)770.004
Comparative Example 52(0.004)(0.004)770.004
Comparative Example 53(0.003)(0.003)770.003
Comparative Example 54(0.003)(0.003)770.003
Comparative Example 55S(0.005)(0.005)550.005
Comparative Example 56(0.004)(0.004)550.004
Comparative Example 57(0.004)(0.004)550.004
Comparative Example 58(0.003)(0.003)550.003
Comparative Example 59(0.003)(0.003)550.003
Comparative Example 60(0.003)(0.003)550.003
Comparative Example 61None0.03
Comparative Example 620.03
Comparative Example 630.02
Comparative Example 640.02
Comparative Example 650.03
Comparative Example 660.02
Comparative Example 670.02
Comparative Example 680.04

TABLE 3-3
Properties of plating layer
Anti-
PlatingPlatingAlloyingpowderingSliding
No.appearanceadhesionratepropertyproperty
Example 31
Example 32
Example 33
Example 34
Example 35
Example 36
Example 37
Example 38
Example 39
Example 40
Example 41
Example 42
Example 43
Example 44
Example 45
Example 46
Example 47
Example 48
Example 49
Example 50
Example 51
Example 52
Example 53
Example 54
Example 55
Example 56
Example 57
Example 58
Example 59
Example 60
ComparativeXXXXX
Example 37
ComparativeXXXXX
Example 38
ComparativeXXXXX
Example 39
ComparativeXXXXX
Example 40
ComparativeXXXXX
Example 41
ComparativeXXXXX
Example 42
ComparativeXXXXX
Example 43
ComparativeXXXXX
Example 44
ComparativeXXXXX
Example 45
ComparativeXXXXX
Example 46
ComparativeXXXXX
Example 47
ComparativeXXXXX
Example 48
ComparativeXXXXX
Example 49
ComparativeXXXXX
Example 50
ComparativeXXXXX
Example 51
ComparativeXXXXX
Example 52
ComparativeXXXXX
Example 53
ComparativeXXXXX
Example 54
ComparativeXXXXX
Example 55
ComparativeXXXXX
Example 56
ComparativeXXXXX
Example 57
ComparativeXXXXX
Example 58
ComparativeXXXXX
Example 59
ComparativeXXXXX
Example 60
ComparativeXX
Example 61
ComparativeXX
Example 62
ComparativeXX
Example 63
ComparativeXX
Example 64
ComparativeXX
Example 65
ComparativeXX
Example 66
ComparativeXX
Example 67
ComparativeXX
Example 68

TABLE 4-1
Adhered substanceOxidation treatment
Quantity ofQuantity of
specifiedUltimateoxygen inHematite
SteelConcentrationelementApplied/temperatureoxide filmcontent
No.typeKind(g/l)(mg/m2)Not applied(° C.)(g/m2)(%)
Example 61KAmmonium15090Applied6500.8210
Example 62Lsulfate0.810
Example 63M0.815
Example 64N0.810
Example 65O0.7715
Example 66P0.7720
Example 67Q0.8525
Example 68R0.8220
Example 69S0.8210
Example 70T0.8215
Example 71U0.7720
Example 72V0.7915
Example 73W0.7920
Example 74X0.820

TABLE 4-2
Properties of segregated layer
Segregated
componentThickness of segregatedDegree ofQuantity of oxide
below platingcomponent (μm)segregation (%)containing Si
No.layerGDSEPMAGDSEPMA(g/m2)
Example 61S33000.15
Example 6233000.15
Example 6333000.16
Example 6433000.15
Example 6533000.12
Example 6633000.1
Example 6733000.18
Example 6833000.15
Example 6933000.15
Example 7033000.15
Example 7133000.14
Example 7233000.15
Example 7333000.15
Example 7433000.15

TABLE 4-3
Plating quality
Anti-
PlatingPlatingAlloyingpowderingSliding
No.appearanceadhesionratepropertyproperty
Example 61
Example 62
Example 63
Example 64
Example 65
Example 66
Example 67
Example 68
Example 69
Example 70
Example 71
Example 72
Example 73
Example 74

TABLE 5-1
Adhered substanceOxidation treatment
Quantity ofQuantity of
speficiedUltimateoxygen inHematite
SteelConcentrationelementApplied/temperatureoxide filmcontent
No.typeKind(g/l)(mg/m2)Not applied(° C.)(g/m2)(%)
Example 75APotassium50100Applied6000.410
Example 76Bchloride0.430
Example 77C0.390
Example 78D0.350
Example 79G0.420
Example 80H0.410
Example 81BAmmonium100800Applied5500.3920
Example 82Coxalate0.3525
Example 83G0.3240
Example 84H0.3660
Example 85I0.3120
Example 86J0.3255
Example 87ASulfuric5080Applied5500.420
Example 88Bacid0.430
Example 89C0.440
Example 90E0.420
Example 91F0.450
Example 92H0.410
Example 93ASodium301Applied6000.5110
Example 94Bhydroxide0.5210
Example 95C0.5315
Example 96D0.520
Example 97G0.4930
Example 98H0.5645
Example 99ASodium30.5Applied6500.590
Example 100Btetraborate0.580
Example 101C0.65
Example 102E0.575
Example 103F0.5510
Example 104H0.620
Comparative Example 69BnoneNoneNoneApplied6500.3275
Comparative Example 70C0.2975
Comparative Example 71G0.1590
Comparative Example 72H0.1295
Comparative Example 73I0.3575
Comparative Example 74J0.1595
Comparative Example 75ASulfuric5080Not
Comparative Example 76Bacidapplied
Comparative Example 77C
Comparative Example 78E
Comparative Example 79F
Comparative Example 80H
Comparative Example 81AAmmonium100800Applied4500.0480
Comparative Example 82Boxalate0.0485
Comparative Example 83C0.0385
Comparative Example 84D0.0390
Comparative Example 85G0.0290
Comparative Example 86H0.00595

TABLE 5-2
Properties of segregated layer
Segregated
componentThickness of segregatedDegree ofQuantity of oxide
below platingcomponent (μm)segregtion (%)containing Si
No.layerGDSEPMAGDSEPMA(g/m2)
Example 75Cl, KCl: 3, K: 3Cl: 300, K: 3000.15
Example 76Cl: 3, K: 3Cl: 300, K: 3000.14
Example 77Cl: 3, K: 3Cl: 300, K: 3000.16
Example 78Cl: 3, K: 3Cl: 300, K: 3000.14
Example 79Cl: 3, K: 3Cl: 300, K: 3000.13
Example 80Cl: 3, K: 3Cl: 300, K: 3000.13
Example 81C, NC: 30, N: 30C: 500, N: 5000.06
Example 82C: 30, N: 30C: 300, N: 3000.06
Example 83C: 30, N: 30C: 300, N: 3000.05
Example 84C: 30, N: 30C: 300, N: 3000.07
Example 85C: 30, N: 30C: 300, N: 3000.06
Example 86C: 30, N: 30C: 300, N: 3000.06
Example 87S33000.04
Example 8833000.05
Example 8933000.06
Example 9033000.04
Example 9133000.04
Example 9233000.05
Example 93Na21000.17
Example 9421000.15
Example 9521000.16
Example 9621000.14
Example 9721000.13
Example 9821000.15
Example 99Na, BNa: 2, B: 2Na: 100, B: 1000.14
Example 100Na: 2, B: 2Na: 100, B: 1000.15
Example 101Na: 2, B: 2Na: 100, B: 1000.14
Example 102Na: 2, B: 2Na: 100, B: 1000.16
Example 103Na: 2, B: 2Na: 100, B: 1000.16
Example 104Na: 2, B: 2Na: 100, B: 1000.13
Comparative Example 69None0.001
Comparative Example 700.001
Comparative Example 710.001
Comparative Example 720.001
Comparative Example 730.001
Comparative Example 740.001
Comparative Example 75S(0.001)60.002
Comparative Example 76(0.001)60.003
Comparative Example 77(0.001)60.002
Comparative Example 78(0.001)60.002
Comparative Example 79(0.001)60.002
Comparative Example 80(0.001)60.002
Comparative Example 81C, N(0.004)C: 6, N: 60.002
Comparative Example 82(0.004)C: 6, N: 60.002
Comparative Example 83(0.004)C: 6, N: 60.003
Comparative Example 84(0.004)C: 6, N: 60.002
Comparative Example 85(0.004)C: 6, N: 60.003
Comparative Example 86(0.004)C: 6, N: 60.002

TABLE 5-3
Plating quality
Anti-
PlatingPlatingAlloyingpowderingSliding
No.appearanceadhesionratepropertyproperty
Example 75
Example 76
Example 77
Example 78
Example 79
Example 80
Example 81
Example 82
Example 83
Example 84
Example 85
Example 86
Example 87
Example 88
Example 89
Example 90
Example 91
Example 92
Example 93
Example 94
Example 95
Example 96
Example 97
Example 98
Example 99
Example 100
Example 101
Example 102
Example 103
Example 104
ComparativeΔXXXX
Example 69
ComparativeΔXXXX
Example 70
ComparativeXXXXX
Example 71
ComparativeXXXXX
Example 72
ComparativeXXXXX
Example 73
ComparativeXXXXX
Example 74
ComparativeXXXXX
Example 75
ComparativeXXXXX
Example 76
ComparativeXXXXX
Example 77
ComparativeXXXXX
Example 78
ComparativeXXXXX
Example 79
ComparativeXXXXX
Example 80
ComparativeXXXXX
Example 81
ComparativeXXXXX
Example 82
ComparativeXXXXX
Example 83
ComparativeXXXXX
Example 84
ComparativeXXXXX
Example 85
ComparativeXXXXX
Example 86

TABLE 6-1
Adhered substanceOxidation treatment
Quantity ofQuantity of
specifiedUltimateoxygen inHematite
SteelConcentrationelementApplied/temperartureoxide filmcontent
NO.typeKind(g/l)(mg/m2)Not applied(° C.)(g/m2)(%)
Example 105AAntimony2010Applied5500.350
Example 106Bchloride0.390
Example 107C0.40
Example 108D0.360
Example 109G0.3710
Example 110H0.3910
Example 111BAmmonium3050Applied6000.540
Example 112Csulfate0.520
Example 113G0.490
Example 114H0.530
Example 115I0.510
Example 116J0.50
Example 117ALead11Applied6500.5945
Example 118Bchloride0.645
Example 119C0.6250
Example 120E0.5960
Example 121F0.5865
Example 122H0.5965
Example 123AThiourea2070Applied6000.560
Example 124B0.580
Example 125C0.550
Example 126D0.540
Example 127G0.580
Example 128H0.560
Example 129ASodium255Applied6000.490
Example 130Bchloride0.520
Example 131C0.515
Example 132E0.495
Example 133F0.4810
Example 134H0.5120
Comparative Example 87BNoneNoneNoneApplied5500.1290
Comparative Example 88C0.0390
Comparative Example 89G0.0195
Comparative Example 90H0.00595
Comparative Example 91I0.0990
Comparative Example 92J0.0195
Comparative Example 93ASodium255Not
Comparative Example 94Bchlorideapplied
Comparative Example 95C
Comparative Example 96E
Comparative Example 97F
Comparative Example 98H
Comparative Example 99AThiourea2070Applied4500.0575
Comparative Example 100B0.0675
Comparative Example 101C0.0580
Comparative Example 102D0.0385
Comparative Example 103G0.0295
Comparative Example 104H0.00895

TABLE 6-2
Properties of segregated layer
Segregated
elementThickness of segregatedDegree ofQuantity of oxide
below platingcomponent (μm)segregation (%)containing Si
NO.layerGDSEPMAGDSEPMA(g/m2)
Example 105Cl23000.08
Example 10623000.05
Example 10723000.08
Example 10823000.07
Example 10923000.06
Example 11023000.05
Example 111S34000.15
Example 11234000.14
Example 11334000.13
Example 11434000.14
Example 11534000.14
Example 11634000.15
Example 117Cl23000.13
Example 11823000.12
Example 11933000.14
Example 12023000.12
Example 12123000.12
Example 12223000.13
Example 123S56000.14
Example 12456000.15
Example 12556000.14
Example 12656000.14
Example 12756000.16
Example 12856000.14
Example 129Na, ClNa: 2, Cl: 2Na: 300, Cl: 3000.14
Example 130Na: 2, Cl: 2Na: 300, Cl: 3000.14
Example 131Na: 2, Cl: 2Na: 300, Cl: 3000.14
Example 132Na: 2, Cl: 2Na: 300, Cl: 3000.15
Example 133Na: 2, Cl: 2Na: 300, Cl: 3000.15
Example 134Na: 2, Cl: 2Na: 300, Cl: 3000.14
Comparative Example 870.002
Comparative Example 880.002
Comparative Example 890.003
Comparative Example 900.002
Comparative Example 910.002
Comparative Example 920.002
Comparative Example 93Na, Cl(Cl: 0.004, Na: 0.003)Cl: 5, Na: 50.002
Comparative Example 94(Cl: 0.004, Na: 0.003)Cl: 5, Na: 50.001
Comparative Example 95(Cl: 0.004, Na: 0.003)Cl: 5, Na: 50.001
Comparative Example 96(Cl: 0.004, Na: 0.003)Cl: 5, Na: 50.002
Comparative Example 97(Cl: 0.004, Na: 0.003)Cl: 5, Na: 50.002
Comparative Example 98(Cl: 0.004, Na: 0.003)Cl: 5, Na: 50.003
Comparative Example 99S0.00450.002
Comparative Example 1000.00450.003
Comparative Example 1010.00450.003
Comparative Example 1020.00450.002
Comparative Example 1030.00450.002
Comparative Example 1040.00450.003

TABLE 6-3
Plating quality
Anti-
PlatingPlatingAlloyingpowderingSliding
NO.appearanceadhesionratepropertyproperty
Example 105
Example 106
Example 107
Example 108
Example 109
Example 110
Example 111
Example 112
Example 113
Example 114
Example 115
Example 116
Example 117
Example 118
Example 119
Example 120
Example 121
Example 122
Example 123
Example 124
Example 125
Example 126
Example 127
Example 128
Example 129
Example 130
Example 131
Example 132
Example 133
Example 134
ComparativeXXXXX
Example 87
ComparativeXXXXX
Example 88
ComparativeXXXXX
Example 89
ComparativeXXXXX
Example 90
ComparativeXXXXX
Example 91
ComparativeXXXXX
Example 92
ComparativeXXXXX
Example 93
ComparativeXXXXX
Example 94
ComparativeXXXXX
Example 95
ComparativeXXXXX
Example 96
ComparativeXXXXX
Example 97
ComparativeXXXXX
Example 98
ComparativeXXXXX
Example 99
ComparativeXXXXx
Example 100
ComparativeXXXXX
Example 101
ComparativeXXXXX
Example 102
ComparativeXXXXX
Example 103
ComparativeXXXXX
Example 104

TABLE 7
Adhered substanceProperties of segregated layer
Quantity ofOxidation treatmentSegregatedThickness of
specifiedUltimatecomponentsegregated
SteelConcentrationelementApplied/temperaturebelow platingcomponent (μm)
No.typeKind(g/l)(mg/m2)Not applied(° C.)layerGDSEPMA
Example 135GSulfuric5070Applied600S55
Example 136Eacid80550S55
Example 137G30600S33
Example 138E30550S33
Example 139GAmmonium30100Applied650S1010
Example 140Esulfate80550S66
Example 141G30600S33
Example 142E30550S33
Example 143GThiourea2070Applied700S22
Example 144E70700S33
Example 145G20700S11
Example 146E20700S11
Properties of segregated layerPlating quality
Quantity of oxideQuantityAnti-
contining Si(Number/PlatingPlatingpowderingSliding
No.(g/m2)Product20 μm)appearanceadhesionpropertyproperty
Example 1350.7Granular8.8
Example 1360.8MnS10.6
Example 1370.52.4
Example 1380.43
Example 1390.1Granular6.2
Example 1400.1MnS8
Example 1410.062.2
Example 1420.042.8
Example 1430.09Granular6.6
Example 1440.07MnS8.4
Example 1450.030.2
Example 1460.021.2

INDUSTRIAL APPLICABILITY

The present invention provides a hot-dip galvanized steel sheet showing excellent plating adhesion and sliding property even with a substrate steel sheet containing a large quantity of Si. Furthermore, an alloyed hot-dip galvanized steel sheet obtained by alloying the hot-dip galvanized steel sheet shows also excellent anti-powdering property. Both the galvanized steel sheets are manufactured at high productivity.