Title:
Wearing member having a pad-welded surface layer high in wear-resistance and heat crack-resistance
United States Patent 3929428


Abstract:
A wearing member having a pad-welded metallic surface layer with high wear and heat crack-resistance and having no irregular hardness is formed by pad-welding deposited steel in a composition range of 0.1 to 0.5 % C, 0.1 to 1.3 % Si, 0.3 to 2.0 % Mn, 1.0 to 5.0 % Cr, 0.5 to 5.0 % Mo and 0.5 to 3.0 % V, the rest being Fe and unavoidable impurities, or further containing one or more of less than 2.0 % W, less than 5.0 % Ni and less than 3.0 % Co.



Inventors:
Nishi, Takeshi (Kitakyushu, JA)
Kimura, Tsurugi (Kitakyushu, JA)
Moriguchi, Isao (Kitakyushu, JA)
Yokoi, Kiyoshi (Kitakyushu, JA)
Nakakobo, Isojiro (Tokyo, JA)
Kumagai, Ryohei (Narashino, JA)
Application Number:
05/113771
Publication Date:
12/30/1975
Filing Date:
02/08/1971
Assignee:
YAWATA IRON & STEEL CO., LTD.
Primary Class:
Other Classes:
29/895.32, 228/262.41, 420/111, 428/926, 428/939
International Classes:
B23K35/30; (IPC1-7): C22C38/24
Field of Search:
29/196
View Patent Images:



Primary Examiner:
Rutledge, Dewayne L.
Assistant Examiner:
Steiner, Arthur J.
Attorney, Agent or Firm:
Wenderoth, Lind & Ponack
Claims:
What is claimed is

1. A roller for hot rolling operations comprising an alloy layer welded to a steel substrate, said alloy consisting essentially of 0.1 to 0.5% C, 0.1 to 1.3% Si, 0.3 to 2.0% Mn, 1.0 to 5.0% Cr, 0.5 to 5.0% Mo and 0.5 to 3.0% V, the remainder being Fe.

2. A roller for hot rolling operations comprising an alloy layer welded to a steel substrate said alloy consisting essentially of 0.1 to 0.5% C, 0.1 to 1.3% Si, 0.3 to 2.0% Mn, 1.0 to 5.0% Cr, 0.5 to 5.0% Mo and 0.5 to 3.0% V, and at least one member selected from the group consisting of W, Ni and Co, said members being present in amounts sufficient to improve strength but less than 2% W, less than 5% Ni and less than 3% Co, the remainder being Fe.

3. A roller according to claim 1 wherein the thickness of the finished weld of said alloy is 5 to 20 mm.

4. A roller according to claim 2 wherein the thickness of the finished weld of said alloy is 5 to 20 mm.

5. A roller according to claim 1 wherein the steel substrate is carbon steel, low carbon alloy steel or cast steel.

6. A roller according to claim 2 wherein the steel substrate is carbon steel, low carbon alloy steel or cast steel.

7. A roller according to claim 1, wherein the substrate composition is 3.0% C, 1.2% Si, 0.5% Mn, 0.3% P, 0.06% S, 0.1% Mo, 0.1% Ni and 0.4% Cr, the remainder being Fe.

8. A roller according to claim 2 wherein the substrate composition is 3.0% C, 1.2% Si, 0.5% Mn, 0.3% P, 0.06% S, 0.1% Mo, 0.1% Ni and 0.4% Cr, the remainder being Fe.

9. A roller according to claim 1 wherein the substrate composition is 0.74% C, 0.36% Si, 0.76% Mn, 0.012% P, 0.019% S, 0.28% Mo, the remainder being Fe.

10. A roller according to claim 2 wherein the substrate composition is 0.74% C, 0.36% Si, 0.76% Mn, 0.012% P, 0.019% S, 0.28% Mn, the remainder being Fe.

11. A roller according to claim 2 wherein said member is W.

12. A roller according to claim 2 wherein said member is Ni.

13. A roller according to claim 2 wherein said member is Co.

Description:
BACKGROUND OF THE INVENTION

1. FIELD OF INVENTION 0.2-

This invention relates generally to a wearing member having a surface layer part high in the wear-resistance and more particularly to such machine part having a pad-welded metallic surface layer part high in wear and heat crack-resistance and having no irregular hardness such as a hot or cold-rolling roll, rotary shaft, or the like.

2. DESCRIPTION OF THE PRIOR ART

In various industries, there are used various kinds of machines and apparatus which have rotating or sliding parts subject to wear. For such wearing part, a wear-resistant part is used or a wear-resistance is imparted, improved or reproduced. In imparting, improving or reproducing such wear-resistance, generally, pad-welding is extensively carried out. There is known a pad-welding method for obtaining a deposited metal containing a large amount of chromium(Cr) or the like for such purpose. ensure Extrusions such

However, the deposited metal layer obtained by such known pad-welding can attain the object only in respect of the wear-resistance but can not be said to be satisfactory in respect of the crack-resistance, hardness uniformity and other mechanical properties, is disadvantageous in respect of economy and has thus many defects.

As the known method has such numerous defects as mentioned above, it is difficult to apply it to hot-rolling rolls, for example, in the iron manufacturing industry. Further, these rolling rolls are machine parts contribute significantly to steel material rolling cost. Therefore, in order to improve the durability of such machine part to be used at high heat as the hot-rolling roll, there must be used a pad-welding steel which is high in the thermoheat crack-resistance, annealing-resistance and hot-hardness and has no welding defects.

SUMMARY OF THE INVENTION

An object of the present invention is to provide such machine part having a surface part of a pad-welded metal layer high in the wear-resistance, heat crack-resistance, annealing-resistance and heat-hardness by removing such conventional defects as are mentioned above.

Another object of the present invention is to provide a pad-welding steel which is used to economically pad-weld such wearing part as a machine part so that a high wear-resistance and heat crack-resistance may be given or reproduced with very few welding defects.

In order to attain such objects as are mentioned above, the present invention is to form a padding deposited metal layer consisting of 0.1 to 0.5 % C, 0.1 to 1.3 % Si, 0.3 to 2.0 % Mn, 1.0 to 5.0 % Cr, 0.5 to 5.0 % Mo and 0.5 to 3.0 % V, the rest being Fe and unavoidable impurities, preferably 0.1 to 0.5 % C, 0.1 to 1.0 % Si, 0.5 to 2.0 % Mn, 2.0 to 5.0 % Cr, 2.0 to 5.0 % Mo and 1.0 to 3.0 % V, the rest being Fe and unavoidable impurities, or a padding deposited metal layer further containing one or more of less than 2.0 % W, less than 5.0 % Ni and less than 3.0 % Co in the above mentioned padding deposited metal composition in at least an operating part to be a wearing part on the surface of the body of a cold-rolling roll, hot-rolling roll, conveyer roller or friction machine part.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention shall be explained in detail in the following.

In the present invention, at least the operating surface of a hot-rolling roll, cold-rolling roll or machine part is coated with a deposited metal layer of such composition as is shown in Table 1.

Table 1 ______________________________________ Composition Content in % by weight ______________________________________ C 0.1 to 0.5 Si 0.1 to 1.3 Mn 0.3 to 2.0 Cr 1.0 to 5.0 Mo 0.5 to 5.0 V 0.5 to 3.0 W Less than 2.0 Ni Less than 5.0 Co Less than 3.0 ______________________________________

The deposited steel of such composition is obtained by such welding means as automatic welding by using either a welding rod made with any required alloying elements in a core wire or a coating, or a welding wire made by charging a hollow pipe with such powdery mixtures as of ferro-chromium, ferro-vanadium and metallic nickel. By said means, the operating portion of a machine part such as a rolling roll is coated in a thickness of 5 to 20 mm. by pad-welding.

For the above mentioned welding there may be employed a submerged arc-welding or any other welding method.

The deposited metal layer of such composition as is shown in Table 1 is easily obtained by properly selecting the composition of the welding rod depending on the welding method and welding conditions. The reasons for limiting the composition of the deposited metal in the present invention as in Table 1 shall be further described in the following.

First of all, if only the wear-resistance is an object, the content of carbon may be made about 1.5 to 2.0 % C and the contents of the other alloying elements may be reduced. However, in such case, the welding property will be reduced very much and such defects as cracks and blowholes will be likely to occur. Therefore, in the present invention, the upper limit of the carbon content is 0.5 %. On the other hand, if the carbon content is less than 0.1 %, the required strength and hardness will not be obtained in the deposited metal. Therefore, the lower limet is so set.

Silicon (Si) and manganese (Mn) are added to improve the heat- and wear-resistance. However, if more than 1.3 % Si and more than 2.0 % Mn above the upper limits are contained, the welding property will be impaired. On the other hand, if less than 0.1 % Si and less than 0.3 % Mn below the lower limits are present, the effect of the addition will not be well obtained.

Chromium (Cr) is a comparatively cheap element which will form a carbide, will elevate the heat-hardness and will increase the annealing-resistance. But, if the content of Cr is more than 5 % which is the upper limit, many cracks will be produced in the deposited metal. On the other hand, at the content of less than the lower limit of 1 % Cr, an insufficient effect can be expected.

Vanadium (V) and molybdenum (Mo) are most effective to improve the heat-hardness and annealing-resistance of the deposited steel. Mo is limited to be 0.5 to 5.0 % and V is limited to be 0.5 to 3.0 %. However, if the contents are more than the respective upper limits, the amount of the residual austenite will become so large as to cause hardness irregularities and cracks. On the other hand, if they are below the respective lower limits, the objective effect of the invention will not be able to be obtained.

Tungsten (W) also has the same effect as of V and Mo but is dearer than the other elements and can therefore be present in a range of 2.0 % in such machine part to be used particularly hot as, for example, a hot-rolling roll but need not be specifically present in a part to be used cold.

Further, when nickel (Ni) and cobalt (Co) are contained in a deposited steel, they will have an effect of improving its toughness. They can be present in the case that a high toughness is also specifically required. But, in such case, Ni should not exceed 5 % and Co should not exceed 3.0 %. When the contents of these elements Ni and Co exceed the above mentioned contents, there will be no improvement of the effects in proportion to their contents in the deposited metal and the cost will be high in vain.

The present invention is characterized by adding a small amount of each of several hardening elements as described above. This is based on the acquisition of a great advantage in that the hardness irregularities of the deposited steel by the production of a residual austenite when comparatively large amounts of a few kinds of elements are contained, can be prevented from occurring.

The present invention is characterized by coating at least the operating surface to be a wearing part of such machine part as a rolling roll, specifically a caliber in section steel rolling, a rotary shaft or a sliding shaft with a deposited metal of such composition as is mentioned above by means of a welding machine. In the present invention, though the hardness as pad-welded is high (for example, when the contents of the respective elements are at the upper limits, the Shore hardness will be 85 to 90 and, when they are at the lower limit, the Shore hardness will be 60 to 65), the welding property is so high that, if preheating at about 300°C. is carried out in welding, there will be no fear of the occurrence of such defects as cracks and blowholes and further the annealing-resistance is so high that, even in a use at such high temperature as about 600° to 650°C., there will be little reduction of the hardness and, even in a use in which heating and cooling are repeated, the heat crack-resistance will be high and there will be no fear of the production of cracks. Therefore, the present invention is adapted also to pad-welding of a cold-rolling roll for steel strips in which hardness irregularities should be specifically avoided.

The present invention can be applied to such various machine parts as rolling rolls and rotary shafts as mentioned above. In applying the present invention, it is necessary to take the kind of the flux to be used, the composition of welding metal material, the presence or absence of preheating and the welding method into consideration in response to such material of said machine part as for example carbon steel, low-carbon alloy steel, cast steel or cast iron. Further, under such circumstances as where the part to which the invention is to be applied is difficult to weld, a type of steel easy to deposit may be used as an intermediate material and a padding layer may be formed on it.

In case a precision is required, the above mentioned deposited metal layer should be finish-worked with a grinding machine.

The present invention has been explained in detail in the above. Further, examples shall be described in the following.

EXAMPLE 1

By using a welding wire made by charging a hollow wire with an alloy of the below mentioned composition in the hollow part and using a flux (of a composition of 42 % SiO2, 40 % MnO, 10 % CaO, 3 % Al2 O3 and 1 % MgO, the rest being impurities), a worn roller (of a composition of 3.0 % C, 1.2 % Si, 0.5 % Mn, 0.3 % P, 0.06 % S, 0.1 % Mo, 0.1 % Ni, 0.4 % Cr, the rest being Fe and impurities) of a hot run table in a steel plate hot-rolling plant was turned, was further shrink-fitted with a soft steel tube and was coated on the surface with a steel to be 6 mm. thick by pad-welding by a submerged arc-welding method.

The composition of the alloy with which the welding wire was charged (in percentages on the total composition of the wire) was 1 % ferro-silicon, 0.8 % ferro-manganese, 4.75 % ferro-chromium, 5.90 % ferro-molybdenum, 3.2 % ferro-vanadium, 0.35 % graphite and 11 % iron powder, the rest being Fe and impurities. The hardness of this deposited steel was in a range of 70 to 75 by Shore. Its chemical composition was 0.27 % C, 0.58 % Si, 1.65 % Mn, 2.84 % Cr, 3.5 % Mo and 1.61 % V.

A chilled roller was mostly used for the above mentioned hot run table roller. It was very difficult to directly pad-weld it. When it was repaired, as mentioned above, the hardness was rather higher than the hardness of the body of 60 to 65 by Shore, no crack occurred during the use and a quality higher than before could be obtained at a very low cost.

EXAMPLE 2

The surface of a blooming roll (of a composition of the Table 2 mentioned below) was pad-welded by submerged arc-welding by using a welding wire made by charging a hollow wire with 1 % ferro-silicon, 0.8 % ferro-manganese, 4.75 % ferro-chromium, 3.65 % ferro-vanadium, 0.90 % ferro-cobalt, 2.25 % ferro-nickel, 0.2 % graphite and 11 % iron powder and using the flux in Example 1. In this case, the thickness of the deposited metal was 10 mm. and its hardness was 60 to 65 by Shore. The chemical composition of the deposited metal was 0.15 % C, 0.65 % Si, 1.80 % Mn, 2.90 % Cr, 2.20 % Mo, 1.41 % V, 2.14 % Ni and 0.85 % Co, the rest being Fe and impurities.

In the above mentioned blooming roll of the present invention, the wear reduced to be one-third as high as in a conventional cast iron roll and there was substantially no heat cracking caused by the repetition of heating and cooling. It was excellent.

EXAMPLE 3

When a test piece taken from a known roll material and a test piece obtained by pad-welding a base by submerged arc-welding by using a welding wire made by charging a hollow pipe with 1 % ferro-silicon, 0.8 % ferro-manganese, 3.50 % ferro-chrome, 3.65 % ferro-molybdenum, 3.20 % ferro-vanadium, 1.05 % ferro-tungsten, 0.90 % ferro-cobalt, 2.25 % ferro-nickel, 0.35 % graphite and 11 % iron powder and using the flux in Example 1 were subjected to repeated tests of quickly heating with high frequencies and cooling with sprayed water between 20° and 700°C., in the test piece taken from the known roll material, cracks occurred at 100 repetitions but, in the deposited metal coated test piece of the present invention, no cracking occurred even at 300 repetitions. The composition of the known roll material and the composition of the coating deposited metal of the test piece of the present invention 2. respectively as in Table 2

Table 2 ______________________________________ Composition in % Known roll Deposited metal of material the present invention ______________________________________ C 0.74 % 0.31 % Si 0.36 % 0.65 % Mn 0.76 % 1.30 % P 0.012 % 0.021 % S 0.019 % 0.024 % Mo 0.28 % 2.05 % Cr -- 2.10 % V -- 1.51 % W -- 1.05 % Ni -- 2.20 % Co -- 0.78 % ______________________________________