Title:
Heat-insulating board for covering the top surface of a feeder head
United States Patent 3923526
Abstract:
A heat-insulating board for covering the top surface of a feeder head. The heat-insulating board is composed of a plate-like molding and a composition which contains a heat-expandable material or a mixture of heat-expandable materials, attached to the outer edge of the molding or uniformly mixed with the plate-like molding.
US Patent References:
Insulating cover
Charman - February 1949 - 2462255
Insulating cover
Charman - February 1949 - 2462256
Hot top composition for casting molds
Edstrom - January 1967 - 3297296
Hot top
De Geer - January 1967 - 3300322
Method of hot topping using vermicular graphite
Osborn - March 1967 - 3308514
Insulating cover
Charman - February 1949 - 2462255
Insulating cover
Charman - February 1949 - 2462256
Hot top composition for casting molds
Edstrom - January 1967 - 3297296
Hot top
De Geer - January 1967 - 3300322
Method of hot topping using vermicular graphite
Osborn - March 1967 - 3308514
Application Number:
05/321425
Publication Date:
12/02/1975
Filing Date:
01/05/1973
View Patent Images:
Export Citation:
Assignee:
Aikoh Co., Ltd. (Tokyo, JA)
Primary Class:
Other Classes:
249/204, 106/38.250, 106/38.280, 249/106, 106/38.270
International Classes:
B22D7/10; B22D7/00; B28B7/36
Field of Search:
106/38.22,38.27,38.25
US Patent References:
Primary Examiner:
Morris, Theodore
Attorney, Agent or Firm:
Sughrue, Rothwell, Mion, Zinn & Macpeak
Claims:
What is claimed is
1. A heat-insulating board for covering the top surface of a feeder head which comprises a plate-like molding and a composition attached to the outer rim of the plate-like molding; said composition comprising 5-80% by weight of a chemically treated heat-expandable material of flake-like graphite or pitch treated with an acid and/or an oxidizing agent, 0-92% by weight of a refractory material, 0-30% by weight of an easily oxidizable metal, 0-30% by weight of an oxidizing agent, 0-40% by weight of a non-metallic fibrous material, 0-20% by weight of a carbonaceous substance, 0-10% by weight of an oxidation accelerating agent and 3-20% by weight of a binder; said plate-like molding comprising 20-94% by weight of a refractory material selected from the group of silica sand, quartz, magnesia (magnesium oxide), alumina (aluminum oxide), olivine, aluminum ash, dolomite, magnesite, limestone, chamotte, corundum, diatomaceous earth, lapilli, expanded vermiculite, expanded shale, expanded obsidina, expanded perlite and expanded pitch-stone, 3-40% by weight of a fibrous material, 0-30% by weight of an easily oxidizable metal, 0-30% by weight of an oxidizing agent, 0-20% by weight of a carbonaceous substrate, 0-10% by weight of an oxidation accelerating agent and 3-20% by weight of a binder; the heat-insulating board being adapted to expand upon being heated.
2. A heat-insulating board according to claim 1 wherein the plate-like molding comprises a two-layer molding having an inner layer which is placed in contact with the top surfact of the molten metal, and an outer layer; the inner layer comprising 3-30% by weight of an easily oxidizable metal, 3-30% by weight of an oxidizing agent, 10-88% by weight of a refractory material selected from the group of silica sand, quartz, magnesia (magnesium oxide), alumina (aluminum oxide), olivine, aluminum ash, dolomite, magnesite, limestone, chamotte, corundum, diatomaceous earth, lapilli, expanded vermiculite, expanded shale, expanded obsidina, expanded perlite and expanded pitch-stone, 3-40% by weight of a fibrous material, 0-20% by weight of a carbonaceous substance, 0-10% by weight of an oxidation accelerating agent, and 3-20% by weight of a binder; and the outer layer comprising 40-94% by weight of a refractory material selected from the group of silica sand, quartz, magnesia (magnesium oxide), alumina (aluminum oxide), olivine, aluminum ash, dolomite, magnesite, limestone, chamotte, corundum, diatomaceous earth, lapilli, expanded vermiculite, expanded shale, expanded obsidina, expanded perlite and expanded pitch-stone, 3-40% by weight of a fibrous material and 3-20% by weight of a binder.
3. A heat-insulating board according to claim 1, wherein said board expands primarily in a plane of its greatest dimension when heated to completely cover and seal the top surface of said feeder head.
1. A heat-insulating board for covering the top surface of a feeder head which comprises a plate-like molding and a composition attached to the outer rim of the plate-like molding; said composition comprising 5-80% by weight of a chemically treated heat-expandable material of flake-like graphite or pitch treated with an acid and/or an oxidizing agent, 0-92% by weight of a refractory material, 0-30% by weight of an easily oxidizable metal, 0-30% by weight of an oxidizing agent, 0-40% by weight of a non-metallic fibrous material, 0-20% by weight of a carbonaceous substance, 0-10% by weight of an oxidation accelerating agent and 3-20% by weight of a binder; said plate-like molding comprising 20-94% by weight of a refractory material selected from the group of silica sand, quartz, magnesia (magnesium oxide), alumina (aluminum oxide), olivine, aluminum ash, dolomite, magnesite, limestone, chamotte, corundum, diatomaceous earth, lapilli, expanded vermiculite, expanded shale, expanded obsidina, expanded perlite and expanded pitch-stone, 3-40% by weight of a fibrous material, 0-30% by weight of an easily oxidizable metal, 0-30% by weight of an oxidizing agent, 0-20% by weight of a carbonaceous substrate, 0-10% by weight of an oxidation accelerating agent and 3-20% by weight of a binder; the heat-insulating board being adapted to expand upon being heated.
2. A heat-insulating board according to claim 1 wherein the plate-like molding comprises a two-layer molding having an inner layer which is placed in contact with the top surfact of the molten metal, and an outer layer; the inner layer comprising 3-30% by weight of an easily oxidizable metal, 3-30% by weight of an oxidizing agent, 10-88% by weight of a refractory material selected from the group of silica sand, quartz, magnesia (magnesium oxide), alumina (aluminum oxide), olivine, aluminum ash, dolomite, magnesite, limestone, chamotte, corundum, diatomaceous earth, lapilli, expanded vermiculite, expanded shale, expanded obsidina, expanded perlite and expanded pitch-stone, 3-40% by weight of a fibrous material, 0-20% by weight of a carbonaceous substance, 0-10% by weight of an oxidation accelerating agent, and 3-20% by weight of a binder; and the outer layer comprising 40-94% by weight of a refractory material selected from the group of silica sand, quartz, magnesia (magnesium oxide), alumina (aluminum oxide), olivine, aluminum ash, dolomite, magnesite, limestone, chamotte, corundum, diatomaceous earth, lapilli, expanded vermiculite, expanded shale, expanded obsidina, expanded perlite and expanded pitch-stone, 3-40% by weight of a fibrous material and 3-20% by weight of a binder.
3. A heat-insulating board according to claim 1, wherein said board expands primarily in a plane of its greatest dimension when heated to completely cover and seal the top surface of said feeder head.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat-insulating board for covering the top surface of the molten metal in a feeder head during the casting of a molten metal, particularly a molten steel.
More precisely, the present invention provides a heat-insulating board for covering the top surface of a feeder head of molten metal which contains a material which expands upon being heated, or a mixture of such materials. The heat-insulating board is used in combination with a heat-insulating sleeve or slab for heat-insulating the side surface of the feeder head, and the heat-insulating board is expanded during use when the heat-expandable material(s) expand by the action of the heat from the molten metal to be cast, whereby any gap between the heat-insulating board and the sleeve, slab or a side wall of a casting mold is closed.
2. Description of the Prior Art
In the casting of molten metal into a mold to form a cast product, it is important to keep the metal in the feeder head (hot top) molten long enough to feed the shrinkage cavity, commonly known as a pipe, by preventing the loss of heat from the metal in the feeder head. Usually the head of the mold (or a head box fitted to the mold) is lined with one or more heat-insulating sleeves or slabs, and the top surface of the molten metal is covered with either a heat-insulating agent such as an exothermic powder, or with a plate-like heat-insulating board, at a time after the molten metal has been completely poured in the said mold.
However, a heat-insulating agent such as an exothermic powder, as is conventionally used for covering the top surface of the feeder head, is composed of fine powdery light substances, and these fine powdery substances are violently scattered when the agent is added to the top surface of molten metal, and during the exothermic reaction which occurs after the addition of the same. Consequently, a large amount of smoke and dust is generated which interferes with the casting operation. Moreover, the smoke and dust are harmful to humans and thus the use of such a heat-insulating agent is unfavorable from the view-point of environmental sanitation.
The heat-insulating boards which have been used to cover the top surface of the feeder head eliminate the abovementioned defects of the heat-insulating agent. In the conventional heat-insulating board, however, a gap occurs between the board and the sleeve or slab which is provided to heat-insulate the side surface of the feeder head or the side wall of the mold. Thus, it is impossible using such a heat-insulating board to completely cover the top surface of a molten metal in the feeder head, and it is difficult to adequately heat-insulate the feeder head.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to eliminate the above defects in conventional heat-insulating boards for covering the top surface of the feeder head and to improve the heat-insulating effect on the feeder head.
The present invention provides a novel heat-insulating board for covering the top surface of a feeder head which consists of a plate-like molding and a heat-expandable composition.
The heat-expandable compositon may be attached to the outer face of the plate-like molding or may be uniformly mixed with the plate-like molding. The "outer face" of the plate-like molding will be referred to as the "rim" thereof.
If desired, as shown in the drawings, the heat-expandable composition, when attached to the outer face, need only be provided at a part of the outer face to achieve the expansion/sealing action upon heating. Although shown in the drawings as being at the upper portion of the outer face of the plate-like molding, a similar expansion/sealing effect is achieved when the heat-expandable materials are provided at only the lower portion of the outer face of the plate-like molding.
Further, while it has been indicated that the plate-like molding may be a homogeneous mixture with the heat-expandable material, it will be obvious that an embodiment intermediate those described above is operable if only the outer portions of the plate-like molding are mixed with the expandable material, e.g., during water removal if a slurry is formed.
Since the diameter of the plate-like molding is much greater than the thickness, in both embodiments described above when the plate-like molding is heated on contact with the molten metal, it expands primarily in a plane perpendicular to the sides of the mold, and thereby seals any gap between the plate-like molding and the side of the mold or sleeve or slab (if such is interposed between the plate-like molding and the wall of the mold,) and completely covers the top surface of the molten metal in the feeder head. Accordingly, the heat-insulating effect on the feeder head is greatly improved by the use of the present heat-insulating board.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of an upper part of a mold in which a heat-insulating board according to the present invention is provided in the upper portion thereof.
FIG. 2 is an enlarged section of the heat-insulating board of FIG. 1.
FIG. 3 and FIG. 4 are sectional views of other embodiments of heat-insulating boards in accordance with the present invention.
FIG. 5 is a sectional view of the upper part of a mold in which still another heat-insulating board according to the present invention has been provided in the upper portion thereof.
FIG. 6 and FIG. 7 are sectional views of additional embodiments of heat-insulating boards according to the present invention which are different from those shown in FIGS. 1-5.
DETAILED DESCRIPTION OF THE INVENTION
The composition containing heat-expandable materials of the present invention preferably consists of the following ingredients:
Natural mineral heat-expandable material and/or chemically treated heat-expandable material 5-80% (by weight) Refractory material 0-92% (by weight) Easily oxidizable metal 0-30% (by weight) Oxidizing agent 0-30% (by weight) Fibrous material 0-40% (by weight) Carbonaceous substance 0-20% (by weight) Oxidation accelerating agent 0-10% (by weight) Binder 3-20% (by weight)
As heat-expandable natural minerals, vermiculite, shale, obsidian, perlite, pitch-stone, bloating clay, etc. are suitable.
As chemically treated heat-expandable materials, flake-like graphite, pitch, etc. treated with an acid and/or an oxidizing agent are suitable.
These heat-expandable materials are known, and have been used as an ingredient for a feeder head heat-insulating composition.
As indicated, the above described heat-expandable composition is attached to or will comprise the outer rim of the plate-like molding. The plate-like molding is preferably either a one-layer molding comprising a uniform composition, or a two-layer molding comprising an exothermic inner layer which will be in contact with the top surface of the molten metal and an adiabatic outer layer. Preferred embodiments of a one-layer molding and a two-layer molding are described below:
(1) One-layer molding Refractory material 20-94% (by weight) Fibrous material 3-40% (by weight) Easily oxidizable metal 0-30% (by weight) Oxidizing agent 0-30% (by weight) Carbonaceous substance 0-20% (by weight) Oxidation accelerating agent 0-10% (by weight) Binder 3-20% (by weight) (2) Two-layer molding (i) Exothermic inner layer Easily oxidizable metal 3-30% (by weight) Oxidizing agent 3-30% (by weight) Refractory material 10-88% (by weight) Fibrous material 3-40% (by weight) Carbonaceous substance 0-20% (by weight) Oxidation accelerating agent 0-10% (by weight) Binder 3-20% (by weight) (ii) Adiabatic outer layer Refractory material 40-94% (by weight) Fibrous material 3-40% (by weight) Binder 3-20% (by weight)
As another embodiment of the heat-insulating board of the present invention, the above described heat-expandable material(s) may be uniformly incorporated into the plate-like molding. The heat-insulating board thus prepared will expand primarily outwardly towards the walls of the mold to closely seal any gap between the board and a sleeve or slab for heat-insulating the side surface of the feeder head of the side wall of a mold, and simultaneously the board is expanded also in its thickness thereby to become a porous heat-insulating board. Thus, a heat-insulating board of this kind will have an improved heat-insulating effect.
In the following, a preferable composition constituting such a board is shown:
Natural mineral heat-expandable material and/or chemically treated heat-expandable material 5-67% (by weight) Refractory material 10-89% (by weight) Fibrous material 3-40% (by weight) Easily oxidizable metal 0-30% (by weight) Oxidizing agent 0-30% (by weight) Carbonaceous substance 0-20% (by weight) Oxidation accelerating agent 0-10% (by weight) Binder 3-20% (by weight)
As the refractory material which is one of constituents of the heat-insulating board of the present invention, the following materials are exemplary: Non-porous refractory material such as silica sand, quartz, magnesia (magnesium oxide), alumina (aluminum oxide), olivine, aluminum ash, dolomite, magnesite, limestone, chamotte, Corundum, Alundum (trade name), and the like, and porous refractory materials such as diatomaceous earth, lapilli, expanded vermiculite, expanded shale, expanded obsidina, expanded perlite, expanded pitch-stone, and the like.
As the easily oxidizable metal, the following are preferred: Aluminum, magnesium, aluminum-magnesium alloys, calcium-silicon alloys, iron-silicon alloys, and the like. These metals react witn an oxidizing agent by an exothermic reaction to heat the top surface of the feeder head. As the oxidizing agent, the following are exemplary: Metal oxides such as ferrous oxide, ferric oxide, tri-iron tetraoxide, manganese dioxide, chromic oxide and the like, and nitrates such as potassium nitrate, sodium nitrate, barium nitrate, and the like.
As the fibrous material, the following are preferred: Refractory inorganic fibrous materials such as asbestos, rock wool, slag wool, glass wool, refractory clays and fibrous materials, and the like, and organic fibrous materials such as cellulosic materials derived from paper, paper wood, saw dust, wood meal, chemical fibers and the like. These fibrous materials reinforce the heat-insulating board so that the board is not damaged by any impact during the treatment of the board such as a transfer thereof, the disposition thereof in the mold, etc. Further, by the use of such a fibrous material, the resulting heat-insulating board can become a porous board which has a low bulk specific gravity, whereby the heat-insulating effect thereof is improved.
The carbonaceous substance is, for example, coke, charcoal, coal, black lead, graphite, carbonized materials such as carbonized grain stems, carbonized grain seed husks and the like.
As the oxidation accelerating agent, sodium fluoride, calcium fluoride, cryolite and the like are suitable. These substances accelerate the oxidation reaction of the easily oxidizable metals described above.
As the binder, the following can be used: Resin binders such as phenol-formaldehyde resins, urea-formaldehyde resins, furan resins, epoxy resins, and the like, and water glass, various types of cements, various kinds of clays, dextrin, starch and the like.
Some preferred embodiments of the heat-insulating board of the present invention will now be described in detail with reference to the drawings attached hereto.
Referring to FIG. 1, a heat-insulating board of the present invention is provided in a mold 1 in such manner that the hollow space of the upper portion of the mold is covered with the board, which mold is lined with a slab 2 at the inner surface of the upper part thereof for the purpose of heat-insulating the side surfaces of the feeder head. The board consists of a plate-like molding 3 and a composition 4 attached to the outer rim of the molding 3, which composition 4 contains a heat-expandable material or a mixture of such materials. The board is fixed to the mold by means of a thin steel plate or a steel wire 5 fixed to the board by a nail or a rivet 6.
Into this mold, a molten metal, particularly a molten steel, is cast by the known bottom pouring method until the surface of the molten metal or molten steel is close to or is contacted with the heat-insulating board. In this heat-insulating board, the composition 4 is expanded by the action of a heat of the molten steel to fill the gap between the board and the slab 2, whereby the atmosphere is excluded from the surface of the molten metal and the heat-insulation of the feeder head is improved.
FIG. 2 is an enlarged section of the heat-insulating board shown in FIG. 1.
In FIGS. 3 and 4 there are shown other heat-insulating boards according to the present invention which are different from the board shown in FIGS. 1 and 2. Referring to FIG. 4, the heat-insulating board consists of a plate-like molding 3 which is composed of two layers, namely, an exothermic inner layer 7 in contact with the top surface of the molten metal and an adiabatic outer layer 8.
Referring to FIG. 5, which shows still another embodiment according to the present invention, a heat-insulating board is provided in a mold 1, where the upper portion thereof is lined with a slab 2 for heat-insulating the side surfaces of the feeder head, in such a manner that the board covers the hollow space of the mold 1. A piercing hole 9 is provided in this heat-insulating board. The piercing hole 9 is closed with a plug 10, provided with a bent metal fitting 11, immediately after pouring of the molten steel has been completed.
Referring now to FIGS. 6 and 7 which show still other embodiments of the present heat-insulating boards 12, wherein heat-expandable materials are uniformly incorporated therein, the board 12 is expanded outwardly to closely seal the cap between the board and a sleeve or slab for heat-insulating the side surfaces of the feeder head or the side wall of the mold, and simultaneously the board expands in the direction of its thickness, whereby the board becomes a porous heat-insulating board which provides an improved heat-insulating effect.
Referring to FIG. 7, a number of small holes 13 are shown in the heat-insulating board. From these small holes 13 any gas which is generated during the casting operation can be discharged. These small holes 13 will be closed due to the expansion of the board after the gas has been discharged, i.e., when the top surface of the molten steel comes close to or comes in contact with the board.
The present invention will now be explained in more detail by examples of several preferred embodiments of the invention.
EXAMPLE 1
1. A composition to be provided on the outer rim of a molding was formed of the following ingredients:
Natural vermiculite 50% (by weight) Cellulosic material derived from paper 6% (by weight) Wood meal 5% (by weight) Diatomaceous earth 10% (by weight) Silica sand 23% (by weight) Phenol-formaldehyde resin 6% (by weight)
2. A plate-like molding was formed of the following ingredients:
Aluminum 8% (by weight) Ferrous oxide 16% (by weight) Aluminum ash 38% (by weight) Cellulosic material derived from paper 10% (by weight) Asbestos 6% (by weight) Carbonized rice husks 12% (by weight) Cryolite 3% (by weight) Phenol-formaldehyde resin 7% (by weight)
FORMATION METHOD
To mixtures of materials as set-out at (1) and (2) water was added to form the respective slurries. Using a model for dehydrating and molding, water contained in the slurry of mixture (2) was removed to form a plate-like molding. The slurry of mixture (1) was charged on the rim of the thus prepared molding, and water was removed to form a plate composed of the mixture (2) with the mixture (1) present only on the outer face of the plate. Drying, the thus formed assembly a heat-insulating board as shown in FIG. 2 was prepared which had a size of 830 mm (length)×830 mm (width)×40 mm (thickness). Using the heat-insulating board thus prepared, six steel ingots each weighing 8 tons were cast by the bottom pouring method, using the construction shown in FIG. 1. Steel ingot-making using the board of the present invention was compared with conventional steel ingot-making (six steel ingots) by using a heat-insulating board consisting of only the above described composition (2) under the same conditions, and the results obtained were as follows: The average yield of the ingots cast using the heat-insulating board according to the present invention was improved 1.3% as compared with the ingots cast using the conventional board. This was due to the superior heat-insulating effect of the heat-insulating board of the present invention which results from the close sealing of the gap between the board and the slab.
EXAMPLE 2
A heat-insulating board was formed of the following ingredients:
Flake-like graphite treated with acid 18% (by weight) Aluminum 6% (by weight) Ferrous oxide 12% (by weight) Aluminum ash 33% (by weight) Cellulosic material derived from paper 7% (by weight) Slag wool 5% (by weight) Carbonized rice husks 10% (by weight) Potassium nitrate 3% (by weight) Phenol-formaldehyde resin 6% (by weight)
In the manner as described in Example 1, a slurry was prepared from the mixture of the above ingredients. The slurry was charged into a model for dehydrating and molding, and the water in the slurry is removed. The thus treated slurry was molded to form a plate-like molding. Drying the molding, a heat-insulating board is prepared as shown in FIG. 6, which had a size of 830 mm (length)×830 mm (width)×40 mm (thickness). Using the thus prepared heat-insulating board, three steel ingots were cast in the same mold as the Example 1. The steel ingot-making process of this invention was compared with a conventional steel ingot-making process (three steel ingots) under the same conditions but using a heat-insulating board consisting of the above described ingredients wherein the acid-treated graphite (18%) was replaced by aluminum ash.
The results were as follows: The average yield of the ingots cast using the heat-insulating board of the present invention was improved 1.4% as compared with the ingots cast using the conventional board. This was due to the superior heat-insulating effect attained by the use of the present board on the feeder head of the molten steel.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
1. Field of the Invention
The present invention relates to a heat-insulating board for covering the top surface of the molten metal in a feeder head during the casting of a molten metal, particularly a molten steel.
More precisely, the present invention provides a heat-insulating board for covering the top surface of a feeder head of molten metal which contains a material which expands upon being heated, or a mixture of such materials. The heat-insulating board is used in combination with a heat-insulating sleeve or slab for heat-insulating the side surface of the feeder head, and the heat-insulating board is expanded during use when the heat-expandable material(s) expand by the action of the heat from the molten metal to be cast, whereby any gap between the heat-insulating board and the sleeve, slab or a side wall of a casting mold is closed.
2. Description of the Prior Art
In the casting of molten metal into a mold to form a cast product, it is important to keep the metal in the feeder head (hot top) molten long enough to feed the shrinkage cavity, commonly known as a pipe, by preventing the loss of heat from the metal in the feeder head. Usually the head of the mold (or a head box fitted to the mold) is lined with one or more heat-insulating sleeves or slabs, and the top surface of the molten metal is covered with either a heat-insulating agent such as an exothermic powder, or with a plate-like heat-insulating board, at a time after the molten metal has been completely poured in the said mold.
However, a heat-insulating agent such as an exothermic powder, as is conventionally used for covering the top surface of the feeder head, is composed of fine powdery light substances, and these fine powdery substances are violently scattered when the agent is added to the top surface of molten metal, and during the exothermic reaction which occurs after the addition of the same. Consequently, a large amount of smoke and dust is generated which interferes with the casting operation. Moreover, the smoke and dust are harmful to humans and thus the use of such a heat-insulating agent is unfavorable from the view-point of environmental sanitation.
The heat-insulating boards which have been used to cover the top surface of the feeder head eliminate the abovementioned defects of the heat-insulating agent. In the conventional heat-insulating board, however, a gap occurs between the board and the sleeve or slab which is provided to heat-insulate the side surface of the feeder head or the side wall of the mold. Thus, it is impossible using such a heat-insulating board to completely cover the top surface of a molten metal in the feeder head, and it is difficult to adequately heat-insulate the feeder head.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to eliminate the above defects in conventional heat-insulating boards for covering the top surface of the feeder head and to improve the heat-insulating effect on the feeder head.
The present invention provides a novel heat-insulating board for covering the top surface of a feeder head which consists of a plate-like molding and a heat-expandable composition.
The heat-expandable compositon may be attached to the outer face of the plate-like molding or may be uniformly mixed with the plate-like molding. The "outer face" of the plate-like molding will be referred to as the "rim" thereof.
If desired, as shown in the drawings, the heat-expandable composition, when attached to the outer face, need only be provided at a part of the outer face to achieve the expansion/sealing action upon heating. Although shown in the drawings as being at the upper portion of the outer face of the plate-like molding, a similar expansion/sealing effect is achieved when the heat-expandable materials are provided at only the lower portion of the outer face of the plate-like molding.
Further, while it has been indicated that the plate-like molding may be a homogeneous mixture with the heat-expandable material, it will be obvious that an embodiment intermediate those described above is operable if only the outer portions of the plate-like molding are mixed with the expandable material, e.g., during water removal if a slurry is formed.
Since the diameter of the plate-like molding is much greater than the thickness, in both embodiments described above when the plate-like molding is heated on contact with the molten metal, it expands primarily in a plane perpendicular to the sides of the mold, and thereby seals any gap between the plate-like molding and the side of the mold or sleeve or slab (if such is interposed between the plate-like molding and the wall of the mold,) and completely covers the top surface of the molten metal in the feeder head. Accordingly, the heat-insulating effect on the feeder head is greatly improved by the use of the present heat-insulating board.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of an upper part of a mold in which a heat-insulating board according to the present invention is provided in the upper portion thereof.
FIG. 2 is an enlarged section of the heat-insulating board of FIG. 1.
FIG. 3 and FIG. 4 are sectional views of other embodiments of heat-insulating boards in accordance with the present invention.
FIG. 5 is a sectional view of the upper part of a mold in which still another heat-insulating board according to the present invention has been provided in the upper portion thereof.
FIG. 6 and FIG. 7 are sectional views of additional embodiments of heat-insulating boards according to the present invention which are different from those shown in FIGS. 1-5.
DETAILED DESCRIPTION OF THE INVENTION
The composition containing heat-expandable materials of the present invention preferably consists of the following ingredients:
Natural mineral heat-expandable material and/or chemically treated heat-expandable material 5-80% (by weight) Refractory material 0-92% (by weight) Easily oxidizable metal 0-30% (by weight) Oxidizing agent 0-30% (by weight) Fibrous material 0-40% (by weight) Carbonaceous substance 0-20% (by weight) Oxidation accelerating agent 0-10% (by weight) Binder 3-20% (by weight)
As heat-expandable natural minerals, vermiculite, shale, obsidian, perlite, pitch-stone, bloating clay, etc. are suitable.
As chemically treated heat-expandable materials, flake-like graphite, pitch, etc. treated with an acid and/or an oxidizing agent are suitable.
These heat-expandable materials are known, and have been used as an ingredient for a feeder head heat-insulating composition.
As indicated, the above described heat-expandable composition is attached to or will comprise the outer rim of the plate-like molding. The plate-like molding is preferably either a one-layer molding comprising a uniform composition, or a two-layer molding comprising an exothermic inner layer which will be in contact with the top surface of the molten metal and an adiabatic outer layer. Preferred embodiments of a one-layer molding and a two-layer molding are described below:
(1) One-layer molding Refractory material 20-94% (by weight) Fibrous material 3-40% (by weight) Easily oxidizable metal 0-30% (by weight) Oxidizing agent 0-30% (by weight) Carbonaceous substance 0-20% (by weight) Oxidation accelerating agent 0-10% (by weight) Binder 3-20% (by weight) (2) Two-layer molding (i) Exothermic inner layer Easily oxidizable metal 3-30% (by weight) Oxidizing agent 3-30% (by weight) Refractory material 10-88% (by weight) Fibrous material 3-40% (by weight) Carbonaceous substance 0-20% (by weight) Oxidation accelerating agent 0-10% (by weight) Binder 3-20% (by weight) (ii) Adiabatic outer layer Refractory material 40-94% (by weight) Fibrous material 3-40% (by weight) Binder 3-20% (by weight)
As another embodiment of the heat-insulating board of the present invention, the above described heat-expandable material(s) may be uniformly incorporated into the plate-like molding. The heat-insulating board thus prepared will expand primarily outwardly towards the walls of the mold to closely seal any gap between the board and a sleeve or slab for heat-insulating the side surface of the feeder head of the side wall of a mold, and simultaneously the board is expanded also in its thickness thereby to become a porous heat-insulating board. Thus, a heat-insulating board of this kind will have an improved heat-insulating effect.
In the following, a preferable composition constituting such a board is shown:
Natural mineral heat-expandable material and/or chemically treated heat-expandable material 5-67% (by weight) Refractory material 10-89% (by weight) Fibrous material 3-40% (by weight) Easily oxidizable metal 0-30% (by weight) Oxidizing agent 0-30% (by weight) Carbonaceous substance 0-20% (by weight) Oxidation accelerating agent 0-10% (by weight) Binder 3-20% (by weight)
As the refractory material which is one of constituents of the heat-insulating board of the present invention, the following materials are exemplary: Non-porous refractory material such as silica sand, quartz, magnesia (magnesium oxide), alumina (aluminum oxide), olivine, aluminum ash, dolomite, magnesite, limestone, chamotte, Corundum, Alundum (trade name), and the like, and porous refractory materials such as diatomaceous earth, lapilli, expanded vermiculite, expanded shale, expanded obsidina, expanded perlite, expanded pitch-stone, and the like.
As the easily oxidizable metal, the following are preferred: Aluminum, magnesium, aluminum-magnesium alloys, calcium-silicon alloys, iron-silicon alloys, and the like. These metals react witn an oxidizing agent by an exothermic reaction to heat the top surface of the feeder head. As the oxidizing agent, the following are exemplary: Metal oxides such as ferrous oxide, ferric oxide, tri-iron tetraoxide, manganese dioxide, chromic oxide and the like, and nitrates such as potassium nitrate, sodium nitrate, barium nitrate, and the like.
As the fibrous material, the following are preferred: Refractory inorganic fibrous materials such as asbestos, rock wool, slag wool, glass wool, refractory clays and fibrous materials, and the like, and organic fibrous materials such as cellulosic materials derived from paper, paper wood, saw dust, wood meal, chemical fibers and the like. These fibrous materials reinforce the heat-insulating board so that the board is not damaged by any impact during the treatment of the board such as a transfer thereof, the disposition thereof in the mold, etc. Further, by the use of such a fibrous material, the resulting heat-insulating board can become a porous board which has a low bulk specific gravity, whereby the heat-insulating effect thereof is improved.
The carbonaceous substance is, for example, coke, charcoal, coal, black lead, graphite, carbonized materials such as carbonized grain stems, carbonized grain seed husks and the like.
As the oxidation accelerating agent, sodium fluoride, calcium fluoride, cryolite and the like are suitable. These substances accelerate the oxidation reaction of the easily oxidizable metals described above.
As the binder, the following can be used: Resin binders such as phenol-formaldehyde resins, urea-formaldehyde resins, furan resins, epoxy resins, and the like, and water glass, various types of cements, various kinds of clays, dextrin, starch and the like.
Some preferred embodiments of the heat-insulating board of the present invention will now be described in detail with reference to the drawings attached hereto.
Referring to FIG. 1, a heat-insulating board of the present invention is provided in a mold 1 in such manner that the hollow space of the upper portion of the mold is covered with the board, which mold is lined with a slab 2 at the inner surface of the upper part thereof for the purpose of heat-insulating the side surfaces of the feeder head. The board consists of a plate-like molding 3 and a composition 4 attached to the outer rim of the molding 3, which composition 4 contains a heat-expandable material or a mixture of such materials. The board is fixed to the mold by means of a thin steel plate or a steel wire 5 fixed to the board by a nail or a rivet 6.
Into this mold, a molten metal, particularly a molten steel, is cast by the known bottom pouring method until the surface of the molten metal or molten steel is close to or is contacted with the heat-insulating board. In this heat-insulating board, the composition 4 is expanded by the action of a heat of the molten steel to fill the gap between the board and the slab 2, whereby the atmosphere is excluded from the surface of the molten metal and the heat-insulation of the feeder head is improved.
FIG. 2 is an enlarged section of the heat-insulating board shown in FIG. 1.
In FIGS. 3 and 4 there are shown other heat-insulating boards according to the present invention which are different from the board shown in FIGS. 1 and 2. Referring to FIG. 4, the heat-insulating board consists of a plate-like molding 3 which is composed of two layers, namely, an exothermic inner layer 7 in contact with the top surface of the molten metal and an adiabatic outer layer 8.
Referring to FIG. 5, which shows still another embodiment according to the present invention, a heat-insulating board is provided in a mold 1, where the upper portion thereof is lined with a slab 2 for heat-insulating the side surfaces of the feeder head, in such a manner that the board covers the hollow space of the mold 1. A piercing hole 9 is provided in this heat-insulating board. The piercing hole 9 is closed with a plug 10, provided with a bent metal fitting 11, immediately after pouring of the molten steel has been completed.
Referring now to FIGS. 6 and 7 which show still other embodiments of the present heat-insulating boards 12, wherein heat-expandable materials are uniformly incorporated therein, the board 12 is expanded outwardly to closely seal the cap between the board and a sleeve or slab for heat-insulating the side surfaces of the feeder head or the side wall of the mold, and simultaneously the board expands in the direction of its thickness, whereby the board becomes a porous heat-insulating board which provides an improved heat-insulating effect.
Referring to FIG. 7, a number of small holes 13 are shown in the heat-insulating board. From these small holes 13 any gas which is generated during the casting operation can be discharged. These small holes 13 will be closed due to the expansion of the board after the gas has been discharged, i.e., when the top surface of the molten steel comes close to or comes in contact with the board.
The present invention will now be explained in more detail by examples of several preferred embodiments of the invention.
EXAMPLE 1
1. A composition to be provided on the outer rim of a molding was formed of the following ingredients:
Natural vermiculite 50% (by weight) Cellulosic material derived from paper 6% (by weight) Wood meal 5% (by weight) Diatomaceous earth 10% (by weight) Silica sand 23% (by weight) Phenol-formaldehyde resin 6% (by weight)
2. A plate-like molding was formed of the following ingredients:
Aluminum 8% (by weight) Ferrous oxide 16% (by weight) Aluminum ash 38% (by weight) Cellulosic material derived from paper 10% (by weight) Asbestos 6% (by weight) Carbonized rice husks 12% (by weight) Cryolite 3% (by weight) Phenol-formaldehyde resin 7% (by weight)
FORMATION METHOD
To mixtures of materials as set-out at (1) and (2) water was added to form the respective slurries. Using a model for dehydrating and molding, water contained in the slurry of mixture (2) was removed to form a plate-like molding. The slurry of mixture (1) was charged on the rim of the thus prepared molding, and water was removed to form a plate composed of the mixture (2) with the mixture (1) present only on the outer face of the plate. Drying, the thus formed assembly a heat-insulating board as shown in FIG. 2 was prepared which had a size of 830 mm (length)×830 mm (width)×40 mm (thickness). Using the heat-insulating board thus prepared, six steel ingots each weighing 8 tons were cast by the bottom pouring method, using the construction shown in FIG. 1. Steel ingot-making using the board of the present invention was compared with conventional steel ingot-making (six steel ingots) by using a heat-insulating board consisting of only the above described composition (2) under the same conditions, and the results obtained were as follows: The average yield of the ingots cast using the heat-insulating board according to the present invention was improved 1.3% as compared with the ingots cast using the conventional board. This was due to the superior heat-insulating effect of the heat-insulating board of the present invention which results from the close sealing of the gap between the board and the slab.
EXAMPLE 2
A heat-insulating board was formed of the following ingredients:
Flake-like graphite treated with acid 18% (by weight) Aluminum 6% (by weight) Ferrous oxide 12% (by weight) Aluminum ash 33% (by weight) Cellulosic material derived from paper 7% (by weight) Slag wool 5% (by weight) Carbonized rice husks 10% (by weight) Potassium nitrate 3% (by weight) Phenol-formaldehyde resin 6% (by weight)
In the manner as described in Example 1, a slurry was prepared from the mixture of the above ingredients. The slurry was charged into a model for dehydrating and molding, and the water in the slurry is removed. The thus treated slurry was molded to form a plate-like molding. Drying the molding, a heat-insulating board is prepared as shown in FIG. 6, which had a size of 830 mm (length)×830 mm (width)×40 mm (thickness). Using the thus prepared heat-insulating board, three steel ingots were cast in the same mold as the Example 1. The steel ingot-making process of this invention was compared with a conventional steel ingot-making process (three steel ingots) under the same conditions but using a heat-insulating board consisting of the above described ingredients wherein the acid-treated graphite (18%) was replaced by aluminum ash.
The results were as follows: The average yield of the ingots cast using the heat-insulating board of the present invention was improved 1.4% as compared with the ingots cast using the conventional board. This was due to the superior heat-insulating effect attained by the use of the present board on the feeder head of the molten steel.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.