US2361386A - Hot top for steel ingot molds - Google Patents

Description

Patented Oct. 31, 1944 UNITED STATES PATENT OFFICE 2,361,386 HOT 120? FOR STEEL INGOT MOLDS Thomas C..Eayrs, Buffalo, N. Y. Application March 6, 1942, Serial No. 433,643

7 Claims.

It is well known to those skilled in the art that hot tops of present-day design for usein connection with steel ingot moldsare usually made in one piece and of fire brick or other refractory materials which must go through a cycle of treatment at high temperature for an extended period of time, occupying, as they do, considerable space in storage, and being made from material which cannot be salvaged. Where hot tops have heretofore been made of sections, these sections have been separate from the assembly wire and fastened together by means of such separate wire passed around the exterior of the hot top.

One of the principal objects of my invention has been to provide a hot top which shall be made from a plurality of sections having a permanently attached wire reinforcing mesh, portions of which are located preferably at or near the outer surface of the sections and connecting the panels in hinged manner.

Another object of my invention has been to construct a hot top of such material that it can be bonded by the use of a temperature sufficient only to mature the composition but not sufilcient to oxidize the embedded Wires.

A further object of my invention has been to make my hot top of materials which shall produce an endothermic effect as a result of contact with the molten steel, whereby the heat of the steel contacting the hot top will be so rapidly absorbed as to quickly solidify any molten metal which would otherwise escape through a loose joint or crack.

Moreover, the composition of my hot top is such that a carbon dioxide gas is generated at the surface thereof which is in contact with the heated metal which gas acts as a barrier to the flow of heat to the interior of the wall of the hot top, thereby making it possible to use relatively thin walls and yet protect the embedded wires against excessive heat.

Furthermore, it has been an object to use such materials in my hot top which will not chemically combine by direct contact with steel; either molten or solidified, thereby avoiding adhesion between the hot top and the steel.

Another object has been to use a basic material for the composition of my hot top which is not only readily available but which in many cases constitutes what is ordinarily waste material, thereby greatly reducing the cost of my hot top.

Moreover, it has been an object to provide a composition for hot tops and a method of making the hot top therefrom which shallrequire only suflicient heat to mature the composition a but insufficient to decompose the refractory materials employed in the composition.

Another object has been to provide a hot top formed with a plurality of panels secured to gether by means of flexible metallic reinforcing wires, whereby the hot top when not in use may be stored in fiat position, the wires between sections functioning as hinges when the hot top is formed into shape and ready for use, the extreme ends -of the wires projecting beyond the adjacent end surfaces of the outer sections whereby the entire hot top may be fastened together by twisting such wires.

A further object of my invention has been to make my hot top of a composition which, after the hot top has been discarded, may be used as part of a regular standard charge to any blast furnace, thereby making it possible to salvage the otherwise useless hot top.

The above objects and advantages have been accomplished by the device hereinafter described, made from my composition and in accordance with my method.

Fig. 1 is a plan view of my hottop folded and installed within the top of a steel ingot mold;

Fig. 2 is an elevational view of a steel ingot mold, partly in section, showing my hot top fully in section and in position upon the mold;

Fig. 3 is an exterior view of my hot top with the panels lying fiat in extended manner, in which position they may be conveniently stored, handled or shipped;

Fig. 4 is an edge View of my hot top showing it in the position occupied in Fig. 3; and,

Fig. 5 is an enlarged view of portions of two adjacent panels showing the bevel at the joining edges and a cut-away portion at the hinged joint therebetween.

suitable molds and preferably in the positions shown in Figs. 3 and 4, I prepare a reinforcing wire mesh. This mesh comprises a number of continuous reinforcing wires l2, l3 and it spaced apart and extending longitudinally across all of the panels as shown in Figs. 3 and 4 and lying,

when in position, either adjacent to the outer surface of the panels or slightly embedded below such surface.

The portions of the wires and H to which they are secured preferably by means of welding. By providing the saw-tooth formation, the body parts of the lateral wires IE will be .embedded somewhat within the panel so as to reinforce the panels and to securethem more firmly to the wires l2, l3 and 14. These wires are extended beyond the extreme edge of each end panel in ends l2a, I30. and Ma. These ends are sufficiently long so that when the panels are folded as shown in Figs. land 2, they may be twisted together so as to hold the panels firmly in position and thereby provide a unitary structure.

As shown in Fig. 5, the lateral edge ll of each of the panels is cut away at an angle so as to permit the folding of the hot top. So as to facilitate the folding of the panels and to more readily bring the edge surfaces together, it is desirable to provide a space H] between adjacent panels.

On the exterior surface of each of the panels there are provided lugs 6 which are so positioned as to allow only a portion of the hot top to enter the mouth of the mold. These .1ugs'.may be formed integrally with the panels in the molding thereof, or they may be made of metal and secured to the wires l3 and M by means of welding.

In my composition, I use preferably limestone or its equivalent as a base material because it has all of the desirable characteristics, and thereby enables me to carry out the objects hereinbefore set forth. Limestone is universally available, and large quantities of waste limestone in the form of tailings are usually procurable at low cost at plants where commercial limestone is crushed and sized. Owing to the generation of carbon dioxide gas caused by contact of the molten steel with the limestone of my hot top, it is preferable to have a small amount of combustible material as a part of my composition, whereby porosity of the finished hot top may be had. Furthermore, it is necessary to have a suitable bond in my composition. I have found that the following materials and proportions by volume are suitable: for carrying out my invention, it being obvious that some changes in the proportions and materials may be made without departing from the spirit of my invention:

Per cent Limestone tailings, or crushed limestone,

passing inch square mesh screen '74 Saw-dust passing through the same screen... 10 Green bond a commercially available pulverized mixture consisting of 3 parts strong plastic clay, one and one-half parts of bentonite, and one and one-half parts coke-oven foundry pitch which is a cokeoven residue and which, as is well known, has little adhesion up to substantially 350 F. (not a petroleum derivative) 6 Foundry pitch as above described (separately added) 10 After suitable molds have been prepared and the wire reinforcing mesh placed in position, my composition is placed within the molds and about the lateral reinforcing wires. The panels are then baked to a temperature of only approximately 600 F. for four hours. This temperature causes the saw-dust and foundry pitch to practically disappear, leaving the panel composition approximately:

Percent Limestone as CaCOa (wholly non-combustible) 94 Plastic clay and bentonite (wholly noncombustible) This baking treatment of the panels develops great physical strength, which, due to the reinforcement of the panels, enables me to use a panel which is much thinner than can be used in any hot top of present-day design.

When my hot top is .placed in use upon an ingot mold and molten steel comes into contact with my composition, an endothermic reaction is instantly started CaCOa-l-heat=CaCO"+COz). This endothermic reaction continues at a temperature far below the solidifying temperature of the steel ingot and any liquid steel which flows in between the panels is quickly solidified. This solidified portion cannot be remelted by the molten steel behind it without re-establishing the endothermic reaction and, therefore, the portion remains solidified. Since neither calcium oxide CaO nor carbon dioxide (CO2) combine chemically with liquid or solid steel merely by direct contact with each other, there can be no adhesion between my hot top and the steel ingot.

From the foregoing it will be understood that my composition in the carbonate .or raw. state is at least basic. Furthermore, it will be obvious that instead of raw limestone (CaCOc), raw dolomitic limestone (CaMgC-iOe) or raw magnesite (MgCOa) may be used. It is well known to those skilled in the art that the last two mentioned materials are seldom if ever used by the steel industry except in their calcined or deadburned state, i. e., CO2 burned out. Due to my method of manufacturing, much of the limestone remains in its raw carbonate form in which form either the limestone dolomite or magnesite will sustain the complex smelting and fluxing reactions occurring in the operation of a blast furnace, thereby making my hot top readily salvageable as a blast furnace charge. The almost negligible weight of steel wire in the mesh theoretically acts as seed in the group of reducing reactions in the blast furnace, when liquid metallic iron is about to start separating from the iron ore. In other words, the presence of the steel mesh in my composition when used as a blast furnace charge stimulates the first throwdown.

My hot top is furthermore, suitableas a blastreverts to CaCOs, it is obvious that 94% of the mineral mass of my hot top is suitable as a limestone charge of a blast furnace.

Obviously, due to the use of limestone or its equivalent, the calcining action, produced by contact with the hot steel, generates carbon dioxide gas (CO2) which acts as a barrier to the flow of heat through the panels of the hot top thereby providing an insulating wall of gases which continue at a temperature below the solidifying temperature of the liquid steel. The presence of this gas prevents deep calcining penetration into the panels thereby not only protecting the embedded wire mesh but leaving the hot top in such condition that it is suitable after normal use as a part of a blast furnace charge.

Since the small amount of combustible material is burned out of the panels ofmy hot top during the initial baking process at low temperature, suitable porosity of the material is brought about. This porosity not only acts as a further insulator against the passage of heat into the panels, but also provides for rapid escape of the carbon dioxide gas.

While I have described the use of limestone as a basic component of my composition, it is obvious that any other waste or by-product, calcium hydroxide and/or calcium carbonate, procurable as waste products in many industrial operations, can. be substituted therefor. Instead of the foundry pitch it is obvious that I may use any other heat-developed binder having similar characteristics, or any other binder which will give to my composition the desiredphysical strength.

What I claim is: a

1. A granular hot top composition composed of crushed, screened limestone in major amount to effect an endothermic reaction and the generation of carbon dioxide gas when subjected to molten steel, a combustible saw-dust to provide connecting pores in the finished product after initial baking to permit the escape of said gas, a green bond, and foundry pitch in minor amount but of a suificient quantity to bind the composition together in a coherent mass.

2. A granular hot top composition comprising substantially 74% of crushed screened limestone, substantially of saw-dust, substantially 6% of green bond, and substantially 10% of foundry pitch.

3. A method of making a hot top for steel ingots, comprising the preparation of a composition consisting in major amount of metal carbonate which is capable of decomposition when subjected to the heat of molten steel, a granular combustible material, and a bond in minor amount containing carbonaceous material, then molding said composition into suitable form, and then subjecting the molded form to a temperature suflicient to burn out the combustible material, said temperature being insuificient to decompose said metal carbonate, whereby connectsequent use of the hot top.

4. A method of making a hot top for steelingots, comprising the formation of a plurality of permanently connected and reinforced panels, each being composed in major amount of a metal carbonate which is subject to decomposition in the presence of the heat of molten steel, a granular combustible material, and a bond in minor amount including foundry pitch and clay, and then subjecting the panels to a temperature sufficient to burn out the combustible material, said temperature being insufiicient to decompose said metal carbonate, whereby connecting pores are produced in the structure permitting the escape of carbon dioxide gas upon subsequent use of the hot top.

5. The method of making a hot top comprising the formation of .a mixture of refractory materials composed of crushed screened limestone in major amount, saw-dust, a green" bond, and foundry pitch in minor amount, molding said composition into suitable form, and baking the hot top at a temperature sufliciently high to burn out the saw-dust and pitch but not sufilciently high to decompose the limestone, whereby connecting pores are produced in the structure permitting the escape of carbon dioxide gas upon subsequent use of the hot top.

6. A hot top comprising a walled body formed in major amount with a decomposable metal carbonate as an essential ingredient, a suitable bond in minor amount, and a granular combustible material uniformly dispersed throughout the composition prior to the baking process duringmanufacture, whereby upon baln'ng connecting pores are produced in the structure permitting the escape of carbon dioxide gas upon subsequent use of the hot top.

'7. A method of making a hot top for steel ingots, comprising the preparation of a composition having substantially '74 parts of a metal carbonate, a substantially 10 parts of foundry pitch bond, substantially 10 parts of a combustible material, and substantially 6 parts of a plastic binder, molding said composition in desired form, and then reducing the bond and binder content of the finished product by the application or a temperature suflflcient to carbonize a portion of the bond and binder, whereby the finished product will contain substantially 96 parts of the carbonate and substantially 4 parts of the bond and binder. r

THOMAS C. EAYRS.

Patent No. 2 361386.

Certificate of Correction w October 31, 1944. THQMAS O. EAYRS.

It is hereby certified that errors appear in the printed specification of the above numbered patent requirmg correction as follows: Page 2, first column, line 61, for the words bond :1 read b0nda; andsecond column, line 19, for CaCO +heat=CaCO +00 read (CaCO +heat=-Ca0+C0 and that the said Letters Petent'should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 23rd day of January, A. 1945.

[SEAL] LESLIE FRAZER,

Acting Commissioner of Patents.

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