US1978996A - Method of and means for producing ingots - Google Patents

Description

' lOdi. 30, 1934. E GATHMANN 1,978,996

METHOD OF AND MEANS FOR PRODUCING INGOTS Filed June 8. 1935 2 Sheets-Sheet 2 Patented ct. 30, 1934 METHOD OF AND MEANS FOR PRODUC'ING INGOTS Emil Gathmann, Baltimore, Md. Application June 8, 1933, Serial No. 674,930

14 Claims.

This invention relates to methods of and means for producing ingots, and more particularly to methods of and means for producing ingots from fully degasiied or deoxidized steel, that is, ingots known to the art as killed steel ingots. Considered in one of its aspects, the method of producing ingots in accordance with the present invention constitutes an improvement of the method of producing ingots disclosed and claimed in my prior United States Patent 1,911,228, of May 30, 1933. f lPrior to my invention of the method disclosed in the prior patent referred to, the greater 'tonnage of killed steel ingots has been produced 5 in big-end-up cast iron molds adapted to retard the solidication of the upper portion of the ingot relative to that of the lower portion and tted with re clay shrinkhead casings so as to confine the pipe or cavity incident to the shrink- 0 age of the ingot metal from the liquid to the solid state to the extreme upper portion ofthe ingot. The shrinkhead portion of the ingot also provided a projection above the mold proper, making it possible to lift or strip the ingot with the soaking pit tongs, whereas without such a projecting portion the molds had to be upended and the ingots dumped.-

The primary function of a shrinkhead casing is to retard the solidiflcation of the upper portion 3 of an ingot until the lower and intermediate portions have cooled and solidified through the absorption of the heat of the forming ingot by the mold Walls. While, prior to the invention disclosed in my Patent 1,911,228, no satisfactory substitute had been found, the use of fire brick shrinkhead casings has a number of disadvantages. Being made of brick or loam, small particles of the shrinkhead casing at times break off and drop into the mold when the casing is being positioned on the mold, and it sometimes happens that the pouring ladle is not centered accurately over the. mold and the stream of y molten metal washes away a portion of the casing during teeming. In this way particles of the brick or yloam are carried into the ultimate product. The surface of that part of the ingot cast within theshrinkhead casing invariably is very `vrough and is pitted with minute blow holes, and

it cannot be rolled satisfactorily into usable or` 0 salable products. Furthermore, shrinkhead casings are expensive and increase materially the i cost of sound ingot production.

Iny accordance with the method disclosed in Y myy Patent 1,911,228 before referred to, molten metal is poured into a big-end-up mold and a1- lowed to `solidify throughout only a predetermined part of its volume, at which time the ingot is raised partially through the mold until the top part only of the ingot protrudes from the t'op 0i? the mold. Air then is admitted through the mold bottom into the annular space between the mold `Walls and the partially stripped ingot, whereby cool air flows up through the annular space, cooling the lower and intermediate parts of the ingot A relatively rapidly. The protruding upper portion 55 of the ingot,` being surrounded by more or less dead air, is not cooled so quickly, the metal at the top thereby remaining molten longer than at other parts of the ingot and thereby serving to feed the shrinking ingot so as to connne 7@- the shrinkage cavity to the upper portion of the ingot. Due to the rapid cooling effected by the draft of air owing up around the ingot, the total time required for solidication of the ingot is y, reduced materially and a relatively sound homogeneous ingot is produced.

An object of the present invention is to provide a method for producing metallic ingots of at least as large cross section at the top as at the I I bottom thereof in such manner that the ingot 8@ sides are skin-chilled initially throughout their entire lengths by metallic mold Walls so as to form a. smooth surface; and in which chilling of the intermediate and lower portions of the ingot is continued after the initial chill skin has been formed while the upper portion of the ingot is insulated eiciently against escape of heat so as to retard solidieation at the top and to feed the shrinking ingot, thereby producing a smooth surfaced, sound, homogeneous ingot, the shrink 90 age cavity of which is confined to the extreme upper portion of the ingot itself. Another object is to provide a method in which the intermediate and bottom portions of an ingot are cooled rapidly by air moving in contact therewith and in which the top surface and upper side surfacesare insulated eiciently against loss of heat and preferably are heated during the solidiflcation of the ingot.

Generally stated, in practicing the method of the present invention,l I pour molten metal into a chill mold and immediately thereafter place on the top surface of the ingot metal a measured quantity of loose heat-conserving material. After the ingot metal has solidified sufficiently to form a shell capable of sustaining the weight 'or ferro-static pressure of the molten metal inside of the shell, the ingot preferably is 'raised partially through the mold until the top port1on I Qi the ingot is projected into and encompassed ingot metal, and loose combustible material,

preferably in lump form, which is placed on top of the heat-insulating material. Since the combustible material acts to prevent escape of heat from the molten ingot metal, the combustible material as well as the insulating material is a heat-conserving material, and throughout the description and claims this term will be understood as including eithery heat-insulating material or combustible material or both.

A further object is to provide an ingot mold especially adapted for use in producing ingots in accordance with my improved method. Other objects and the more detailed nature of the method and mold of the invention will be understood from a reading of the following description, the appended claims, and the accompanying drawings, in which:

y Figure 1 is a transverse vertical sectional view of apparatus for practicing my improved method, the illustrative embodiment comprising a mold support or car and an ingot mold supported thereon, the ingot metal within the mold being shown graphically as in the initial stage of solidiication, and heat-insulating material being shown on top of the Iingot metal;

Figure 2 isV a view similar to Figure 1 but omitting the car and showing the ingot at a subsequent stage of solidication and showing combustible heat-producing material on top of the ingot metal and insulating material;

Figure 3 is a view similar to Figure 2A but showing the ingot partially stripped and the metal at a subsequent stage of solidication;

Figure 4 is a view similar to Figure 3 but showing the ingot completely solidified;

Figure 5 is a vertical sectional view of a modived form of mold constructed in accordance with the invention;

Figure 6 is a top plan view of the mold shown in Figure 5; and

Figure 7 is a chart illustrating graphically the comparative time phases of solidication of ingots produced in accordance with thevinvention.

Referring to the apparatus shown by way of illustration as being suitable for use in practicing the method in accordance with the invention, a mold generally designated M of the bigend-up type is supported on a stool S, which in turn is carried by a car C. The mold is provided with a tapered bottom opening 1 which is closed vby means of a closure 2 which may be of any suitable` kind but which preferably is of the kind disclosed in my copending application Serial No. 638,208,1'lled October 17, 1932 which matured intoy Patent 1,915,729, of June 27, 1933. The' stool is provided with an opening?, in alignment with'the opening 1 in the bottom of the mold, andthe car is provided with an opening 4 in alignment with the openings v1 and 3.

A stripper rod 5 is mounted for 'sliding movements within the opening 4 in the car, and is adapted to be moved upwardly through the openings 4, 3, and 1 into engagementwith the closure for moving the ingot relatively upward through the mold. The' stripper rod is provided with a longitudinally extending groove 6, which receives for sliding movements the inner end of a latch rod 7, the latter being urged inwardly into engagement with the root of the groove 6 by a spring 8. The stripper rod is formed with notches 9 near the bottom of the groove 6 which are adapted to receive the inner end of the latch rod 7 when the stripper rod 5 has been raised and the ingot Apartially llifted or stripped from the mold to the desired extent.

The openings 1 in the mold and 3 in the stool preferably are considerably larger than the head of the stripper rod so as to provide for the passage of air up into the mold when the stripper rod and ingot are raised. In order to provide for the entrance of air into the openings referred to, the car is formed with a plurality of openings 10 dlrectly under the stool. Stripping apparatus of the general nature referred to above is described more in detail in my copending application Serial No. 619,807, filed June 28, 1932, and my Patent 1,897,696, issued February 14, 1933.

In accordance with one feature of the present invention, I employ a mold or mold assembly iron or other suitable material having highheat- 11@ conducting capacity, so that the body of an ingot I cast therein will be chilled rapidly.

The upper section 13, in the form shown, includes vertically extending walls l5 spaced laterally beyond the inner surfaces of the walls of the 115 ingot-forming section and adapted to seat upon the top of the mold proper. Preferably the walls l5 embrace a reduced portion 16 at the top of the mold thereby to maintainthe upper section 13 against accidental displacement. The mold or mold assembly is so arranged as to provide openings or air passages leading from the top of the ingot-forming chamber, or from a point just above the top of the chamber, to the outside of the mold...

In the form shown in Figures 1, 2, 3, and 4, a

stream of metal enters the mold substantially along the vertical axis thereof, or as nearly so as practicable. This centering of the stream of metal is advisable in order to prevent undue splashingand sticking of the steel to themold matrix walls. When the ,level of molten metal has reached a predetermined height in the mold somewhat below the upper end of the mold chamber 12, pouring is stopped.' As quickly thereafter 145 as practical, a predetermined quantity of heatinsulating material is placed directly on top of the ingot metal as indicated at 18.` I prefer to employ diatomite, a loose, nely divided material ha'ving very high heat-insulating qualities, as the heatinsulatingmaterial, because, in addition to having excellent heat-insulating characteristics, this material is non-fusible and neutral, having no tendency to alter the analysis of the ingot metal. The insulating material 18 maintains the upper portion of the ingot fluid during the initial solidi- Ailcation oi the metal caused by absorption of put on the ingot metal, I place a quantity of combustible material 19-such for example as charcoal, preferably in lump form-on top of the insulating material 18, and within the non-ingotforming section 13.

In some. cases, for example in rainy weather, it is preferable to. place a vented cover, such as that designated 20, on topv of the upper section 13 in order to prevent the material 18-19 from becoming wet when the mold or mold assembly is moved through the yards from one building to another.

When there has been formed a surface skin or shell 21 suiiiciently thick to sustain the pressure of the molten metal 22 at the inside of the ingot, a shell of such thickness being shown in Figure '2, the stripper rod 5 is raised so as to engage the closure 2 and to lift the ingot partially upwardly through the mold chamber so as to project the top portion Iof the ingot and the insulating material 18 into the combustible material 19 so as to be encompassed thereby, as shown in Figure 3, it being noted that at this stage the ingot metal at the central portion of the ingot is still molten. The exact degree to which the ingot is lifted through the-mold will vary somewhat with practical considerations such, for example, as the analysis of the steel, the length and cross section of the ingot, and the pouring temperature. Generally stated, however, the ingot should be lifted a sucient distance to locate between ilve per cent to twenty per centby volume of the ingot metal within the upper mold section and encompass it by the material 19.

, The time during which the ingot should be left in its initial position, as shown in Figure 1, will also vary somewhat, depending upon practical considerations such as the pouring temperature, the temperature of the molds when teeming is started, and the chemical composition of the steel. The diagram shown in Figure 7 illustrates graphically the approximate values V of ingot volume solidiiied in time T when metal of average analysis is poured into cast iron ingot molds under the usual conditions of temperature. The abscissaa represent elapsed time, and the ordinates percentage of volume solidified. The lines a and a' represent the amount of solidication .which has taken place during corresponding periods of elapsed time while the ingot metal is in its lower or Figure 1 position, in which the surface of the ingot contacts with the mold walls throughout its length. The lines b and b represent the progressive solidication of the ingot metal after the ingot has been raised to its Figure 3 position. In some cases it will be satisfactory to raise the ingot partially when substantially one-fourth of its total volume has been solidied, which usually will occur when substantially one-twelfth of the totaltime required for complete solidilcation has elapsed, after which the ingotis raised partially through the mold, the ingot then becoming solidified as indicated by the lines a-b. In other cases it is advisable to allow substantially one-half of the ingot metal to solidify, which will occur when about one-sixth of the total time required for complete solidiiication has elapsed, after which the ingot is partially raised through the mold in the manner described above. The solidication in this case will occur as indicated at a'-b. When the ingot is about twenty inches square in cross section and requires approximately one hundred and twentyminutes for complete solidiflcation of the lower and intermediate portions, partial stripping of the ingot can be performed safely about ten minutes after teeming, and should be performed not later than about fifteen minutes after teeming. l

The insulating material 18 serves both to insulate the molten metal during the interval between completion of teeming of the mold and placing of the combustible material 19 in the upper section 13, and to form a neutral protective layer between the molten metal at the upper central portion of the ingot and the combustible Inaterial 19. As is well known, molten steel has a decided tendency to absorb carbon from any carbon-bearing material with which it comes in contact, the absorbed carbon diifusing rapidly throughout the molten metal and the chemical analysis of the latter thereby being changed. For this reason it is desirable to interpose the layer of material 18 between the molten metal 22 and the carbon-bearing combustible material 19. The material 18, as stated above,preferably is infusorial earth or diatomite, which has no tendency to alter the analysis of molten metal with which it comes invcontact.

By the time that the combustible material is placed within the upper section 13, the upper inner'edges of the walls of the lower section ll will have become heated to a red heat, so that, as soon as the combustible material cornes in contact with the upper portions of the walls, it will become ignited, combustion of the material 19 being supported by air entering through the openings 17, the burning of the material 19 creating a region of high temperature within the upper section 13.

When the ingot is raised partially through the mold in the manner previously described, the extreme upper portion of the ingot and the heat- -insulating material 18 thereon will become enabsorbing carbon from the material 19, and, as

Stated above, the blanket of neutral insulating material 18 will prevent the molten metal 22 from absorbing carbon from the material 19 directly above the ingot metal. When the ingot is held in its partially stripped position, the top portion thereof, being located in a region of high temperature, will be maintained molten, while relatively cool air will enter through the openings 10, 3, and 1 into the mold and will pass upwardly through the annular space between the mold chamber walls and the ingot so as to cool the lower and intermediate portions of the ingot. Air

passing up through the annular space will pass through and contact with the combustible material 19, thereby effecting rapid combustion of the latter and maintaining a high temperature within the section 13 so as to keep the metal in the'upper portion of the ingot in a molten state for a relatively long time.

The air entering the mold bottom opening and contacting with the bottom portion of the ingot will be relatively cool as compared to the air which has been in contact with the bottom of the ingot and which has passed along the ingot, the result being that the air has a cooling eii'ect on the ingot which is progressively less from the bottom upwardly to the portion thereof which is encompassed and insulated by the material 18. Thus, while the lower and intermediate portions of the ingot are cooled at a rate which gradually diminishes from the bottom upwardly, the extreme upper portion is heat-insulated effectively, thereby being maintained molten long after the bottom and intermediate portions have solidified. By discontinuing chilling of the upper five per cent to twenty percent of the ingot while continuing to air-chill the lower ninety-five per cent -to eighty per cent thereof, the metal in the upper portion of the ingot is kept molten and thereby is able to feed the shrinking ingot very effectively so as to produce a sound homogeneous ingot structure.

After the ingot has solidied completely, the material 18 may be recovered by suitable apparatus, such for example as that shown in my prior Patent No. 1,719,542, of July 2, 1929, and the upper section 13 lifted oi the lower section ll,

lugs 23 on the upper section serving to facilitate its removal. The protruding upper end` of the ingot will then be grasped by the usual lifting tongs and the ingot removed completely from the I mold. .A

In the modification shown in Figures 5 and 6, the lower ingot-forming section l1 and the upper non-ingotA-forming section I3' are formed integrally, the walls 15. of the non-ingot-forming section being spaced laterally beyond the inner surfaces of the ingot-forming section to provide a ledge or shoulder 16". Air passages 17' are "formed in the walls 15'. Two opposed walls 15 are provided with cut-out openings 24-24, the vertically extending side edges of which are groovedf as at 25-25 for the reception of separable closure plates 26-26. When u sing this form of mold, the plates 26'-26 can be removed after the-ingot has solidied completely; thereby providing ample space for the lifting tongs to be moved in laterallyv to grasp the ingot for lifting the latter completely from themold for removal to the soaking pit. In mostv instances the plates 26-26, which are relatively thin, maybe left in the m`old and removed by the tongs with the ingot.

Theoretically, it' should be possibleto produce ingots by my improved method having av pipe section amounting to only slightly more than three percent to four per cent of thevolume of the ingot, three per cent to four per cent .being the actual shrinkage in the ingot metal from the moltenvto the solid state. Practically, however, there is always some escape ofheat from the upper portion of the ingot during the time interval between the completion of teeming of the metal and the placing of. the heat-conserving material on top of the ingot, so^-that thelactual depth of the pipe is slightlyl greaterrthan the minimum theoretical depth. In my Patent No.

1,711,052, of April v30, 1929, I have disclosed and claimed a method for producing ingotsA containing a minimum pipe section. By the method of the present invention, it is possible to produce ingots of such minimum piped section more eiliciently and at considerably less cost.

In addition to the--advantage of producing sound ingots comprising a minimum pipe section, the method of the present invention also makes possible the production of ingots which are smooth along the entire length of their side surfaces, this being due to the fact that the side surfaces are initially chilled throughout their entire length by contact with the metallic mold walls as distinguished from the usual prior practice inv which the upper portion of the ingot was cast within a shrinkheadcasing and subjected to the formation of blow holes and adhesion of the material of which the shrinkhead casing was formed, such adhesion invariably having resulted in a rough surface rendering the upper portion of the ingot unsatisfactory for rolling into usable or salable products. A still further advantage results from the fact-that there is no danger of particles of heat-conserving materials or the like falling into the mold prior to teeming, or falling off during teeming, and thus being incorporated in the ingot structure.

I claim:

1. The method of producing metal ingots which comprises pouring molten metal into a chill mold, placing on the top` surface of the ingot metal a quantity of loose heat-conserving material greater in horizontal area than the top part of the ingot, and then partially raising the ingot through the mold and thereby projecting the top portion of the ingot into said heat-conserving material to be encompassed thereby when the outer ingot metal has solidied sufiioiently to form a shell capable of sustaining theV molten ingot metal inside of said shell.

2. The method of producing metal ingots which comprises pouring molten metal into a chill mold, placing on the top surface ofthe ingot metal a quantity of heat-conserving material greater in horizontal area than the top partof the ingot, and then raising the ingot through the mold until from five per cent to twenty per cent of the volume of the ingot metal has been pro- 'jected into and encompassed 4by said material.

3. r'I'he method of producing metal ingots which comprises pouring molten metal into a chill mold, placing on the top surface of the ingot metal a 'quantity of heat-conserving material Agreater in horizontal area than the top part of the ingot, and partially raising the ingot through the mold and thereby projecting the top portion of the ingot into said material to be encompassed thereby when from one-twelfth to one-sixth of the time required for total solidication of the y ingot metal has expired since pouring the ingot metal.

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4 The method of producing metal ingotsl which 'comprises coniining a mass of molten metal Within chill walls defining a vertically extending matrix adapted to produce an ingot-of at least as large cross sectional area at the top as at the bottom, thereby to chill the outer vertically extending surface, of vsaid mass of metal,V

and discontinuing chilling of the upper portion .of said side surfaces and encompassing said upper portion side surfaces with heat-conserving mafrom sixty to ninety per cent of the ingot metal Y terial in direct contact with the ingot metal when 5. The method of producing metal ingots which comprises pouring molten metal into a chill mold, placing on the top surface of the ingot metal a quantity of loose combustible heat-producing material greater in horizontal area than the top part of the ingot, and then partially 'raising the ingot through the mold and thereby projecting the top portion of the ingot into said heat-producing material to. be encompassed thereby.

6. The method of producing metalI ingots which comprises pouring molten metal into a chill mold, placing on the top surface of the ingot metal a quantity of loose material greater in horizontal area than the top part of the ingot and including heat-insulating and heat-producing material, and then partially raising the ingot through the mold and thereby projecting the top portion of the ingot into said material to be encompassed thereby.

7. 'I'he method of producing metal ingots which comprises skin-chilling a body o1' molten metal throughout its length until a shell of solidified metal has formed, and then moving the ingotbodily and projecting the upper end portion into heat-conserving material.

`8. The method of producing metal ingots which comprises pouring molten metal into a chill mold,

" placing heat-insulating material on the top\sur face of the molten metal, placing on top of said heat-insulating material a quantity oi loose ccm- 4bustible material greater in horizontal area than placing nely divided heat-insulating material outside the mold to the annular space between the mold and ingot whereby air will rise through said space along Aand in contact with the lower-and intermediate portions of the ingot.

10. An ingot moldl comprising walls defining a vertically extending ingot-forming chamber o1 big-end-up contour and a non-ingot-forming chamber above and of larger horizontal cross sectional area than said ingot-forming chamber, said non -ingot-forming chamber having opposed openings in its side walls extending downwardly from the top thereof, and closures removably positioned in said openings. Y

11. A big-end-up ingot mold comprising side walls defining a vertically extending big-end-up ingot-forming chamber an'd a non-ingot-forming chamber above the ingot-forming chamber, there lbeing provided an opening in the bottom of the mold and an opening extending from the ingot-forming chamber .to the outside of the mold at a level between said ingot-forming chamber and said non-ingot-forming chamber.

12. A big-end-up ingot mold comprising unitary sidewalls defining a vertically extending bigend-up ingot-forming chamber and a non-ingotforming chamber above the ingot-forming chamber, there being provided an opening in the bottom of the mold and an opening extending from said non-ingot-forming chamber completely through one of said side walls.

13. The method of producing metal ingots which comprises pouring molten metal into a chill mold, placingmon the top surface of the ingot metal a quantity of loose combustible material greater in horizontal area than thetop part of the ingot, theny raising the ingot through the mold until the top portion of the ingot metal is removed from contact with the chill mold walls and projected into andrencompassed by said material, and admitting air from outside the Vmold to the space occupied by said combustible ma.- terial at a level adjacent to the top of the raised ingot.

14. The method of producing metal ingots which comprises pouring molten metal into a chill mold, placing on the top surface of the ingot metal a quantity of loose combustible material greater in horizontal area than the top part of the ingot, then raising the ingot through the mold until the top portion of the ingot metal is removed from contact with the chill mold walls and projected into and encompassed by said material, admitting air from outside the mold to the space occupied by said combustible material at a level adjacent to the top of the raised ingot, and admitting air, from outside the mold to the space between the mold and ingot at a level below the bottom of the'raised ingot.

. EMIL GA'I'HMANN.

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