US1911228A - Method of producing ingots - Google Patents

Description

May 30, 1933. E GATHMANN l 1,911,228

METHOD OF PRODUCING INGOTS Filed July 6, 1932 l GttornegS latentecl May 30, 1933 l ,9 1 l UNITED STATES PATENT @FFlCE EMIL GATHMANN'-, OF BALTIMORE, MARYLAND METHOD F PRODUCING NGOTS dpplicatlon filed July 6, 1932. Serial No. 621,160.

rlhis invention relates to methods of pro- 0f pipe in the ingot, small quantities of heatducing big-end-up ingots, and more particproducing materials, such as straw, and ocularly to methods of producing big-end-up oasionally heat-insulating substances, such ingots from ully-degasilied or deoxidized as infusorial earth, have been thrown on the 5 steel, that is, ingots known to the art as upper surface of the ingot to some advan- 55 killed steel ingots. Apparatus suitable tage, but the value of complete insulation of 'for use in carrying out my improved method the top surface oit an ingot has not heretofore is shown in my prior Patent No. 1,897,696, been fully realized. The practice of placing issued February 14, 1938, and in my copendsuch material on the top surface oit an ingot l@ ing application Serial No. 619,807 led dune 1s disclosed for example in my Patent No. @o

28, 1932. 1,711,052 of April 30, 1929.

Prior to the present invention, the greater ln accordance with my present method, tonnage oi killed steel ingots has been prothe use of shrinkhead casings in the producduced in big-end-up castiron molds adapted tlon of most grades of steel is not essential la to retard the solidiiication of the upper poror even desirable. tion oi the ingot relative to that of the lower lt will be understood that, when an ingot portion and iitted with ireclay shrinkhead has been teemed, the walls of the forming casings so as to comine the pipe or cavity inmold expand due to the heat of the molten cident to the shrinkage of the ingot metal lngot metal within, and the solidiying im from the liquid to the solid state to the eX- got decreases in cross section due to the contreme upper portion of the ingot. The traction incident to cooling. rlhis results iu shrinkhead portion of the ingot also prothe formation of an annular air space bevided a projection above the mold proper, tween the mold matrix and the sides of the m making it possible to lift or strip the ingot lngOt, this space being described in my Pat J with the soaking pit tongs, whereas without ent No. 983,357 of February 7, 1911.v The V475 Such a projooting portion the molds must be air in this space is rariiied and stagnant and upended and the ingots dumped. serves to insulate the ingot from the mold rlhe primary function of a shrinkhead and to retard the solidification of the ingot., Casing is 1go retard the soldioation of the This insulation is so effective that the oneuppor portion of an ingot until the lower fourth of the ingot volume last to solidify and intermediate portions have cooled and takes epprOXInately as much time as the solidilied thru the absorption of the heat of rSt three-fourths. the forming ingot by the mold walls. While An object of the present invention is to n, heretofore no satisfactory substitute had provide a method for producing metallic been found, the use of iirebrick shrinkhead ingots in such manner that the total time casings has a number of disadvantages. required for complete solidiiication of the Being made of brick or loam, small particles ingot is materially reduced. lln accordance of the shrinkhead casing at times break od with this method, the ingot is pushed up or and drop into the mold when the casing is partially stripped from the mold after a prebeing positioned on the mold, and it somedetermined portion of the molten ingot mass times happens that the pouring ladle is not has solidified and air is caused to dow thru centered accurately over the mold and the the space between the ingot and mold mastream of molten metal washes away a portrix. llt is important that the partial stription of the casing during teeming. ln this ping of the ingot be performed at a time way particles of the brick or loam are carwithin a predetermined stage of solidiiicaried into the ultimate product. Furthertion. Best results are obtained when the inmore, shrinkhead casings are expensive and got is raised when between Asixty and ninety increase materially the cost of sound ingot percent of its volume has solidified, the time 5G production. required for solidilication varying with the Frequently, in order to reduce the depth square of the cross section of the mold chamber. Heretofore ingots have been partially stripped from their molds before complete solidiiication of the metal, for example as shown in my Patent No. 1,059,668 of April 22, 1913, but in accordance with such prior practice, the ingot was stripped without particular reference to the degree of solidification and without providing for the rapid cooling of the ingot thru free circulation of air between the mold and ingot. The primary purpose of early stripping as practiced in the prior art was to lower the cost of re heating the ingots by placing them in the soaking pits before complete solidification and to lengthen the life of the molds.

Other objects will become apparent from a reading of the following description, the appended claims and the accompanying drawing, in which:

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 solidification;

Figure 2 is a View similar to Figure 1 but omitting the car and showing the ingot metal at a subsequent stage of solidiication;

Figure 3 is a view similar to Figure 2 but showlng the ingot partially stripped from the mold and in a late stage of solidification;

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

Figure 5 is a horizontal sectional view of a device for insulating the top surface of the in ot;

igure 6 is a sectional view taken on the line 6-6 of Figure 5; and

Figure 7 is a graphic chart illustrating the comparative time phase of solidification of an ingot cooled entirely within the mold matrix and the time phase of solidification of an ingot of the same cross section and volume produced in accordance with my present invention.

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 M of the big-end-up Gathmann t pe now well, known to the art and shown gbr example in my Patent No. 1,806,- 7 53 of May 26, 1931, is supported on a stool S, which in turn is carried by a car C. The mold is provided with a necked-in tapered bottom opening 1, which is closed by means of spaced closure plugs 2 and 3. The stool is provided with an opening 4 in alignment with the opening 1 in the bottom of the mold, and the car is provided with an opening 5 in alignment with the openings 1 and 4.

A stripper rod 6 is mounted for sliding movements within the opening 5 in the car, and is adapted to be moved upwardly through the openings 5, 4 and 1 into engagement with the closure plugs for moving the ingotrelatively upward thru the mold. The stripper rod is provided with a longitudinally-extending groove 7, which receives for sliding Inoven'lents the inner end of a latchrod 8, the latter being urged inwardly into engagement with the root of the groove 7 by a spring 9. The stripper rod is formed -with notches 10 near the bottom of the groove 7, which are adapted to receive the inner end of the latch rod 8-when the stripper rod 6 has been raised and the ingot partially lifted or stripped from the mold to the desired extent.

The openings 1 in the mold and 4 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 11 directly under the stool. Apparatus of the nature referred to above is described more in detail in my copending application Serial No. 619,807, filed June 28, 1932, and my Patent N o. 1,897,696, issued February 14, 1933.

Referring now to the method employed in producing killed steel ingots in accordance with the invention, the well-deoxidized steel is poured in the usual manner into the mold M, which may or may not be fitted with a shrinkhead casing. Immediately after teeming the ingot to the required level below the top of the mold, a measured quantity of refractory heat-insulating material 12 is placed on the surface of the molten metal. This material preferably comprises thoroughly dried, finely-divided diatomite or infusorial earth.

Shortly after the metal has been poured,

the chilling effect of the iron will cause the.

ingot metal which is in contact with the bottom and walls of the mold to solidify, the initial stage of solidification being shownin Figure 1, wherein the chilled solidified portion of the ingot metal is indicated at 13, the molten metal is indicated at 14, and the heatinsulating material on top of the ingot metal is indicated at 12.

The ingot metal is allowed to solidify further until approximately sixty to ninety percent of the metal has solidified, at which time the formation of the partially solidified ingot and the remaining molten metal will be substantially as shown in Figure 2. It will be noted that when the solidification reaches this stage, a small annular air chamber will have been formed between the ingot metal and the mold due to the expansion of the mold and the contraction of the ingot.

In accordance with the prior practice generally followed, the ingot is left in the mold until completely solidified. Due to the insulation aiorded by the air space, solidiication is very slow after the formation of this space and it is necessary to leave the ingots in the molds for a relatively long time to insure complete solidification. As much as two hours is required for the solidification of an ingot of 22 cross section by this method. This means that Vthe molds are tied up, production is delayed and axial segregation oi the metalloids-carbon, sulphur, phosphorous and the like-is increased in the slowly cooling ingot.

ln accordance with the present invention, when the solidiication has taken place throughout a predetermined volume of the ingot metal, between sixty and ninety percent and preferably about 75% thereof, the

, stripper rod 6 is raised by any suitable means,

such for example as those shown in the copending applications referred to, in order to raise or strip the ingot partially from the mold. The position ofthe ingot after this partial stripping operation is shown in Figure 3 and it will be noted that the upper portion only of the ingot has been moved up beyond the top oi the mold. en the ingot is in this position, relatively cool air is caused to llow upwardly thru the openings ll in the car, the openings 4 in the stool and the opening l in the mold and into the bottom of the mold chamber. The air, becoming highly heated and rariiied by contact with the hot mold walls and the hot ingot, automatically `llows upwardly through the annular gap between the ingot and mold very rapidly, due to the draft created by the heating of the air. lt is apparent that the entering air contacting with the bottom portions of the ingot will be relatively cooler as compared to the air which has been in contact with the bottom el the ingot and which has passed along the ingot, the result being that the air contacting with the ingot has a cooling elect on the latter which is progressively less from the bot-A tom to the top of the ingot. This results in more rapid heat abstraction and consequent quicker solidifcation of the lower and intermediate portions of the ingot than of its upper portions, so that the formation of a deep-seated shrinkage cavity or pipe within the body ci the ingot is prevented. ln other werds, the ingot metal is caused to cool and solidify more rapidly and yet progressively trom the bottom towards the top. lt is to be understood that progressive solidilication `trom bottom to top is absolutely necessary to insure physical soundness in the ingot product. Vlfhen the solidiiication of the in got is complete, the vertical cross section of the ingot will be substantially as graphically shown in Figure 4, wherein it will be noted that the shrinkage cavity is confined to the extreme upper part oi the ingot.

The time phaseof solidilication el ingots made in accordance with the prior art and' with my present method is illustrated graphically in Figure 7. The vertical lines T, T1, T2, T3 and T4 designate successive intervals of time during solidification and the horizontal lines V, V1, V2, V3 and V4 designate the volumes of metal solidified. The solid inclined line K shows the relative rateof solidification of an ingot when inclosed by the mold during its entire period of solidification. It will be noted that approximately l?5% of the ingot has solidified at T1 where the air chamber is completely formed, when the rate of cooling is abruptly retarded, as shown by the inclination of the line K from its point of intersection with lines T1 and V3. In my new method, the line K1 runs coincident with the line K for about 7 5% of its length, at which time the ingot is stripped or lifted up a predetermined distance and lair is induced to flow thru the chamber between the mold and ingot. Cooling then proceeds at approximately the same rate as before the formation of the air gap, as indicated by the line K1. The time of complete solidiication of both types of ingots is indicated by the intersection of the cooling lines K and K1 with the time lines T4 and T2 respectively.

My new method is particularly advantageous when it is desired not to use shrinkhead casings, but may be used in connection with such casings if their use in the production of the particular type of steel being poured is considered desirable.

A properly designed big-end-up mold without a shrinkhead casing or other provision for insulation of the top of the ingot will produce an ingot having a relatively deep,

unnel-like pipe or shrinkage cavity, necessitating a top crop of at least eighteen or twenty percent of the ingot volume, whereas, by practicing the method of the present invention, it is possible to reduce the depth of the shrinkage cavity to the top eight to twelve percent of the ingot volume. Not only is progressive solidification of .an in ot thus accomplished without the use oi a shrinkhead casing, but the total time required for the metal to solidify is reduced very materially, as graphically shown in Figure 7, thereby releasing the mold for further use and lengthening its life.

ln order to obtain the full advantages of my process, it is desirable that the insulating material l2 placed on the top of the ingot metal be as moisture-free as practical and that a sufficient amount be used to at least completely lill the shrinkage cavity as it terms due to the contraction incident to solidification. lln prior practice, whenever material to conserve the heat of the ingot has been placed on the top ot the ingot, it has been usual for an unskilled laborer simply to throw an indeterminate and usually insuiiicient quantity of the material from a shovel or the like. The material having been taken from a pile on the pouring floor or from an open container, contains a considerable amount of moisture, which varies with the humidity of the air and which tends to chill the top of the forming ingot. EX- perience has demonstrated that for the best results thc heat-insulating material should be as dry as possible and should have a depth of from about one-quarter to three-quarters of the minimum cross section D of the ingot at its top, as shown in Figure 6 of the drawing. For instance, where the ingot has a cross sectional dimension of 20 22, the depth or thickness of the blanket of heatinsulating material should be at least 5 and usually need not exceed 15, the specific depth being dependent upon the temperature and analysis of the steel being poured. In order that the material applied to the top of the ingot in practicing my method be as moisture-free as possible and in order to insure the use of a suflicient'amount, I prefer to employ a substantially moisture-proof carton-a paper bag or the like-lled with a measured quantity, two to six percent of the volume of the ingot metal, of dry, loose, finely-divided material, preferably diatomite or infusorial earth, which is readily obtainable, inexpensive and when dry is one of the best non-conductors of heat known for the purpose. One embodiment of this device isjillustrated in Figures 5 and 6, wherein a jacket 15 of moisture-proof, combustible material is shown filled with a quantity of loose, finelydivided heat insulating material. For certain types of steel, this material may comprise an admixture of comminuted straw and diatomite or the like. When the ingot metal has been poured, the carton containing the measured quantity of insulating material is at once deposited bodily on the top surface of the fluid ingot metal, whereupon the jacket 15 will be burned and the material 12 will be deposited substantially evenly over the surface of the molten metal, as shown in Figure 1 of the drawing. The upper contacting surface of the ingot will then remain molten and will feed the contracting ingot to compensate for the shrinkage of the lower portions, until the entire mass has cooled and solidified progressively from bottom to top. When solidification is complete, the shrinkage cavity should be substantially full of the heat-insulating material. If desired, this heat-insulating material may be retrieved and used again in accordance with the method shown and described in my Patent No.

' 1,719,542 of July 2. 1929. The top of the ingot, being considerably extended above the top of the mold, is readily engageable by the soaking pit tongs or other apparatus for removing the ingot from the mold.

Although I prefer to employ means such 5 as are illustrated herein for facilitating the depositing of the desired predetermined quantity of dry heat insulating material on top of the ingot metal, it is obvious that my improved method may be practiced without using the specific means described above. The insulatmg means is disclosed and claimed in a division of the present application, filed September 26, 1932, Serial No. 634,950.

Due to the complete insulation of the top of the ingot and the rapid cooling effected by the air draft during the later stages of solidlfication by this new method, it is possible to obtain a sounder and more homogeneous ingot structure than has been possible in prior practice. The rapid cooling of the ingot decreases segregation to the minimum and lengthens the life of the mold, allowing of the production of a greater number of ingots in the mold. By this new method, the danger of non-metallic inclusions in the ingot resulting from chipping or spawling of shrinkhead'casings is eliminated and a superior product is produced at comparatively low cost.

I claim:

1. The method of producing big-end-up metallic ingots which consists in pouring molten metal into a big-end-up mold, then raising the ingot only partially through the mold as soon as the ingot-forming metal has solidified through sixty to ninety per cent of its volume, admitting air from the outside of the mold to the bottom of the annular space between the mold and ingot, and supporting the ingot in said partially raised position until solidification is complete.

2. The method of producing big-end-up metallic ingots which consists in pouring molten metal into a big-end-up mold, covering the top surface of the molten metal with heat-insulating material, then raising the ingot only partially through the mold as soon as the ingot-forming metal has solidified throughout sixty to ninety per cent of its volume, admitting air from the outside of the mold to the bottom of the annular space between the mold and ingot, and supporting the ingot in said partially raised position until solidification is complete.

3. The method of producing big-end-up ingots from well deoxidized steel which consists in pouring the steel into a big-end-up mold, then raising the ingot only partially through the mold as soon as the ingot-forming metal has solidified throughout substantially seventy-five per cent of its mass, admitting air from the outside of the mold to the bottoni of the annular space between the mold and ingot, and supporting the ingot in said partially raised position until solidification is complete.

4. The method of producing big-end-up metallic ingots which consists in pouring molten metal into a big-end-up mold, then termes raising the ingotonly partially through the mold until the top portion of the ingot projects above the mold and with the bottom portion of the ingot still extending down into the mold as soon as the ingot-forming metal has solidified throughout sixty to ninety per cent of its volume, admitting air from the outside of the mold to the bottom ofthe annular space between the mold and ingot, and supporting the ingot in said partially raised position whereby cool yair will iow lnto the bottom of the mold and up through the annular space between the mold and ingot for cooling the letter at a progressively decreasing rate from the bottom to the top thereof.

ln testimony whereof', l have hereunto subscribed my name.

EMIL GTHMANN.

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