US1327987A - Process for casting steel ingots - Google Patents

Description

a, G400ATES." PROCESS FORCASTING STEEL msoIs.

APPLICAT/ION FILED Aua.2o. 1917.

FIG. I

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. ENVENTB W W fia fi w Patelited an. 13, 19 20.

RAY G. COATES, or rAsADENA, CALIFORNIA, ASSIGNOR, BY DIRECT AND MESNE ASSIGNMENTS, T0 VALLEY MOULDAND mon CORPORATION, or NEW YORK, N Y., A CORPORATION or NEW YORK.

PROCESS FOR cAs'rINc STEEL moors.

Specification of Letters Patent.

Patented Jan. 13, 1920.

Application filed August 20, 1917. Serial No. 187,166.

iron chills, usually set vertically. Due to well known reasons a pipe forms in the central upper part of the ingot; a tendencyto segregation of certain of the constituents occurs in the region of the pipe; the gases discharged from the molten metal. in solidifying have to travel from the lower part of p the mold to the upper part to .be discharged I l at the .surface and it results that a large part of these gases fail to reach the surface.

'The various methods of heating the upper part .of the ingot so as to keep feeding the pipe with fluid metal have been but partially successful in preventing the pipe,-the segregation'of constituents, the accumulation of gases in a part of the ingot, and the forma-' tion of scrap With all of the present precautions rails rolled from the twoends of the ingot have different characteristics in some degree.

Figure 1 illustrates one form of mold in which my process may be carried out. Fig.

2 illustrates a different type of chill mold. Fig. 3 is a cross-sectional View showing a hot cover over the mold and illustrating in dotted lines the formation of crystallization zones.

The principal-object of my invention is to render the various cross sections f the ingot of a more nearly average chem'ic'a'. and

' physical constitution than now obtains, and

to do away with the pipe to such an extent that cropping of the ingot will not be necessary for either physical or chemical reasons. Incidental advantages will appear later. a

. Another object of the present invention is the method of forming steel ingots by casting the ingots in a shallow mold and controlling the temperature over the surface of the molten steel by means of a hot gaseous envelop through which gases expelled from the steel may freely escape, and controlling the temperature-in such manner that solidification of the ingot travels gradually from the bottom thereof to the top surface thereof.

A further object of the present invention is the production of an article of manufacture comprising an ingot of steel wherein the zones of solidification extend lengthwise 0f the ingot and are in cupped form with the long side of the ingot comprising the mouth of the cups and with the cups of decreasing depth when measured on the mid cross-section plane at right; angles to the said long side.

' These results I'accomplish by casting the metal in chills in whichthe axis of the in ot is horizontal and in which a long side,.1nstead of,"an end, of the ingot is open, and by maintaining thev metal hot on this long side by the application of heat while the metal of the ingot is crystallizing from the [bottom and sides of the chill. When cast in this position the gases discharged from the crystallizing metal in order to reach the surface have to travel through the fluid metal an average distance of only half the thickness of the ingot instead of an average distance of half the length of the ingot as when cast vertically. Preferably the application of heat to the metal of the ingot is accomplished through the use ofa heated atmosphere maintained over the surface ofthe molten steel, in such manner that the heated atmosphere or gaseous envelop does not interfere with the free emission of gases from the molten steel as it cools. This gaseous envelop or atmosphere may be se-' cured by means 'of a heatradiating substance or otherwise. The fiotational tendency of the gas bubbles is greater since the' I head of metal isless than in thervertically" cast ingot and the bubbles are therefore less compressed consequently they more quickly' reach the still fluid surface and are released from the ingot. Since the horizontal cross section of; the metal is larger than in the vertically cast ingot the gases do not travel toward the surface in the same paths anditresults that such as are not discharged do not gather ;into large accumulations near the top of theingot. The tendency to form a pipe is very small since there are only three chilled side's cross sectionally of the ingot,

thusallowing the relatively large area ofthe top to feed the'contraction of the metal below, there being more top surface of the ingot, than when cast vertically, for heat absorption to keep the metal fluid until it crystallizes from' the bottom anchsides of the chill. The pipe degenerates into a slight sinking in of the top surface of the ingot and this will roll out in thefir'st pass in rolling. Whatever variation in the chemical constitution of the ingot may occur, due to glflNlty and the direction of cooling toward the last remaining fluid surface such variation will still result in a homogeneous condition longitudinally of the ingot since each cross section Will be approximately alike. Thus the rolled product from both ends of the ingot will be similar.

This is a matter of great importance in the draft here being toward the top of the chill. The ingot is released by turning the chill over. Fig. 3 represents any of the intermediate cross sections of Fig. 2 and also shows a section of a hot refractory cover, 3, applied to the chill, 1, and a section of the ingot, 4, in the chill. The dotted lines in this figure represent planes of crystallization advancing from the heat absorbingwalls of the chill. The final plane is almost flat and coincides with the surface of the ingot. The under side of this refractory cover, 3, is to be heated above the melting point of the steel being cast and applied in'unediately after the chill is filled so as to cause the surface below it to be the last of the metal to solidify. i

In applying heat to the top of the ingot to delay the surface solidification I contemplate using any of the methods 'now practised in this art. I prefer the preheated cover since it has no chemical action on the metal if, as should be the practice, the chill is not filled clear to the top.' The fact that the cover will lose heat Will not prevent the desired effect since it is only intended that the surface solidification should be the last to occur and the effe t of the cover is to furnish the necessary delay and to prevent any air chilling and consequent crusting over of the metal.

In the present practice the greater the length of the ingot for heavy work the greater the lossdue to pipes and spongy tops. It results that thick ingots with an amount of rolling more than enough a develop the desired fiber in the finished product is the common practice. In my process the ingot may be cast with a large ratio of length to its Weight and no unnecessary rolhng need be done on it, An approximately square ingot with a length of from eight to twelve times its thickness will crystallize more quickly and therefore with less segregation by my method than by the"com1non practice'.

In mymethod the chemical and physical variations, induced by the position of the chill and the consequent directions of cooling and crystallization, will occur trans versely of the resulting ingot. All crosssections of the ingot will be alike since each one will contain i'ts proportionate part of the top and bottom of the ingot.

Outside of the chills, heretofore described,

the apparatus required forlcarrying out my improvement is not of any especial design.

degree that crusting over of the top surface does not occur until the final solidification. Ingots have been cast horizontally in chills.

,Such ingots, being chilled on four long sides have no relief from the pipe that form from,

the contraction .of the heated centra part after the outer shell has cooled enough'to solidify. In. this case a pipe forms in the upper longitudinal part of the ingot, the gases are trapped and the ingot is not solid.

In making chills for my process it is not necessary to use the particular design shown in the drawings. Those are shown merely to indicate the change in general effect required,

bymy process. Chills for my process may be made by any construction now practised in this art when due consideration is given to the change of conditions under Which the chill is used. The thickness of metal in the chill and the amount of draft required to readily release the'ingot are easily adaptable from the present art. I claim:

1; The process of forming an elongated.

ingot by pouring molten steel into an elongated horizontal chill, adapted to chill the bottom and both sides of the resulting ingot, and the immediate application by means of a hot gaseous envelop of sufficient heat to the surface of the metal just poured to cause said surface to be the last of the metal to solidify and to permit the escape of gases being expelled from the steel.

2. The process of forming steel ingots temperature of the poured steel by radiant heat whereby the isothermal-zone of fusion measured at a mid transverse cross-section of the mass gradually advances inwardly and upwardly from coincidence with the surfaces of the mold to coincidence with the top surface of the steel'mass.

The process of forming steel ingots to eliminate defects in said ingot, which process comprises pouring molten steel to form a shallow pool of molten steel; then controlling the temperature of the steel by controlling the temperature of the gases over the steel in such manner that solidification proceeds gradually from the sides and bottom of said pool while the surface thereof is maintained fluid, until the top surface of the ingot is the last portion thereof to soli dify.

4. The method of forming steel ingots and the like, which method comprises forming the ingot on its side by pouring the molten steel into a shallow elongated mold; then controlling the temperature of the molten mass by radiant heat applied to the surface of the mass to-cause the molten steel to gradually solidify from the bottom of the ingot to the top in such manner that the isothermal zone, of solidification gradually travels from the sides and bottom of the steel mass upwardly and inwardly with 'the maximum depth of molten steel maintained at the middle of the cross-section of the ingot and the zoneof maximum heat maintained at the surface of the ingot so that the steel at the surface of the ingot is the last to solidify.

5.. The method of forming steel ingots, which'method comprises providing a mold having its maximum longitudinal directionsubstantially horizontal; then pouring molten steel into said mold;'then applying heat by means of a hot gaseous atmosphere to the surface of said mold while allowing the bottom and side portions of said mold to cool, whereby the top surface of said mold is maintained liquid up until the moment of total solidification of the metal, thereby permitting free escape of the gases being expelled from the steel.

6. The method of forming ingots of steel and the like, which method comprises providing a relatively long shallow mold; then pouring the molten metal into said mold; then controlling the ten'iperature gradients in said metal by means of a hot gaseous envelop maintained over the metal in such manner that the crystallization of the metal mass proceeds inwardly and upwardly from the side walls and bottom of the mold toward the top surface of the ingot so that gases expelled during the crystallization of the metal escape from the metal mass by rising upwardly through a shallow molten layer and over an area \vhlch substantially includes the n'iaxnnum length of said ingot.

7. The process of forming steel ingots'to' produce an ingot of substantially uniforn'i cross-section from one end to the other thereof, which process comprises pouring the steel into shallow molds; then controlling the temperature of the steel by maintaining a hot gaseous envelop over the surface of the steel with the temperature control such that cooling of the metal mass proceeds gradually from the sides and bottom of said mass whereby gases expelled during solidification at all times may escape vertically through molten metal and wherein metal at the surface of themold is last to solidify.

8. The method of forming steel ingots and the like, which method comprises pouring the molten steel into a shallow elongated chill mold, then controlling the term perature of the molten steel by providing a hot gaseous envelop in contact with the surface of the steel to cause the solidification of the steel to occur along cupped zones which radually change in shape from substantia ly the form of the chill mold surfaces to that of the top surface of the ingot whereby vertical lines from any portion of the solidifying zone extend upwardly through molten steel to the hot gaseous envelop.

9. The process of forming ingots of steel having substantially a uniform cross-section from one end to the other, which process comprises pouring the molten steel into a shallow elongated chillmold; then maintaining a hot gaseous envelop in contact with the surface of the steel to control the temperature of the steel whereby crystallization of the ingot gradually proceeds from the bottom and sides of the ingot toward the .top thereof in such manner that vertical lines from the zone of crystallization at.all

times pass through molten steel to. the hot gaseous envelop, whereby gases emitted during the crystalllzation process may escape into the hot gaseous envelop.

10. The method of forming steel ingots i the sides of the mold to the angle of the top surface of the ingot and in such manner that a layer of molten steel at all times covers the crystallizing zone up'until complete solidification has taken place.

111 The method of, forming steel ingots and the like, which method oomprises castof said steel whereby the heat gradient at all times during solidification runs from the top surface of the steel to the bottom and side Walls thereof, and the action of solidification moves from the bottom of the mold to the top surface of the ingot. 12. An article of manufacture comprising an ingot of steel With the lines of isocrystallization therein comprising cupped zones extending length-Wise of said ingot With the width of the mouth of the cups be ing substantially constant and with the mafi'mum zone, being substantially the shape of the sides and bottom of said ingot and the minimum zone being substantially coincident With the top side of the ingot.

mama? extending lengthwise of the ingot and from the bottom side of said ingot to the top side thereof With the maximum zone being substantially coincident with the ends, side Walls, and bottom side of said ingot and the minimum zone being substantially coincident With the top of said ingot.

Signed at Los Angeles, California, this 11th day of August, 1917. I

RAY G. COATES.

Witnesses v Y W. V. MERWIN, H. S. RoLLINs.

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