US1757663A - Ingot mold and ingot - Google Patents

Description

y 1930. E. GATHMANN INGOT MOLD AND INGOT Filed May 23, 1929 2 SheetsSheet l 2W I m r 1111/ fi M j H.

EWZZZ G amUb Ihwentor, gattomegs.

Patented May 6, 1930 nun. GATHMANN, or BALTIMORE, MARYLAND I moor new AND moor Application .flled May 23,

My invention relates to ingot molds and ingots, and more particularly to the kindof molds and ingots known to those familiar with the art as slab or plate molds and Gingots. Heretofore in the production of sound steel from slab or plate ingots twogeneral difl'iculties have-been encountered. The first of these difiiculties arises in the productionof a relatively sound ingot. This isdue to the fact that since the cross sectional contour of the ingot mold and ingot formed therein is generally rectangular, different portions of the body of the ingot are chilled by the mold walls with varying rapidity. This 5 results in segregation and the formation of shrink holes.

The other mentioned difiiculty encountered in the production of sound steel from slab in gots arises in the rolling of such ingots to the desired thickness without producing what is well known to those familiar. with the art as fish tailing. This fish tailing consists in the outward bulging of the top and bottom surfaces of the ingot resulting in the formation of an inwardly extending curvature along the edge of the ingot, such curvature often developing into-a seam extending longitudinally along the edge of the finished slab.

In my U. S. Patent No. 1,440,535 of J anuary 2, 1902, and in my Patent No. 1,484,940 of February 26, 1924:, I have shown and described ingot molds and ingots ha ving contours including widened corner walls that merge with primary side walls by means of a plurality of outwardly extending curved.

salients. The present invention embodies refinements and improvements of molds and ingots of the kind shown in said patents.

- By my present invention, and by the employment of the novel contours hereinafter described, I am able to greatly reduce the de fects resulting from the causes before mentioned. f a

The object ofmy invention is to provide an ingot mold, the chamber of which has a cross section of such" contour that an ingot cast therein is free to contract during solidification without danger of skin or surface portionsof the ingot hanging against or being 1929. Serial No. 365,455.

bound by the mold walls, and so'shape the walls of the ingot produced in such a mold that the ingot may be rolled or reduced in cross section without up-ending or turning of the-ingot andwith a minimum danger of reduction laps, cracks, or tears forming in the unworked surface of the ingot due to the displacement of metal by the rolling or working thereof. t

A further object of my invention is th so shape the cross section of the ingot that little or no fish tailing will occur along the edges thereof when the ingot is reduced to a slab or bloom by the rolling action. A mold constructed in accordance with my invention preferably embodies the following characteristics. It is provided with two relatively wide primary side walls and two relatively narrow secondary side walls, the primary and secondary side walls being connected by widened or obtuseangled cornerwalls,

the apex of each of these corner walls being preferably formed of rounded contour. The central portions of the primary side walls are preferably formed with inwardly extending or slightly bellied contours, these contours merging into adjacent outwardly inclined or diverging portions of the primary side walls by means of outwardly extending curved salfents, each salient being defined by a rela-' tively short are. The secondary side walls each comprises two outwardly inclined or di-.

verging portions each connected at one end to an adjacentc'orner wall, and connected at its other end to the other side wall portion by means of an outwardly curved salient, the apexofwhich salient islocated on the neutral line of shrinkage passing through the mold chamber and the ingot contained therein on' its major or longer transverse axis. The two inclined portions of each of the secondary sidewalls preferablyinclude an obtuse an gle and the adjacent portions of the connected primary 'and secondary side walls also preferably include an obtuse angle.

The accompanying drawings show the preferred form of cross section of the mold chamber used in carrying out my invention, and the preferred form of ingot cast therein. The

drawings also illustrate various steps in the rolling of the ingot.

Figure 1 is. a bottom plan view of an ingot mold embodying my present invention;

Figure 2 is a vertical sectional view taken on the line 2-2 of- Figure 1; A

Figure 3 is a verticaPsectional yiew taken on the line 3-3 of Figure 1; v

Figure 4 is an enlarged fragmentary horizontal sectional view of approximately a guarter section of the ingot mold shown in the oregoing figures;

Figure 5 is a perspective view of an ingot formed in the mold shown in Figures 1, 2, 3, and 4; y

Figure 6 is a transverse sectional view of the ingot as cast and after having been removed from the mold; e

Figure 7 is a transverse cross sectional view of the ingot 'made in accordance with my invention after it has been through the initial roll pass;

Figure 8 is a view similar to Figure 7 showing such an ingot after having been through the next roll pass;

Figure 9"is a view similar toFigures 7 and 8 showing the shape of the ingotafter subsequent roH passes Figure'fi is a fragmentary sectional view of the edge portion of a slab ingot made in accordance with heretofore existing prac- Figures Figure 6 and-illustrate the fish tai'hng of the ingot in prior practice resulting from rolling passes corresponding to those 122) which the ingot has been subjected as shown in Figures 7, 8, and 9 res ectively.

It will be observed by reference to Figures 7, 8 and 9 t hat fish tailing has been produced when the ingots cast in accordance with prior practice have been rolled in the usual Figures 1 to 4 inclusive illustrate a mold A made of cast iron of suitable composition and provided with an ingot forming chamber B, the cross sectional contour of which 1s of a generally oblong configuration. The mold A is of the kind known as a big-end-down mold. It is open at the bottom andthe top and is adapted to be positioned upon a mold stool not shown) when metal is being poured '1I1t0 t emold.

In order to permit stripping of the ingot by the simple operation of raising-the mold and leaving the ingot positioned on the'mold stool, the walls of the mold chamber are all tapered inwardly. from bottom to top.

' cross'sectional contdurl as that of the. mold Figure 5 shows an ingot I of a kind cast in a mold such as shown in Figures 1 to 4 inclusiver It'will be observed that it has the same chamber B. a A y Neutral lines of shrinkage are indicated by the lines N'N- and N'.-w (Figure 4), these 7, 8, and 9* are-views similar tomoldch amber, each of which primaryside walls comprises a central portion D- preferably of slightly inwardly bellied contour'and outwardly inclined substantially straight portions C, connected to the central portion'D by means of outwardly arched salients G.

The other two sides of the mold chamber are bounded by outwardly cambered secondary side walls, each of said secondary side walls c'omlprising two outwardly inclined portions H, each of which is connected at one end to an adjacent primary side wall by an outwardly curved corner wall K, the two inclined portions of each secondary side wall being connected to each other at their other ends by a relatively narrow outwardly arched salient M..

The inwardly bellied central portion of each of the primary side walls is preferably of a len h somewhat less than one-third of the max1mum cross. sectional dimension F of the moldchamber. The outwardly inclined primary side wall portions C of each primary side wall diverge away from the-major axis of the mold chamber at an angle of from 2 to 10 from a line tan cut to the inwardly bellied central portion T) andgperpendicular to the minor axis of the mold chamber. Preferably, the inclined portions H of each secondary side wall diverge away from the minor axis N, N of the mold chamber at an angle of from 2 to 10 to a line tangent to the outwardly curved salient M and perpendicular to the major axis N, N.

It will be apparent that the angle included between each of the primary side wall portions C and the adjacent secondary side wall portions H willbe more than 90, or, in other words, it will beat an obtuse angle. The outwardly arched salients G and M are defined by relatively short arcs, .these arcs" being subtended by angles materially less.

In order that an ingot cast in a mold of the kind described, may be readily stripped orwithdrawn from the mold, it is desirable that the mold walls be tapered'inwardly from bottom to top as shown in Figures 2 and 3. I have found that the taper of the secondary 'side walls may be, somewhat less than that of the primary sidewalls, this being due to the fact that the inward shrinkage of the ingot and the outward expansion of the mold walls resulting from the transfer of heat from the ingot .to the mold is greater along the major axis of the ingot than along the minor axis'the'reof. It is evident that this difference in the amount of linear contraction of '45 stated, suitable temperature control and a produced from low or medium carbon steels deoxidized to an-' extent justnot quite sufliciently to form a sound homogeneous ingot structure, Blow .holes or gas pockets are formed during the solidification of steel of this character, and it is the desire of the steel melterand ingot producer to deep-seat these blow holes as much as possible, or rather as far as is practicable, without the formation of a central longitudinal shrinkage cavity or pipe in the-ingot, since such a pipe would usually make large top cropping necessary. The contraction of the ingot "metal from the liquid to the solid state is compensated for by the increasein the volume of the ingot caused by the formation of blow holes and a pipe or central shrinkage zone in the upper part of the ingot is thus prevented, or at least greatly reduced in volume and extent.

Steel of this kind should bepoured slowly while hot so as toassure the formation of a solid outer skin before the releasing or evolution of any material quantity of the occluded gases which are held in solution by the hot liquid steel. It has been found that the higher the temperature of the steel the more soluble are the gases therein and the greater the percentage of the occluded-gases in the liquid ingot.

the higher temperatures are released, which results in the formation of so-called' skin blow holes. The thickness of the initial skin or the amount of steel solidified before the formation of blow holes determines the type and quality of the ingot produced. As before.

proper rate of teeming are large factors in determining the skin thickness, that is, the thickness of steel in the outer walls of themgot defining the blow holes and the outer or skin surface of the ingot.v I

The employment of'a mold chamber contour having a plurality of salients and corners defined by obtuse angles in its horizontal cross section enhances the'chilling of the mold walls oil the ingot surface, and thus assures.

a thicker initial ingot skin before the .evolution of any appreciable volume of gases r-esulting from the lowering of the temperature of the mass of the ingot has commenced. Even though some blow holes should occur near the outer or skin portions of the ingot, material damage .due to large cracking or socalled snakes in the surface of the ingot cannot occur, for, as before described, such blow As the temperature of the liquid.

-'prising two outwar ingot lowers and surface solidification pro-.

got surface, these salients being of relatively dense metal which serve to arrest the spreading or progression of such defects.

Inthe production of fully finished or killed steels, my new. cross sectional mold contour should be incorporated in a mold of the bigend-up type, that is, a mold having a larger cross sectional area at the upper portion of the ingot forming chamber than at the lower portion thereof. Such molds should preferably be provided with refractory hot tops or shrink head casings having a*contour cone forming to the contour of the particular mold in connect-ion with which the shrink head casing is used. It is apparent that my invention consists in a mold having a novel and eflicient contour, and of an ingot cast in such a mold. The contour of the mold chamber and the dis position of the metal in the mold walls is of vital importancein producing a sound ingot of the desired shape, and the shape of the ingot is such thatduring" the rolling operations fishtaili'ng is prevented and reduce tion laps, cracks and tears are largely reduced.

What I claim is 1. A slab-like ingot mold having a chamber of substantially rectangular cross sectional contour defined by a pair-of oppositely-disposed relatively wide primary side walls, and a pair of oppositely disposed relatively narrow secondary side walls connected to the primary side walls by outwardly arched corner walls, each of the :(primary side walls com-' ly inclined portions connected by an inwardly curved salient, each of said inclinedportions'extending at an angle of from 2 to 10 to a'line tangent to said inwardly curved salient and perpendicular to the inner axis of the mold chamber.

j 2. A metallic ingot mold of slab-like contour 'having a chamber provided with two primary side walls, the central portion of each of which is inwardly bellied through out its vertical length and two secondary side walls, the central portionof each of which is of anoutwardly cambered contour, allof said walls being tapered'inwardly from the bottom to top, and the taper of said primary side walls being greater than the taper of said secondary walls.

3. A metallic ingot mold of slab-like cone tour having a cliamber provided with two primary .side walls, the-central portion of each of which is inwardly bellied throughout its vertical length and two secondary side walls, the

central portion of each of which is of .an outwardly camber-ed contour,-sa1d primaryside walls being 'connected to the secondary side walls. byputwardly' arched corner walls, all of 1 said'wallsbeing' tapered inwardly from bottom to top, the; taper of said primary side walls, being greater than the taper of sa d the cross section of the ingot will result in the tween the ingot and the primary side walls. Inasmuch as the moldhwalls are tapered for thepurpose of facilitating the stripping of the ingot, and since, for other considerations, it is not desirable to have the ingot so tapered, I provide the several walls witha minimum of taper consistent with the ease of stripping the ingot from the molds. In other words, the primary side walls between which relatively slight contraction of the ingot takes place are provided with a relatively large amount of taper at their central portions, whereas, the secondary side walls between which the contraction of the ingot is somewhat greater are provided with a less amount of taper. Preferably, the taper of the primary side walls gradually decreases from the central portions D toward the 'outwardly curved corner walls K.

Asbefore stated, ingots'cast in molds hav a generally oblong shaped chamber are ubject to shrinkage and pipe imperfections due to the unequal cooling of the various portions .'of the ingot which results from the different lengths ofthe walls of the mold chamber. In order to reduce such difliculties, I so apportion the thickness of the walls of the mold that the various portions of the bod of the ingot will be cooled at as nearly uni orm a rate as practicable. For accomplishing this purpose, the primary side walls are made thickest attheir central portions, the thickness of these wallsdecreasing gradually from the central portions to the curved corner walls. In a similar manner, the secondary side walls are'made to gradually decrease in thickness from the outwardly curved salients at the center of these walls to the outwardly curved corner walls.

It will thus be seen that the mold walls adjacent the center of theingot, at which point the metal has a tendency to remain fluid longest, are thicker than any other part of the walls, thus serving to accelerate the chilling of-the central portion of the ingot. The

' thinner corner walls and those portions of scribed.

Figure 6 shows a cross section of an ingot such as shown in Figure 5, and illustrates the various surfaces which are formed by the different portions of the mold walls. Thus the central portions D of the primary side walls of the ingot correspond to the central portion D of the primary mold Walls, and' the outwardly inclined wall portions HT, H

approximately the same time.

of the ingot correspond to the inclined secondary wall'portion's H, H of the mold, and

so on.

The outwardly curved corner portions .K, K of the ingot surface are described by arcs subtended by angles greater than 90, so that these. corner portions are more resistant to the cutting or burning action of the heat of 'the soaking pit or reheating furnace than are the more acutely rounded corners of ingots of the kind heretofore made.

When ingots of the generally oblong contour 'hereinbefore described are reduced to slabs preliminary to being further reduced to plates or sheets, the initial-reduction is usually accomplished by means of a slabbing or universal mill, that is, a mill provided with both horizontal and vertical. rolls, the horizontal rolls acting upon the primary surfaces of the ingot and-the vertical rolls acting upon the secondary surfaces thereof. In such a mill'these rolling pressures are exerted on the primary sidesand on the secondary sides at Due to the relatiyely wide corner walls ofthe v ingot, which walls are defined by arcs subtended by obtuse angles, and due to the curvature of the salients G,-M provided on the primary and secondary side walls respectively, transverse and vertical rolling cracks are largely prevented. If a crack should form in any section of the ingot surface during rolling, it will "not usually extend beyond one of the salients G, M or 'thecorners K, since the metal of. the ingot at these sections is more nearly solid and homogeneous than at adjoining parts of the ingot, and is of greater cohesive strength and more resistant to the spreading action or progression of incipient cracks or defects'than is the surface of an ingot of relatively plane contour.

When rolling ingots having a" cross section such as before described, the formation of fish tails along the edges of the ingot is largely eliminated. This is due to the fact that the ingot -is so-shapedthat the horizontal rolls acting upon the primary surfaces of the ingot contact with the central portion only of the primary sides during the earlier roll passes. This results in a squeezing of the ingot at its central portion before the edge portions are compressed, thus effecting a tendency for metal at the center of the ingot body to bulge outwardly along the major axis of the ingot cross section. -Fish tailing at the edges of the ingot is also largely prevented by means of the outwardly cambered shape of the secondary side walls. During the early roll passes, these secondary walls will be worked upon by the vertical rolls at their central portions. only, thus givingthe metal at'the central portions increased toughness by means of an extra amount of working. when the ingot is caused to go through succeeding passes, greaterxportions of the secondary secondary walls, the taper of said primary walls gradually diminishing from the inwardly bellied central portions toward the outwardly arched corner walls.

4. A metallic ingot mold of slab-like contour having a chamber provided with two primary side walls, the central portion of each of which is inwardly bellied throughout its vertical length, and twosecondary side walls, the central portion of each of which is of an outwardly cambered contour, said primary walls being connected to the secondary walls by outwardly arched corner walls, the thickness of said side walls gradually diminishing from their central portions towards said corner walls.

5. An ingot of slab like contour having two primary sides and two secondary'sides, the primary sides each having a relatively wide inwardly bellied central portion and the secondary sides each having a relatively narrow outwardly bellied central portion.

6. A. slab-like ingot having a. pair of oppositely disposed relatively widedprimary side walls and a pair of oppositely isposed relatively narrow secondary side walls connected to the primary side walls by outwardly arched corner walls, each of the secondary side walls comprising two outwardly inclined portions connected by an outwardly'curved' salient, each of said inclined portions extending at an angle of from 2 to 10 to a line tangent to said curved salient and perpendicular to the major axis of the ingot.

' In testimony whereof, I have hereunto subscribed my name.

EMU. GATMEANN.

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