US1643241A - Ingot mold and ingot - Google Patents

Description

Patented Sept. 20, 1 927.

UNITED STATES EMIL GATHMANN, OE BALTIMORE, MARYLAND.

INGO'J. MOLD AND INGOT.

Application filed January 18, 1927. Serial No. 161,807.

This invention relates to the construction and contour of metallic ingot molds and to the contour of ingots cast within the mold chambers, and particularly to molds of the 5 class in which the largest cross sectional area of the ingot is cast. uppermost, the mold chamber having for the greater part of 1ts volume, metallic heat-absorbing walls-the value or rate of which decreases from the bottom of the moldupwar'dly, a relatively small section at the upper portion of the mold having walls constructed of refractory material of low-heat-absorptive value.

The object of my present invention is to so shape the walls of the mold chamber that they will more effectively promote progressive solidification of degassified ingot metal from the bottom upwardly to insure soundness, and at the same timeto so shape the ingot in its vertical contour that it canbe more readily reduced in cross sectional area and in fewer initial mill passes than has heretofore been found practicable.

In the accompanying drawings, which are is largely diagrammatic:

. Figure 1 shows a vertical section through an ingot mold embodying my invention.

Figure 2 shows a vertical perspective elevation of an ingot embodying my improve- 59 ments cast in a mold of the kind illustrated in Figure 1.

Figure 3 is an illustration of an initial reduction pass in a rolling mill of an ingot embodying my improvements.

As is now well-known to those familiar with the art and as described in numerous patents heretofore granted to me, sound omogeneous ingot structure is obtained most economically when an ingot is so cast that 40 approximately 85% of its volume is formed and completely solidified. in a heat-absorbing metallic mold having a big-end-up chamher, and substantially 15% of its volume is formed in a mold top or shrink head casing constructed of heat conserving material.

I have found that certain contours and definite relations of various ingot dimensions to one another are of economical and technical value in producing uniformlysound in 5 gots for most economical reduction by the rolling action of a blooming mill or the like. In working and squaring up a steel ingtot to form a bloom, which is accomplished during the first reduction passes) it is desirable to 66 work the cast metal and reduce the size of the crystalline, surface dendritic structures by compressing all of the sides of the bod of the ingot before elongating to any consi erable degree any one part of the relatively coarsely crystalline metal originally forming the in ot. Hence, for most eflicient blooming m1 1 practice the dilference in cross sectional area of the ingot from top to bottom should be as small as possible, being, how-- ever, great enough to insure of interior soundness of the ingot structure upon its solidification. I g

In the usual big-end-up mold, as generally used prior to my present invention, it has been the practice to form the metallic chamber walls with vertically-extending singleplane or substantially straight faces from the bottom or necked-in portion to the top of said metallic mold chamber, such walls having a uniform upward and outward well as inthe upper part of the ingot, which 30 is fed by the shrink head or reservoir of. molten metal contained in the poor heat con-- ducting portion of the mold, a degree of taper relative to the longitudinal axis of the chamber is necessary that makes diflicult b5 and costly the rolling of the ingot because of the increased number of preliminary squaring or blooming passes required. This I have remedied by applying certain different contours or degrees of taper to definite portions of the mold chamber length and the ingots formed therein. By means of this differential taper, the lower portion of the walls of the chamber can be tapered to the desired extent to insure ingot soundness andto a greater degree than has heretoforebeen deemed practicable, and yet the total ta er of the chamber'and ingot is considerab y less than that heretofore considered necessary for ingot soundness. In this manner I produce not only a more uni,- formly sound structure but one more readily reduced to a bloom contour without danger of excessive fracture of the cast, coarsely crystallized ingot skin in the initial mill passes.

Other features of my invention are hereinafter specified more fully.

An essential characteristici of an ingot mold in its function of forming a sound,

homogeneous ingot is that it shall promote progressive solidification of the molten mass within the mold chamber from the bottom upwards in order that there may be at all" times a reservoir of hotter molten metal superimposed upon the earlier solidifyingv issue of this patent, many-types of molds have been proposed and patented for carrying out thebasic method of manufacturing steel ingots disclosed therein and many millions. of tons of sound ingots have been produced in accordance with this method in 0th big-end-down and big-end-up types of molds.

When ample taper of the chamber walls -is provided, the big-end-up type of mold has been found by those familiar with the art to be by far the most efficient and practical construction for carrying out the fundamental requirement in the production of uniformly sound and homogeneous ingots. Mill ingots of the big-end up type with suflicient taper to insure soundness throughout their body length, however, have heretofore been more difiicult and costly to roll and reduce initiall into blooms than ingots having substantia ly parallel'walls, or big-end-up and big-end-down types having but relatively slight taper.

Although m invention may be applied to big-end-up mo ds of any kind, I have shown in Figure 1 a big-end-up ingot mold M of the Gathmann type. The walls A. of the mold body are constructed of heat-absorbing material and the walls S of the top portion of the mold are constructed of heat-insulating material in a manner now well-known to those familiar with the art. The vertical height of the heat-absorbing walls defining the mold chamber is designated at H and N, the vertical height 'of the heat-insulating portion by H and the entire or total height of the chamber at Y. Lugs of any suitable construction for lifting the mold during handling or stripping operatlon for the removal of the ingot I are shown at L and L. S is the shrink head casing or mold top made of refractory material having poor heat-conducting qualities. E, B, C and D are various sections of the mold chamber from the bottom to the top respectively. Corresponding portions of the ingot are designated at EL' BI, CI and DI. b is the lowest horizontal cross section of the ingot mold chamber and ingot, from which substantially straight outwardly tapered walls radiate upwardly to 0', these .walls having a greater taper per inch of vertical height than the cross sections beginning at a and tapering upwardly and outwardly to 01.

Dotted lines d in the same plane as the Walls radiating from b to 0 are shown ending at d, which would be the upper terminal of the mold cavity if the taper from the cross section b were continued, as is the case in the one-plane old type chamber walls. The height of the chamber section E is designated by N, the height of the taper of chamber B by O, that of the chamber C by P, and the shrink head portion D by H. The bottom of the mold is preferably closed with asealing or closure plug V and the refractory poor-heat conducting mold top S is preferably supported on the mold by means of removable blocks as shown at'l. The shrink head casinghas its cross sectional dimension indicated at W. The shrink head portion S of the ingot I shown in Figure 2 is somewhat shorter than the length of the mold top or shrink head casing S due to contraction of the ingot during solidibothas to solidification of the metal in the ingot and ease of rolling mill operations, I have found that the taper from b to 0 should be approximately per foot through the height 0, and the taper from c to (1' should be approximately per foot through the height P. In the illustration given a straight taper from b to d would amount to 3", but by the use of my differential taper the total difference in the taper from b to d is only 21 2' As previously stated, it has heretofore been the practice to employ a continuous taper from b to d and such ingots, although generally sound when suflicient taper is employe have been found more diflicult to reduce in rolling practice than when my present in vention of differential taper in chamber sections 0 and P is employed. The liquid steel in the shrink head portion S7 of the ingot when amounting to approximately 12% or more of the volume of the ingot feeds downwardly so as to insure of a solid ingot interior to a depth of approximately one and one-half to two diameters of the shrink head dimension W. The shrink head dimension W should for technical reasons be As'previously stated, I have found that the hot molten metal in the shrink head feeds downwardly to and supplies hot metal to the contracting, solidifying lower ingot portion somewhat beyond the horizontal dimensions 0' and if a were the actual base or bottom of the ingot, the taper per foot from c to 11 would be ample to insure sound interior ingot structure when employing such a short ingot and relatively large shrink head chamber. The influence of the hot metal in the shrink head does not,.however, usually exceed beyond one-half of the length-of the mold chamber H and, therefore, I make the length P somewhat less than half of the length of the chamber so as to insure of the action of the shrink head molten metal feeding to or slightly through the portion of the ingot at the cross section 0'.

By means of the relatively increased taper of the mold walls and the ingot formed therein from section b to c of the chamber, I have found that the metal freezes in a uniformely sound condition from the bottom of the mold upwardly and that all the shrinkage cavity or pipe and porosity due to decrease of section from liquid to solid is contained in the upper two-thirds of the shrink head S, as shown by dotted lines at F of the in ot I illustrated in Figure 2.

lteferring now to Figure 3, the rolls X and X are so spaced that a single pass through the rolls will work all the metal of the ingot on the two sides being rolled and the ingot being turned 90 on its longitudinal axis and given a second pass, all the metal on the surface of the ingot will be initially worked and reduced from the usual coarse crystallization of an ingot casting to a semi-forged state. These initial passes must, however,

not be of such a severe degree that the free 1 sides of the ingot not being worked on during the initial passes will split and tear, due to overstress of the unforged metal. practice it has been found that an initial reduction of 2 or at most 2 is the maxi mum that the cast steel in the ingot will ordinarily withstand without cracking and producing surface flaws.

In accordance with the old method of straight plane walls of big-end-up mold chambers and ingots, the taper which would produce interior soundness in the dimension of ingot specified amounts to 3", as reviously stated, in its height H, from b to (1 By my new improvement of differential tapered walls the amount of taper in the example before given on the section of the mold chamber and ingot shown at 0 would amount to per foot or a taper of 1%" from b to c for height OI The taper from c to d of per foot would amount to or slightly over A" for height P. The

2 or to be exact 2 1 as a ainst a total 7 a 7 E1 7 o mum difference of cross section two passes.

are required for the initial skin forging. The economy thus effected is considerable, inasmuch as the four sidesof a rectangular ingot of my differential vertical wall contour obviously require only two passes as against the four passes necessary in the, old type of ingot wall contour. and length of chamber 0. and P may be varied somewhat for different wei ht ingots, but the length P should not excee two-fifths of the total ingot length, as this is the limit of feeding capacity of 'a shrink head casing containing from 12% to 16% of the volume of the fluid metal forming the ingot.

I claim for my invention:

1. An ingot mold comprisinga heat-absorbing body portion and a heat-insulating upper part, the mold chamber in said body portion being defined by metallic heat-absorbing walls which taper upwardly and outwardly in the same general direction irom bottom to top of said chamber, the taper of the lower portion of said chamber walls being considerably greater than the taper of the upper portionthereof.

2. An ingot, mold comprising a heat-absorbing body portion and a heat-insulating upper part, the mold chamber in said body portion being defined by metallic heat-absorbing walls of a flat or plane contour which taper upwardly and outwardly in the same general direction from bottom to top of said chamber, the taper of the lower portion of the said chamber walls being considerably greater than the taper of the upper portion thereof.

3. In a metallic ingot mold, an ingotforming chamber defined by metallic heatabsorbing walls of a flat or plane contour, all tapering upwardly and outwardly from bottom to top of said chamber, the taper of the lower three-fifths being considerably greater than the taperof the upper twofifths of the height of such chamber.

4. In a metallic ingot mold of the bigend-up. type, an ingot mold chamber characterized by metallic heat-absorbing walls which taper upwardly and outwardly in the same general direction, the upper portion of said walls having less than half the taper per inch of the lower portion of the walls.

5. A big-end-up ingot having a body portion with an outward and upward taper, the

upper part of the ingot body which tapers in the same generaldirection as the lower The points 0' tion, and having also a necked-in portion at its top. a

8. A big-end-u ingot having its base portion rounded an necked-in, and having a body portion with an outward and upward taper, the upper part of the ingot having a considerably less taper per inch of height than the lower portion, and having aneckedin portion at its top.

In testimony whereof, I have hereunto subscribed my name.

EMIL GATHMANN.

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