US1719544A - Method of making ingot molds - Google Patents

Description

July 2, 1929- E. GATHMANN l.r7l9.544 y July 2, 1929. E. GATHMANN METHOD OF'MAKING INGOT MOLDS o'riginai Filed sept. 15, 1926 2 Sheets-Sheet if Gttorneg.

Patented July 2, 1929.

-EMIL GATHMANN, 0F BALTIMORE, MARYLAND.

METHOD OF MAKING INGO'l` MOLDS.

Original application'led September 15, 1926, Serial No. 135,586. Dividedl October 8, 19278. Serial No. 311,203.

This application is a division of my application for patent No. 135,586, tiled September 15, 1926, which contains claimsto an ingot mold having the characteristics shown in the accompanying drawings and hereinafter described.

This invention relates to vmetallic ingot kmolds of the class having vertical ingotforming chambers and particularly to molds which are open at top and bottom with walls relatively thick in their lower portion and graduallyl decreasing in thickness upwards. In pouring or teeming such molds the stream of highly heated molten metal, in the iirst part of the pouring, strikes the mold chamber walls in the lower portion of the mold chamber with great force and heretofore has often cut into the mold walls and suddenly heated them. thereby setting up strains or stresses which 'cause cracks or recesses to be formed which often seriously impair the life or eiiieiency of the mold and make the stripping operation diiiieult.

The object of my present invention is to prevent the formation of such cracks or rccesses and to thus lengt-hen the life of the` mold and to facilitatethe strippingoperation.

Broadly stated, my invention consists in rendering harder and more heat resisting the `lower portion of the inner walls of the mold chamber than Ithey moldl Walls above such lower portion so that saidllower walls may receive the impact of the stream of molten metal without being injured while the upper walls retain the desirable characteristics of the cast iron usually employed in A:ssl

making ingot molds.

The accompanying drawings are largely diagrammatic, but suiiiciently illustrate the best ways now known to me of carrying out my' invention.

Figure 1 shows `a vertical'section of an ingot mold of well'known construction wit/h my improvements applied.

Figure 2 is a sectional view of the lower portion of the mold, the section being taken on the line 2-2 of Figure 1.

Figure 3 shows a vertical section of an ingot mold provided with a modified form of my invention. l

Figure 4 is asectional view of the lower portion of themold, the seetionbeing taken on the line 4`4 of Figure 3.

Figure 5is a view similar to Figure 4, the

vention.

v ing Patent No. 1,188,751, of June 27, '1916.

' from 3% lwhich at first 'are relatively and this application nl'ed' sectign being taken on lthe line 5-5`of F igure Fig. 6 is a central, vertical sectional view of a sand' forming mold used for casting an ingot mold embodying vone form of my in- 6o Fig. 7 is a view similar to Figure 6 and showing a sand forming mold used for casting an ingot mold embodying another form of my invention. f

I will first describe `the characteristics of the molds shown in the drawings and will then describe the method of making them.

The mold shown in Figure 1 has an ingot forming chamber A. larger in diameter or cross section in its upper than in its lower portion, the chamber gradually or progressively increasing in width from bottom up-` wards. The mold is open at top and at bottom and the lower portion of the mold chamb'er is necked-in by inner mold walls a hava concavo-conveir contour ofthe kind shown, described, and claimed in' In e bottom opening B of the mold may be closed by 'a plug C in the usual way or by other suitable means. The walls of the mold are thicker in their lower portion than in their upperpart for a urpose now -well understood and the mold, for the most part, is made of cast iron ofthe usual kind. Generally such molds are made of an open grade of bessemer cast iron containing approximately the following ingredients: silicon 1.25; manganese 0.80; sulphur (under) 0.06; phosphorus (under) 0.20; total carbon 3.75. The conta-ined graphitic carbon usually runs to .3l/2%. Cast iron, havin these characteristics being of a so-calle open structure, admirably fuliills an important requirement in ingot molds, viz: It has the capacity of expanding and contracting correspondingly with the variations in temperature incident tothe formation of ingots in the mold chamber without fracturin o f the mold walls or excessive cracking. ut the melting point of vsuch cast iron or mold metal (2,200`F. to 2,3009 F.) is relatively low compared with the temperature of steel while being cast, which varies from 2,600.

kF. to 2,900 F. and at times is even higher.

As a highly heated stream of molten metal enters a mold-'chamber and strikes the bottom or lower walls of the chamber,

cool, it often 11 cuts, erodes, or even melts the mold walls with which it comes in contact, or so Aheats said walls as to cause such strains or stresses to be produced as will cause cracks or recesses therein. This has often so changed the cont-our of the lower portion of the mold chamber as to render the mold linefficient and this has often occurred long before the upper portion of the mold has been seriously impaired. This wearing away of the mold walls is primarily due to cumulative strains produced by continued expansion and contraction of the mold walls caused by temperature changes.

If an ingotmold were made entirely of steel, which has a high melting point and hence greater heat resisting qualities than cast iron, the mold walls would be more resistant to the cutting Land erosive action of the liquid steel poured into the mold, but

steel walls are not suitable for making ingot molds because such steel walls do not so readily expand and contract as do mold walls made of cast iron, and therefore they would warp to such an extent as to prevent the removal of the ingot from the mold. Furthermore, the cost of steel molds would be so muchgreaterthan cast iron molds that ste-el could not be used economically. I therefore make the mold principally of cast iron as heretofore and so form or so Itreat the lower portion of the inner mold walls as to render them harder and more heat resisting than the remaining walls. This may be accomplished in various'ways. @ne way is to form the low-er inner mold walls of an alloy of iron with a substance having a high melting point, such as vanadium, molybdenum, tungsten, chrome, or other such metal. Vanadium, for instance, has a melting temperature of approximately 3100o F., which 1s considerably higher than the temperature of-steel when teemed into a mold.

It will be understood that the lower portion only of the mold walls should be given the heat resisting qualities above mentioned morder thatthe upper part of the walls shall h ave the desirable characteristics of expanding and contracting without cracking, which, as before stated, is inherent in gray iron of the kind generally employed 1n making ingot molds.

Ingot molds of the kind shown are usually cast in sand ii'asks, bottom end uppermost.

Fig. 6 illustrates a forming mold set up whichmay be used for producing an ingot mold provided at its lower chamber p0rtion with a block of heat resisting material according Vto my invention. The mold setup includes the usual flask H, sand I rammed therein,l a sand core J supported upon a metal plate K and positioned centrally with- 1n the mold cavity, and a sprue L through which molten iron is introduced into the mold cavity. Inl preparing the flask to cast molds of the kind shown in Figures l and 2 with my improvements applied, the core J of thesand mold shown in Fig. 6 is formed in the usual wa;7 and a block D of high heat resisting material or having its inner surface provided with heat resisting material is placed on the core at its upper end so that themolten inet-nl will surround the block when it rises in the ask and will be firmly Aunited therewith when the metal cools and solidiies. The block thus` constitutes the upper end of the core during the casting operation. Preferably the block D of high heat resisting material or having its inner surface lprovided with heat resisting material is of the form shown in Figures l and 6, being tapered as shown and having a serrated upper edge whereby it may be firmly locked to the main mold walls. In the construction shown in Figure 1, the bottom of the mold chamber is formed in the block D and the necked-in portion of the mold chamber is formed in this block. The block may be`formed of an iron alloy of the kind previously described and is. of course,y made separatelyand placed in the same mold in the manner above explained. The block' D in the completed mold is not separable from the mold; it is a permanent part there- The mold shown in Figures 3, Il, and 5 has the lower walls of the east-iron mold treated to render vthese walls highly heat resisting. To accomplish this result, the loam or foundry sand composing that portion of the core for forming the lower part of the mold chamber ,is impregnated or coated with a flour-like metallic dust adapted to alloy with molten iron when brought into contact therewith such as powdered vanadium, molybdenum, chrome, and the like made into a paste with molasses and water or other such binder. The sand forming mold and core J are then set up as shown in Figure 7 and molten metal introduced into the mold cavity through th-e sprue L. When the molten metal rises in the sand flask and surrounds thpe treated core, this treated part of the core or a part thereof adheres to or is absorbed by the cast metal. In this-way a lining or a casing of high heat resisting iron or iron alloy is provided in the lower portion of the mold chamber. InFigures 3, 4, and 5 the lining or treated portion of the mold wall is indicated at E. The high heat resisting material should not extend to any considerable extent above the necked-in part tion were materially changed. While I have shown in the drawings two practical ways of embodying my lnvention' in ingot molds, it

will be understood that the details illustrated and described may be varied Without departing from the novel features of my invention.

The forming molds in which the ingot molds are cast are of usual construct-ion except as lmodified in the manner above described.

I claim as my invention:

1. The herein described method of forming an ingotl mold which consists in treating the upper end only of thescore of a forming ing the upper curved necked-in portion onlyy of the core of the forming mold with metallic alloying material which is adapted to alloy with molten iron when brought into contact therewith and which is highly heat resistant to the cutting action of liquid steel, and then pouring the-ingot mold metal into said forming mold, whereby said metal will combine with the heat resisting material placed on said curved necked-in portion of the core thus forming the inner walls of the lower portion of the ingot I nold chamber of an alloyed more heat-resisting to the cutting action of liquid steel than the upper portion of said mold walls.

Y 3. The method herein-before described of producing an in ot mold which consists in forming a core o a forming mold of suitable material, treating the upper portion only of said core with a finely divided alloying material which is adapted .to alloy with molten iron when brought into contact therewith and which is of high melting point, and then pouring the ingot mold metal into the forming mold and around the core whereby said alloying material will be transferred to said mold thus rendering the lower chamber portion only of the resulting ingot mold more highly resistant to the cutting action of liquid steel cast therein than the remainder of the mold.

4. The hereindescribed method of forming aningot moldvwhich consists in placing upon that end portion of the core of the forming mold whiclhuisstowtorm `the lower matrix Wall of the ingot moldgwmetallic material adapted to unite with nilten iron when brought into contact therewith, and which is more heat resisting to thel cutting action of liquid steel than the ingot mold metal, and then pouring the ingot mold metal into the forming mold and around the core whereby said material is united with the ingotr mold at the lower chamber portion'thereof.

In testimony whereof, I have hereunto subscribed my name.

EMIL GATHMANN.

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