US2116483A - Mold - Google Patents

Description

May 3, 1938. c. E. WILLIAMS ET AL Filed Dec. 19, 193

e I la 5 arence BY 5;

I VENTORS c/yaly E. W// 07 C/ hf L 7' W7 ATTORNEYS.

Patented May 3, 1938 UNITED STATES PATENT OFFICE MOLD tion of Ohio Application December 19, 1934, Serial No. 758,275 1 Claim.- (01. 22-139 Our invention relates to molds. It has to do particularly with molds for casting steel, iron, aluminum, or other metals and which are especially applicable to the casting of ingots, although 5 it is not necessarily limited thereto.

' In the prior art of casting ingots from such materials as steel, aluminum, copper, or other metals, it has been customary to use molds all parts of which were composed of iron or steel and being of a shape or form consistent with the production of ingots of a shape or form most readily adapted to subsequent fabrication, forging and rolling operations. Although the use of such cast iron or steel molds is practically universal in the steel industry, in the casting of steel ingots, these cast iron or steel molds have serious limitations and disadvantages which arise chiefly from the inherent properties of the material from which they are made.

In the past, big-end-up molds have usually been made from cast iron and in a single piece. It has been found that such molds are subject to an excessive amount of thermal cracking. During use of the mold, the constant expansion and as contraction forces set up by heating and cooling of the mold, since the mold is made in one piece, causes cracking around the bottom.

Such molds also do not satisfactorly resist the cutting action caused by metal being poured into them. It is not uncommon for the bottoms of cast not scrapped immediately when the first signs of cutting appear, they do produce ingots which must be cropped at the bottom more extensively to remove the defects caused by the imperfect molds which are cut. Many cast iron molds are screwed even before thermal cracks have made them useless, due to the fact that they have been severely cut by the pouring of the metal therein.

Big-end-down molds have usually been made of cast iron and have embodied a body portion having an open lower end which is closed by a separable cast iron stool. Since the stool is made of 5 cast iron,-it does not resist the cutting action proiron molds to be severely cut away upon pouring the first ingots into them. Though the molds are' portion of the mold facilitates, to a certain extent, the removal of the ingot from the mold. However, it has been'found that many times the lower end of the ingot will weld to the cast iron stool and cannot be removed therefrom without difli culty and without disastrous results to either the ingot or the mold stool.

In pouring the metal into ingot molds having an integral cast iron bottom or a separate cast iron stool, due to the comparatively low thermal conductivity of a cast iron bottom, the metal in the lower portion of the mold does not cool as quickly as desirable, which permits 01 the spreadingof the oxides, formed during the initial pouring action, upwardly through the ingot to an undesirable extent thereby lowering the quality of the ingot. 'It is desirable to bring about fairly 'quick cooling and solidification of a thin layer at the lower end of the ingot with a consequent entrapment of the oxides in this layer, so that the portion subsequently cropped from the lower end of the ingot contains practically all of the oxides formed'during the initial pouring action.

It is also desirable to bring about the initial rapid cooling of the lower layer, because this greatly minimizes the splashing tendency with its consequent formation of cold shuts, scabs, etc. In order to reduce the amount of necessary croppingof the lower end of the ingot and the tendency of splashing of the metal during the initial pouring action, a depression has been provided in the bottom of the mold' 'or in the stool thereof. This depression or concavity serves as a continuation of the mold cavity so that immediately when the pouring action is initiated, a pool of metal is formed which greatly minimizes the splashing of the metal during the pouring operation. This also produces a convexity on the lower end of the ingot which reduces the amount of cropping necessary. The depression in the bottom of the mold is of a predetermined size and shape. However, since the bottom of the mold is made of cast iron, when the metal is poured into contact with the cast iron bottom, due to the cutting action of the metal thereon, the contour of this depression will be completely destroyed after one or a few pouring operations.

The cutting of the bottom of the cast iron mold or of the cast iron mold stool caused by the pouring of the metal, produces cavities therein which become successively deeper with each pouring operation. In addition to destroying the uniform contour of the lower end of the ingot, this formation of cavities is accompanied by a welding of the ingot to the bottom or stool, so that this interfitting and more or less welded condition greatly increases the difficulty of stripping and sometimes makes it impossible without pulling away certain portions of the ingot or pulling away certain portions of the stool.

Another disadvantage encountered in the use of a mold embodying a cast iron body portion and a cast iron stool, is the comparatively large size of the fin which forms when a portion of the initially poured molten metal runs into any open space between the stool and the side walls of the mold. Due to the low thermal conductivity of the cast iron, the fin metal is comparatively slowly chilled and consequently the size of the fin will be greater than if the fin metal chilled more rapidly. The fin metal tends to break the mold side walls during stripping and the larger its area the more danger there is of breakage of the mold.

One of the objects of our invention is to provide a mold for casting ingots which is of such a nature that the ingots which are produced will be of the highest quality.

Another object of our invention is to provide a mold which comprises a main body portion and a separable stool member, the stool member being of such a nature that the metal stream will not tend to cut the surface thereof when it impinges thereagainst and the ingot will not weld thereto.

Another object of our invention is to provide a mold for casting ingots whereby during the initial pouring'operation, the oxides formed in the lower layer of the ingot will be entrapped in this layer and will be prevented from spreading upwardly through the ingot to an undesirable extent.

Another object of our invention is to provide a mold or stool or both of such a nature that the splashing tendency of the metal being poured will be greatly minimized.

Another object of our invention is to provide amold or stool or both of such a nature that the cutting of the mold or stool and the consequent splashing of the material thereof followed by the contamination of the ingot by such material will be obviated.

Another object of this invention is to provide a mold for ingots which will have a longer life than the cast iron or steel molds now in use.

We preferably provide a mold of such a nature 7 by a stool member composed of copper or copper alloy. The stool which we preferably use is of pure copper. However, it may be of other copper or of copper alloy, though it is desirable that it be of such a nature that it will have a thermal conductivity at least as high as sixty five per cent of the conductivity of pure copper.

The metal preferably is poured from a substantial height into contact with the surface of the copper or copper alloy stool member which preferably supports and closes the lower end of the cavity in the mold. This copper or copper alloy stool member is of such cross-section that it is self-cooling and, owing toits relatively great heat conducting capacity, it immediately brings about a cooling and solidification of a thin layer at the lower end of the ingot with a c seq nt entrapment of the oxides in this layer. Conse quently, that portion subsequently cropped from the lower end of the ingot contains practically all of the oxides formed during the initial pouring action, as distinguished from the slower initial cooling which results when the metal is poured upon cast iron which permits of the spreading of the oxides upwardly through the ingot to a much greater extent.

A further advantage of this method arises from the fact that neither the stool nor the mold will be cut away and that, therefore, all danger of contamination of the ingot by the material of the mold or stool will be eliminated. Thus, one of the disadvantages characteristic of cast iron molds or stools is obviated.

Furthermore, the initial rapid cooling which thus results from the pouring of the metal into contact with a surface of copper greatly minimizes the splashing tendency with its consequent formation of cold shuts, scabs, etc. This advantageous result is further materially enhanced by the use of a depression in the stool which communicates with the mold cavity and which immediately brings about a chilling of a local pool of the metal and greatly minimizes the splashing of the metal during the pouring operation. In other words, the use of a copper or copper alloy stool having a concavity formed therein results in an extension of the mold cavity so that the pouring of the molten metal into this concavity produces a rapidly cooled projecting lower end for the ingot with a consequent localizing of the undesirable oxides in this relatively small portion of the ingot, which portion is to be ultimately cropped.

With this method the lower portion of the ingot is quickly cooled because of the copper or copper alloy stool. However, since we contemplate making the side walls of cast iron which has a comparatively low thermal conductivity, the portion of the ingot above the thin layer which is quickly cooled will cool at a rate slower than the rate at which said thin layer was cooled. Consequently, the rate of cooling of the outer side walls of the ingot will be sufiiciently slow to avoid cracking of the ingot.

A further advantage of the use of a copper or copper alloy stool arises from the fact that the rapid chilling of the lower end of the ingot creates a condition which facilitates stripping. Thus, in

. a big-end-down mold, the rapid chilling, setting,

and increased contraction of the lower end of the ingot, in conjunction with the continued expansion of the lower side wall of the mold, creates a greater air gap and facilitates the separation of the ingot and the mold.

Likewise, with a big-end-up mold, the use of a copper or copper alloy stool in combination with a main body portion of cast iron, results in an important decrease in the size of any fin, which forms when a portion of the initially poured molten metal runs into any open space between the stool and the side walls. When a copper or copper alloy stool is used, this fin metal, as well as a thin layer within the mold cavity, is quickly chilled. Moreover, this chilling takes place before there can be any material expansion of the cast iron side walls. Since the fin metal is thus quickly chilled, its position and its size are fixed and determined. Subsequent expansion of the mold side walls takes place in a direction away from the ingot and from the fin, while, coincidentally, the ingot shrinks or contracts and undoubtedly causes some contraction of the fin metal.

One result of this is that the fin metal overlapping the end of the mold side walls at the time ,of stripping is less than would be the case where a cast iron base or stool is used and, consequently, where the fin metal does not chill as rapidly. Since the fin metal tends to break the mold side walls, during stripping, any decrease of bearing area or size of the tin on the end of the mold side walls'tends to minimize breakage of the mold.

uniform contour of the lower end of the ingots,

this formation of cavities is accompanied by a welding of the ingot to the bottom, so that this interfitting and more or less welded condition greatly increases the difliculty of stripping and sometimes makes it impossible without pulling away certain portions of the ingot or pulling away certain portions of the stool.

This application is a continuation in part of our application on Molds, Serial No. 698,456, flied November 17, 1933.

Illustrative embodiments of molds made in accordance with our invention and used in performing our method are shown in the accompanying drawing wherein:

Figure l is a vertical section of a mold of the big-end-up type and embodyingv a main body portion of cast iron with a separable stool of copper or copper alloy closing the open lower end thereof, the stool member being provided with a concavity in its upper surface.

Figure 2 is a vertical section of a mold similar to that of Figure 1, means being provided for preventing displacement of the body portion of the mold relative to the mold stool.

Figure 3 is a vertical section of a big-end-up mold embodying a cast iron body portion and a copper or copper alloy stool, the concavity in the upper surface of the stool being eliminated in this instance. r

Figure 4 is a vertical section of a big-end-down mold embodying a body portion of cast iron and a separable copper or copper alloy stool.

Figure 5 is a vertical section of a mold embodying a body portion of cast iron and a separable stool of copper or copper alloy, the stool having a cavity in both its upper and lower surfaces.

In Figure 1, we show a mold which is of the big-end-up type. This mold comprises a main body portion l which is preferably madeof cast iron.- This body portion has amoid cavity 2 formed therein which .is open at both its upper and lower ends. A stool member 3 is provided for supporting the body portion l and for closing the lower end of the mold cavity 2. This stool member 3 will be of copperor copper alloy and will be of suiiicient cross-sectional area and mass to eiIect rapid cooling of the lower end of the ingot. Since the body portion i of the mold is made of cast iron, the upper portion of the ingot will be cooled ata slower rate.

The upper surface of the mold stool I is provided with a concavity 4. This concavity 4 serves as a continuation of the mold cavity 2 and is of a predetermined size and shape in order to reduce the amount of cropping of the lower end of the ingot which will be subsequently necessary.

In the past, it has been attempted to produce a convex lower end on an ingot, in order to reduce the amount of necessary cropping, by the use of cast iron molds having the lower ends of the cavities formed therein of a shape similar 'tothat shown in Figure l and of a predetermined size. However, when metal is poured into such a cast iron mold, due to the cutting action thereof, the contour of the cavity in the bottom or stool of the mold will be materially altered. However, if the mold bottom or stool is made of copper or copper alloy, the molten metal poured therein will not cut the bottom or stool and will not destroy the contour thereof, at least, for a long period of time? Thus, an ingot with a constool is slightly smaller in diameter than the lower end of the mold cavity 2. Thus the edge of the cavity 4 will be spaced a slight distance from the inner surface of the side wall of the body portion I. Therefore, when the molten metal is initially poured into the mold, splashing against the side walls of the mold will be materially decreased.

Certain inherent physical characteristics of copper or copper alloys make them an excellent material for mold stools. Principal among these characteristics, is its high thermal conductivity, its relatively high melting temperature and heat capacity and its toughness at all temperatures below its melting point. Its thermal characteristics give it the necessary properties to resist thecutting action of the molten metal.

This has been demonstrated in plant tests where many hundred ingots have been poured on a copper stool without once having an ingot weld to the stool. On the other hand, cast iron stools usually weld or fuse to the ingots cast upon them. Due to the cutting and fusing of the cast iron stools to the metal ingots, the normal life oi such stools is approximately '75 heats. In contrast to the short life of cast iron mold stools, a copper mold stool of identical design has now been used for casting 1200 ingots. On the basis of performance to date, it is estimated that the stool will have a life in excess of 1200 pourings, or, at

. steel in the molds. The separation or the bigend-up molds into a cast iron body portion and a stool member of copper or copper alloy extends the life of the mold.

In Figure 2, we show a big-end-up' mold similar to that shown in Figure 1. In this instance, the body portion 5 is made of cast iron and the mold stool 6 is made of copper or copper alloy.

The stool member 8 has a concavity I formed in the upper surface thereof. However, in this in-, stance, the copper mold stool is provided with a shoulder which cooperates with a corresponding and a separable stool member I l of copper or copreadily weld to the copper or copper alloy stool.

and, should it stick to the upper part of the mold, the ingot with said upper part may be lifted from the stool and the ingot ejected by means common in shop practice. However, it will be understood that plugs may be used if desired.

Our invention is not limited to making molds of the big-end-up type with copper or copper alloy stools. Thus, in Figure 4, we show a big-enddown mold which comprises a main body portion I2 which is preferably of cast iron. The mold -stoo1 IS on which the body portion l2 rests is composed of copper or copper alloy.

. The mold stool I3 may also be provided with a concavity in its upper surface which. is similar to the concavity 4, of Figure 1, in order to minimize splashing, and to avoid excessive cropping, as explained previously.

In Figure 5, we show a mold embodying a castiron body portion I4 and a separable stool member I5 of copper or copper alloy. In this instance, however, the stool member has a concavity 16, formed both in its upper surface and its lower surface, which is similar to the concavity of Figure 1, and isprovided for the same purposes. The mold stool l5 should be fairly thick. We provide a stool with a double concavity so that the stool can be turned over after it has been used a very long time, thereby extending the life of it.

It will be understood from the above description that we have provided a mold for casting metals which has many desirable features. As brought out in the preceding description, by making the mold of a cast iron body portion and the mold stool of copper or copper alloy, many desirable results are obtained. It is important to have the mold stool made of material having a higher thermal conductivity than the metal of the body portion of the mold.

By the term "copper, used in the following claim, we also intend to cover copper alloys.

Having thus describedour invention, what we claim is:

A mold for casting iron or steel ingots comprising a body portion composed of cast iron and having a mold cavity formed therein, and a base for closing the lower end of said mold cavity, said base being composed of copper, said copper base being of such a size that it will extend outwardly past the inner surface of the wall of the mold cavity and having its upper surface exposed so that metal poured into the mold cavity will contact with said surface.

CLYDE E. WILLIAMS. CLARENCE H. LORIG.

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