US2099670A - Stool to be used in the casting of metal - Google Patents

Description

Nov. 23, 1937. c. H. ALDRICH STOOL TO BE USED IN THE CASTING OF METAL Filed (Jet. 22, 1935 INVENTOR Patented Nov. 23, 1937 UNITED STATES PATENT OFFICE Charles H. Aldrich, Elizabeth, N. J., assignor to The American Metal Company; Limited, New York, N. Y., a corporation of New York Application October 22, 1935, Serial No. 46,096

.8 Claims.

geal therein, whereupon the mold is removed and again used. In carrying out the casting process it has been found that the poured metal tends to cut away parts of the mold, and that the tremendous amount of heat which is released by the molten ingot frequently results in a cracking of the mold surfaces. Usually it is the bottom of the mold which gives way first. Consequently, in the past, it has been the practice to form the bottom' of the mold separately from the side portions thereof, whereby the bottom, or stool as it is called, may be replaced when it becomes worn.

In the past several diflerent types of stools have been proposed. One of the earliest of these was made of a solid block of cast iron; This metal, as is well known, has a relatively low coefiicient of heat conductivity, and consequently the heat of the poured metal was unevenly and rather slowly distributed therethrough, and dissipated there- .from. In other words, the heat tended to concentrate at that point, or in that area, against which-the stream of molten metal first impinged .as it was poured into the mold. Now, uneven heating results in uneven expansion; and where one part expands more than another then the metal will buckle or crack. Accordingly, after a relatively short period of time, these cast iron stools became so covered with cracks as to be of no further use.

Later it was proposed to build the stool from a solid block of copper which, having a much greater coefficient of heat conductivity, would tend to distribute the heat of the casting morerapidly and more evenly. This expedient was relatively satisfactory, and such stools had a far greater life than the prior cast iron one. However, in time the stream of molten metal would begin to cut and erode the surface, and further, cracks and fissures eventually appeared.

In both of the foregoing typesof stool considerable trouble was caused by the tendency of the poured metal to weld itself to the stool. This, as can readily be understood, resulted in a very considerable loss of time in separating the ingot from the stool, and further, it tended to contaminate the metal of the ingot.

The principal object of the present invention is to overcome these difliculties and thereby to lengthen the useful life of the stool. This generally is done by subdividing the stool into a plurality of component parts which are yieldingly pressed together so that they may expand and contract independently one of another whereby opposed expansional stresses are avoided; and by utilizing different materials in different parts of the stool to counteract different destroying forces. The latter feature is accomplished by making that portion of the stool against which the molten metal first strikes, termed the area of direct-impingement from a material which will resist to a maximum degree the cutting action of the stream of molten metal and which is of such character as not to become welded to the ingot; I and by making the remaining portion of the stool, termed the area of non-impingemen from a material which will distribute the heat evenly and rapidly therethroughout.

Other objects and various features of the invention willbe more apparent from the following description to be read in connection with theaccompanying drawing, in which Figure 1 is a plan view of a stool which incorporates the principles of my invention;

Fig. 2 is a cross-sectional view taken along the line 2-2 of Fig. 1; V

Fig. 3 is a fragmentary cross-sectional view of a stool embodying my invention and showing a modified form thereof;

Fig. 4 is a similar view of another modification of the invention;

Fig. 5 is a fragmentary plan view of a stool in which either of the modifications of Fig. 3 or 4 may be included. Y

' One embodiment of the invention, as'shown in Fig. 1, comprises a plurality of relatively narrow bars II and I2 which are disposed in side by side relation and mounted upon a suitable bed l3. As can be seen, the bars are of a length somewhat less than the width of the bed. Consequently, any expansion lengthwise of the bar will not be opposed by the sides of the bed; that is, the bars are free to move in that direction. Further, the bars are yieldingly pressed together in such manner that any expansion crosswise thereof may be absorbed by the yielding means. Accordingly, each bar may expand in this -direction independently of every other bar. Thus, as will be apparent from the foregoing, the component parts of the stool are free to adjust themselves in any direction whereby opposed expansional and contractional forces are completely avoided.

When molten metal is poured into a mold mounted upon such a stool it will usually strike the latter at one point or within a relatively small area and then flow over the remaining portions thereof. After the stool has been used a number of times it will be found that this area of direct impingement has become corroded to a very marked extent; and that the ingot tends to weld itself to this area. In other words, the stream of molten metal tends to cut away the part of the stool against which it strikes, and then to weld itself thereto. The extent of these effects will be found to differ with the character of metal which is being cast. Thus, in general, high carbon steel and certain alloys have a greater tendency to cut the stool and to become welded thereto than do low carbon steels and other alloys. Accordingly, the bars II which constitute the area of direct inpingement are preferably made of amaterial which will oppose these tendencies to a maximum degree. In practice, it has been found that cast iron and certain alloys will resist these destructive effects when certain types of metal are being cast, while in other cases such refractory materials as carbon, graphite, carborundum, fire clay, magnesite, chromite and the like, must be used. Thus, the material which is to constitute the area .of direct impingement will be selected in accordance with the character of the metal which is to be cast. The remaining bars I2 constituting the area of non-impingement are preferably made from copper, or other material having a comparatively high coefficient of heat conductivity.

Inindividual cases it will be found that the area of direct impingement may constitute a greater, or lesser, proportion of the total area of the stool; and a greater, or lesser, proportion of the total depth thereof; and the arrangement" of this area may be varied in several ways. In Fig. 3, for example, the direct impingement bars Ila are only approximately half as deep as the adjoining bars l2, and they are underlaid by an equal number of bars [211 which preferably are formed of the same metal as the bars l2. Further, these bars may extend the total width of the stool, as is illustrated in Fig. 1, or they may be fore-shortened, as is shown in Fig. 5. In the latter case the area of direct impingement will be substantially surrounded by the bars constituting the area of non-impingement; that is, it will be adjoined on both sides by bars l2, on the ends by bars I25, and it will be underlaid by bars I211; 1

Another variation is shown in Fig. 4, in which the area of direct impingement may constitute a solid block of the desired material; and this block may extend the full depth of the stool, or it may be in a lesser proportion. Further, it may extend the full width of the stool or it may be foreshortened in a manner similar to that illustrated in Fig. 5.

Considering the advantages of the stool as a whole it will be seen that the composite character permits a selection of those materials which will best counteract the destructive effects of the molten metal. Thus, the bars II which are intended to resist cutting and welding may be chosen in accordance with the character of the metal which is to be cast; and the bars l2 may be made from a metal which will evenly and rapidly distribute the heat of casting. The laminated character of the stool not only avoids cracking, as hereinbefore described, but it permits an easy and rapid change of the character of the area of direct impingement.

Each of the foregoing features tends to lengthen the effective life of the stool. Accordingly, in practice, it will be found that this composite type stool has a considerably longer normal life than anything heretofore proposed. Further, such a stool may be very readily and inexpensively repaired. Thus, the laminated construction makes replacement of worn bars a relatively simple matter; and the inexpensive character of the area of direct impingement, wherein most wear occurs, permits replacement of this area at a very small cost.

Since certain changes may be made in the embodiment of the invention without in any way departing from the true scope thereof, it is intended that the foregoing shall be construed in a descriptive rather than in a limiting sense.

What I claim is:

1. A composite stool for an open bottomed ingot mold having an area of direct impingement formed from a material which is highly resistant to the corrosive action of a stream of poured molten metal, and an area of non-impingement formed from metal having a high coefficient of heat transfer whereby it may rapidly and evenly distribute heatthroughout the entire stool, both the area of direct impingement and the area of non-impingement being formed from bars which are disposed in side by side relation, and the stool being further characterized in that the area of direct impingement is underlaid by a portion of the area of non-impingement.

2. A composite stool for an open bottomed ingot mold having an area of direct impingement formed from a plurality of relatively narrow bars of cast iron which is adapted to resist the corrosive action of a stream of poured molten metal, and an area of non-impingement adjoining the area of direct impingement, the area of nonimpingement comprising a plurality of relatively narrow copper bars disposed in side by side relation and adapted to distribute the heat of the cast ingot rapidly and evenly throughout the entire stool.

3. A composite stool for an open bottomed ingot mold comprising a plurality of relatively narrow bars disposed in side by side relation with the side surface of one bar in contact with the side surface of the adjacent bar so that their tops form substantially a continuous surface upon which an ingot may be cast, certain of the bars constituting that portion of the stool against which a stream of poured metal would be most likely to strike being formed from a material which is adapted to resist the corrosive action of such a stream, the

constituting that portion of the stool against which a stream of molten metal would be most likely to strike are made of cast iron.

6. A composite stool for an open-bottomed ingot mold having an area of direct impingement comprising a plurality of bars of metal highly resistant to the corrosive action of a stream of poured molten metal, and an area of non-impingement comprising a plurality of bars of metal having a high heat transfer coeificient whereby it may rapidly and evenly distribute heat throughout the entire stool, the stool being further characterized in that all of the bars are disposed in side by side relation, and that the bars comprising the area of direct impingement are underlaid and adjoined on two sides by the bars constituting the area of non-impingement.

7. A composite stool for an open-bottomed ingot mold having an area of direct impingement comprising a plurality of bars of metal highly resist ant to the corrosive action of a stream of poured molten metal, and an area of non-impingement comprising a plurality of bars of metal having a high heat transfer coefficient whereby it may rapidly and evenly distribute heat throughout the entire stool, the stool being further characterized in that all of the bars are disposed in side by side relation, and that the bars comprising the area of direct impingement are underlaid and surrounded by the bars constituting the area of non-impingement.

8. A composite stool for an open-bottomed ingot mold, comprising a plurality of relatively narrow bars of substantially identical size and shape disposed in side by side relation with the side surface of one bar in contact with the side surface of an adjacent one, so that their tops form substantially a continuous surface upon which an ingot may be cast, the middle bars constituting that surface against which a stream of poured molten metal will first impinge being formed from cast iron so as to resist the corrosive action of such molten stream, and the remaining bars constituting the end surfaces being formed of copper so as to distribute the heat of casting rapidly and evenly throughout the stool, the cast iron bars being of substantially the same depth as the copper ones.

CHARLES H. ALDRICH.

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