US1961721A - Casting method - Google Patents

Description

June 5, 1934. A. A. VAN LANTSCHOOT CASTING METHOD Filed June 29, 1932 Patented June 5, 1934 STATES PATE OFFECE CASTING METHOD Application June 29, 1932, Serial No. 619,861

3 Claims.

lViy invention relates to an improvement in casting methods.

One of the objects of my invention is to provide a method which will minimize the bad effects 5 of shrinkage in castings. The term shrinkage as used herein and as understood in foundry practice refers to an action which results in imperfections in the casting caused by the tearing apart of particles of metal within the casting just after pouring. This shrinkage, caused in great measure by the tendency of the fluid metal on one side to pull away from the metal on the other side usually produces its worse effects where a heavier section of a casting joins a lighter section. Two attempted remedies have been used in the past to lessen the bad effects of shrinkage. 1 One attempt was the provision of a feeder for the casting so located that the molten metal from the feeder forces itself by gravity into the casting 20 while it is contracting and solidifying. This has some beneficial effect in the prevention of porosity and voids. Such feeders, however, are expensive because they necessitate amounts of additional molten metal and excessive grinding of large gates which are essential to pouring. Furthermore, the design of the casting itself often prevents the use of such a feeder.

The other remedy-proposed heretofore is the use of metal chills, usually pieces of cast iron placed in the mold or cores in the vicinity where the shrinkage occurs. The chills are so located that one or more surfaces of the chill are exposed to the molten metal which freezes quickly when it contacts with the chill. This also has a beneficial effect in lessening the evils of shrinkage. Usually it causes the shrinks to be driven to a less important section of the casting. The use of such chills, however, also involves considerable additional expense for replacement due to wear in use and in slower production, due to the necessity of handling the chills.

Many of the castings in which the use of my invention. is beneficial are of complex design so that the practice of making the sections uniform cannot well be adhered to. Furthermore, some of them are of such a nature that they cannot be fed effectively because of the distance of the heavy section from the gate and the heavy section cannot be chilled effectively because the contraction of the casting during solidification would n \place while ramming up the core. Furthermore,

excessive this may be accomplished by fastening the chill I to the outside of the core whereas in the ordinary practice in the past the chill actually replaces a part of the core or mold. Chilling a casting in the manner disclosed in this application is inexpensive and unusually effective because the chilling takes place with a maximum exposure of the chill exactly where needed. Furthermore, the location, size and shape of the chill can be varie to suit the specific requirement.

lent from the description and claims. In the drawing, in which my invention is illustrated,

Figure 1 is a side elevation of a base plate casting in which my method may be used to advantage;

Fig. 2 is a plan view of the casting of Fig. 1;

Fig. 3 is an axial section showing the casting located in the mold with the core and chill properly located; and

Fig. 4 is a perspective view showing the manner in which the chill may be combined with the core.

Referring to the drawing in detail, the base plate casting shown comprises the circular plate proper 1 having an enlarged hub portion 2 on its lower side and an elongated tubular extension 3 on its upper side. In pouring this casting, without using my method, a sponginess and tearing Further objects of the invention will be apparapart occurs at or around the base of the elongated extension 3 and internally between the hub 2 and the extension 3.

To minimze these bad effects, a metal chill 5 is used, slots being cut in the two halves of the core box large enough to hold the chill in the exact place where it is desired. The two halves of the box are closed up with the chill in place and the core sand is rammed into the core in the usual manner, so that when the two halves of the core box are withdrawn from the core the chill clings rigidly to the outside of the core, as shown in Fig. 4. When the core '7 is located in the mold 8 as shown in Fig. 3 the chill 5 will be adjacent the line of juncture 4 of the heavier hub portion 2 of the casting with the lighter plate portion 1 of the casting. The results of this placing of the chill are remarkable and satisfactory. The resulting castings are almost perfect, showing no signs of cavities or tearing apart of the metal between the heavier section and the lighter section. When the casting is removed from the mold, the core is removed, leaving the metal chill as an integral part of the casting.

As indicated above, if the casting is made in the ordinary manner without any attempt to minimize the bad efiects of shrinkage, practically all of the castings are ruined by the shrinkage at the line of juncture between the relatively thin plate portion and the relatively heavy hub portion. By the use of my method practically all of the castings are substantially perfect at the line of juncture.

Further modifications will be apparent to those' skilled in the art and it is desired, therefore, that the invention be limited only by the prior art and the scope of the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. The herein described method of embedding an integral annular chill in the juncture of portions of relatively large and small cross-sections of a casting, during the making thereof, which includes positioning the chill around a core so that the latter supports the former inserting the core in the mould to bring the chill at the point of said juncture, pouring molten metal into the mould to surround the core and the chill, and removing the core without removing the chill after the pour whereby the chill forms a part of the casting at said juncture.

2. A method of making a base plate casting comprising a thin plate portion, a central boss extending from said plate portion, and reinforcing ribs uniting said central boss and plate portion and extending radially from said central boss, said boss and plate portions having a central opening therethrough whereby the boss is hollow, a substantial portion of the walls of said hollow boss being materially thicker than the adjacent portions of the casting, said method comprising forming a core for the central opening, placing an integral annular chill in a position to surround said core, and placing said core and chill in a mold in position to form a casting cavity wherein the chill will occupy a portion of the space defining the thick walls of the boss whereby the remaining portions of the thick walls are substantially the same thickness as the adjacent portions of the casting, and pouring molten metal into the mold to imbed the chill in said position, so that the detrimental effects of shrinkage in the casting are minimized.

3. A method of making a base plate casting comprising a thin plate portion, and a central boss extending from said plate portion, said boss and plate portions having a central opening therethrough whereby the boss is hollow, a substantial portion of the walls of said hollow boss being materially thicker than the adjacent portions of the casting, said method comprising forming a core for the central opening, placing an integral annular chill in a position to surround said core, and placing said core and chill in a mold in position to form a casting cavity wherein the chill will occupy a portion of the space defining the thick walls of the boss whereby the remaining portions of the thick walls are substantially the same thickness as the adjacent portions of the casting, and pouring molten metal into the mold to imbed the chill in said position, so that the detrimental effects of shrinkage in the casting are minimized.

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