US2359234A - Inserts for metal casting molds - Google Patents

Description

Patented Sept. 26, 1944 OFFICE INSERTS Fort METAL cAsTING MOLDS iiritia Mobs, J olinstown, Pa. N6 Drawing, Application June 6,

* Serial No. 4%,131

In accordance with the present'inventionthere are provided certain improvements in the com-v position of metallic inserts, or chaplets, which are tobe used in connection with, or placed in, molds receiving molten metal.

As is well known, such inserts, or chaplets, are employed to support cores in molds for receiving molten'metal or as internal members which," when placed in irregular shaped molds, provide more uniform cooling of the'irregular-shaped casting.

It, is, of course, a primary consideration in'the production of metal castings to produce a sound product, and the productionof soundcastings is oneof the major problems of the casting industry, because, as is well known, casting is resorted to to make 'products'of many different sizes and shapes, and unless a uniform cooling rate is maintained as the metal passes from the liquid to the solid state, some sections and intersections of the castings may be defective through the formation of piping, internal shrink cavities, and other defects. Where such difliculties cannot be remedied by the design of the molds, the method of feeding the metal into the molds, or the use of external chills, the metallic inserts must be used. The insert by its presence must not embrittle the section or weaken it.

The present invention is concerned particularly with the composition of inserts which are employed in the customary manner for eliminating internal defect of metal castings. In accordance with standard practice, the chaplets and/or internal insert members are made of low carbon steel and are used in all types of castings irrespective of the chemical analysis of the metal being cast. Such a low carbon insert has a high heat conductivity, and, therefore, causes the minimum fusion of the same with the surrounding metal, even though a chilling effect i produced. Furthermore, such a type of insert quite often produces or causes so-called contraction cavities, as well as a probable contamination and weakening of the casting. Because of these reasons, chaplets, or internal inserts have been avoided wherever possible in" the production of metal castings.

In accordance with the present invention, the foregoing difliculties are overcome by utilizing an insert made of a metal having a relatively low heat conductivity, such as, for example, stainless steel, which may be either of the straight chrome I type (12% chromium), or chrome-nickel type (18% chrome and 8% nickel), although such steels can include th following general compositions:

Inpractice, the insert preferably is employed in rectangular cross sections, because more surface is exposed per unit area, and it has been found in practice that there is a more or less definite relation between the cross sectional area of the insert and the cross sectional area of the casting as poured about the insert. For example, it has been noted in practice that the best results are obtained with a ratio of 1.5:; that is to say, the sectional area of the chill is approximately 1 percent of the area of the section being chilled.

It is important that the insert have a low conductivity; that is to say, the capacity of the insert metal for conducting heat must be substantially less than that of the metal with which the mold is filled. The straight chromium types of stainless steel have a coefficient of thermal conductivity which is about one-third that of ordinary (low carbon) steel. Chrome-nickel types have a coeflicient thermal conductivity about onefourth of that of low carbon steel.

At the same time, the insert metal should have a melting point that is within a reasonable range of the melting point of the metal with which the mold is filled. Otherwise, either (1) proper fusion may be retarded by the high refractoriness of the material, or (2) the insert will melt prematurely and float or diffuse. In the case of a chaplet, if the material composing it has a low melting point, it function as a support for a core is lost before the surrounding metal has solidified.

The insert of the present invention has the following advantages among others:

1. The insert has a relatively low thermal conductivity, which provides the maximum amalgamating efiect with the surrounding metal and results in a union producing an extremely sound casting.

2. The insert of the present invention is of the type wherein the melting point is not excessively high or low when contrasted to the melting :point of a metal being cast thereabout.

3. By virtue of the fact that the present insert is composed of stainless steel, the section of the metal as cast is materially strengthened due in part to some alloying eifect with the adjacent metal.

4. The insert of the present invention further exhibits the property of not cracking or disintegrating at the first shock of molten metal surrounding it, thus definitely locating and holding the predetermined point of chill or localized cooling action. 7

5. Because of the fact that the insert of the present invention is made of stainless steel, it is not susceptible to corrosion, and due to the absence of metal oxides thereon, it minimizes contamination of the metal in which it is located.

It will be understood that the term insert, as employed in the description and claims hereof, is intended to include both the chaplets and the internally inserted chills.

The present improved stainless steel insert is adapted particularly in the casting .of low alloy ferrous metal shapes. As has been indicated clearly herein, these improved inserts have a heat conductivity of not more than one-third of low carbon steel. By the term low alloy as used herein and'in the claims is meant, therefore, a ferrous metal alloy containing more than 50% iron, and having a heat conductivity of at least three times that of stainless steel.

I claim:

1. In casting low. carbon low alloy ferrous metal shapes, the improvement which consists in a mold core, having an insert of stainless steel having a heat conductivity of not more than onethird of low carbon steel.

2. In the casting of low carbon low alloy ferrous metal shapes, the improvement which consists in pouring the metal into a mold having a core in the presence of an insert of stainless steel having a heat conductivity of not more than onethird of that of low carbon steel.

3. In the art of casting low alloy ferrous metal shapes, the improvements which consist in pouring the metal in a mold having a core in the presence of an insert of stainless steel having a heat conductivity of not more than one-third of that of low carbon steel, and proportioning the cross sectional area of the insert to the cross sectional area of the casting so that the cross sectional area of the insert is approximately 1.5% of the area of the cross sectional area of the casting.

4. In the casting of low carbon low alloy steels, the improvement which consists in casting the steel in the presence of an insert of stainless steel having a heat conductivity of not more than onethird of that low carbon steel.

5. In the casting of low carbon low alloy steels, the improvement which consists in casting the steel in the presence of an insert of stainless steel having a heat conductivity of not more than onethird of that of low carbon steel, and proportioning the cross sectional area of the insert'to the cross sectional area of the casting so that the cross sectional area of the insert is approximately 1.5% of the cross sectional area of the casting.

6. In the casting of steel, the improvement which consists in casting the steel in the presence of an insert of stainless steel having a heat conductivity of not more than one-third of that of low carbon steel, the steel being poured being of a substantially different composition and type of alloy than the insert, and containing more than iron.

ERWIN H. MEBS.