US2143423A - Method of casting metal - Google Patents

Description

Jan.. l0, 1939. W, E, REMMERS 2,143,423

METHOD OF CASTING METAL Filed March 27, `1935 5 Sheets-'Sheet l /A/ Vf N TOR W t'. RfMME/is 5y Afro/Mfr Jan. 10, 1939. w. E. REMMERS METHOD OF CASTING METAL Filed March 27, 1935 3 Sheets-Sheet 2 rrd ATTR/VEY `Fan. 10,1939. wl E. REMMERS METHOD OF CASTING METAL Filed March 27, i935 5 Sheets-Sheet 5 ATTORA/fy tienta im. ic, i939 PATENT oFFic METHOD OF CASTING METAL Walter E. Remmers, Western Springs, Ill., assignor to Western Electric Company, Incorporated, New York York, N. Y., a corporation of New Application March 27, 1935, Serial No. 13,229

' 2 Claims.

This invention relates to a method of l'casting metal and more particularly to a method of casting cobalt steel magnet parts.

The casting of cobalt steel articles presents many difculties. Due to the high shrinkage of cobalt steel, it is diiiicult to cast the metal to proper size and in many cases voids are formed in the center of large castings. There is also a tendency for cast cobalt parts to be porous.

An object of the present invention is to provide an effective and efcient method of casting cobalt steel magnet parts.,

In accordance with one embodiment of the invention, a high percentage of aluminum is added to the molten cobalt steel and the molten metal is cast in sand molds provided with liberal gatings and when large flat surfaces are involved, the

top of the mold cavity is crowned to obtain a,

hat surface in the molded article.

Other objects and advantages will appear as the description proceeds.

A complete understanding of the invention may be had by reference to the following description taken in conjunction with the accompanying drawings, in which Fig. 1 is a plan View of a mold for casting small magnet parts;

Fig. 2 is a sectional view taken on line 2--2 of Fig. l; a

Fig. 3 is a plan view of a mold for casting large magnet parts;

Fig. 4 is a sectional view taken on line 4--4 of Fig. 3;

Fig. 5 is an end view of the mold shown in Fig. 3;

- Fig. 6 is a plan view of a mold for casting another type of magnet part;

' Fig. 7 is a sectional view taken on line 1-1 Fig. 8 is a plan view of a mold for casting a horseshoe type magnet part; and

9 is an end view of the mold shown in 'Ihe type of material to which this invention particularly relates is cobalt magnet steel which usually contains cobalt from 5% to 40%, carbon from .4% to 1.25%, manganese from .1% to 2.5%, silicon .05% to 1.5%, chromium from 1.5% to 10.0%, tungsten 1.5% to 10.0%, and the balance iron. 'I'hese percentages refer to the more cornmonly used cobalt steels for permanent magnets; however, the invention is applicable to permanent magnet cobalt steel including other ingredients i and proportions. y

In the manufacture of cobalt steel in accord- (Cl. 'Z5-124) ance with this invention, a furnace, such as an arc furnace, may be charged with the proper proportions of scrap steel, cobalt and a high carbon iron, such as washed metal, and the charge melted. Ferro chromium, ferro manganse, ferro-silicon and ferro-tungsten are then added to the charge in proportions determined by the character of the scrap steel andthe composition of the final product desired. This charge is melted under a suitable slag covering. When the charge and the alloy additions are molten, a high percentage of aluminum ranging from .07% to .30% is added. It appears that when a charge such as described above is molten, oxygen is dissolved by. certain portions of the charge forming on solidication inert materials, poorly magnetic materials and generally deteriorating the steel by solutions of oxides therein and by preventing the proper alloying of the desired constituents. The addition of the aluminum not only tends to de- 'oxidize the materials of the charge but it also decreases the porosity of the resultant steel and improves its magnetic properties.

The molten metal is then cast into baked sand molds which are made of sand mixed with linseed oil in the proportion of about 60 parts of sand to 1 part of linseed oil. Figs. v1 and 2 illustrate a mold for casting small magnets. This mold comi. prises a lower portion 5 and an upper portion 6 having cavities l in the shape of articles to be cast and a large gate 8 is provided in the upper mold. On account of the high shrinkage of the cobalt steel upon solidication, the gate 8 should be extremely liberal. As shown in Figs. 1 and 2, the gate for casting the small magnets is of such a size as to hold approximately as much of the molten metal as comprised in the volume of the articles being cast. From the lower portion of the gate 8 the material ows through a narrow opening 9 into the cavities 1.

In the casting of larger magnets, as illustrated in Figs. 3 to 5, a liberally sized gate I l is also provided Which is supplemented by a large riser l2.

The cavity I3 of lthis mold is used for casting a In casting an article of the type illustrated in Figs. 3 to 5, in which a large plane surface is required over a large mass of material, it has been found advantageous to place the gate and riser as closely adjacent the largest mass of the article as possible. However, Where shapes such as shown in Figs. 6 and 7 or Figs. 8 and 9 are involved, the gate should be located at a portion of the article Where its mass is relatively small; and if the article is elongated, it should preferably be located at one end of the article.

Referring particularly to Figs. 6 and 7, a mold is shown having upper and lower mold portions 2l and 22. A gate 23 is provided at the peripheral edge of a small mass of the magnet part. A large vent 24 is provided above a portion 25 of the mold cavity which receives the largest mass of the article to be cast.

Figs. 8 and 9 illustrate a mold for casting a horseshoe type magnet part and comprises upper and lower mold portions 3l and 32. A gate 33 is provided at the end of one leg of the horseshoe shaped cavity and a small riser or vent 3d is provided at the end of the other leg.

The methods described prevent the formation of voids in the interior of the castings and produce castings of high density and good magnetic properties.

It will be understood that the embodiments of the invention herein disclosed are merely illustrativeand that many changes and modications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A method of cast-ing cobalt steel magnets which comprises melting a charge of cobalt steel having from 5% to 40% cobalt, .4% to 1.25% carbon, .1% to 2.5% manganese, .05% to 1.5% sili-

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