US1544710A - Casting magesium - Google Patents

Description

UNITED STATES cross REEERENCE 1,544,710 PATENT OFFICE.

ODIN WILHELMY, OF CLEVELAND, OHIO, ASSIGNOR TO AMERICAN MAGNESIUM COR- PORATION,

OF NIAGARA FALLS, NEW YORK, A CORPORATION OF NEW YORK.

' CASTING MAGNESIUM.

No Drawing.

To all whom it may concern:

Be it known that ODIN VILHELMY, citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, has invented certain new and useful Improvements in Casting Magnesium, of which the following is a specification.

My invention relates to the casting of magnesium and high magnesium alloys and one of the objects is to provide a sand core which will not cause defects in the cast metal such as blow holes, rough surface and discoloration which now result from the use of the customary materials.

Another object of the invention is to provide a. core having such-strength and rigidity as will permit handling without breaking and yet will crush when the surrounding metal shrinks.

A further object of the invention relates to the treatment of the sand mold to give it a smooth hard surface.

With these and other objects in view, my invention consists of the ste s hereinafter fully described and particu arly pointed out in the claims.

In the casting of magnesium, it is neces sary to pour the metal as near as possible to its melting point, in order 'to prevent excessive oxidation and burning, with the result that the metal solidifies quickly after pouring.. Due to the lightness of the metal, which prevents the forcing of trap ed gases through the cores and mold, and a so to its quick solidification, trapped gases, cold shuts and blow holes have always been serious problems and have made it necessary to seek solutions other than those applied in the case of other metals. In fact, all the problems which arise in the casting of other metals seem to be present in an aggravated form in the casting of magnesium and magnesium base alloys.

While. proper venting of the cores and molds has very often remedied these faults to some extent, by im rovement has been in the direction of the e imination of'certain factors in the customarycores and molds, which are deleterious on account of the peculiar properties of magnesium. The first step in my improvement has been to eliminate from the core material, any ingredients which would volatilize at the pouring temperature of the metal.

Organic binders, such as molasses, oils,

Application filed January 23, 1922. Serial No. 531,291.

which the binder is completely decomposed or at which it is no longer volatile at the pouring temperature, then it becomes weaker and less suitable for use.

The exigencies of the situation therefore necessitate the selection of an inorganic binder which will undergo no change at the pouring temperature of the metal which it has not already undergone atthe baking temperature of the core. The material which I have found to best meet these reqnirements and is otherwise suitably adaptcd is water glass.

In using it as a binder, a solution of commercial water glass is diluted with an equal quantity of water and thoroughly mixed.

This is then mixed with a more or less standard coarse sand mixture in the proportion of about 1 lbs. of liquid to 20 lbs. of dry sand. Additional water is added to the mixture as the consistency of the sand requires. After having molded the core into the desired shape, it is sprayed all over with the diluted water glass solution and baked at a temperature of approximately 250-350 degrees On baking the core, the water glass becomes dehydrated and assumes an amorphous form. Whether or not all of the chemically combined water is driven off by the baking heat cannot be definitely stated, but apparently there is no further substantial dehydration of the water glass when the molten magnesium comes in contact with the baked core. v

In using this core material, no gases seem to be liberated at the temperature of the molten ma nesium, which are not already drivenoii during the baking.

Castings made with'such cores show none of the defects resulting from the use of or- EXAMINER a' binder and is then sprayed over with a diluted water glass solution and thereafter baked at a temperature sufiicient to dehydrate the water glass.

The efi'ect of spraying the outside of the cores and the faces of the molds is to give a smoother, harder surface, which eliminates the crumbling of the dried sand after baking and results in a smoother surface on the finished casting.

In the case of the water glass facing for the mold, it is possible also that it'acts to prevent escape of gases into the 'metal from the mold. a

It will be understood that other modes of applying the principle of my invention may be employed than that specifically herein set forth and while I have described the preferred embodiment thereof, it will'be understood that I reserve the right to all changes properly falling within the scope and spirit of the appended claims.

I claim: a

1. The process of making a casting of magnesium which comprises forming a core from sand with a binder containing water glass, substantially dehydrating the water glass and casting molten magnesium in a mold around said core.

2. The process of making a casting of magnesium which comprises forming a core from sand with a binder containing water glass, applying a coatin of water glass to the said core, substantially dehydrating the Water glass, and casting molten magnesium in a mold around said core.

3. The process of making a casting of magnesium which comprises forming a core.

nesium in a mold around said core.

4. The method of making cores for casting magnesium comprising mixing sand and water glass to the desired consistency, forming said mixture'into the desired shape and then baking at a temperature sufficient to drive off all matter volatile at the temperature of molten magnesium.

5. A sand mold or core for casting magnesium having a smooth hard exterior of subst-antiall dehydrated water glass.

6. A san( mold or core for casting magnesium having a smooth hard exterior of substantially dehydrated Water glass and a soft interior.

7. A sand core for casting magnesium characterized by asmooth hard exterior of substantially dehydrated water glass and a