US2236831A - Method of alloying calcium with magnesium - Google Patents

Description

Patented Apr. 1, 1941 r METHOD OF ALLOYING CALCl UM wrrn MAGNESIUM Charles E. Nelson, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich" a corporation of Michigan No Drawing. Application October 25, 1939,

Serial No. 301,170

2 Claims.

The invention relates to a method of alloying calcium with magnesium or magnesium base alloys.

It is a well known fact that, if an attempt is made to alloy a small amount of calcium with magnesium to produce magnesium base alloys, it is exceedingly difficult, if not impossible, to predict the amount of' calcium that will be required in order that an alloy of the desired composition will be produced. This is due to the fact that the melting point of the calcium is so high, that it tends to burn or oxidize before it can be properly alloyed, even when protective means are employed in carrying out the operation. For this reason, an unpredictable or unknown amount of calcium is lost during the alloying operation, thus resulting in an alloy of unknown calcium content. A further difliculty is encountered when attempting to alloy calcium with magnesium due to the fact that it is difiicult to keep the surface of the calcium metal clean enough to alloywith magnesium. For example, since calcium metal deteriorates rapidly in storage due to the formation of an oxide or hydroxide coating on its surface. it is usually necessary to thoroughly clean the surface of the metal by sand blasting every time it is used. This is not only a time-consuming operation, but it also results in loss of a very substantial amount of metal due to oxidation if the calcium 1 is stored for any length of time.

It is, therefore, an object of the invention to provide a source of calcium having a low melting point so that it may be suitably alloyed with magnesium base alloys without burning of the 1 a definite amount of calcium to be readily added to magnesium base alloys and at the same time a source of calcium is provided that may be stored over long periods of time without loss of metal due to surface oxidation. Further, the surface of the calcium alloys containing a small pertion or deterioration had taken place.

centage of magnesium resist corrosion so efiectively that it is usually unnecessary to subject the metal to a cleaning operation before alloying it with magnesium base alloys.

The amount of magnesium to add to form a calcium base alloy having the above characteristics is from 18 to 23 per cent and preferably between about 20 to 22 per cent. Alloys of this composition have a melting point of from 430 to 470 C. as compared to 810 C. for pure calcium and thus serve as a source of calcium that may be readily alloyed with magnesium without burning of the calcium. As aforementioned, these calcium alloys possess highly desirable surface corrosion characteristics.

As an illustration of the superior surface oxidation characteristics of the calcium rich alloys as compared to calcium metal, a calcium alloy was made up containing about 20 per cent magnesium and stored for over a year. After this time, it was observed that no appreciable oxida- On the other hand, pure calcium stored in a similar manner deteriorated rapidly from day to day so that a block of the metal completely disintegrated in much less than a years time.

These alloys containing from 18 to 23 per cent magnesium are best made by adding the requisite amount of clean pure calcium to molten magnesium with stirring while protecting the surface of the molten metals with natural gas. It is preferable to add the calcium to the molten magnesium, since the temperature required is much lower than when the metals are alloyed in the reverse order, and thus less loss due to burning of the calcium takes place.

In employing the above alloys as a source of calcium when making calcium additions to magnesium or magnesium base alloys, it is preferable to bring the desired quantity of the calcium rich alloy into contact with the molten magnesium or magnesium base alloy. It is generally preferable to make the addition under the protection of a suitable flux such as the conventional potassium chloride-sodium chloride flux or while the molten magnesium is maintained under a protective gas such as natural gas, sulphur dioxide, hydrogen or the like.

In this manner, a predictable and definite amount of calcium can be added to magnesium base alloys as desired without difliculty due to burning of the calcium, and at the same time a convenient source of calcium is furnished which may be stored over long periods of time without loss due to surface oxidation.

Other modes of applying the principl of my invemfiion may be employed instead of the one explained, change being made as regarrds the method herein disclosed, provided the step stated by any of the following claims or the equivalent of such stated step be employed.

I therefore particularly poinl: out and distinctly claim as my invention:

1. The method of alloying calcium with magnesium which comprises incorporating molten 10 CHARLES E. N ELSON.