US1685653A - Magnesium alloy and method of making same - Google Patents

Description

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MAGNESIUM ALLOY AND METHOD OF MAKING SAME.

We Drawing.

The present improved alloy is one in which magnesium is the predominant elementfthe' object being to develop an alloy that will possess the characteristic lightness i'which is obtained by the use of magnesium tin-excess of,80 per cent, while such alloy will be characterized-by high strength and toughness as well as by having a fine grained structure when cast in the usual manner.

So far as I am aware, it has not heretofore been found feasible to heat the metals in question together for the purpose of alloying the same since this will presumably involve the use of a temperature above the boiling point of magnesium. By the present improved method, however, it hasbeen found possible to produce alloys of these two metals containing substantial amountsof chromium. corresponding with the amount for instance employed in various commercial steels in which chromium is 'an effective ingredient and exercising a marked influence in the resultant product. Such product having a a chromium content of less than 1 per cent is for all practical purposes no heavier than pure magnesium which of course is very much lighter than aluminum and the commercial' aluminum alloys; at the same'time, if properly cast, such alloy is of considerable greater tensile strength and impact-toughness without being-pnduly hard, while at the same time it possesses, as noted above, an

unusually fine grained structure when'made I up in the form of a casting, I

The invention, then, consists of a new product containing magnesium. and chromium in approximately the proportions indicated, together with the steps involved in the making of such alloys hereinafter fully described and particularly set forth in the claims. The following description, it will be understood, thus sets forthbut one of the various ways in which the principle of the invention may be carried out.

Briefly. stated, the improved. method of making the alloy in hand consists in interfusing a limited amount of a suitable chromium compound with an excess of magnesium, whereby such compound is reduced to the metal and thereupon fprms an alloy with the residuum of magnesium still largely exceeding the amount of the chromium thus reduced from the compound employed. Preferably chromium sesquioxide, C501, is

employed, although anhydrous chromic chlo- Y By the foregoing method I have succeeded r10 Application filed December 19, 19%. Serial No. 757,035.

ride, (lrCl may be utilized. The latter may be conveniently prepared by evaporatin a solution of the normal. chloride to a thick viscous syrup. This thick mass is then heated in an atmosphere of dry hydrochloric acid gas, whereupon the material swells to'many times its original bulk and gradually changes in color from green to pink, the final product being very light and fluffy.

For the purpose of introducing the chromium, a mass. of molten magnesium is first prepared preferably usinga flux of slightly greater specific gravity than the molten metal and having a sufiicient surface tension to cause it to form a film thereover and thus prevent exposure of the metal to the atmosphere. The chromium oxide, or chloride, as the case may be, is then added to such molten magnesium, the coating of flux on the latter being pushed aside so as to permit such oxide to come directly into contact with the metallic surface of the magnesium since it the oxide becomes wetted with the flux, it does not react or at least react readily. If necessary, a thorough inter-mixture of the oxide with the molten magnesium may be insured by stirring. However, the reaction of the magnesium. with the oxide occurs almost immediately, the latter being reduced to metallic form and incorporated in' the mass of molten magnesium to form the de sired alloy.

The molten alloy may then be conveniently removed from the crucible or melting pot by means of an ordinary ladle and is cast into bars or such other shapes as may be desired. The theoretical amount of chromium derived from any given quantity of the oxide may of course be readily calculated, but some of this apparently is lost in the reaction, at least less than the theoretical amount of chromium appears in the final alloy. However, the amount of oxide that requires to be added to the given alloy containing the desired number of hundredths per cent of chromium may be determined by deducting such loss in the theoretical amount as may be encountered in practice, all of which will be readily understood by anyone skilled in such matters. The amount of such alloying ingredient actually introduced may be checked by analysis, using the method ordinarily employed in the analysis of chrome-vanadium steel.

in combining as much as eight-hundredths (0.08) per cent of chromium with magnesium. In taking samples of this alloy, the metal comes. off in long ribbons instead of breaking into chips under the drill aspure magnesium does and in other respects, as hereinbefore set forth, a marked improvement in structure and physical qualities is obtained. I have also found it possible to add metallic chromium directly to molten mag nesium by heating the former with the latter in an iron crucible for a sufficient time, for example a half hour, and stirring with an iron rod: In order to clear the resultant alloy from occlusions'of flux and from. particles of the chromium that have not become properly alloyed, it is desirable to re-melt such alloy one or more times. By this method I have likewise obtained an alloy containing as high as eight-hundredths (0.08) per cent of chromium.

It will be understood that the foregoing method using chromium oxide with an excess of metallic magnesium, whereby the oxide is reduced to metal and thereby incorporated to form the desired alloy, is also applicable to the preparation of other alloys of magnesium with other metals of the chromium group. 1

Ot er modes of applying the principle of my invention may be employed instead of the one explained, change being'made as regards the composition and method herein disclosed, provided the ingredients or steps stated by any of the following claims or the equivalent of such stated steps be employed.

I therefore particularly point out and distinctly claim as my invention':--

1. As a new product, an alloy of magnesium with from one one-hundredth fto onetenth of one per cent of chromium.

2. As a new product, an alloy consisting of magnesium and a substantial amount but less than one tenth of one per cent of chromium. V

3. As a new product, an alloy consisting of magnesium and between approximately one one-hundredth and one-tenth of one per cent of chromium.

4. The 'method of making an alloy of chromium with magnesium which consists infusing into an excess of magnesium a small amount of a chromium compound to be reduced to metallic state by magnesium.

5. The method of making an alloy of chromium with magnesium, which consists in interfusing a'limited amount of chromium oxide in an excess of magnesium.

6. The method of making an'alloy of chromium with magnesium, which consists in adding to a body of magnesium in molten .state a small amount of a chromium compound adapted to be reduced to metallic state by the magnesium the amount of magnesium being'considerably in excess of that required to'reduce such compound, whereby the desired proportion of chromium is'incorporated.

7. The methodxof making an alloy of chromium with magnesium, which 7 consists in adding a limited amount of chromium oxide to a body of magnesium in molten state, the amount of magnesium beingconsiderably in excess of that required to reduce such oxide, whereby the desired proportion of chromium is incorporated; v

Signed by me this 17th day of December,

1924.. WILLIAM R. VEAZEY.