US1743849A - Light metal alloy - Google Patents

Description

Patented Jan. 14, 1930 UNITEDS'TATES PATENT OFFICE JOHN A. GANN, OF MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COMPANY, OI MIDLAND, MICHIGAN, A CORPQRATIQN OF MICHIGAN LIGHT METAL ALLOY Application filed' July 26,

In Patent N 0. 1,377,374 to 'W. R. Veazey, dated May 10, 1921, there is described and broadly claimed a light metal allo of manganese with magnesium, in which t e magnesium largely predominates, as well as a method for preparing the same; also in another patcut to the same party, No. 1,334,193, dated March 16, 1920, there is described and claimed an alloy of the same type consisting specifically of manganese and copper with magnesium in predominant amount. The advantages resulting from the incorporation of a small amount of manganese in alloys of this 180 Drawing.

type are realized to even a fuller degree, I

5 have found, in connection with certain light metal alloys of the type in question but of a more complex character in that they include alsolimited amounts of certain other metals, for example, aluminum, cadmium and zinc,

2 or one or more of such last named metals in addition to copper'and manganese, and of' course, the base, which in all cases consists of 1 magnesium in predominant amount.

I am aware that a light metal alloy in which magnesium is the predominant element, such metal being preferably present in excess of 80 percent is described in Patent No. 965,485, to Pistor et al., dated July 26,

1910, aluminum being indicated as a desirable metal to make up the balance of the alloy; also in Patent N 0. 982,022 to Riibel, dated January 17 1911, the incorporation of magnesium with zinc in an amdunt from one to six percent is disclosed. However, the present combination of ingredients results in a product possessing distinctive and highly desirable properties which indicatea wide held of usefulness and render the alloy particularly desirable for employment in the manufacture of pistons for internal combustion engines and the like.

The invention then consists of the new product consisting of an alloy of the metals in question together with the steps involved in the making of such alloy, hereinafter ful- 1y described and particularly set forth in the claims. The following description it will be understood thm sets forth but several of M the various combinations of ingredients and 1926. Serial-No. 125,127.

but several of the various ways in which the invention may be carried out. I

The following formula which, savefor the last. mentioned ingredient is disclosed and separately claimed in theco-pending application of H. H. Dow and myself, filed December 12,-1921, Serial No. 521,695, is particus larly suitable for use in the pistonsor other like articles hereinbefore referred to viz: v

(1) Magnesium 88 percent; aluminum 8.00 percent to 8.25 percent; copper 2.00 percent; cadmium 1.00 percent; zinc 0.50 percent;and 0.25 percent manganese. The relative amounts of the ingredients may be varied from the foregoing and if desired,'one as or more of the ingredients other. than the manganese may be entirely left out e. g. the ,zinc, as indicated in the following formula v1z:

(2) Magnesium 91.75 percent; aluminum 2.0 percent; copper 4.0 percent; cadmium 2.0 percent; and manganese 0.25 percent.

In making the present improved alloy certain precautions require to be observed in view of the difficulty in introducin manganese inasmuch as the direct inter us'ion of this metal with magnesium involvesa temperature above the boiling point of such last mentioned metal. However, where aluminum is one of the otheringredients in the final 30 alloy the manganese may be first alloyedwith the aluminum in predeterminedamount so as to give, for example, an alloy having the .composition of7 5 percent aluminum and 25 percent manganese; or similarly, a cuproas manganese alloy maybe. prepared where coper is to be included in the finished. product;

uch alumino-manganese or cupro-manganese alloyis then added to the magnesium either before'or after the other metals e. g. cadmium and/or zinc are added and a homogeneous intermixture of the ingredients secured. 7

Another and entirely satisfactory method for preparing the present alloy is to make 05 up an alloy -'*'consisting of the ingredients other. than man ese; as prescribed in the foifmulas given aib e or other equivalent for- .-mnlas,lmaintaining a body of such alloy in a- 8uitable melting pot, taking therefrom, a 10! small quantity of the alloy in molten condition, for example, in a ladle, and addin thereto metallic manganese in powdered form. Upon then stirring up the metal in the ladle a certain amount of the manganese will enter into the alloy mixture, the balance remaining in solid i. e. undissolvedform in the bottom of the ladle. The molten contents of the latter are now poured back into the main body of the metal and a further quantity of the latter dipped into the ladle and stirred up with the residual manganese, this operation being repeated until the amount of manganese present in the mixture in the pot equals that called for by the formula.

Where copper is employed as an ingredient of the alloy under consideration it is always present in the eutectic and the cadmium is always present in solid solution. The zinc will also be present in solid solution but the amount present in this condition will vary somewhat depending upon what other constituents are employed in addition thereto. The rate of cooling of the casting also has an efiect on the percentage of such last mentioned metal that remains in solid solution, and so it is desirable that the highest limit possible be not approached as otherwise there is danger that some of the low melting magnesium-zinc eutectic will be formed. The introduction of manganese even in the relatively small amount indicated apparently not only improves the physical properties of the resulting alloy but has also the efiect of inhibiting corrosion. Presumably it is the manganese that goes into solid solution with the magnesium, forming a binary alloy that leads to this last mentioned result. while manganese even in finely powdered form has a distinct tendency to settle out of the magnesium, it is possible by the method last described above for making the alloy to have present a substantial excess of the manganese in the ladle and this has a mass. effect in tending to increase the amount that thus goes into solid solution. The aluminum of course also goes into solid solution with magnesium and as a result has the effect to salt out the manganese. It is accordingly desirable to restrict the percentage of aluminum to the minimum amount required to give the well known and desirable physical properties which this mgredient imparts. The copper on the contrary does not tend to the same extent to replace the manganese inasmuchas it does not go'into solid solution at all and for the foregoing reasons a formula on theorder' of the second one given above ismore readily made up with the desired amount of manganese and for certain purposes at least constitutes a superior product for the various uses to which light metals of the kind may be put.

one explained, change being made as regards the steps herein disclosed or the ingre 'ents employed in car g out such steps, provided the steps or ingredients set forth in the following claims or the equivalent of such steps or ingredients be employed.

1 therefore particularly point out and distinctly claim as my invention 1. As a new product, an alloy containing magnesium in excess of eighty per cent from one to ten per cent (1% to 10%) of aluminum, from one to five per cent (1% to 5%) of copper, from one-half of one per cent to four per cent (0.50% to 4%) of cadmium, and from one-tenthof one per cent to one per cent (0.10% to 1%) of manganese.

2. As a new product, an alloy containing magnesium in excess of eighty per cent (80%), from one to ten per cent (1% to 10%) of aluminum, from one to five per cent (1% to 5%) of copper, from one-half of one per cent to fourper cent (0.50% to 4%) of cadmium, from one-tenth of one per cent to one per cent (0.10% to 1%) of zinc, and from one-tenth of one per cent to one per cent (0.10% to 1%) of manganese.

3. As a new product, analloy containing approximately ninety per cent of magnesium, from two to eight per cent (2% to 8%) of aluminum, from two to four per fee cent (2% to 4%) of copper, from one to two cent to one per cent (0.10% to 1%) of man:

ganese.

5. As a new product, an alloy containing approximately ninety per cent (90%) of magnesium, from two to eight per cent (2%-8%) of aluminum, from two to four per cent (2%-4%) of copper, from one to two per cent (1%-2%) of cadmium, and onefourth of one per cent (0.25%) of manganese. 6. As a new product, an alloy containing approximately ninety per cent (90%) of magnesium, from two to eight per cent (28%) of aluminum, from two to four per cent (2%-4%) of co per, from one to two percent (1%-2%) o cadmium, one-half of one per cent (0.50%) of zinc, and one-fourth of one per cent (0.25%) of manganese.

Signed by me this 23rd day of July, 1926.

- JOHN A. GANN.

Other modes of applying the. principle of my invention may be employed instead of the