US1680262A - Light metal alloy - Google Patents

Description

lgg J. A. GANN LIGHT METAL ALLOY Original Filed OCT.. 27. 1921 BY @9a7 v ,1 TTORNEYA Patented Aug. 7, 192

A tata au @ico JOHN A. GANN, F MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COM- PANY, OF MIDLAND, MICHIGAN, A. CORPORATION 0F MICHIGAN.

LIGHT METAL ALLOY.

- Application led October 27, 1921, Serial No.'v510,794. Renewed August 26, 1926.

The present improved alloy is one in which magnesium is the predominant element, the object being to develop an alloy that will possess the characteristic lightness which is obtained by the use of magnesium in excess of 80 per cent, while such alloy will be characterized by high strength and high toughness, without sacrificing hardness unduly.

The field of use in the mechanical arts to lo which an alloy possessing the lightness and physical characteristics enumerated above may be applied is extensive and need not be described in detail for the purpose in hand. Where hardness rather than softness may be i5 considered desirable, as for example, when the metal is to be used in pistons of internal combustion engines, this characteristic may be improved if desired by adding one or more other metals in varying quantities, as will be hereinafter explained, the present invention consisting of an alloy of magnesium and tin with or without the addition of such further metals, together with the steps involved in the making of such alloy hereinau after fully described and particularly pointed out in the claims. The annexed drawing and following description, it will be understoodset forth but several of the various ways in which the invention may be carried out.

' In said annexed drawing The single ligure there appearing is a diagrammatic representation of certain physical properties discovered in a binary magnesium-tin alloy of the class in hand.

In such diagrammatic figure, the physical properties represented, it will be noted, are

, the impact-toughness, hardness and tensile strength, the hardness being determined by a@ the Brinell method and scaled to correspond with the single blow impact-toughness. Such impact toughness drops very rapidly with the addition of tin. The curve indicating this property becomes more nearly horizontal at higher percentages of added metal.

rlhe tensile strength, on the contrary, in-

creasesrapidly at first, then more slowly, and nally begins to fall ed, while the Brinell hardness increases slowly with the addition 5o of tin throughout the major portion of the range under consideration. For abinary alloy that will be properly balanced in respect 7to the characteristics in question, l prefer to use between 6 and 10 per cent tin.

ce ACastings made from the resulting alloy,

Where between 6 and 10 er cent of tin is thus utilized, the balance eing magnesium, will have a specific gravity from 1.80 to 1.90; tensile strength, from 18000 to 20000 pounds per square inch; Brinell hardness, from 38 to 41; and single blow impact-toughness, from to 30. l

U Where the alloy is to be used for pistons 1n internal combustion engines, or under conditions involving similar strains and temperatures, I have found that the addition of a small proportion of aluminum is advantageous to impart increased hardness and toughness to the resulting product. A satisfactory formula for such a ternary alloy using my improved binary magnesium-tin alloy as a base, is as follows :-88 per cent magnesium, 8 per cent tin, and 4 per cent aluminum, Still better results arey obtained for the particular field of use referred to by the further addition of a small proportion of copper or cadmium, a satisfactory formula iin such case being as follows, viz :-86 per cent magnesium, 8 per cent tin, 4 per cent aluminum and 2 per cent cadmium.

Even where the proportion of aluminum thus added is greater than that of tin, as in the following formula,` viz :-90 per cent magnesium, 8 per cent aluminum and 2 per cent tin, the characteristics noted above as having been, discovered in the simple binary alloy of magnesium and tin will be retained to a perceptible degree.

To make my improved alloy, a measured quantity of pure magnesium metal is first melted in a suitable pot along with the proper amount of a flux that, while heavier than such metal, will have proper surfacetension :to promptly and effectively coat the metal. As an example of such a flux, approximately equal parts of anhydrous magnesium chloride and sodium chloride may be employed, and if the specific gravity of such flux proves inadequate to oat the metal after it has been alloyed, a small amount of barium chloride may be added. A small amount of the molten magnesium metal is then taken up in a ladle and all or a part of the tin, depending on the total percentage of the latter to be added to the batch,v is first placed in such ladle and melted with the magnesium therein, thereby producing an alloy relatively high in tin. The contents of the ladle are then gradually added to the Mtl main.-A body of molten magnesium, with the result that the tin will diffuse throughout the mass and not drop through into the body of flux on which the lat-ter floats and so be lost. As soon as the introduction of the tin alloy has been effected, the whole mass is Well puddled, and the operation may then be regarded as complete and-the molten alloy cast either into ingots or directly into the form of mechanical parts, such as pistons or the like for which it is intended to be used.

Where either aluminum or cadmium, or both, are to be added to the binary alloy in accordance with formulas such as hereinbefore set forth, the relatively small amount of such additional metal or metals may be separately introduced in the same fashion as the tin, or they may be at once added along with the tin in forming the preliminary alloy which is subsequently added to the main body of the molten magnesium metal, resulting in the product-ion of an alloy in which such magnesium is the predominant ingredient. Again, in some cases, it may be more advantageous to add to lthe magnesium in the ladle a magnesium alloy rich in the alloying metal, instead of such metal by itself. p

For convenience in defining the relative proportions of the metals that enter into the alloy, the magnesium may be referred to as present in-.predominant amount, meaning an amount on the order of 80 per cent or more of the total; while in referring to the presence of other constituents in substantial but relatively small amounts, it will be understood that amounts are meant on the order of those specified in the formulas hereinbefore set forth, due regard being given to the fact that the total of such other ingredients will decrease as the amount of the predominant constituent is increased.

Other modes of applying the principle of my invention may be employed instead of the one herein explained, change being made as regards the steps herein disclosed or the ingredients employed in carrying out such steps, Aprovided the steps or ingredients not less than eighty nor more than ninetynine and one-half per cent of magnesium,

and not more than twenty nor less than one half of one per lcentof tin.

2. As a new product, an alloy containing from ninety to ninety-four per cent of magnesium, and from six to ten per cent of tin.

.3. As a new product, an alloy containing not less than eighty nor more than ninetynine per cent of magnesium, not more than twenty nor less than one per cent of tin,

and aluminum in relatively small proportions.

4. As a new product, an alloy containing notless than eighty nor more than ninetynine per cent of magnesium, not more than twenty nor less than one per cent and aluminum and cadmium in relatively small proportions.

5. As a new product an alloy containing approximately the indicated percentages of the following metals, cent of magnesium, eight per cent of tin and four per cent of aluminum.

6. The method of making a magnesiumtin alloy, which consists in first inter-fusing the desired amount small quantity of magnesium, and then adding the resulting alloy to th'e remaining quantity of magnesium in molten state. i

7. The method of making .a magnesiumtin alloy, wherein predominates, which consists in iirst interfusing the desired amont of tin with a relatively small quantity of magnesium, where by an alloy'high in tin is produced, and then adding such result-ing alloy quantity of magnesium.

Signed by me, this 24th day of October,

JOHN A. GANN.

of tin,

of tin with a relatively the magnesium largely to the remaining

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