US2303105A - Alloy - Google Patents

Description

Patented Nov. 24, 1942 ALLOY and Gerald Edmnnds,

Edmund A. Anderson assignors Zine Company, New York,

Palmer-ton, Pa,

oi New Jersey to The New Jersey N. 1., a corporation No Drawing. Application September 9, 1941, Serial No. 410,163

Claims. (Cl. 75-134) This invention relates to zinc alloys and aims to decrease loss of impact strength of zinc alloys containing manganese and aluminum during prolonged aging of such alloys at moderately high temperatures. Our invention contemplates zinc base alloys having manganese as a principal constituent and containing aluminum and characterized by the addition of a small proportion of titanium. These alloys have an appearance similar to that of white metal alloys. They have high tensile strength and high impact strength, as well as the ability to retain adequate impact strength during prolonged heating at moderate temperatures. l

It has been proposed heretofore, for example in our co-pending application SerialNo. 314,086 filed January 16, 1940, (Patent No. 2,272,390, granted February 10, 1942) to alloy zinc with a relatively large proportion, say, 7.5% to 48.5% of manganese. These alloys, which also contain a small proportion of aluminum, say, 0.02% to about 5%, and may contain copper in efiective proportions not exceeding about 26V and iron in eil'ective proportions not exceeding about 6% are characterized by high creep resistance and have, as cast, impact strengths of at least onefoot pound per one-quarter inch square section and tensile strengths of at least 60,000 pounds per square inch. Such alloys have numerous applications because they may be formed into intricate shapes of accurate configuration by die casting, and are also stronger and harder than other heretofore customary zinc die-casting alloys. However, alloys containing zinc, manganese and aluminum tend to lose impact strength upon aging at moderately high temperatures, say, 90 C.-400 C.

As the result of our investigations, the field of application of such alloys has been broadened substantially for we have discovered that the addition of a small proportion of titanium to zinc-manganese-aluminum alloys containing from about l /2% to about 48 /2% manganese and from about 0.02% to about 5% aluminum tends to decrease loss of impact strength during prolonged heating at moderately high temperatures. Thus, we have discovered that titanium in small proportions (say from about 0.2% to about 6%) eflectively decreases loss of "impact strength in zinc-aluminum-manganese alloys which are exposed to moderate temperatures, say, up to 400 F. over long periods.

The alloys contemplated herein may and preferably do contain ingredients other than zinc, manganese, aluminum and titanium.

Copper in eflective proportions up to about 26%% is a desirable ingredient. The optimum copper content for the alloy is dependent upon the manganese content. Thus, as disclosed in our aforementioned ,co-pending application Serial No. 314,086, the proportion of copper present should be so related to the manganese content as to define a point lying within certain areas on trilinear charts representing the zinccopper-manganese system, and the total amount of manganese and copper should not exceed about 56%. These charts are reproduced in the above-entitled co-pendlng application (Patent No. 2,272,390) and show the required relationship of manganese and copper contents to produce alloys having impact strengths respectively in excess of 1, 2, 4 and 8 foot-pounds per onequarter inch square section.

The alloys contemplated herein may also contain a relatively small proportion of iron, say, not to exceed about 6%, the optimum proportion of iron being somewhat dependent upon the copper and manganese content of the alloys as well as upon the proportion of titanium present.

In the manufacture of the alloys of our invention, as described and claimed hereinafter, it is not essential in all cases to employ high grade metal and particularly high grade manganese, for the impurities that may occur in the ordinary commercial grades of the major constituents may be included in our alloys in at least some cases without too serious effect upon the properties of the alloys. Thus, manganese suitable for use in the practice of our invention may contain minor proportions of silicon, phosphorus, carbon, nitrogen, and other impurities. We prefer, however, to employ manganese of high purity (except with respect to iron), for impurities in the manganese may degrade the mechanical properties of the alloy and, in particular, cause the presence of hard particles that may interfere with machining and bufling.

To summarize, our invention contemplates decreasing loss of impact strength during prolonged heating at moderately high temperatures of alloys containing zinc, manganese and aluminum by introducing into the alloys prior to the heating a small proportion of titanium. Thus, our invention contemplates zinc alloys with manganese in proportions ranging from about 7 /2% to about 48 /2%, and titanium in proportions ranging from about 0.2% to about 6%. The alloys of our invention contain, in addition, a small proportion of aluminum (say 002% to 5% and preferably 0.1% to 2%) which improves the casting characteristics of the alloys and also tends to sup- 'preas oxidation of the surfaces of' hot castings so that they may be cooled in air without serious discoloration. Copper may be present in proportions up to 26 and iron in proportions up to 8%, all percentages herein being by weight. The exact amount of zinc present in the alloy is not critical and may be as low as 33% if the maximum amounts of manganese, copper, titanium, and aluminum are present in the alloy, or even as low as about 27% if the alloy also contains the maximum amount of iron. On the other hand, if the manganese, copper, titanium, aluminum, and iron are present in minimum amounts, the amount of zinc present may be as high as 92%.

As indicated above, iron is a desirable ingredient in our alloys. In their manufacture, it is our practice to add the titanium in the form of ferro-titanium containing about 40% titanium the balance being substantially iron), or in the formoi' a manganese-titanium alloy containing about 25% titanium, 62% manganese (the balance beingiron and impurities). The titanium may also be added as high grade metal, but in view of the extremely high price of this high grade titanium, and having regard for the fact that iron not only may be tolerated but actually enhances certain desirable properties of the alloy, preferred practice is to employ ferro-titanium alloys.

The alloys of our invention are relatively hard, having a Brinell hardness ranging from 262 to 140. In general. the alloys having a relatively high copper content are hardest while those of a relatively low copper content are, in general, comparatively soft.

The alloys of our invention are not subject to the temperature embrittlement that occurs in many zinc alloys at very low temperatures. Thus, they may be cooled to temperatures as low as 40 C. without becoming brittle. The alloys also have high creep resistance, a modulus of elasticity as high as 14,000,000 pounds per square inch, and apparent rigidity or stiffness to a degree greater than that of any other zinc alloys of reasonable ductility. All of the alloys of our invention are machinable. The alloys of our invention manifest good resistance to atmospheric corrosion and in this respect are roughly comparable to zinc base die-casting alloys Nos.

xxr, xxm and XV of A. 8. T. M. tentative specification B86-38T-l938.

We claim:

1. A zinc alloy containing titanium ranging between about .2% and about 6%, about 7.5% to about 48.5% manganese,'about .0296 to about 5% aluminum and the balance being made up substantially of zinc, the alloy being characterized by the ability to retain a higher proportion of its impact strength during prolonged heating at moderately high temperature than a zinc alloy oi similar composition but without titanium.

2. A zinc alloy containing titanium ranging between about 2% and about 6%, about 7.5% to about 48.5% manganese, about 0.02% to about 5% aluminum, and copper in effective proportions up to about 26.5%, the remainder of the alloy being made up substantially of zinc.

3. A zinc alloy including about 0.2% to about 6% titanium, about 7.5% to about 48.5% manganese, about 0.02% to about 5% aluminum, and about 27% to about 92% zinc, the alloy being characterized by the ability to retain a higher proportion ofits impact strength during prolonged heating at moderately high temperature than a zinc alloy of similar composition but without titanium.

4. A zinc alloy including about 0.2% to about 6% titanium,about 7.5% to about 48.5% manganese, about 0.02% to about 5% aluminum, iron in eileetive proportions up to about 6%, and about 33% to about 92% zinc, the alloy being characterized by the ability to retain a higher proportion of its impact strength during prolonged heating at moderately high temperature than a zinc alloy of similar composition but without titanium.

5. A zinc alloy including about 0.2% to about 6% titanium, about 0.02% to about 5% aluminum, about 7.5% to about 48.5% manganese, copper in effective proportions up to about 26 /z%, with the total amount of manganese and copper not exceeding about 56%, and about 33% to about 92% zinc, the alloy being characterized by the ability to retain a higher proportion of its impact strength during prolonged heating at moderately high temperature than a zinc alloy of similar composition but without titanium.

EDMUND A. ANDERSON. GERALD EDMUNDS.

I CERTIFICATE OF CORRECT-ION. 1 Patent No. 2,505,105. November 215., EDMUND'A. ANDERSON, ET AL.

It is hereby certified, thaferror appears in the 'printed specification of the above numbered pat ent requiring correction as follows: Page 2, second column', line 3, beforev "we claim-:''' insert the following paragraph:

Alloys corresponding in composition to those of the invention except that they contain substantially no titanimnlose impact strength with relative rapidity and to a serious extent through aging at moderate temperatures. The alloys of our in- I "Yention containing titanium but with substantially no iron re tain adequate impact strengths after aging at moderate temperatures (say 95 C; 200 C and those ing both ir n and titanium tend to be still better, in that they retain a higher proportion of their original impact strengths after long heating periods I and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. p

Signed and sealed this 12th a of January, A'.-D. 1915.

Henry VanArsdale, 1 '(Seal) Acting Commissioner of Patents.