US2380922A - Zinc base alloy - Google Patents

Description

Patented Aug. 7, 1945 2,380,922 zmc BASE ALLOY Edward S. Bunn, Bome, N. Y., to Revere Copper and Brass Incorporated, Home, N. 1., a corporation of Maryland -No Drawing. Application September 9, 1943.

Serial No. 501,869

4 Claims. (Cl. 75 -178) My invention, which relates to zinc base alloys, and has among'its objects the provision of a zinc b'ase alloy of improved characteristics, will be best understoodfrom thefollowing description, the scope of the invention being more particularly pointed out in the appended claims.

Alloys according to the invention contain 0.1 to 5.5% copper, and 0.05 to 0.9% each of aluminum and antimony.

Zinc, it will be understood, has a moderate tensile strength,- very satisfactory ductility, and sumcient plasticity to enable it to be readily worked commercially either hot or cold to produce sheets, rods, etc. Zinc, however, among other defects has that of being subject to pronounced grain growth when it ages and when exposed to temperatures much in excess of, room temperature,- causing its tensile strength to be much reduced and its ductility almost to disapnary commercial zinc when hot rolled will have a tensile strength of about 17,000 pounds per square inch and a ductility represented by an elongation of 45% in 2 inches, and when such hot rolled zinc is heated to 600 F. for'l hour its .20 tensile strength will be reduced to about 6,000

pounds persquare inch and its elongation to about 4% in 2 inches, while'when subjected to moist steam at 95% C. for 10 days, which is the standard accepted test for determining the effect of age on aim and its alloys, will have its tensile strength reduced to about 11,000 pounds per square inch and its elongation to about 2% in 2 inches.

The attempt to. cure grain growth in zinc'by adding to its small amounts of other metals commonly results inthezinc being subject to intercrystalline corrosion. However, applicant has found that grain growth may be much reduced without causing appreciable intercrystalline corrosion by adding small amounts of copper to the zinc, while at the-same time markedlyincreasing its tensile strength-although with an unsatisfactory loss in its ductility for many uses if the amount of copper is increased much above 2%. Although the resulting binary alloy is com-= mercially hot workable, it cannot besatisfactorily commercially cold rolled into sheets if the 1 amount of copper is above 3 to 4%.

Applicant has found that if small amounts of both copper and aluminum are added to zinc, although much increasing its tensile strength as compared towhen copper-alone is added, its ductility and stability of the same with age are reduced to a very unsatisfactory extent. Further, as the resulting alloy ages deleterious intercrystalline corrosion commonly occurs, and likewise an alloy phase changecommonly takes place, either of which acts, among other things, to make the resulting alloy unstable in respect to dimensions. Such zinc-copper-aluminum alloy, besides being unsatisfactory in all the respects above mentioned, further has poor workability. For the above reasons, although the addition of the aluminum is desirable from the standpoint of its securing a great increase in the tensile strength of the alloy, the latter nevertheless has a limited use, being commonly suit- I able only for die castings.

It has further been found by applicant that if a small amount of sflver is added to the zinc with the copper and aluminum, the silver tends to cure the defects tended to be imparted by the aluminum in the ternary zinc-copper-aluminum pear under these conditions. For example, ordi- 20 fectively prevents intercrystalline corrosion,

alloy phase change and dimensional instability. Further, the resulting quaternary alloy still has a very high tensile strength. However its ductility and workability, although far superior to those of the ternary zinc-copper-aluminum alloy, are commonly such as limit the greatest field of usefulness to making articles of high unit strength by hot forging operations.

Applicant also has found that a combination of small amounts of silver and metal of the group consisting of managanese, iron, nickel and cobalt will give superior results when added to the ternary zinc-copper-alumimim alloy as compared to when silver alone is added to it. this combination securing the same beneficial efiects as when silver alone. is added and at the same time securing superior ductility without a great sacrifice in the high tensile strength of the ternary alloy, and also securing greater stability in respect to tensile strength and ductility when the alloy is annealed or aged.

Applicant has found that results, comparable 'to those securedby adding to the'ternary zincby adding small amounts of antimony to it as a corrective, and that when so employed the antimony is less critical than the combination ,rolled into sheets, and this is also true of at least -dition of antimony has a high tensile strength and resistance to shock or impact loading, good ductility, and satisfactory stability in respect to all these properties' for most uses. At the same alloy commonly will have the same time the alloy is not subject to intercrystalline corrosion or deleterious alloy phase change with age. Likewise the improved alloy is satisfactorily free from grain growth, and is stable in respect to maintaining its dimensions with age. It has a high plasticity when hot throughout the ranges I of its constituents. enabling it tobe readily commercially hot rolled, extruded and forged. With amounts of copper about 1.5% or more the im-' proved alloy has a very high cold plasticity enabling it to be very readily commercially cold the alloy with amounts of copper less than 1.5% provided the amount of antimony in such case does not exceed approximately the amount of aluminum. the alloy with this lower amount of copper combined with an amount of antimony exceeding the amount of aluminum being best suited for hot working.

The above results of-the improved alloy will be secured when, within the ranges mentioned of the constituents, the sum of the amounts of aluminum and antimony does not substantially exceed the amount of copper, as otherwiseno assurance will be had that intercrystaliine corrosion will not occur or that the alloy will have satisfactory dimensional stability. Although best results commonly will be secured in respect to ductility when for a given amount of copper the amount of aluminum is substantially greater than the amount of antimony, best. resultsin respect to stability of the ductility with age commonly will be secured when the amount of antimony is not substantially less than,the amount of aluminum. However, gene 7 c nsidered, best results in respect to all around good properties will be secured with at least 0.35%. copper, 0.05 to 0.45% antimony and 0.3 to 0.9% aluminum with twice as much aluminum as antimony.

Further, to secure best results in respect to intel-crystalline corrosion and resistance to corrosive media it is desirable to employ in the improved alloy commercial'zinc of fairly high purity as, for example, that termed Hi h Grade No. 1" in A. S. latter grade contains a maximum of 0.07% each or lead and cadmium of 0.02% iron impurity, thetotal of such of these impurities as may be present not exceeding 0.1%, and is substantially free from. all other impuri- T. M. specification Bil-37. which ties. With poorer commercial grades of zinc the mechanical characteristica'but may be somewhat less corrosion resistant in bothrespects mentioned and have more or less dimensional instability.

The excellent properties of the improved alloy are exhibited by the table, appearing below, in which the steam test referred to is that above mentioned.

Hotroilsd, v Hotrclled, a w new "sisa for 1hr. subicctedto v steamtsst Cu lu Sb '1 a 'r a 'r a o o o' i7 45 s 4 a 2 1 0.0a 0.1:; as 21 so 24 so 1 as 0.1 as as as 25 21 15 s 0.05 0.15 48 so 41 so 41 a0 s as 0.1 s2 so an t 4s 15.

T tensile strength in l 000 ds care inch. E per cent elongation ina chu. q

impurities and a maximum It will be understood that, within the scope of the appended claims, further constituents may be added for modifying the properties of the improved alloy or for securing additional properties, so long as the characteristics imparted to the zinc by the additionof copper, aluminum and antimony are not substantially destroyed.

I claim:

l. Zinc base alloys having. approximately, 0.1 to 5.5% copper. 0.05 to 0.9% aluminum, and 0.05

- to 0.9% antimony. the sumof the percentage amountsof aluminum and antimony not substantially exceeding the percentage amount of copper, the balance being substantially zinc.

2. Hot and cold workable zinc'base alloys having, approximately, 0.1 to 5.5% copper, 0.05 to 0.9% aluminum, and 0.05 to 0.9% antimony, the

percentage amount of aluminum being at least the percentage amount of antimony when the percentage amount of copper does not exceed 1.5%, the sum of the percentage amounts of aluminum and antimony not substantialily exceeding the percentage amount of copper, the balance being substantially zinc.

3; Zinc base alloys having, approximately, 0.35 to 5.5% copper, 0.3 to 0.9%

stantially exceeding the percentage amount or.

copper, the balance being substantially zinc.

4. The alloys according to claim 1 with the percentage amounts of antimony not less thanof aluminum.

the percentage amounts EDWARD S. BUNN.

aluminum, and 0.05 to 0.45% antimony, the percentage amount of