US2392643A - Zinc base alloys - Google Patents

Description

Patented Jan. 8, 1946 ZINC BASE ALLOYS Edward S. Bunn, Baltimore, Md, assignor to Revere Copper and Brass Incorporated, Rome, N. Y., a corporation of Maryland No Drawing. Application November 23, 1943,

Serial No. 511,475

4 Clams. (Cl. 75-178) My invention, which relates to zinc base alloys and has among its objects the provision of a zinc be/se alloy of improved characteristics, will be best understood from the following description, the scope of the invention being more particularly pointed out in the appended claims. 7 Alloys according to the invention contain small amounts of copper, silicon and phosphoruswithin the ranges and proportions hereinafter more particularly pointed out.

As will be understood by those skilled in the art, zinc, although having an excellent degree of ductility and being readily hot and cold worked, has a relatively low tensile strength and a very low degree of toughness. Further, its tensile strength seriously decreases as it ages, and its ductility and toughness almost disappear. For commercial applications of zinc it is therefore highly desirable to increase its tensile strength and toughness while maintaining its ductility and workability, and at the same time prevent the tensile strength, toughness and ductility from.

deleteriously decreasing as the metal ages, and to secure these results without making the metal subject as it ages to deleterious intercrystalline corrosion or deleterious dimensional change, which deleterious effects commonly are encountered in the attempt to secure these results by adding to zinc small amounts of other substances.

Applicant has found that the above mentioned desired results may be'secured by additions to zinc of small amounts of copper, silicon and phosphorus, the tensile strength secured being superior to that of zinc and commonly markedly so with only a slight decrease in the same as the alloy ages. At the same time the ductility is very high without in any instance which has been observed tending to materially decrease as the alloy ages. In fact the ductility of the aged alloy is in most instances as good as or better than that of unaged zinc. The toughness is highly superior to that of zinc in both the aged and unaged conditions, and does not markedly decrease as the alloy ages. Further, these properties are secured without destroying the workability of the zinc, the resulting alloy being hot and cold workable by commercial mill processes as, for example, it may be readily commercially hot and cold rolled into sheets. Moreover these properties are secured without making the resulting alloy deleteriously dimensionally unstable as the alloy ages or making it subject to intercrystalline corroslon.

It has been found that the above results will be secured with additions to zinc of 0.2 to 5% copper, 0.05 to 0.6% silicon, and 0.1 to 0.6% phosphorus, provided the sum or the percentage amounts of silicon and phosphorus does not exceed the percentage amount or copper, and provided the percentage amount of phosphorus is not greater than 80% of the percentage amount of silicon when the latter is between 0.4 and" 0.6%. Preferably 1% or more copper is em ployed in the improved alloys as giving best all around results. Best results in respect to duetility however coupled with a high degree of tensile strength and toughness will be secured with amounts of copper from about 0.5 to 2.3%, while best results in respect to tensile strength coupled with a high degree of ductility and toughness will be secured with amounts of copper in excess of 2.25%. Ithas been found that with less than about 0.2% copper no appreciable increase in the tensile strength of the zinc will be secured, and that the alloy will be subject to grain growth as it ages, making it as it ages deleteriously unstable in respect to tensile strength, toughness and ductility. On the other hand, it has been found that with more than about 5% copper the alloy cannot be readily cold worked by commercial mill .processes if it contains amounts of silicon and phosphorus within the ranges thereof specified. Appreciable results, it has been found, will be secured with as little as 0.05% silicon and 0.1% phosphorus. However, with more than about 0.6% of either phosphorus or silicon in combination with any amount of the other within the ranges thereof specified the duetility of the alloy becomes poor and the alloy commonly subject to intercrystalline corrosion and dimensional instability as it ages. When the silicon is within the range of approximately 0.4 to 0.6% and the phosphorus exceeds about of the amount of silicon it has been found that the toughness-of the alloy or its stability with age is inferior, and its ductility in most instances low. making such alloys undesirable as compared to the improved alloys.

To secure best results in respect to resistance to corrosive media and resistance tointercrystal line corrosion it is desirable to employ in the improved alloy commercialzinc of fairly high purity as, for example, that termed High Grade No. 1" in A. S. T M. specification 36-37, which latter grade contains a maximum of 0.07% each of lead and cadmium impurities and a maximum of 0.02% iron impurity, the total of such of these impurities as may be present not exceeding 0.1%, and is substantially free from all other impurities. With poorer commercial grades of zinc the alloy commonly will have the samemechanical characteristics, but may be somewhat less corrosion resistant in both respects mentioned and have more or'lessdimensional instability.

The excellent properties of the improved alloy are exhibited by the following table, in which the steam test mentioned consists in subjecting the alloy to moist steam at 95 C. for days, this being the standard accepted test for determining the effect of age on zinc and its alloys:

Hot rolled, and sub- 'I=tensiio strength in 1,000 pounds per square inch. E=per cent elongation in 2 inches. O==Charpy impact strength in foot pounds per square inch.

It will be understood that within the scope or 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 addition of copper, silicon and phosphorus are not substantially destroyed.

I claim:

1. Zinc base alloys containing copper, silicon and phosphorus within ranges and proportions approximately as follows: copper 0.2 to 5%, silicon 0.05 to 0.6%, phosphorus 0.1 to 0.6%, the

balance constituting approximately 93.8 to 99.65% of the alloy being substantially zinc, the sum of the percentage amounts of silicon and phosphorus present not exceeding the percentage amount of copper present, and the percentage amount 'of phosphorus present not exceeding 80% of the percentage amount of silicon present when the latter is from 0.4 to 0.6%.

2. The alloys according to claim 1 having at least 1% copper, the balance constituting approximately 93.8 to 98.85% of the alloy.

'3. The alloys according to claim 1' having 0.5 to 2.3% copper, the balance constituting approximately 96.5 to 99.65% of the alloy.

4. Zinc base alloys containing copper, silicon and phosphorus Within ranges and proportions approximately as follows: copper 2.3 to 5%, silicon 0.05 to 0.6%, phosphorus 0.1 to 0.6%. the balance constituting approximately 93.8 to 97.64% of the alloy being substantially zinc, the percentage amount of phosphorus present no. exceeding 80% of the percentage amount of silicon present when the latter is from 0.4 to 0.6%.

EDWARD S. BUNN.