US2401136A - Zinc base alloys - Google Patents

Description

Patented May 28, 1946 Edward S. Bunn, Rome, N. Y., assignor to Revere Copper and Brass Incorporated, Rome, N. Y., a corporation of Maryland No Drawing. Application June 11, 1943,

Serial No. 490,481

6.01aims. (Cl-75-178) My invention, which will be best understood from the following description. relates to zinc base alloys, and has among its objects the provision of zinc base alloys of improved characteristics.

It will be understood by those skilled in the art that commercially pure zinc, when worked hot or cold, possesses a moderate tensile strength and a high degree of ductility. However, both the hot and cold worked metal as it ages is subject to grain growth, causing it gradually to lose much of its tensile strength and most of its ductility, this same effect occurring when the metal is subjected to temperatures much above room temperature for a considerable period.

The standard accepted test for determining the effect of age on zinc and its alloys is to subject articles made of them to moist steam at 95 C. for days. This will cause the same grain growth as would be caused by several years aging of the alloy at room temperature, and further will cause any intercrystalline corrosion to which a zinc alloy is susceptible, this type of corrosion occurring with age particularly in hot and humid climates. It-is mentioned that hot rolled zinc having a tensile strength of approximately 17,000 p. s. i. and an elongation in 2 inches of approximately 45% when subjected to this test has on account of grain growth a tensile strength of about 11,000 p. s. i. and an elongation in 2 inches of only about 2%.

The attempt to cure grain growth in zinc by adding other metals to it commonly causes it to be subject to an alloy phase change or to .intercrystalline corrosion with age, making it dimersionally unstable because either a phase change or intercrystalline corrosion tends to increase its volume. Applicant has found, however, that grain growth can be prevented without causing intercrystalline corrosion or deleterious alloy phase change by adding copper and silver in conjunction with arsenic orphosphorus, or both, and at the same time other very valuable properties will be imparted to the zinc.

It has beeniound that adding copper to zinc to form a binary zinc-copper alloy increases the tensile strength of the zinc, without muchrcducing its ductility except when the amount of copper is over about 2.7%, the resulting ductility in all instances being sufliciently stable for most uses of the alloy as the latter ages. With additions of copper in progressively increasing amounts up to about 10% the tensile strength will be progressively increased. The alloys havworked into sheets and with amounts up to 5% commercially cold worked into sheets.

It has further been found that part of the copper can be substituted by a lesser amount of arsenic to form a ternary zinc-copper-arsenic alloy and secure the same tensile strength with an increase in the ductility in most instances, and without any marked decrease in the tensile strength and ductility as the alloy ages, so long as the copper is within the range of 0.2 to 7.5% and the arsenic within the range of 0.1 to 0.7% and the maximum amount of arsenic does not exceed a value which varies roughly linearly, and

inversely with the amount of copper present within the range of copper specified. Phosphorus, it has been found, has generally the same effect as arsenic, except that with phosphorus the tensile strength is somewhat higher and the ductility somewhat lower. These ternary alloys are hot workable, and if the amount of copper does not exceed about 3 to 4% are cold workable.

Applicant, however, has found that if the copper is kept within the range of 0.2 to 5% and the substance of the group consisting of arsenic and phosphorus within the range of 0.1 to 0.75%, and silver is also added within the range of 0.05 to 0.25%, and these elements are kept within proper proportions; the alloy will have a degree of toughness and resistance to impact loading or shock markedly greater than the alloys without silver. At the same time the alloywill have a greater ductility and tensile strength than it would were the silver' omitted. Further, the alloys have grez.- plasticity when either hot or cold, enabling them readily to be either hot or cold worked throughout the entire range of copper by commercial processes as, for example, rolled into sheets. Still further, the alloys when aged are dimensionally stable and satisfactorily stable in respect to tensile strength, ductility and resistance to impact loading, and are substantially free from intemrystalline corrosion.

These above mentioned results of the alloy containing silver will be secured when the percentage amount of substance of the above mentioned group does not exceed a value represented by 0.78% minus 10% of the sum of the percentage amounts of copper and silver present, best results being secured when the amount of substance of said group is at least twice the percentage amount of silver present. It has been found that when the amount oi substance of said group exceeds the above mentioned value the ductility of the alloy is commonly markedly inv1X18 p to 10% c pper can be commercially hot so ierior as, for example, the alloy was 5% copper,

0.1% silver and 0.2% arsenic has an elongation in 2 inches of about 50%. but it the amount of arsenic is increased to 0.75% the elongation in 2 inches will drop to about 20%, representing a decrease 01 about 60% in the ductility. In general, the tensile strength of the hot rolled alloys according to the invention will have tensile strengths ranging from 34,000 to 47,000 p. s. 1. and an elongation in 2 inches of 37 to 70% depending upon the exact percentages of constituents.

It will be understood that, within the scope of the appendedclaims, other substances may be present in the improved alloy for modifying its properties or imparting additional properties, so

long as the characteristic properties imparted by the combination of copper, silver and substance of the above described group are retained.

I claim:

1. Hot and cold workable alloys of high tensile strength, ductility and toughness, characterized by high stability in respect to such properties and by high dimensional stability, which alloys contain as essential constituents, approximately, 0.2 to 5% copper,-0.05 to 0.25% silver,'0.1 to 0.75% substance of the group consisting of arsenic and phosphorus, the percentage amount of the substance of said group present not exceeding 0.78%

minus 10% of the sum or the percentage amounts, 1

of the copper and silver present, the balance, constituting approximately 94.5 to 99.65% of the alloy, being substantially zinc. I

2. Hot and cold workable alloys of high tensile strength, ductility and toughness, characterized by high stability in respect to such properties and by high dimensional stability which alloys contain as essential constituents, approximately, 0.2 to 5% copper, 0.05 to 0.25% silver, 0.1 to 0.75% substance of the group consisting of'aisenic and phosphorus, the'percentage amount of the substance of said group present being at least twice zinc.

' 3. Hot and cold workable alloys of high tensile strength, ductility-and toughness, characterized by high stability in respect to such properties and by high dimensional tability, which alloys contain as essential constituents, approximately, 0.2 to 5% copper, 0.05 to 0.25% silver, 0.1 to 0.75% arsenic, the percentage amount of arsenic present not exceeding 0.78% minus 10% of the sum of the percentage amounts of the copper and silver present, the balance, constituting approximately 94.5 to 99.65% of the alloy, being substantially zinc.

4. Hot and cold workable alloys of high tensile strength, ductility and toughness, characterized by high stability in respect to such properties and by high dimensional stability, which alloys contain-as essential constituents, approximately, 0.2 to 5% copper, 0.05 to 0.25% silver, 0.1 to 0.75% arsenic, the percentage amount of arsenic present being at least twice the percentage amount of silver present but not exceeding 0.78% minus 10% of the sum of the percentage amounts of the copper and silver present, the balance, constituting approximately 94.6 to 99.65% of the alloy, being substantially zinc.

5. Hot and cold workable alloys of high ten e strength, ductility and toughness, characterizedby high stability in respect to such properties and by high dimensional stability, which alloys contain as essential constituents, approximately, 0.2 to 5% copper, 0.05 to 0.25% silver, 0.1 to 0.75% phosphorus, the percentage amount of phosphorus present not exceeding 0.78% minus 10% of the sum of the percentage amounts of the copper and silver present, the balance, constituting approximately 94.5 to 99.65% of the alloy, being substantially zinc.

6. Hot and cold workable alloys of high tensile