US2002460A - Alloy - Google Patents

Description

Patented May 21, 1935 NlTED STATES ALLOY Richard A. Wilkins, Rome, N. Y., asslgnor to Revere Copper and Brass Incorporated, Rome, N. Y., a corporation of Maryland No Drawing. Application March Serial No. 9,109-

3 Claims.

My invention relates to copper-base alloys. It will be understood that the yield point of an alloy, rather than its tensile strength, is the factor which determines the maximum load to 5 which a part made of the alloy may be safely subjected. Also, it will be understood, the degree of elongation, or ductility, of an alloy is the limiting factor in respect to its suitability for many uses. Further, for economic reasons it is essential that copper-base alloys be capable of being rolled and drawn and otherwise worked both hot and cold, as copper-base alloys which can be worked only cold can be produced by mill processes only at so high a cost as to be pro- 0 hibitive for ordinary uses of the alloys, while copper-base alloys which can be worked only hot have so limited a field of usefulness, if any, as to be economically worthless. Obviously therefore copper-base alloys which may be worked both hot and cold, and have both a high yield point and a high degree of ductility, are for economic reasons very desirable.

Heretofore, it has been attempted to secure alloys having'these properties by mixing copper, silicon and zinc, or copper, silicon and manganese. It has been found however that the attempt to vary the yield point in these alloys by varying the amount of either zinc, manganese or silicon ordinarily results in an undesirable change in the ductility. The reason for this probably is because, to secure a hot and cold workable alloy, the amount of zinc or manganese must be decreased when the amount of silicon is increased, and vice versa, with the result that it is impossible with these prior alloys to regulate or vary the yield point and at the same time secure the degree of ductility necessary to make the alloys suitable for many commercial uses.

Applicant has found that if for the zinc, or manganese, small percentages of tin are substituted, and in. general the copper content increased, the yield point, by proper heat-treatment, may be varied without substantially affecting the ductility, and in many instances slightly increasing the latter when the yield point is increased. By maintaining the amounts of tin and silicon within definite limits, and in proper proportion to each other, a hot and cold workable alloy is produced. Within these limits and proportions, the yield point, tensile strength and ductility may be varied by varying the amounts of both silicon and tin and by varying them in respect to each other. In all these combinations the yield point of the cold worked metal is controllable through heat treatment.

Applicant has found that his improved alloys, as compared to copper-siliconzinc and coppersilicon-manganese alloys, have a remarkably high tensile strength and ductility when in both the fully annealed and cold worked condition, and when cold are susceptible of greater reduction without annealing. For example, applicants alloys are capable of being reduced by cold rolling from 30 to without failure or it being necessary to anneal them during the reducing process. When fully annealed all these alloys have a tensile strength of at least 58,000 pounds per square inch and an elongation of at least 65% in two inches. All the alloys are capable of being cold drawn into rods having a tensile strength of at least 120,000 pounds per square inch and an elongation of 10% in two inches, and are capable of being cold rolled into sheets having a tensile strength of at least 110,000 pounds per square inch and an elongation of 5% in two inches.

Applicants alloys also have the unique property of being capable of heat treatment to relieve cold working stresses without any material change in the tensile strength, ductility, or hardness and with a marked increase in the yield point, whereas with copper-silicon-zinc and copper-siliconmanganese alloys heat treatment to relieve these stresses commonly decreases the ductility at the expense of the tensile strength, yield point and hardness. For example, according to applicants invention, an alloy can be produced which may be cold drawn from the fully annealed condition in which it has a tensile strength of about 61,000 pounds per square inch and an elongation of 75% in two inches to produce a rod which has a tensile strength of about 136,000 pounds per square inch, an elongation of 10% in two inches, a yield point of 88,000 pounds per square inch, and a hardness number of about 94 Rockwell. This rod may be heat treated by heating it to about 500 to 600 F. for 30 to minutes and'slowly cooling it by exposing it to air at room temperature, and after heat treatment its tensile strength will be slightly increased to about 141,000 pounds per square inch, its yield point markedly increased to 111,000 pounds per square inch, its elongation increased to about 11% in two inches, and its hardness number to about 97 Rockwell. In other Words, this heat treatment at so-called relief annealing temperatures, that is to say temperatures below recrystallization temperatures, secures a very marked increase in the yield point without reducing the tensile strength or hardness 01' materially affecting the ductility.

Conveniently, the alloy may be fully annealed by heating it to a higher temperature, say 1000 to 1200 F., and it will be observed that when in such condition, due to its very high ductility and susceptibility of being greatly reduced by cold working without again annealing it, it may be readily fabricated into articles having, as compared to articles made of prior alloys, a high tensile strength, ductility, yield point and hardness,

after which the yield point may be very much increased by heat treatment without destroying the high tensile strength, ductility and hardness.

Further applicant's alloys, when compared with copper-silicon-zinc and copper-silicon-manganese alloys, have a greater corrosion resistancethan either of these and have better welding properties than the copper-silicon-zinc alloys.

Applicants alloys preferably contain 2.75 to 3.5% silicon. Below 2.75% silicon the alloys are deficient in tensile strength, although, from this aspect alone, in some instances the amount of silicon may be as low as 2.25%. With above 3.5% silicon the alloys are economically unsatisfactory with respect to cold rolling and drawing properties and for this reason are commercially undesirable.

The range of the amount of tin is a variable depending upon the amount of silicon employed. Throughout the entire range of silicon above specified alloys having the desired properties will be secured with as little as 0.25% tin. With any amount of silicon less than approximately 3% the amount of tin should not exceed a value which is roughly represented by a linear increase in tin from 1.8% to 2.25% silicon at the rate of approximately tin for 1% increase in silicon, that is to say, a linear increase in tin from 1.8 to 2% as the silicon increases from 2.25 to 3.0% or a linear increase in tin from 1.9 to 2% as the silicon increases from 2.75 to 3%. On the other hand, for any value of silicon more than 3% the amount of tin should not exceed a value which is roughly represented by a linear decrease in tin from 2% at 3% silicon at the rate of approximately 43% tin for 1% increase in silicon, that is to say a linear decrease in tin from 2 to 1.7 %-as the silicon increases from 3 to 3.5%. In other words, the maximum amount of tin that may be employed for 3% silicon is 2%, but if the amount of silicon is increased or decreased to above or below this value the maximum amount of tin that may be employed decreases approximately at the rate of for 1% increase in silicon and approximately at the rate of A% for 1% decrease in silicon.

With values of tin outside the ranges above defined for each value of silicon, the alloys will fail to possess one or more of the desirable properties above mentioned, and if the alloys have amounts of tin greater than those indicated they will not be hot workable. Preferably the amount of tin for the preferred range of silicon is approximately 0.25 to 0.5% as within these ranges the alloys may be readily hot and cold worked and possess the peak values of the characteristic properties of the alloy. Also in these ranges the tin and silicon may be varied, each by itself or relative to each other, to control the yield point, ductility and tensile strength within limits suitable for commercial uses for which copper-base alloys of high tensile strength are employed.

Small amounts of certain metals may be present without affecting the desirable properties of the alloy. For example, iron may be present in very small amounts without destroying any of the herein mentioned properties of the alloy. The presence of aluminum should be avoided, as small amounts even as low as 0.5% destroy the property of the alloy of being susceptible of heat treatment for increasing its yield point. Aluminum in fact causes the alloys when heat treated to exhibit an increase in ductility at a marked expense of their yield point, and further increases the difiiculty with which the alloys may be ho; worked. The alloys are substantially zincless, that is to say, they do not contain more zinc than values under 1%, as values of zinc under this amount do not seem materially to affect the properties of the alloy. For economic reasons it is dimcult to prevent the presence of fractions of a percent of zinc in copper-base alloys, and for this reason it may be desirable, in order to produce a uniform product, to add small amounts of zinc to maintain a zinc content of say about 0.5%, as with this value and other values under 1% the alloy is substantially zincless in so far as appreciable effects of zinc on the mentioned properties of the alloy are concerned.

I claim:

1. Substantially zincless copper-base alloys capable of being worked both hot and cold, and capable when in the cold rolled and drawn condition of being heat treated at temperatures below recrystallization temperatures markedly to increase the yield point without reduction in tensile strength and ductility, consisting essentially of copper, silicon and tin within the following approximate ranges and proportions: silicon 2.25 to 3.5%, tin 0.25 to 2%, balance substantially copper, the minimum amount of tin being 0.25% for all values of silicon, and the maximum amount of tin varying between 1.8 and 2% linearly and directly with the silicon when the latter is between 2.25 and 3%, and varying between 1.7 and 2% linearly and inversely with the silicon when the latter is between 3 and 3.5%, the alloys being further characterized by a tensile strength of at least 55,000 pounds per square inch with an elongation of at least 60% in 2 inches when in the fully annealed condition, and when in this condition being capable of being cold drawn to secure a tensile strength of at least 105,000 pounds per square inch with an elongation of at least 9% in 2 inches or cold rolled to secure a tensile strength of at least 100,000 pounds per square inch with an elongation of at least 4% in 2 inches.

2. The alloys according to claim 1 having 2.75 to 3.5% silicon.

3. Substantially zincless copper-base alloys capable of being worked both hot and cold, and capable when in the cold rolled and drawn condition of being heat treated at temperatures below recrystallization temperatures markedly to increase the yield point without reduction in tensile strength and ductility, consisting essentially of copper, silicon, and tin within the following approximate ranges and proportions: silicon 2.75 to 3.5%, tin 0.25 to 0.5%, balance substantially copper, the alloys being further characterized by a tensile strength of at least 58,000 pounds per square inch with an elongation of at least 65% in 2 inches when in the fully annealed condition, and when in this condition being capable of being cold drawn to secure a tensile strength of at least 120,000 pounds per square inch with an elongation of at least 10% in 2 inches or cold rolled to secure a tensile strength of at least 110,000 pounds per square inch with an elongation of at least 5% in 2 inches.

RICHARD A. WILIQNS.

CERTIFICATE OF- CORRECTION.

Patent No 2,002,460. I May 21, 1935.

RICHARD A. WILKINS.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, line 26, ,for "to" read at; and that 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.

Signed and sealed this 25th dayof June; D. 1935.

Br an M. Battey (Seal) Acting Commissioner of Patents.