US1928747A - Nonferrous alloy - Google Patents

Description

Patented Oct. 3, 1933 UNITED STATES PATENT OFF-ICE NONFERROUS ALLOY No Drawing. Application October 11, 1928 Serial No. 311,968

10 Claims.

This invention pertains particularly to alloys comprising copper, nickel and tin. The primary object is to provide an alloy capable of being strengthened and hardened according to a meth- 0d herein described. This method is applicable to the treatment of known alloys and also to alloys in which copper, nickel and tin are employed in proportions hitherto not known to be available.

The alloys referred to are useful for casting purposes and for cold rolling. The cast material, as well as the rolled material, can be treated at any suitable stage of fabrication to develop strength and hardness.

The alloys referred to contain essentially copper, nickel and tin, but may contain, also, small percentages of other metals, or other materials, such as lead, zinc, iron, aluminum, titanium, silicon, phosphorus, carbon, magnesium, etc.

The alloys amenable to the treatment to be described herein comprise copper and nickel which combinedly. constitute the main percentage of the alloy, and tin which may constitute not less than il to not more than 20% of the combined copper, nickel and tin present in the alloy.

Preferably the percentage of the tin based upon the copper, nickel and tin in the alloy, considered as 100%, is not less than 5%, or greater than 15%. Reasonably good results may be obtained withinthe range of about 4% to 15% tin.

The percentages of nickel and copper in the alloy,

considering tin, nickel and copper as 100%, may

vary from about 3.5% to 50% or more of nickel, the remainder being copper and tin. It is to be remarked, however, that, for the best results, an increase in the nickel content above 15%calls for an increase in the tin content; and while, as indicated, nickel and copper can be interchangeably varied through a considerable range, that is, some of the copper being replaced by nickel, the use of too high a percentage of nickel results in an increased cost of the alloy, due largely to the desirability of a larger preeentage of tin in such case, tin being the most expensive of these three metals.

To secure sound castings and good ductility,

it is desirable for the alloy to contain a small percentage of manganese, or titanium, either alone or with a small percentage of magnesium.

For the purpose of casting, a manganese content of not less than.l% of the nickel content is desirable. The manganese content may be in- 05 creased, but it is undesirable to use the manganese in a percentage exceeding 5% of the nickel.

Small amounts of iron, lead, aluminum, or silicon may be present without harm, although for material that is to be rolled, these constituents should ordinarily not exceed about 1%, combinedly. Zinc may be present and cheapens the alloy. In small quantities, it may be advantageously used, but in alloys containing a high nickel content, it is not desirable to employ more than a small percentage of zinc. Ordinarily, the zinc should not in any case exceed 10%; and if the nickel content is above 25% of the alloy, it is best to exclude zinc.

The alloy may be formed by melting the materials and casting the metal in ingots. If preferred, the metal may be heated considerably above the melting point and the molten metal may be poured, at this high temperature, into the ingot molds. No particular difliculties are experienced in casting the material, but it is desirable that the carbon content of the alloy shall be kept as low as possible.

The alloy may be formed by diffusing tin into the surface of an article formed from a suitable alloy of copper and nickel. The article might be made of an alloy of 40% nickel and 60% copper. Upon heating for some hours at about 850 C., in a suitable container in contact with an alloy containing 25% tin and 75% copper, the surface 35 of the article would be converted into an alloy of copper, nickel and tin, which could be heat treated as hereinafter described.

In accordance with the present invention, the alloy can be softened at any desired stage by annealing the alloy, preferably for at least two hours, at a temperature ranging from 600 C. for an alloy containing about 5% of nickel, to about 900 C.-950 C. for an alloy containing about 50% of nickel; and then rapidly cooling the alloy, preferably by quenching it in water or oil. The annealing or homogenizing temperature chosen should always be below the melting point of the copper-nickel-tin phase but may exceed .the melting point of a lead-rich phase if present.

The alloy can then be hardened and strengthened by reheating to a temperature ranging from about 200 C. to about 550 C. and aging at such a temperature for a period of fifteen minutes to several hours. It has been found that a temperature in the neighborhood of 300 C.-450 C. ordinarily is best suited to the purpose of hardening and strengthening the alloy. It is to be remarked, however, that a lower degree of temperature, in the hardening and strengthening no process, calls for a longer period of heat treatment, The appropriate temperature should be selected, of course, consonant with the proportions of the metals in the alloy.

As noted above, the degree of temperature best suited to annealing operation increases with the nickel and tin content of the alloy; and, also, the temperature best suited to the hardening and strengthening treatment increases with the nickel content.

As an example of the treatment of a coppernickel-tin alloy in accordance with the present process, the following is given:

The alloy is produced by melting the metals and casting an ingot; the cast alloy is then annealed for a prolonged period of time, preferably, at least two hours, at a temperature of preferably 600 to 950 0., depending upon the nickel and tin content; the highly heated alloy is then rapidly cooled, as by quenching in water or oil, thus producing a soft metal; the alloy is then rolled or otherwise fabricated, as desired; and, finally, the alloy is hardened and strengthened by reheating to a temperature ranging from 200 C. to 550 C. and aging for a period of time, preferably several hours, the temperature employed depending upon ,the nickel content and the length of the period of treatment. Where it is deemed desirable to age the material for a long time, the aging temperature employed is preferably considerably below that which will give the maximum hardening in a short time.

To illustrate the hardening and strengthening efiect obtained by the second heat treatment mentioned, namely, the treatment at a temperature within a range of about 200 C. to 550 C. the following experiment may be stated:

An alloy composed of copper, 7.43% nickel, and 7.57% tin was quenched from an annealing temperature of 800 C. This material showed an ultimate tensile strength of 61,000 pounds per square inch, and gave an elongation of 50% in the testing operation.

The same material quenched from an annealing temperature of 800 C. was aged during a period 01' two hours at 300 C. This material showed a tensile strength of 105,500 pounds per square inch and an elongation of 5% under test.

The relative hardness of the materials after the annealing process and after the hardening process were, for the former about 50 B and for the latter about 99 B on the Rockwell scale of hardness. I

As another illustration on this point, an alloy consisting of 45% copper, 40% nickel and 15% tin gave a Rockwell C hardness of 8 after the material had been quenched from an annealing temperature of 950 C. The same material after aging at a hardening temperature of 450 C. for one hour, followed by an aging at 400 C. for

the other hand, the hardening and strengthening treatment at the lower range of temperature mentioned, namely, 200 C.-550 C., and aging at such temperature, results in a precipitation in the body of a compoundof nickel and tin, or of copper and tin which is distributed throughout the body and has the effect of greatly hardening the body and increasing its tensile strength greatly. While the phenomenon of the formation of a precipitate in the body of the compound is indicative of completion of the hardening and strengthening operation, it is, of course, true that the desired result is not due to an instantaneous change, and accordingly the invention is not to be unduly limited. A condition of incipient precipitation, or a sufliciently close approach to the point of precipitation to give the desired effect, is to be regarded within the spirit of the invention. a

- After annealing at a temperature of from 600 to 950 C., the alloy may be allowed to cool very slowly or may be held for several hours at a temperature between 500 C. and 600 C. Either treatment will result in the formation of relatively large size particles of a nickel-tin or copper-tin compound in the alloy. The alloy is then worked, by rolling, pressing, turning, hammering, or the like, as'desired. Subsequently, the alloy is heated to a temperature sufiicient to dissolve the precipitated particles (annealing 'temperature'), is then quenched and thus rendered soft; and finally the material is reheated to the age-hardening temperature, namely 200 C. to 550 C. and is hardened at this temperature for a suitable perior of time, depending on the results desired. During this hardening treatment, precipitation of a nickel-tin compound or phase occurs, and it is assumed that this phenomenon increases the hardness and tensile strength of the material.

It is preferred, for many purposes, to employ from 60 to copper in the alloy, in which case the percentage of nickel preferably ranges from about 33% down to 3.5% and the minimum percentage oftin preferablyranges from about 10% to 3.5%. In certain cases, the tin content may be as low as 2.5%, however the hardening effect with such a low percentage is usually less pronounced. On the other hand, I have discovered that a good alloy can be produced by employing between 35% and 50% of nickel, together with at least 7.5% to 12% of tin and the remainder of the 100% being copper, the tin content increasing with the nickel content of the alloy, but not necessarily in the exact ratio.

I have discovered that the copper-nickel-tin alloys which yield the best results under the treatment herein described have the various metals of the alloy present in about the proportions indicated by the following table:

Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent MOO! fourteen hours, gave a 49 Rockwell C hardness and possessed a high tensile strength.

It may be remarked that the treatment at the higher temperature, namely 600 C-950 C. is a homogenizing treatment; and, apparently, when the material is quickly cooled, or quenched, it remains soft and otquite low tensile strength. On

For an alloy which is to be rolled, the tin content should not exceed 10%. Where a cast product is desired for use, the tin content may be as high as 15% or 20%.

The proportions may vary from those expressed in the table, but ordinarilyit will not .be found 1 desirable to decrease or increase the.tin more than 50 about one-sixth of that stated in the table for any of the given tin-nickel-copper compositions.

From the description given, it will be understood that the improved process involves a hardening and strengthening step by means of heat treatment at a range of temperature permitting the precipitation of a tin-nickel compound in a fine state of subdivision within the body of the alloy; and this hardening and strengthening step preferably follows a previous annealing step at a much higher range of temperature which may be referred to as the homogenizing range, the alloy being preferably quickly cooled from thehigh temperature, as by quenching in liquid, before subjecting the alloy to the hardening and strengthening heat treatment.

It is possible to harden castings of these copper nickel tin alloys, particularly chill castings by heating to the age hardening temperature 200 C. to 500 C. without having previously heated said castings to the high homogenizing temperatures. A small chill casting containing 80% Cu. 10% Sn and 10% Ni, which had a Rockwell hardness of 70 B as cast, hardened to 90 B on reheating to 350 C. for twenty minutes. For castings that are to be used for bearings and the like, this treatment may be desirable. It will be understood that the castings referred to in this paragraph may be such as are cast and cooled in any usual way. However, in those cases where the alloy is subjected to homogenizing treatment and then quickly cooled, it should be understood that such quick cooling may be effected in any desired manner. For illustration, quick cooling should be understood to include ordinary aircooling, as distinguished from the very slow cooling noted above, where some means for retarding the rate of cooling is employed, such as allowing cooling to occur at a very slow rate in a furnace.

The composition set forth in the foregoing table conforms approximately (within the limits of 5% to 50% nickel) to the following formula with respect to tin and nickel, the remainder of the 100% being represented by the copper:

Tin :4.9+.00578 nickel-13) Such a formula may be employed for calculating the percentages of the several metals,'tin, nickel and copper, which yield the best results when treated by the improved process. A more flexible and reasonably satisfactory formula may be stated as follows:

% Tin= 7.5%-l.00578 nickel13):3.

the percent of nickel being not substantially less than 4% and not substantially more than 50%, the remainder of 100% being principally copper.

Alloys of the character described may be advantageously used in many situations. They are resistant to atmospheric corrosion and to quite an extent to the action of acids and alkalies; and,

as has been indicated, when treated by the improved process, the alloys are very hard and possess a high tensile strength.

The present application constitutes a division in part and a continuation in part of my application Serial No. 217,541, filed September 3, 1927.

The presence in the alloy of other materials which do not adversely affect the amenability to the treatment described is not to be understood as a departure from the invention.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

What I regard as new, and desire to secure by Letters Patent, is:

1. A Cu-Ni-Sn alloy comprising 4% to 50% Ni (of the aggregate of the three metals) and Sn=7.5+.003578 (%Ni-13) :3 and substantially within the limits of l t0 18 /270. the remainder of the aggregate (100%) of the three metals being Cu, said alloy having been subjected to a homogenizing treatment at a temperature in the range of about 600 C. to 950 C. followed by rapid cooling, and having been subsequently hardened and strengthened by heat treatment in the range of 200 C. to 550 C.

2. A Cu-Ni-Sn product comprising an alloy as specified in claim 1, in which the alloy, after the homogenizing treatment and before the hardening and strengthening treatment specified in said claim, has been subjected to mechanical working.

3. A cast Cu-Ni-Sn alloy comprising 3% to 20% Sn and 3.5% to 20% Ni, the remainder of the aggregate of the three metals being Cu, said cast alloy having been hardened and strengthened by heat treatment at 200 C. to 550 C.

4. A cast alloy as specified in claim 3, which, previous to the hardening and strengthening step, has been subjected to homogenizing treatment at a temperature below the melting point and not substantially below 600 C. and quickly cooled.

5. A cast Cu-Ni-Sn alloy as specified in claim 3, but having a minimum of 7% of tin.

6. A Cu-Ni-Sn alloy, the tin constituting about 2.5% to 20%; the nickel constituting about 4% to 50%; the remainder of an aggregate of of the three metals being copper; said alloy having been hardened and strengthened by treatment within a range of substantially 200 C. to 550 C.

7. A tin nickel copper alloy having the tin and nickel substantially in the proportions indicated by the following formula, tin=7.5+.00578 nickel-13)i3 and substantially within the limits of 4/ to 18 the per cent of nickel being not substantially less than 4% and not substantially more than 50 the remainder of 100% being principally copper, said alloy having been hardened by heat treatment within the range of 200 C. to 550 C. and having disseminated throughout its body at least an incipient nickeltin precipitate.

8. A cast tin nickel copper alloy in which the tin constitutes from 2.5% to 20% of the alloy, nickel from 4 to 25% of the alloy, the remainder of an aggregate of 100% of the three metals being copper, the alloy having been hardened by heat treatment within the range of 200 C. to 500 C. and having disseminated throughout its body a fine precipitate comprising nickel and tin.

9. A Cu-Ni-Sn alloy comprising 60 90% Cu, 25-12% Sn, 3.5-33% Ni, said alloy having been subjected to a homogenizing treatment between 600 and 800 C. and then quickly cooled.

10. A heat treated, high hardness coppernickel-tin alloy comprising 60 to 90% copper, 2.5 to 12% tin, 3.5 to 33% nickel and having a finely divided nickel-tin containing precipitate distributed throughout the matrix of an alloy EDMUND MERRIMAN WISE.