US2067307A - Stainless copper base alloy - Google Patents

Description

Patented Jan. 12, 1937 FlCE 2,067,307 7 STAINLESS oorrsa BASE ALLOY Richard A. Wilkins, Rome, N. Y., assignor to Revere Copper and Brass Incorporated, Rome, N. Y., a corporation of Maryland No Drawing. Original application May 31, 1933, I

Serial No. 673,768.

Divided and this application November 1, 1934, Serial No. 751,089

2 Claims. (01. 754155) alloy compounded according to the invention, the 10 scope of which latter will be more particularly pointed out in the appended claims.

Heretofore copper base alloys containing nickel and chromium have been employed in practice only for castings. For economic reasons it has been impractical to roll or otherwise mechanically work such prior alloys as they are brittle, dlfii- ;ult to work cold, and next to impossible to work Applicant has found that workable stainless copper base alloys can be produced by compounding copper, nickel and chromium in proper proportions particularly when suitable precautions are taken to secure solution of the chromium and to prevent deleterious secondary compounds. These alloys may be readily cold and hot rolled into sheets and may be otherwise attenuated while cold or hot by usual mill processes to produce various shapes.

The alloy may be compounded with or without zinc, but preferably with it except as hereinafter mentioned, as its presence it has been found facilitates the working of the alloy particularly when itis to be annealed between the attenuating steps in the mill processes. Further,'the alloy preferably is compounded with an additional constituent or constituents, hereinafter for convenience in terminology referred to as "chromium incorporators, which will insure protect ing the chromium from oxidation and insure its solution, and preferably also insure eliminating the effect on the nickel of any sulphur that may be present. In the absence of protecting the chromium from oxidation, the chromium when with which the alloy may be worked. It has been found that manganese will insure the solution of the chromium in the copper base alloy, and, as manganese has a greater aflinity than chromium for oxygen and ajgreater afiinity than nickel for sulphur, any possibility of oxidation of the chromium and formation of nickel-sulphid. is prevented eiiectively by use of this metal. The manganese-sulphid has no appreciableefltectupon the workability of the alloy, and any excess of manganese, over that necessary to secure these results within the range of metals hereinafter stated, enters into solution and augments the efiect of the nickel as a whitener for the alloy.

As a substitute for manganese as a so-called chromium incorporator, small amounts of magnesium and tin may be employed. The magnesium will prevent any possibility of oxidation of the chromium and formation of nickel-sulphid,

while the tin will insure the solution of the chromium. In employing magnesium precaution should be taken not to employ an amount thereof materially in excess of that necessary to take up the oxygen and sulphur, small amounts of magnesium in excess of this, say in the order of 0.25% uncombined metal, deleteriously afiecting the physical properties of the alloy within the ranges of metals herein stated. When magnesium with tin is employed as a substitute for manganese the zinc may be omitted, and in practice ordinarily is.

When desired the tensile strength of the alloy may be increased and controlled by addition of small amounts of vanadium, say from traces up to 0.1%, this metal also much improving the cold working properties of the alloy and its ductility and elongation.

The amount of nickel may be varied to vary the color of the alloy. With a high nickel con-' tent of about 18% a bright, clear -white metal characteristic of the color of stainless steel is secured. By decreasing the nickel content to 10% and below alloys of warmer tones are obtained', with a suggestion of a rose or pinkish tint underlying the white, which warmer tones are desirable for architectural work. I he nickelcontent should ordinarily not exceed approximately from 20 to 22%, as above these values the alloy becomes increasingly diificult to work. On the other hand, the nickel content should not ordinarily be less than approximately from 4 to 5%, as below these values the alloy loses its characteristic color and ceases to be stainless.

The copper content should be relatively high, and ordinarily not less' than approximately of the alloy, as with lower copper values the alloy becomes increasingly brittle and diflicult to Work. Further, the copper content should not exceed approximately when zinc and manganese are employed,. or exceed approximately 93% when zinc is omitted and magnesium with tin is employed as a substitute for manganese.

Further, to secure the desirable properties of the alloy within the ranges of other constituents hereinafter mentioned, the sum of the copper and nickel should not be less than approximately 80%, or when zinc is present exceed approximately 95%, or in the absence of zinc exceed approximately 97%.

It has been found that the amount of chromium ordinarily should not exceed approximately 5% as values in excess of this make the alloy diificult to work, and ordinarily should not be less than approximately 0.5% to insure that the alloy is stainless. It has further been found, that to secure the desirable properties of the alloy within this range of chromium, the amount thereof should vary approximately linearly and inversely with the amount of copper, satisfactory results ordinarily being secured when the amount of chromium is within plus or minus 25% of the value determined by this ratio, 'so long as it is not materially above the maximum or below the minimum values thereof of 5 and 0.5% respectively.

It has been found that under ordinary conditions amounts of manganese less than 0.25% will not insure satisfactory results, and that amounts in excess of 5% are likely to cause the alloy to become brittle and refractory with the range of chromium above stated. Further, to secure best results, the amount of manganese should vary approximately linearly and directly with the amount of chromium, it ordinarily being satisfactory when the amount of manganese is within plus or minus 25% of the va1ue determined by this ratio. When magnesium with tin is employed as a substitute for manganese, to prevent the presence of a deleterious excess of magnesium, over that necessary to prevent both oxidation of the chromium and formation of deleterious amounts of nickel-sulphid, the amount of magnesium should ordinarily not exceed approximately 5%, and, to insure satisfactory results, should ordinarily not be less than approximately 0.25%, while within the range of chromium above stated the amount of tin should not exceed approximately 0.5% or be less than approximately 0.1%. To secure best results, the specific amounts of magnesium and tin should, like the manganese, ordinarily vary approximately linearly and directly with the amount of chro-,

mium, satisfactory results ordinarily being secured when the amounts of magnesium and tin are within plus or minus 25% of the value determined by this ratio.

As hereinbefore mentioned, the zinc, which preferably is employed, particularly when manganese is used to facilitate incorporation of the chromium, should not exceed approximately 20% of the alloy, as zinc values in excess of this tend to make the alloy brittle.

The general approximate formula for the basic copper, nickel, chromium alloys may be stated as copper to 93 parts, nickel 4 to 22 parts, and chromium 0.5 to 5 parts, with the sum of the copper and nickel between and 97 parts. When zinc is added to these basic alloys, the general approximate formula becomes copper 65 to 93 parts, nickel 4 to 22 parts, chromium 0.5 to 5 parts, and zinc the balance to make 100 parts, with the sum of the copper and nickel as before: and if the alloys contain vanadium the same may be substituted for an equal part of the zinc. When a chromium incorporator is employed with these basic copper, nickel, chromium alloys, 0.25 to 5 parts manganese (or 0.25 to 5 parts magnesium plus 0.1 to 0.5 parts tin) may be employed. When both zinc and the chromium incorporator are employed with these basic copper. nickel, chromium alloys, which may be done if desired, the zinc should be largely substituted for part of the copper, in which case the general approximate formula for the alloys becomes copper 65 to nickel 5 to 22%, chromium 0.5 to 5%, manganese025 to 5% (or magnesium 0.25 to 5% plus tin 0.1 to 0.5%) and zinc the balance, the sum of the copper and nickel being between 80 and any vanadium employed being substituted for an equal part of the zinc. As has hereinbefore been mentioned, in all these cases the chromium within the range thereof stated ordinarily preferably should vary approximately linearly and inversely with the amount of copper, and the manganese, magnesium and tin within the ranges thereof stated preferably should vary approximately linearly and directly with the amount of chromium.

As suitable alloys for fabricating sheets for architectural purposes, the following give satisfactory results Percent Copper 75 Nickel 18 Chromium 0.5 to 1 Zinc balance Per cent Copper Q8 Nickel 19 Chromium 3 to 3.5 Manganese 4 Vanadium 0.02 to 0.03 Zinc balance It has been found that excellent alloys satisfactory for ordinary purposes can be compounded according to the invention consisting of Per cent Copper 65 to 93 Nickel 8 to 18 Chromium 1 to 4 Tin 0.2 to 0.4 Magnesium 1 to 4 Vanadium tracesto 0.1

an excellent alloy of this series consisting of Per cent Copper 84 Nickel 11 Chromium 3.5

Tin 025 Magnesium 1.4 Vanadium trace As a suitable method of compounding the above alloys the copper and nickel may be melted together and the temperature of the melt raised to about 2300 F. The manganese may then be added in the form of a copper alloy rich in manganese, say one containing 25% manganese. The chromium may be added in the form of a copper alloy rich in chromium, say one containing 10% chromium, and then the vanadium may be added in the same way. The zinc may be added in the form of brass to cool the melt to about 2000* just before pouring. When the alloy contains tin the same may be added to the molten copper and nickel in the form of bronze scrap, after which the magnesium and chromium may be added, in the form of a copper alloy rich in both these metals, shortly before pouring.

It will be understood that small proportions of other metals than those herein mentioned may be added-to the alloy to give it special characteristics when they 'do not to a material extent change the hereinbefore mentioned desirable physical and chemical properties of the alloy, and also that wide deviations may be made from the embodiments of the invention herein described without departing from the spirit of the t invention.

I claim.

alloys containing copper 65 to 93%," nickel 4 to 20%, chromium 0.5 to' 5%, zinc appreciable" amounts up to 19.5%, the sum of the copper and nickel being between 80 and 95%, the amount of chromium varying roughly linearly and inversely with-v the amount of copper within the ranges of chromium and copper specified, the copper and nickel constituting substantially the balance of the alloy with respect to the other elements specifled.

2. The alloys according to claim 1 containing appreciable amounts up to 0.1% vanadium.

RICHARD A. WILKINS.