US2789899A - Beryllium-copper alloys - Google Patents

Description

April 23, 1957 M. J. DONACHIE 2,789,899

' BERYLLIUM-COPPER ALLOYS Filed July 17, 1952' NOMINAL |.|o/., Be Cu ALLOY TENSILE STRENGTH ELONGATION- 2 in.

TENSILE STRENGTH x IOOO psi.

EL NGATI O 0. O 8

so I l l I" I I I I l 0 2 a 4 5 s 7 a a l0 LEGEND SOLUTION ANNEALEQ ROLLED 4 B B S NOS.--

HARDENING TEMPERATURE 600 F.

.7; I g NOMINAL 2.009 Be Cu ALLOY o TENSILE STRENGTH x .s I N :5 I60 I v I z E |4oj, E '5 I20- 4 (9 Z ELONGATION O w I00 5 UJ so f: as

.1 "a i a a 4' s a a a HARDENING TIME, HRS. INVENTOR.

Matthew J. Don hie ATTOR HEY 2,789,899 BERYLLIUM-COPPER ALLOYS Matthew J. Donachie, Holylke, -Mass., assignor to The Beryllium Corporation, Reading, Pa, a corporation of Delaware Application July 17, 1952, Serial No. 299,411

4 Claims. c1. 75-153 This invention mates to b'erylliiirncopp er alloys and more particularly to cold-workable heat-hardening beryl- Hum-copper alloys and has for its object the provision of a cold-workable heat-hardening beryllium-copper alloy that is more easily cold-worked and less susceptible to over-aging on heat-hardening than alloy compositions heretofore proposed and that is adapted to be employed in the manufacture of end products normally subjected to bulk heat-treating during solution annealing and heathardening. I a t V v I p v Another object is to provide a berylliumj-copper alloy containing about 1% beryllium haying the physical propefrties within a range heretofore obtainable only with the 2% Beryllium alloys which is more (tarra onorked and more difiicult to over-age than the 2% beryllium alloy' A further object is to provide an improved cold-workable, heat-hardeiiable beryllium-copper alloy.

Other objects and advantages will be apparent as the invention is more fully hereinafter disclosed.

in accordance with these objects I have discovered a beryllium-copper alloy that contains about 1% beryllium which is cold-workable and heat-hardenable and which on heat-hardening has physical properties closely similar to those obtainable in a 2% beryllium alloy but which is characterized by being more easily cold-worked than the 2% beryllium alloy to a greater percent reduction in area between solution annealin'gs and at a faster rate of speed and by being particularly difiicult to over-age on heathardening. The alloy of the present invention has the following generic composition:

In this alloy composition, the zinc content is employed mainly as a matrix strengthen'er for the copper and as a primary deoxidiaihg agent in melting and in most instances is preferred to be -present in the final alloy in an amount approximating 2%. The silicon content improves the casting properties of the alloy 7 and also strengthens the copper matrix and in most instances is preferred in an amount within the range .15%-.35%. The silicon and zinc each slow down the reaction rate of precipitation of the hardening phase during heat-hardening and fior this reason should be maintained substantially constant within the preferred ranges for uniformity between successive melts of the alloy. The cobalt content functions as a beryllide former and within the range specified is well within the solubility range at the temperature of solution-annealing. Nickel is a substantial equivalent for cobalt in this alloy composition and may be substituted in part or in whole for the cobalt without departure from the invention. The aluminum and tin content of the alloy contribute to hardening and effects to some extent the slowing down effect of the silicon on the precipitation rate of the hardening phase during heat-hardening, probably by partial precipitation, and for this reason should be maintained substantially constant at about the middle of the ranges specified when the zinc and silicon contents are maintained at the preferred ranges given. The iron in conjunction with either or both nickel and cobalt functions generally as la beryllide former and in that respect is equivalent to these and lowers the amount of cobalt or nickel required in the alloy.

As one specific embodiment of the alloy of the present invention but not as a limitation of the same, the invention will be described with respect to the species alloy of the following composition:

This alloy has been found to be panticularly useful, because of its slower rate of heat-hardening, in the forniing of manufactured products of relatively small size or of variable thickness that must be heated in bulk during solution-annealing and heat-hardening The slower rate of heat-hardening provides a wider latitude in the time factors involved in charging and discharging the bulk articles into and out of the treating furnaces and a less critical time of holding at the heat-hardening temperature, thereby providing for a greater uniformity !of physical properties in the treated products, and between successively bulk treated lots of these products.

Alloys of the above species composition are normally prepared or compounded substantially as heretofore found to be best practice with beryllium-copper alloys generally and the 2% beryllium talloy particularly, and are otherwise treated substantially the same as (the 2% beryllium alloy in hot-working except that it works down further and more easily. For example, the 2% alloy is hot rolled fnom 3 /2" squares to 2%" squares. It is then annealed and rolled to A" thick strip. The 1.1% alloy rolls from 3 /2? squares to A thick strip directly without intermediate annealing. After surface cleaning, the hotworked strip product is conditioned for cold working by a solution'anneal heat-treatment at a temperature within the range l500l575 F. for an extended time interval suflicient to obtain complete solid solution of all precipitated phases present in the alloy. This time interval may vary widely depending on the size and thickness of the hot-worked product but usually is within the range of l-3 hours for A" thick strip. The solution-annealed strip product is then withdrawn from the annealing furnace and cooled relatively rapidly to preserve the solution-annealed structure, as by quenching in water. The relatively slow rate ht which this solid solution phase decomposes by precipitation during this cooling as compared to the decomposition rate of the 2% beryllium alloy facilitates the cooling of relatively thick sectioned products, greatly extending the thickness of the product that may be solunon-annealed and quenched to condition'same fior cold working. In thin sections under 0.015 inch the alloy may be chilled in gas or air or chill roll cooling may be employed.

in cold working the solution-annealed product greater reductions in area per pass and greater total reductions in area between solution-annealings may be employed than with the 2% beryllium alloy, as the alloy has a much lower work-hardening rate. The alloy also may be rolled at speeds up to 3 times faster than that heretofore employed with the 2% alloy. For example, the 2% alloy may be cold rolled in strip form from a size of about .090 mil to .035 mil at an average percent reduction in area per pass of about 22%25% and at a rate of about 75-120 feet per minute between solution-annealings, whereas the present alloy will cold roll readily from a size of about .090 mil to a size of about .015 mil at an average percent reduction in area of about 25 %-27% and at a rate of about 300 feet per minute before the work-hardening developed therein requires solution-annealing to condition the alloy for further cold-working.

The alloy composition of the present invention is con ditioned for heat-hardening by solution annealing at a temperature of 1500-l575 F. for a time interval providing a solid solution structure followed by quenching. This solid solution structure has a hardness within the range Rockwell 1342-48; a tensile strength within the range 55.000 p. s. i. to 64,000 p. s. i. with an elongation within the range 42% to 62%.

The solution-annealedalloy is heat-hardened by heating the same for 4 hours at 400 F. to provide a heathardened product having a tensile strength of about 135,- 000 p. s. i. with an elongation of about or for 4 hours at 500 F.,to 145,000 .p. s. i.

Bysuperimposing cold working on the solution-annealed structure the tensile strength of the heat-hardened product maybe increased. For example, by imposing cold working at 4 numbers (b. s. hardness) the tensile strength of strip material may be increased to about 175,000 p. s. i. with elongation of 4% to 6%.

The alloy is exceedingly insensitive to over-aging. For example, the solution-annealed alloy may be heated for minutes at 700 F. and still yield a heat-hardened product having a tensile strength of 165,000 p. s. i. and after 8 hours heating at 800 F. the alloy still has a heathlardened tensile strength of 148,000 p. s. i. The alloy also is more stable than the 2% beryllium alloy at servvice temperatures within the range 350700 F. as a result of this resistance to over-aging.

The usual properties of the alloy of the present invention particularly its resistance to over-aging adapts the alloy for wide utility in the forming of small sized articles that may vary widely in thickness in different sections and that must be bulk annealed or bulk heat-hardened and wherein variations in physical properties on heathardening between articles in the same batch and between batches are to be held to a low order. The alloy is also adapted to be employed in situations where during service use the article may be heated to temperatures within the range 350-700 F.,tl1e effect of such tempera ture being normally to improve the heat-hardness over an extended time rather than to decrease the heat-hardness by over-aging as in the case of the 2% alloy.

The alloy of the present invention also has excellent fatigue endurance properties, approximating 30,000 p. s. i. for 100,000,000 reversals, which property also closely parallels the 2% alloy in this respect.

The modulus of elasticity of the alloy before hardening approximates 12 million and after hardening approximates 18 million.

For purposes of illustration of the close similarity in physical properties between the alloy of the instant invention and the regular 2% B alloy, I have illustrated in the drawings typical graphs showing the tensile strength, elongation and hardening time characteristics of the two alloys in their solution annealed and cold worked condition as obtained on actual test. The two graphs are selfexplanatory to those skilled in the art and show definitely that the two alloys are closely similar in their physical properties with the advantage lying with the 1% alloy of the instant invention.

Having hereinabove disclosed the present invention generically and specifically, it is believed apparent that the same may be widely varied without essential departure therefrom and all such modifications, departures and adaptations thereof are contemplated as may fall within the scope of the following claims.

What I claim is:

3. An alloy characterized by its combined qualities, when age hardened, :of high tensile strength and good ductility and by its ability to be drastically worked, both hot and cold, without edge slitting or surface defects, which consists of from 1.5% to 3.0% zinc, 0.80% to 1.20% beryllium, and the balance substantially copper.

4. An age hardenable alloy consisting of 1% beryllium 2% zinc, and the balance substantially copper, the alloy being characterized by its ability to be drastically worked, both hot and cold, and by its combination of high tensile strength, good ductility and slow age hardening characteristics produced by solution annealing at approximately 1500" F. and quenching followed by age hardening by prolonged heating at temperatures above 400 F.

References Cited in the file of this patent UNITED STATES PATENTS 1,868,679 Wilkins July 26, 1932 1,975,114 Masing Oct. 2, 1934 2,048,549 Harrington July 21, 1936 2,088,219 Sillem an July 27, 1937 2,192,495 Hessenbruch Mar. 5, 1940 2,412,447 Donachie Dec. 10, 1946 OTHER REFERENCES Beryllium, Rimbach and Michel, Reinhold Pub. Corp, 1.932, pp. 261263 and 265.

Metals Handbook, 1948, page 1248.

Claims (1)

1. 3. AN ALLOY CHARACTERIZED BY ITS COMBINED QUALITIES WHEN AGE HARDENED, OF HIGH TENSILE STRENGTH AND GOOD DUCTILITY AND BY ITS ABILITY TO BE DRASTICALLY WORKED, BOTH HOT AND COLD, WITHOUT EDGE SLITTING OR SURFACE DEFECTS,

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