US2075509A - Copper base alloys - Google Patents

Description

Patented Mar. 30, 1937 UNITED STATES PATENT OFFICE COPPER BASE ALLOYS Charles H. Davis, Cheshire, and Elmer L. Muns'on, Naugatuck, Conn, assignors to The American Brass Company, Waterbury, Conn., a corporation of Connecticut No Drawing. Application April 2, 1935, Serial 13 Claims.

This invention relates to copper base alloys composed mainly of copper, manganese and cadmium. 1

One object of the invention is to provide copj 5 per-base alloys of improved corrosion resistance claims.

One of the important uses for which our new alloys are adapted is for expansion joints in steam lines and other uses where corrosion 'is encountered, especially corrosion resulting from exposure to steam and hot or cold water.

Another important use for the new alloys is for condenser tubes and other metallic parts that are subjected to corrosion resulting from exposure to saline water. The four most important types of corrosion attack are: impingement attack, intercrystalline attack, general thinning, and dezincification. Our new alloys are superior to certain other copper base alloys in their resistance to the first three mentioned types and 5 are not subject to the fourth type because zinc is not present in the alloy.

It has been foundin certain types of steam service, especially at temperatures above 212 F. (100 C.) and pressures above atmospheric, that the steam and (or) gases commonly associated with steam in ordinary manufacturing or commerce cause certain copper base alloys to disintegrate or crack. This disintegration is apparently an intergranular attack with corrosion takmg place at the grain boundaries while the strength of the metal is decreased because the bond-between the crystals has been destroyed. Certain copper base alloys, when under stress, or when. alternately stressed and unstressed,

have been found to be more susceptible to this mium in the proportions and amounts hereinafter mentioned that ofier a remarkable resistance to attack by corrosion. These new alloys are almost impervious to intercrystalline attack or corrosion when exposed to steam and hot water under pressures as high as 140 lbs. per

square inch. This improved resistance to corrosion was found in the new alloys even when stresses as great as percent of the ultimate tensile strength were applied in a steam chamber with the steam pressure maintained at about lbs. per square inch. For example, two copper base alloy wires of the following composition:

Percent Percent Copper '98 Copper s. 97 Manganese 2 Manganese 2 Cadmium 0 Cadmium 1 were stressed to 80% of their ultimate tensile strength in the steam chamber with the steam pressure 130 lbs. per square inch. The first alloy containing no cadmium failed after 81 hours while the new alloy containing about 1% cadmium has not broken after 6,000 hours in the test chamber.

Inpractice, elements other than copper, manganese, and cadmium may be present in slight amounts without injury to the resultant product. Because it cannot be-avoided without too much expense in refining the constituent metals, there ,may be, and usually is, some silicon, chromium and iron present.

The importance of the cadmium addition is evident from the test results given above. Our tests indicate that it is advisable, particularly for corrosion resistance, that the cadmium content be'lowered as the manganese is increased. For example, a copper base alloy containing about 1% manganese should preferably contain about 1 cadmium, whereas a copper base alloy containing about 10% manganese should preferably contain about 0.5% cadmium.

The new alloys not only possess valuable corrosion resistance properties especially useful in steam expansion joints, blades and other parts for steam turbines, condenser tubes, flexible metal hose, flexible corrugated tubes or bellows, tanks, valves, and the like, all of which may be employed to contain or conduct steam, but are also valuable for general structural and fabricating purposes. .In other words these new alloys or articles made from them are particularly valuable for use wherever steam may be in direct contact with them.

Our new alloys are suitable for the operations and uses peculiar to the brass and copper industries. Thus for example, they are adapted for extruding into tubes, for hot and cold rolling, extruding hot and cold, drawing, and for hot pressing shapes of all kinds, as well as drawing into shells, cartridge cases and wire. In addition to the above our new alloys may be drawn into wire, rods, tubes, sheets and shapes and also drawn, stamped or spun into cups and other forms of drawn metal articles.

While the manganese increases the strength,

toughness, resistance to wear and fatigue of the alloy it also changes the hot working range of the copper-cadmium alloys. Thus, while the maximum cadmium in copper-cadmium alloys, which 5 can be commercially hot worked, is about 2.25%, the addition of manganese in amounts up to about 4% gradually decreases the hot working range to approximately 1.5% cadmium. The addition of manganese in amounts from about 4% to about 11% appears to increase the hot working range to approximately 3% cadmium.

The addition of manganese in amounts up to about 11% gradually raises the solidus temperature from about 549 C. to about 850 C.

15 The extension of the alpha phase boundary (solidus) within the temperature range stated is of considerable importance. Heretofore it has not been possible to satisfactorily cold work the copper-cadmium alloyscontaining more than about 1% cadmium because of the presence of from about 549 C. to about 700 C. Our, discov-.

ery, whereby a small amount of manganese is added to the alloys, enables us to satisfactorily cold work all the copper-cadmium alloys containing from 0.01% to about 3% cadmium, and especially those containing from about 1% to about 3% cadmium.

The addition of small amounts of manganese effectively prevents the formation of liquid particles in the aforementioned copper-cadmium alloys at normal annealing and hot working temperatures. The absence of these undesirable liquid particles insures a considerable increase in the strength and ductility of the hot and/ or cold Worked alloys.

We have also noticed that the addition of small amounts of manganese to these copper-cadmium alloys containing up to about 3% cadmium apparently effects the removal of many casting defects. These defects such as voids, oxides, liquid particles, et al., are frequently present in the.

binary copper-cadmium alloys aforementioned. Evidently the manganese serves as a. degasifier in addition to the functions previously stated.

:The addition of manganese in amounts up to about 11% to the copper-cadmium alloys also increases the grain size considerably.

' We have found that the makeup of the ternary equilibrium diagram for copper-cadmium-manganese alloys is excellent for purposes of precipitation at low temperatures and solution (alpha phase) at the higher temperatures where annealing and hot working may be carried on. We have observed the presence of a finely divided precipitate in these alloys containing from about 1% to about 3% cadmium and from about 0.25%

to 3% manganese. This visible precipitation occurs when the alloys have been annealed at about 800 C. and quenched followed. by reheating at a temperature of about 475 C. for about 2 hours. There is no great increase in hardness in the above mentioned alloys containing a visible precipitation after heat treatment at temperatures of about 475 C. and up to about 550 C. If these alloys are heat treated at temperatures in the neighborhood of 400 C., no visible precipitate is noted but an appreciable increase in hardness is obtained.

As the manganese content is increased in the copper-cadmium alloys containing from about 1% to about 3% cadmium, the precipitated particles gradually become reduced in s z un they are more or less invisible ('submicroscopic) in those alloys containing more than 3% manganese when heat treated at temperatures from about 300 C. to 550 C. This reduction in visibility is accompanied by a gradual increase in hardness as the manganese is increased up to about 11%. For example, a copper base alloy containing 2.17% cadmium and 2.30% manganese, when annealed at 800 C. for 1 hour and quenched, had a Rockwell F. hardness value of 50, which was decreased to 49 after a 2 hour heat treatment at 475 C.; whereas a copper base alloy containing 1.8% cadmium and 4.0% manganese, similarly treated, had a Rockwell F hardness value of 55, which was increased to 61 after heat treatment; while a copper base alloy containing 2.1% cadmium and 6.78% manganese, similarly treated, had a Rockwell F hardness value of 62, which was increased to 75 after heat treatment.

The addition of manganese and/or cadmium in amounts up to 11% and 3% respectively increases the hardness of the annealed, wrought and/or heat treated copper base alloys. Likewise the heat treating temperature range, wherein maximum hardness is obtained, is raised from 350 to 450 C. to the approximate range 450 to 550 C. as the manganese and cadmium content is increased.

The importance of this age hardening or precipitation hardening is readily apparent. Articles' may be fabricated from the annealed or wrought alloy, and when finished may be hardened and strengthened by a low temperature heat treatment.

The complete composition range of these new copper-manganese-cadinium alloys is approximately Percent Copper -1 86.0 to 99.9 Manganese 0.01 to 11.0 Cadmium 0.01 to 3.0

Alloys within this composition range may be hot or cold worked or both in accordance with the limitations herein stated.

' The preferred composition range of these new copper-manganese-cadmium alloys is approximately I Percent Copper 86.5 to 99.6 Manganese 0.25 to 11.0 Cadmium 0.15 to 2.5

We anticipate the fact that a certain alloy within our specified composition range may have some slight preference over other alloys in the range for some specific use. alloy containing about 97% copper, 1% cadmium, and 2 manganese has a relatively high electrical and thermal conductivity value combined with excellent resistance to corrosion attack; whereas For example, an

erties combined with good resistance to corrosion ganese to the molten copper.

melted, the required. amount of an addition alloy composed of about 50% cadmium and 50% copper 0.3% cadmium.

molten into suitable molds or shapes. The cadmium metal should be added to the melt just prior to the pouring operation to prevent undue loss of the volatile element.

The new alloys are preferably prepared by introducing the required amount of an addition alloy composed of about 85% copper and man- When this has of one or more additional elements such as iron,

tin, phosphorus, et al., are present.

Having thus set forth the nature of our invention, what we claim is:

1. An alloy composed of copper, manganese and cadmium in proportions substantially within the following range:

Percent Copper 86.0 to 99.9 Manganese 0.01 to 11.0 Cadmium 0.01 to 3.0

2. An alloy composed of copper, manganese and cadmium in proportionssubstantially within the following range:

- Percent Copper 86.5 to 99.6 Manganese 0.25 to 11.0 Cadmium 0.15 to 2.5

3. A copper base alloy composed of approximately 97% copper, 2% manganese, and 1% cad- 4. A copper base alloy composed of approximately 94.4% copper, 5.0% manganese and 0.6% cadmium.

5. A copper base alloy composed of approximately 89.7% copper, 10.0% manganese and 6. A corrosion resistant'copper base alloy composed of copper, manganese and cadmium in which the cadmium is decreased from. about 3% to about 0.01% as the manganese is increased from 0.01 to 11.0% and as the copper is decreased from 97.4 to 88.9%.

7. A copper base alloy characterized by imrosion when stressed in steam and capable of being hot" and/or cold worked composed of approximately 87.5% to 99.9% copper, 0.01 to 11%;manganese and 0.01% to 1.5% cadmium.

9. A copper base alloy characterized by improved resistance to intergranular attack or corrosion when stressed -in steam and capable of being hot and/or cold worked composed of approximately 94.5% to 99.9% copper, 0.01% to 4% manganese, and 0.01% to 1.5% cadmium.

10. A copper base alloy characterized by superior resistance to intergranular attack or corrosion when stressed or' unstressed in steam composed of approximately 86% to 95.9% copper, 4% to 11% manganese, and 0.01 to 3.0% cadmium.

11. An age-hardenable copper base alloy characterized by superior resistance to intergranular attack or corrosion when stressed -or unstressed in steam, wherein the improved hardness is obtain by heat treatment at temperatures from about 300 C. to about 550 C., composed of ap-' proximately 86% to 95% copper, 4% to 11% manganese, and 1% to 3% cadmium.

12. In the heat treatment of the copper-manganese-cadmium alloys composed of from about 1% to 3% cadmium, from about 3% to 11% manganese, and from about 86% to 96% copper, the steps which comprise heating such an alloy at temperatures above a transition point, which lies in the neighborhood of 600-0., but below its melting point, quenching and age hardening by prolonged heating at temperatures above 300 C. but below 600 C.

13. In the heat treatment of the copper-manganese-cadmium alloys composed of from about 1% to 3% cadmium, from about 3% to 11% manganese and from about 86% to 96% copper, the steps which comprise heating such an alloy at temperatures above a transition point, which lies in the neighborhood of 600 C., but below its melting point, quenching, cold working and age hardening by prolonged heating at temperatures above 300 C. but below 600 C.

CHARLES H. DAVIS. ELMER L. MUNSON.