Copper Alloys


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Copper Alloys

 

alloys based on copper. They were the first man-made alloys. Until about the mid-20th century, copper alloys were first among nonferrous alloys; aluminum alloys have since taken over the leading position.

With many elements, copper forms a wide range of substitutional solid solutions, in which the atoms of the added metal occupy the sites of copper atoms in the face-centered cubic lattice. In the solid state, copper dissolves up to 39 percent zinc, 15.8 percent tin, 9.4 percent aluminum, and an unlimited percentage of nickel. The formation of solid solutions based on copper increases its strength and electrical resistance and de-creases the temperature coefficient of electrical resistance. The corrosion resistance may increase significantly, and the plasticity remains sufficiently high. The addition of an alloying element in excess of the solubility limit leads to the formation of compounds,

Table 1. Composition, typical mechanical properties*, and uses of brasses
BrandCompositionUltimate
strength
σb(MN/m2)1
Relative elongation δ (percent)Brinell
hardness
HB (MN/m2)
Uses
*Properties shown for wrought brasses are for the annealed state f1 MN/m2 = 0.1 kgf/mm2
L96 .............95-97% Cu; remainder Zn24050470Radiator pipes
L90 .............88-91 % Cu; remainder Zn26045530Sheets and bands for cladding
L80 .............79-81 % Cu; remainder Zn32052540Wire screens for the paper and pulp industry; bellows
L68 .............67-70% Cu; remainder Zn32055550Articles produced by cold pressing and deep drawing
L63 .............62-65% Cu; remainder Zn33049560Strip, sheet, band, wire, tubes, rods
LA77-2 .............76-79% Cu, 1 .75-2.50% Al; remainder Zn40055600Condenser tubes
LAZh60-1-1 .............58-61 % Cu, 0.75-1 .50% Al, 0.75-1.50% Fe, 0.1-0.6% Mn; remainder Zn45045950Tubes and rods
LAZhMts66-6-3-2 .............64-68% Cu, 6-7% Al, 2-4% Fe, 1 .5-2.5% Mn; remainder Zn65071,600Large cast worm screws and nuts for thrust screws
LAN59-3-2 .............57-60% Cu, 2.5-3.5% Al, 2-3% Ni; remainder Zn38050750Tubes and rods
LZhMts59-1-1 .............57-60% Cu, 0.6-1.2% Fe, 0.5-0.8% Mn, 0.1-0.4% Al, 0.3-0.7% Sn; remainder Zn45050880Strip, wire, rods, and tubes
LN65-5 .............64-67% Cu, 5.0-6.5% Ni; remainder Zn35065700Manometer tubes, condenser tubes
LO70-1 .............69-71% Cu, 1.0-1.5% Sn; remainder Zn35060590Condenser tubes, heat engineering equipment
LS74-3 .............72-75% Cu, 2.4-3.0% Pb; remainder Zn35050570Parts for clocks and motor vehicles
LK80-3L .............79-81% Cu, 2.5-4.5% Si; remainder Zn300201,050Equipment exposed to water; ship parts
LKS80-3-3 .............79-80% Cu, 2.5-4.5% Si, 2-4% Pb; remainder Zn35020950Cast bearings and bushings

particularly electron compounds, that are characterized by a definite electron concentration (the ratio of the total number of valence electrons to the number of atoms, which may be 3/2, 21/13, or 7/4). The formulas conventionally attributed to these compounds are CuZn, Cu5Sn, Cu31Sn8, Cu9Al4, CuBe, and so on. Multicomponent copper alloys frequently contain complex metallic compounds whose composition has not been established, which are considerably harder than the copper-based solutions but are very brittle (the proportion of such compounds in the structure of two-phase and multiphase copper alloys is usually much smaller than the proportion of the solid solution based on copper).

Copper alloys are produced by melting copper with alloying elements or intermediate alloys (hardeners) containing the alloying elements. The addition of small quantities of phosphorus (a few tenths of a percent) is widely used for deoxidation (reduction of oxides).

A distinction is made between wrought and foundry copper alloys. Wrought copper alloys are poured into ingot molds or by the continuous method to give round or flat ingots, which then undergo hot or cold working, rolling, extrusion through dies, or drawing to produce sheets, bands, rods, profiles, tubing, and wire. Copper alloys are readily workable under pressure, and semifinished products manufactured by forming methods account for the bulk of their production. Foundry copper alloys have good casting properties; they are used to produce shaped articles, as well as decorative products and sculpture, by means of casting in sand or chill molds.

Table 2. Composition, typical mechanical properties*, and uses of bronzes
BrandCompositionUltimate
strength
σb(MN/m2)1
Relative elongation δ (percent)Brinell
hardness
HB (MN/m2)
Uses
*Properties of Br OF10-1, Br OTsS5-5-5, Br OTsSN3-7-5-1, and Br S30 alloys are shown for castings in sand molds; properties of Br 82 and Br KN1-3 alloys, for worked articles tempered at 780°C and 850°C and aged at 320°C (2 hr) and 450°C (4 hr), respectively; properties of other alloys, for the annealed state after working *1 MN/m2 = 0.1 kgf/mm2
Br OF10-1 .............9-1 1 % Sn, 0.8-1 .2% P2503900Bearings, pinions, teeth, bushings
Br OF4-0.25 .............3.5-4.0% Sn, 0.2-0.3% P34052600Tubes for manometer springs
Br OTsS5-5-5 .............4-6% Sn, 4-6% Zn, 4-6% Pb1506600Antifriction parts and fittings
Br OTsSN3-7-5-1 .............2.5-4.0% Sn, 6.0-9.5% Zn, 3-6% Pb, 0.5-2.0% Ni1808600Equipment used in fresh and salt water and in a steam atmosphere
Br A7 .............6-8% Al42070700Springs and elastic parts
Br AZh9-4 .............8-10% Al, 2-4%Fe600401,100Pinions, bushings, valve seats
Br AZhMts10-3-1.5 .............9 -11%AI, 2.4% Fe, 1-2% Mn610321,300Pinions, bushings, bearings
BrAZhNI 0-4-4 .............9.5-11.0% Al, 3.5-5.5% Fe, 3.5-5.5% Ni600351,500Pinions, valve seats
Br AMts9-2 .............8-10% Al, 1.5-2.5% Mn400251 600Parts of oceangoing ships’ electrical equipment
Br Mts5 .............4.5-5.5% Mn34030800Forgings
Br B2.............1 9-2 2% Be 0 2-0 5% Ni1 3501 53 500Springs and elastic parts in aviation and instrument-making
Br KN1-3 .............0 6-1 1 % Si 2 4-3 4% Ni 0.1-0.4% Mn600121 800Guide bushings and other critical parts
Br S30 .............27-33% Pb705450Stuffing boxes
Table 3. Composition, typical mechanical properties*, and uses of cupronickel alloys
BrandCompositionUltimate
strength
σb(MN/m2)1
Relative elongation δ (percent)Brinell
hardness
HB (MN/m2)
Uses
*Properties shown are for the annealed state *1 MN/m2= 0.1 kgf/mm2
MN19 (melchior) .............18-20% Ni + Co35035700Articles produced by stamping and chasing
MNZhMts30-0.8-1 (melchior).........29-33% Ni + Co, 0.8-1.3% Mn, 0.6-1.0% Fe38040700Condensor tubes for shipbuilding; thermostat tubes
MNTsI 5-20 (nickel silver).............13.5-16.5% Ni + Co, 18-22% Zn40045700Parts of apparatus in precision mechanics; dishes
MNMts43-0.5 (copel).......42.5-44.0% Ni + Co, 0.1-1.0%40035850Wire for thermocouples
MNMts40-1 .5 (constantan).............Mn 39-41% Ni + Co, 1-2% Mn45030800Wire for rheostats and thermocouples

The mechanical properties of copper alloys vary within wide limits during cold working or annealing. Cold forming may be used to increase the hardness and the tensile strength of copper alloys by a factor of 1.5 to 3, with a simultaneous reduction in plasticity, and subsequent recrystallization annealing makes possible complete or partial restoration of the original forming properties, depending on the temperature and duration of the heat treatment. Softening annealing of copper alloys after cold working is performed at 600°-700°C. Most copper alloys do not undergo thermal treatment (quenching or aging) for strengthening, since such treatment is either impossible (if the alloy is single-phase at all temperatures) or the degree of such strengthening is very small. Alloying elements that form intermetallic compounds with copper or among themselves (for example, CuBe, NiBe, or Ni3Al) are used to produce copper alloys that are capable of thermal hardening. The solubility of the intermetallic compounds in the copper-based solid solution decreases with decreasing temperature. Quenching of such alloys produces a supersaturated solid solution, from which disperse intermetallic compounds that strengthen the copper alloy separate during artificial aging.

Copper alloys are divided into brasses, bronzes, and cupronickels. In brasses, the principal additive is zinc; in bronzes the principal additive may be any element except zinc and nickel. The industrial brands of copper alloys produced in the USSR are designated by starting with the first letter of their names: L (latun’) for brass, Br (bronza) for bronze, and M (mednonikelevye splavy) for cupronickels. The alloying elements are designated by the letters A (aliuminii) for aluminum, N (nikeP) for nickel, O (olovo) for tin, Ts (tsink) for zinc, S (svinets) for lead, Zh (zhelezo) for iron, Mts (marganets) for manganese, K (kremnii) for silicon, F (fosfor) for phosphorus, and T (titan) for titanium. The brand symbol of a simple (binary) brass contains a number that corresponds to the average copper content. Thus, L90 brass contains 90 percent copper and 10 percent zinc. The brand symbol of a multicomponent brass contains numbers, the first of which indicates the average copper content and the following indicate the content of alloying elements. For example, LAN59-3-2 brass contains 59 percent Cu, 3 percent Al, and 2 percent Ni (the remainder is zinc). Letters and numbers in the symbols of various brands of bronzes and cupronickels indicate the percentages of the alloying elements. For example, Br AZhMts 10-3-1.5 bronze contains 10 percent Al, 3 percent Fe, and 1.5 percent Mn. The letter L at the end of a brand designation indicates that it is designed for shaped casting (for example, LK80-3L).

The composition, typical mechanical properties, and examples of uses of copper alloys are listed in Tables 1-3. All copper alloys are distinguished by high resistance to atmospheric corrosion. Oxygen at room temperature does not affect copper alloys; carbon dioxide does not react with them. Dry or moist uncontaminated vapor acts very weakly on bronzes. Hydrogen sulfide reacts vigorously at low moisture levels with copper alloys, particularly at high temperatures. Nitric and hydrochloric acids react vigorously with brass and tin bronzes; sulfuric acid reacts much more weakly with them.

Copper alloys are used as structural, spring, antifriction, and corrosion-resistant materials; as alloys with high electrical and thermal conductivity and with high electrical resistance and low thermal coefficient of electrical resistance; as alloys for thermocouples; for artistic casting; and for dishes. They are used in general machine building, in the construction of aircraft and motor-vehicles, in shipbuilding, in railroad transportation, in electrical engineering, and in instrument-making, as well as in the construction of water and steam equipment.

REFERENCES

Bochvar, A. A. Metallovedenie, 5th ed. Moscow, 1956.
Smiriagin, A. P. Promyshlennye tsvetnye metally i splavy, 2nd ed. Moscow, 1956.

I. I. NOVIKOV

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