Machinery's Handbook, 31st Edition
308 Spring Materials temperatures around 600°F, for 2 to 3 hours. This treatment produces a high hardness combined with a high tensile strength. After hardening, the material becomes quite brittle and can withstand very little or no forming. It is the most expensive alloy in the group and heat treating is expensive due to the need for holding the parts in fixtures to prevent distortion. The principal use of this alloy is for carrying electric current in switches and in electrical components. Flat strip is frequently used for contact fingers. Nickel-Base Spring Alloys.— Nickel-base alloys are corrosion resistant, withstand both elevated and sub-zero temperatures, and their non-magnetic characteristic makes them useful for such applications as gyroscopes, chronoscopes, and indicating instruments. These materials have a high electrical resistance and therefore should not be used for con ductors of electrical current. Monel * : (67 percent nickel, 30 percent copper) This material is the least expensive of the nickel-base alloys. It also has the lowest tensile strength but is useful due to its resistance to the corrosive effects of sea water and because it is nearly non-magnetic. The alloy can be subjected to stresses slightly higher than phosphor bronze and nearly as high as beryl- lium copper. Its high tensile strength and hardness are obtained as a result of cold-drawing and cold-rolling only, since it can not be hardened by heat treatment. It can be used at tem- peratures ranging from − 100 to +425°F at normal operating stresses and is available in round wires up to 3 ∕ 16 inch in diameter with quite high tensile strengths. Larger diameters and flat strip are available with lower tensile strengths. “K” Monel * : (66 percent nickel, 29 percent copper, 3 percent aluminum) This material is quite similar to Monel except that the addition of the aluminum makes it a precipitation- hardening alloy. It may be formed in the soft or fairly hard condition and then hardened by a long-time age-hardening heat treatment to obtain a tensile strength and hardness above Monel and nearly as high as stainless steel. It is used in sizes larger than those usually used with Monel, is non-magnetic and can be used in temperatures ranging from − 100 to +450°F at normal working stresses under 45,000 pounds per square inch. Inconel * : (78 percent nickel, 14 percent chromium, 7 percent iron) This is one of the most popular of the non-magnetic nickel-base alloys because of its corrosion resistance and because it can be used at temperatures up to 700°F. It is more expensive than stainless steel but less expensive than beryllium copper. Its hardness and tensile strength is higher than that of “K” Monel and is obtained as a result of cold-drawing and cold-rolling only. It cannot be hardened by heat treatment. Wire diameters up to 1 ∕ 4 inch have the best tensile properties. It is often used in steam valves, regulating valves, and for springs in boilers, compressors, turbines, and jet engines. Inconel “X” * : (70 percent nickel, 16 percent chromium, 7 percent iron) This material is quite similar to Inconel but the small amounts of titanium, columbium and aluminum in its composition make it a precipitation-hardening alloy. It can be formed in the soft or partially hard condition and then hardened by holding it at 1200°F for 4 hours. It is non- magnetic and is used in larger sections than Inconel. This alloy is used at temperatures up to 850°F and at stresses up to 55,000 pounds per square inch. Duranickel * : (“Z” Nickel) (98 percent nickel) This alloy is non-magnetic, corrosion resistant, has a high tensile strength and is hardenable by precipitation hardening at 900°F for 6 hours. It may be used at the same stresses as Inconel but should not be used at temperatures above 500°F. Nickel-Base Spring Alloys with Constant Moduli of Elasticity.— Some special nickel al- loys have a constant modulus of elasticity over a wide temperature range. These materials are especially useful where springs undergo temperature changes and must exhibit uni form spring characteristics. These materials have a low or zero thermo-elastic coefficient *Trade name of the International Nickel Company.
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