NICKEL STEEL, an alloy of iron, carbon and nickel; nickel primarily conferring strength and toughness. Experience gained with ordnance steels resulted in the present large use of alloy steels for making case hardened parts, for high strength castings, boiler plate, bridge steel, forgings and for special electrical alloys. High grade nickel steel is now made in the open-hearth furnace. Nickel oxide is not stable at any stage of the process, consequently nickel in the scrap steel charged is completely recovered and the shot nickel needed for correct analysis may also be added at any time. Surface conditions of alloy steel ingots, slabs, and forgings are especially important. Ingots are stripped as soon as solidified and placed immediately in a hot soaking pit. Billets are cooled, any surface defects chipped out, then reheated slowly and rolled to final dimensions. Nickel steel boiler plate or structural shapes to be used without heat treatment must be finished slightly above the transformation range, and slowly cooled in a pile protected from drafts. While chromium steels were the first alloy steels to be used for hard parts, nickel was first in the field to toughen steels. Plain nickel steels now in use ordinarily contain less of Steel A is an inexpensive water hardening steel for parts of mod erate importance. Steel B can be oil quenched direct from the carburizing heat for a tough core and file-hard case; it has good machining properties and is widely used for roller bearings, gears, piston pins, and drive shafts. Steel C usually is given a more elaborate heat treatment for a strong, tough core; it is used for gears, shafts, and machine parts requiring extra toughness as well as surface hardness and constancy of dimension. Steel D is hard
to work, but after proper case hardening gives parts having extreme hardness and resistance to shock.
A very useful, all-purpose, series of steels contains 3 to 3.5% nickel and 0.20 to 0.55% carbon; it goes into heat-treated forg ings, heat-treated castings and high strength structural and boiler steels. A 0.45% carbon, 3.5% nickel steel forging of moderate size oil quenched from 1,450° F will have the following properties after the respective draws:— Annealed eye-bar tension members (carbon 0.37%, nickel 3.3%) were first used in 1902 on a cantilever bridge across the East river, New York. The physical properties of this material in 16 by 2 in. bars were:— Design stresses on this bridge were 30,000 lb. per square inch; 50% more than customary for regular carbon steel eye-bars. Structural shapes with slightly lower carbon have been used in many long bridges since. High-pressure locomotive boilers of nickel steel are used on Canadian and American railroads. Proper ties in comparison with plain carbon steel boiler plate follow:— electrical properties. "Fernico" (28% nickel, 18% cobalt) has the same coefficient of expansion as glass, and is used for lead-in wires and glass-metal seals in electric light globes and radio tubes. "Nickeloy" (50% nickel) has high magnetic permeability, and is used for radio transformer cores. Permalloy (78% nickel) is dis cussed under TELEPHONE. Invar (35% nickel) is treated under INVAR. (See also ALLOYS ; IRON AND STEEL.) See J. S. Marsh, Alloys of Iron and Nickel. (E. E. T.)