Much medium-carbon steel is alloyed with nicked, chromium or vanadium to provide material of superior strength and elasticity for moving parts of marine engines, automobile parts and other fittings where lightness and great strength are desirable in a steel of moderate cost. The strength and reliability of these forgings are increased by a process of heating to a red heat, quenching in oil (a residue of petroleum or a fish oil) and then annealing slightly. The effects of this treatment vary with different percentages of contained carbon and with different quenching temperatures. These have been studied and tabulated at some length by investigators. Gun forgings, and in some processes, armor and projectiles, are oil tempered.