Cold Working

a change in the structures—and correspondingly the properties—of metals and alloys caused by plastic deformation of a workpiece at a temperature below its recrystallization temperature. The industrial process of producing a strengthened state of materials by cold plastic deformation of the surface is also called cold working.

The phenomenon of cold working may be explained by the accumulation within the metal of part of the energy of deformation that is expended on distortion of the crystal lattice, formation of predominantly oriented crystals (structures), changes in the dislocational structure, and an increase of the specific volume of the metal in the layer. Cold working may also be the result of action of external deformation forces (deformation cold working) or, less frequently, of phase transformation (phase cold working). Cold working is accompanied by an increase in strength and hardness and a decrease in plasticity.

Cold working is used for surface hardening of parts. In addition, it generates a favorable system of residual strains in the surface layer of the metal; the effect of such strains is mainly responsible for the large strengthening effect of surface plastic deformation, which is reflected in increased fatigue strength and sometimes in increased wear resistance.

Cold working is performed by special methods, using special equipment. For example, cold rolling of cylindrical surfaces is performed by rollers, gear teeth are hardened by rollers or toothed rollers, shaped articles are hardened by shot peening, and other articles are hardened by impact tools.

REFERENCES

Kudriavtsev, I. V.Poverkhnostnyi naklep dlia povysheniia prochnosti i dolgovechnosti detalei mashin, 2nd ed. Moscow, 1969.

Bernshtein, M. L. , and V. A. Zaimovskii. Struktura i mekhanicheskie svoistva metallov. Moscow, 1970.