8. Thermal Cycles of Metal During Welding

Heating of the welded joint is applied in almost all welding techniques. The thermal cycle of a metal (the change in the temperature of the metal in time) is determined by dimensions of the welded joint, initial and boundary conditions, thermophysical properties of the metal, parameters of the heating source and position of the metal to the source. Since the welding sources of heat are concentrated (as a rule, their dimensions are much smaller than the dimensions of the welded body), the heating of the metal is characterised by significant non-uniformity both in time and in space. For example, in arc welding of steel, the gradient of the peak temperature near the weld can reach hundreds of degrees per millimeter. Therefore, the thermal cycles of the metal of the adjacent zones of welded joint can be significantly different.