scope:

The quality of a weld is a function of many factors: the type and quality of metal deposited, the heat treatment inevitably experienced by the deposited metal and by the parent metal around the weld (the heat-affected zone), and the residual stresses left in both the parent and deposited metal. This discussion will be concerned with the qualality of a weld as affected by heat flow, that is, temperature and temperature histories. Both temperature and time affect the heat treatment experienced by both the deposited and parent metal. Temperature and temperature distributions affect expansion and contraction and the relationship between stress and strain and thus, residual stresses. These relationships are known but because of the complexity of the heat flow and stress-strain relationships, few quantitative relationships useful to a practicing welding engineer exist. Thus reliance has been quite properly placed on experience and an empirically developed knowledge. Fundamental work in understanding these relationships has been going on and while completely precise relationships are not yet available, the subject is now well enough systematized to serve as useful background material for a practicing welding engineer.