Prior austenite grain growth in heat-affected zone of a O.5Cr-Mo-V steel

Abstract

A weld thermal-simulation technique has been used to produce prior austenite grain sizes similar to those observed in the heat-affected zones (HAZs) of O.5Cr-Mo-V welds. Grain-size measurements have been used to develop an Arrhenius equation for grain growth in artificial HAZs. This equation is in reasonable agreement with an ‘impurity drag’ theory for grain growth. In applying the equation to weld HAZs it was found that the steep thermal gradients present resulted in a ‘thermal pinning’ effect which inhibited growth. A final expression has been obtained which describes prior austenite grain growth in manual metal arc weld HAZs in 0.5 Cr-Mo- V steel as a function of heat input. The practical implications of this equation are discussed in terms of grain-size control in the HAZ during welding and these indicate that finegrained HAZs can be produced by low heat inputs and a suitable weld-bead overlap technique. In principle, the approach described