Diagram for the prediction of weld heat-affected zone microstructure

Abstract

The performance of welded joints, both during fabrication and operation, can depend critically upon the microstructure ofthe heat-affected zone, which, in a steel of given composition, is a function of the welding procedure andjoint geometry. The selection of suitable welding conditions which avoid the formation of crack-sensitive structures is clearly desirable. Standard heat-flow equations have been used in conjunction with continuous cooling transformation diagrams, determined using a weld simulation and dilatometric technique, to predict as-welded heat-affected zone microstructures for a wide range ofwelding conditions. A novel microstructure-welding diagram is described in which the variation in heat-affected zone microstructure as a function of process heat input, joint thickness, and preheat temperature is presented in a readily comprehensible form. A 0.5Cr-Mo-V steam-pipe composition is used as a detailed example, but the method is, in principle, applicable to a wide range ofsteel compositions.