An overview of the heat-affected zone sensitization and stress corrosion cracking behaviour of 12% chromium type 1.4003 ferritic stainless steel

摘要

This document presents an overview of the findings of several investigations into thesusceptibility of 12% chromium type 1.4003 ferritic stainless steel to heat-affected zonesensitization and intergranular stress corrosion cracking. A description of the sensitizationbehaviour of these steels is complicated by the partial transformation of d-ferrite to austeniteon cooling. During slow cooling or annealing below the A1 temperature, this austenitedecomposes to form desensitized ferrite and M23C6-type carbide precipitates. The rapidcooling rates associated with welding, however, prevent the transformation of austenite toferrite at lower temperatures, and any austenite formed on cooling transforms to martensitebelow the Ms-temperature. Four distinct modes of heat-affected zone sensitization havebeen identified to date. Sensitization of the martensite phase may occur on welding materialinadvertently annealed above the A1 temperature (Mode 1), or when multiple welds arepositioned in such a way that the heat-affected zone of the 2nd pass overlaps the heataffectedzone of the 1st pass (Mode 2). Rapid cooling after very low heat input welding maysensitize the ferrite phase (Mode 3), whereas very slow cooling after welding at excessivelyhigh heat input levels may lead to sensitization of the austenite phase (Mode 4). Resultsexamining the influence of Modes 1 and 2 heat-affected zone sensitization on the incidenceof intergranular stress corrosion cracking are presented.