Influence of heat input and pre- weld heat treatment condition on properties of maraging steel weldments

Abstract

This study is focused on the dependence of microstructure and mechanical properties of maraging steel welded joints on both heat input and pre-weld heat treatment condition. Two different procedures were used for producing fully heat treated welded joints. Procedure I included solution annealing before welding then, aging after welding. Procedure II included full heat treatment (solution annealing and aging) before welding then, aging after welding. It is found that optimizing heat input decreased austenite content and prevented coarsening of weld metal dendritic structure, HAZ grain size and grain boundary precipitates which in turn prevented softening of welded joints. Restoring properties in the HAZ and developing good strength in the weld metal are depended on pre-weld heat treatment condition. Optimum combination of tensile strength, elongation, toughness and structure of welded joints are attained using procedure I. This is due to forming of homogeneous microstrcture consisting of fine weld metal dendrites, fine martensite and fine intermetallic compounds in addition to less retained austenite. However, satisfactory welded joints can be obtained using procedure II which should be applied in the case of manufacturing large-size welded assemblies since only the welding zone are treated locally after assembly. Key words : Maraging steels, GTA welding, Heat input, Pre-weld heat treatment condition, Post weld heat treatment, HAZ and weld metal microstructures. Tensile strength, Elongation, Ductility, Toughness.