Cold-rolling performance of non-equilibrium martensitic stainless steel produced by laser-arc hybrid welding

Abstract

The cold rolling with the reduction up to 75% of martensitic stainless steel (MSS) weld was achieved on the basis of the sound laser-arc hybrid weld. The evolutions in the microstructure and crystallographic characteristics of this non-equilibrium structure were studied, which focused on the lower part of the weld because it was the poorest area. With the increase of the rolling reduction, the unordered austenite transformed to the fibrous martensite paralleled to the rolling direction. It decreased the weld toughness and increased the risk of breakage during continuous rolling. The tensile strength of the rolled weld increased by a factor about 2 compared to the weld before rolling, while the tensile ductility decreased by a factor of 10. The microstructure transformation mechanism was illustrated according to the thermodynamic analysis, which was depended on the nucleation probability of martensite, and the stress concentration caused by dislocation multiplication. The work hardening behavior was discussed on the basis of the phase transformation theory and dislocation strengthening. The microstructure-mechanical properties-rolling reduction relationship was established according to the measured data.