Properties of Welding Heat Affected Zone of a Cu Precipitation Strengthened Ferrite Steel

By Gleeble simulation tests,microstructures and properties of the heat affected zone(HAZ) for a low carbon Cu nano-precipitation strengthened ferrite steel are investigated. The results show that the microstructures of HAZ are ferrite except for those in coarse-grain HAZ which are dominated by bainite plus granite bainite. Cu nano-precipitation changes to the thermal cycle course,affecting the properties of HAZ. The coarse-grain HAZ exhibits comparable impact energy and microhardness to the unaffected base metal,while the impact energy in other HAZ regions are higher than the base metal and a certain loss of microhardness is observed as a result of dissolution of the Cu precipitates after the weld thermal cycle. The coarse-grain zone is sensitive to heat input in the range of heat inputs investigated in the study. With the t_8/5increasing,the microstructure coarsens and more granular bainites are produced and the impact energy decreases obviously.