Effect of stress relief on microstructure and mechanical properties of flow formed maraging steel weldment by electron beam welding

The technique of forward flow forming has been used to produce a long and thin wall tube of C-250 maraging steel. The work hardening effect of solution treated C-250 by flow forming is small. Therefore aging treatment after flow forming is required to increase hardness and strength. Final formed C-250 tubes are usually manufactured by combining aging treatment and electron beam welding (EBW). The hardness and tensile strength of aged C-250 maraging steel weldment decreased to the corresponding values obtained in the solution annealed state. Thus, the formed tube by EBW requires stress relieving treatment (and similarly for the aged condition) to increase hardness and strength and thus meet the required specification. The strength requirement was successfully achieved but the elongation of the aged, EBW, and stress relieved specimen was 88.5% lower than that of the unwelded specimen. (C) 2003 IoM Communications Ltd. Published by Maney for the Institute of Materials, Minerals and Mining.