Effect of heat treatment on microstructures of flow formed C-250 maraging steel

The technique of forward flow forming has been used to produce a long thin walled tube of C-250 maraging steel. Forward flow forming can conserve material, increase strength and reduce production process time. Since the hardness of solution treated C-250, using flow forming, can be increased by approximately 16·2%, flow formed tube must be given an additional aging treatment to increase hardness and strength. Direct aging treatment yields low elongation, which is not suited to design requirements. Using a homogenisation treatment, the microstructure of C-250 was of coarse grained lath type on aging and of needle type after solution treatment and aging. These treatments resulted in low tensile strength, and tensile fracture showed a tendency to brittleness. A 'solution + aging' treatment yielded greater strength and elongation.