Cracking Behavior during DP980 Steel Plate Roll-Bending to Rectangular Tubing

Cracking behavior during DP980 steel plate roll-bending to rectangular tubing was investigated by microstructure and micromorphology observation. The results show that during the forming of the DP980 steel rectangular tubing, the plasticity near inner surface at the corner position was significantly lower than that near the outer surface. Cracks at the corner initiated from the inner surface and propagated along the location of martensite aggregation from inner surface to outer surface. At the initial stage, the cracks propagated in transgranular mode, and the fracture was cleavage fracture. The fracture at the end of cracks and the artificial fracture showed a mixed feature with quasi-cleavage fracture and ductile fracture.