Effects of rolling process and microstructure on the brittle crack initiation and arrest of a marine steel under low-temperature

The effects of the rolling process and microstructure on the brittle crack initiation and arrest of marine steel were systematically investigated. The microstructures of two steel plates produced by different rolling processes were observed and analyzed. The results demonstrated that the rolling process significantly influenced the microstructure. As the rolling temperature decreased, the grain size decreased, the high-angle grain boundary (HAGB) content increased, and the average grain misorientation angle increased. The brittle crack initiation and the arrest abilities were evaluated by initiation fracture toughness and crack arrest toughness, respectively. The initiation fracture toughness and crack arrest toughness increased with the decreasing grain size and the increasing content of HAGBs. Finally, the influence of microstructure on the brittle crack initiation and arrest ability was explained from two aspects: (1) the critical event of crack initiation at low temperatures, and (2) the hindering effect of HAGB on the propagation of brittle cracks. The average grain size decreased with the decreasing rolling temperature. The high-angle grain boundary content and the grain misorientation angles increased with the decreasing rolling temperature. The critical fracture stress increased with the decrease in the critical crack size. The high-angle grain boundary altered the brittle crack propagation path and improved the crack arrest ability.