Development and Applications of New Generation Ni-Containing Cryogenic Steels in PR China

In the present paper, an overview on the developments and applications of Ni-containing cryogenic steels is described with regard to the manufacturing processes. The relationship among Ni content, processing parameters and formation of reversed austenite has been worked out, which demonstrated that content and size of reversed austenite in Ni-containing steels can play important roles in improving their toughness. Based on extra-dephosphorization and desulphurization, new processing technologies have been developed. Controlled rolling in the aim of microstructure refinement and ultra-fast cooling (UFC) after hot rolling as on-line direct quenching has been successfully applied. Combining with inter-critical quenching and tempering after UFC-TMCP, the reversed austenite content was increased from 1.8 to 6.5%, leading to significant improvement of toughness. Several China’s steel works such as NISCO and Angang are capable of manufacturing high quality plates of Ni-containing steels, which are finding wide applications to building extra-large tanks for liquefied gases.