Microalloying, processing optimisation and friction stir welding of ferretic stainless steel thick plate

With the breakthroughs in metallurgical technology and their excellent performance in hostile environment, ferritic stainless steel (FSS) grades are developed and extensively applied to replace pricy austenitic groups. Among ferritic groups, the frequently-used grades are 18Cr-2Mo and 17Cr ultra purified FSS stabilised by the elements of Nb, Ti and V. However, the bottleneck of ferritic groups with thick scales (above 4 mm) is their relatively high ductile-brittle transition temperature (DBTT). Thus, it is imperative to develop FSS with lower DBTT. On the other hand, to extend the use of FSS, welding is an indispensable process to produce steel structures in main industry. The development of novel welding methods attracts much attention.