Newly developed welding process and its applications to ultra-fine-grained steel

Abstract

Low carbon low alloy high strength steel materials for welding structures developed and used in service applications are roughly divided into: 1) steels with low content of alloying elements and which are hot-rolled, or which have annealed structures (eg. SM steel); 2) thermo-mechanically treated steels with restricted additions of alloying elements (eg. TMCP steel); 3) steels strengthened with the addition of alloying elements and through the thermal refining process (eg. high strength low carbon and low alloy steels like HT780). In recent years, in view of saving resources, reducing costs and making welding easier, research and development have been carried out to produce high strength steels for welding structures with tensile strength of 800 MPa level with the low carbon equivalence of mild steel levels.^1,2