Oxide metallurgy technology plays an important role in inclusion control and is also applied to improve the weldability of high strength steel. Based on the requirements of the weldability in high strength steel, the influencing factors of weld heat affected zone (HAZ) as well as the development and application status of oxide metallurgy technology are summarized in this review. Moreover, the advantages and difficulties in the application of rare earth (RE) oxide metallurgy technology are analyzed, combined with the performance mechanism of RE and its formation characteristics of fine and high melting point RE inclusions with distribution dispersed in liquid steel. With the weldability diversities of different high strength steels, the research status of weldability of high strength steel with high carbon equivalent and the effects of RE on the microstructure and properties of HAZ are discussed, and some suggestions about further research in the future are proposed.

In the present work, the carbides and inclusions in H13 steel with different magnesium contents were investigated with the scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and were calculated by the ThermoCalc and FactSage softwares, respectively. The growth of the MgAl₂O₄ spinel and Al₂O₃ at 1500°C in molten H13 was analysed by the confocal laser scanning microscopy (CLSM). The disregistries between the carbides and other phases were computed. The results are as follows. The primary carbides formed in H13 ingots were M(CN) and M₆C, which existed in the segregation areas only. The MgAl₂O₄ particles, acting as more effective heterogeneous nuclei and providing more nucleation sites than Al₂O₃ particles, induced the formation of more developed austenite dendrites, and a greater number, smaller size and more uniform distribution of primary carbides, which finally relieved carbide segregation.

The evolution of the carbides and mechanical properties of 7Cr17MoV stainless steel used as cutlery material during cold rolling was investigated in this study. The results demonstrate that the microstructure of the rolled steel is composed of pearlite and spheroidal carbides. After cold rolling, the aggregation of carbides was no longer evident, and the carbides appeared to be small in size and uniformly distributed, whereas carbides in hot-rolled strips are clearly aggregated. Decreasing the thickness of the cold-rolled strips decreased the size of the carbide particles while increasing their number, which improved the particle distribution. A large number of fine, even nano-scaled carbides were observed in the material. The carbide phase, which primarily consisted of M₂₃C₆, did not change during cold rolling and annealing. The tensile strength and yield strength first decreased and then increased, and the elongation increased as the thickness of the cold-rolled strips decreased. Dimples and inclusion particles were readily observed upon tensile fracture. The inclusions are identified to be primarily carbides and oxide inclusions.