| In 21st century, a lot of changes is expected in industrial and social circumstance due to the fast development in technology and high performance structural steels are required to response to the new environment more efficiently. Remakable improvements in strength, toughness and weldability and good recyclability are discussed as the quality requirements for new high performance structural steels. Among various metallurgical methods, grain refinement to 1㎛ size was selected as the most promising method to meet the quality requirement of new structural steels. Multi-variant, multi-axis deformation, deformation induced transformation and the use of high magnetic field have been discussed as the new technologies for ultra grain refining. In this paper, theoretical background and recent experimental results of new technologies are critically reviewed and the future research and developing direction of ultra fine grain steel was discussed. |
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