A NEW TECHNOLOGY OF LOCAL EXPLOSION SHOCK WAVE DEFORMATION FOR IMPROVING WELDED JOINT TOUGHNESS BEFORE WELDING

摘要

It is well known that the toughness of HAZ was damaged after steels were experienced welding thermal cycles. Compared with weld metals, the toughness in HAZ is difficult to control and adjust. In order to meet the requirement for more and more high toughness in HAZ, generally such measures are taken to remarkably increase the toughness of parent metals in the production of steels that the toughness in HAZ would be lift to some degree simultaneously. But these measures are not economical and will take much time. In addition, the most position in the structures made by these steels is too enough to be wasted according to design specification.In order to overcome these shortages, a new technology, local explosion pre-treatment was developed to locally improve the worst HAZ, which make HAZ be subjected to explosive shock wave deformation before welding. In these local zones,highly density of sub structure defects such as dislocations and defaults and twins are generated and homogeneously distributed, so these defects will be helpful to the improvement of toughness in HAZ as following factors: ● To refine the grain sizes because these defects become as the nuclear of re-crystallization. ● To fasten carbon diffusion which makes transformation more homogeneous and equilibrium. ● To fasten hydrogen transmission from weld metal to parent metal to avoid cold cracking in HAZ and Weld metal.