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QP980淬火-配分钢热模拟激光焊接热影响区性能

Thermal simulation laser welding heat affected zone performance of QP980 quenching-partitioning steel

  • 摘要: 文中采用Gleeble-3500热模拟系统对QP980淬火-配分钢激光焊接热影响区(heat affected zone,HAZ)不同亚区进行热模拟,通过研究HAZ不同亚区的组织和性能,并与焊接接头HAZ相同区域进行比较. 结果表明,热模拟获得的焊接HAZ各亚区组织与激光焊接接头相同区域的组织一致. 力学性能分析表明,在热模拟试样中,亚临界热影响区(sub-critical heat affected zone,SCHAZ)抗拉强度和硬度都最低,断后伸长率在整个焊接HAZ中最大. 拉伸试验中SCHAZ发生了明显的伸长,表明延展性能最好. 焊接接头横截面硬度分析表明,焊接接头的临界热影响区(inter-critical heat affected zone, ICHAZ)硬度低于母材( base metal, BM),为焊接接头的软化区. 焊接接头的拉伸性能及横截面硬度分布表明焊接接头的薄弱区域位于焊接HAZ的ICHAZ,与模拟焊接HAZ的性能吻合. 通过对SCHAZ的组织进行分析,相比BM的几何必须位错密度(geometrically necessary dislocations,GND)减少,平均晶粒尺寸增大,小角度晶界晶粒含量下降.

     

    Abstract: In this study, Gleeble-3500 thermal simulation system was used to simulate the different sub-regions of the heat affected zone of QP980 quenching-partitioning steel laser welding. The microstructure and properties of each sub-zone were studied and compared with the same area of the heat affected zone of the welded joint. The results showed that the microstructure of each sub-region of the welding heat affected zone obtained by thermal simulation is consistent with that of the same region of the laser welded joints. The mechanical properties analysis showed that the tensile strength and hardness of the sub-critical heat affected zone(SCHAZ) are the lowest in the thermal simulation samples, and the elongation after fracture is the largest in the whole welding heat affected zone. In the tensile test, obvious elongation also occurred in this area, indicating that its ductility was the best. The hardness analysis of the cross section of the welded joint showed that the hardness of the inter-critical heat affected zone(ICHAZ)of the welded joint is lower than that of the base metal(BM), which is the softening zone of the welded joint. The tensile properties and cross-sectional hardness distribution of the welded joint showed that the weak area of the welded joint is located in the ICHAZ, which is consistent with the performance of the simulated welding heat affected zone. Through the analysis of the microstructure of the SCHAZ, compared with the BM, the geometrically necessary dislocations (GND) must be reduced, the average grain size is increased, and the small angle grain content is decreased.

     

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