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为了提高车用超高强钢激光焊接技术的发展,采用光纤激光器对1.9mm厚的22MnB5钢板进行激光对焊以及22MnB5与Q235钢板的激光拼焊。研究了激光焊接接头的微观组织、硬度以及拉伸性能的变化,分析了焊接速度对接头组织、性能的影响。结果表明,22MnB5钢焊缝组织主要是板条马氏体,22MnB5热影响区可分为完全淬火区、不完全淬火区和回火区,而Q235热影响区不存在回火区。焊接接头硬度分布不均匀,在焊缝边缘硬度最高。热影响区很窄,硬度急剧下降,22MnB5热影响区存在严重的软化区,最低硬度仅为319.6HV,Q235热影响区不存在软化区。随着焊接速度的增加,焊缝组织变得细小,马氏体含量增多,当焊速达到5m/min时,22MnB5焊缝最高硬度达到544.2HV。在垂直于焊缝的负载下,焊接速度为3~5m/min时,22MnB5拉伸试样均断裂在热影响区,塑性较差,断后延伸率仅为2%左右,而母材的断后延伸率却达到了8.9%。
In order to improve the development of automotive ultra-high-strength steel laser welding technology, the fiber laser was used to laser butt weld the 1.9mm thick 22MnB5 steel plate and the laser welded steel plate of 22MnB5 and Q235 steel. The microstructure, hardness and tensile properties of the laser welded joint were studied. The effect of welding speed on the microstructure and properties of the joint was analyzed. The results show that the weld microstructure of 22MnB5 steel is mainly lath martensite. The heat affected zone of 22MnB5 can be divided into fully quenched zone, incomplete quenched zone and tempered zone, while there is no tempering zone in Q235 heat affected zone. The weld joint hardness distribution is not uniform, the highest in the weld edge hardness. The HAZ is very narrow and the hardness drops sharply. There is a serious softening zone in the heat-affected zone of 22MnB5 with the lowest hardness of only 319.6HV. There is no softening zone in the Q235 heat-affected zone. With the increase of welding speed, the weld microstructure becomes small and the content of martensite increases. When the welding speed reaches 5m / min, the maximum hardness of 22MnB5 weld reaches 544.2HV. When the welding speed is 3 ~ 5m / min under the load perpendicular to the weld, the tensile specimens of 22MnB5 fracture in the heat-affected zone, the plasticity is poor, the elongation after fracture is only about 2%, while the base material elongation after fracture The rate has reached 8.9%.