NULCB钢激光焊接接头组织、性能的研究

为了研究新一代超低碳贝氏体(NULCB)钢的焊接性,利用kW CO2激光对NULCB钢进行了焊接,并分析了焊接接头组织、性能的变化规律.试验结果表明,激光焊接接头显微硬度均高于母材,未出现明显的软化区;焊缝区和热影响区粗晶区组织均为贝氏体板条和M-A组元组成的粒状贝氏体;热输入由120J/mm～600J/mm范围内变化时,随着热输入的增大,M-A组元的平均宽度、总量、形状因子增大,M-A组元线密度减少;随热输入的增大,激光焊接焊缝区冲击吸收功先增大然后减小.合适的激光焊接条件下,激光焊接焊缝区具有良好的韧性,其低温冲击吸收功高于母材.

Microstructure and mechanical properties of laser welded joint of NULCB steel

In order to investigate the weldability of a new ultra-low carbon bainitic(NULCB) steel,the steel is welded with a 3kW CO_2 laser and the microstructure and mechanical properties of the weld joint are investigated.The experimental results indicate that the hardness of welded joint is higher than that of the base metal while the laser heat input is between 120J/mm and 600J/mm,and no obvious zone is softened after laser welding.The microstructure of the weld metal and the coarse-grained heat-affected zone are both granular bainite that consists of the bainite lath and the M-A constituent.When the heat input increases from 120J/mm to 600J/mm,the average width,gross and shape parameter of M-A increases,but the line density decreases.As the heat input of laser welding increases,the impact energy of the weld metal increases at first and then decreases,and it is higher than that of the base metal under appropriate laser welding conditions.