激光焊接800MPa级RPC钢接头组织特征

RPC钢是一种具有超细的贝氏体组织和较好力学性能的新一代钢铁材料。激光焊接有很快的加热和冷却速度 ,热作用范围窄 ,在合适的工艺条件下可避免RPC钢HAZ的软化 ,激光焊接是高质量焊接RPC钢的方法之一。本文利用 4kWYAG激光对RPC钢焊接接头组织进行了实验研究 ,分析了在激光焊接工艺条件下焊接接头组织及其变化规律。实验结果表明 ,RPC钢激光焊接接头的主要组织是由板条状的贝氏体铁素体板条和板条间呈方向性分布的岛状的M -A组元组成的粒状贝氏体 ;随着热输入的增大 ,M -A组元的平均宽度、总量增大 ,M -A组元单位长度的数量减少 ,长条形M -A组元比例下降 ,而方块形M -A组元比例上升 ;焊接接头显微硬度随热输入的增大而减小 ,均高于母材 ,未出现明显的软化区。

Microstructure character in laser welding of 800MPa grade RPC steel

MPa grade RPC steel is the recently developed new generation steel, which has ultra-fine bainite and better mechanical properties. In order to avoid the possible softening of HAZ in welding of RPC steel, laser welding is one of the best methods due to its faster heating and cooling rate and narrower HAZ. The microstructure of laser welded joint of 800MPa grade RPC steel was investigated by a 4kW YAG laser. The experimental results indicate that the main microstructure of the laser welded joint is granular bainite which consists of the bainitic ferrite and the M-A constituent. As the heat input increases, the average width and areal fraction of M-A constituent increases, the number of the M-A constituent per mm decreases, the ratio of the elongated M-A constituent decreases and that of the massive M-A constituent increases. With the heat input of laser welding increases, the hardness of HAZ decreases, but it is higher than that of the base metal, indicating no softened zone after laser welding.