热输入对3Cr耐候钢MAG焊缝金属组织和性能的影响
Effect of heat input on microstructure and properties of weld metal in MAG welding of weathering steel
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摘要: 采用三种热输入进行3Cr耐候钢MAG焊，借助金相显微镜、扫描电子显微镜及透射电子显微镜分析了热输入对焊缝金属组织和性能的影响.结果表明，三种热输入焊缝金属组织主要由板条贝氏体、粒状贝氏体和M-A组元组成.随着焊接热输入的增加，焊缝组织中粒状贝氏体含量增加；M-A组元含量增加且尺寸增大.随着热输入的增加，焊缝金属冲击韧性降低.组织粗化、M-A组元含量增加尺寸增大是导致其韧性降低的主要原因.接头不同区域耐蚀性能相当，腐蚀产物主要由α-FeOOH组成.热输入为8~12 kJ，采用所选焊丝焊接高强耐候钢能够获得强韧性、耐蚀性匹配良好的焊接接头.热输入为8 kJ，接头综合性能最佳.Abstract: The 3Cr weathering steels were welded by MAG with three heat inputs, and the effects of heat input on microstructure and properties of the weld metal were investigated by means of optical microscopy, scanning electron microscopy and transmission electron microscopy. The results indicate that the microstructure of the three weld metal consists predominantly of lath bainite, granular bainite and M-A constituent. With the increasing of the heat input, the amount of granular bainite and M-A constituent increase, and the size of M-A constituent increases. The impact toughness of weld metal drops with the increasing of heat input. Microstructure coarsening and the increasing of the content and size of M-A constituent are the main reasons of toughness deterioration. The welded joints show nearly the same corrosion resistance property for different region, and the corrosion product consists predominantly of α-FeOOH. Welded joints with good properties can be obtained with the heat input between 8 to12 kJ, and joint with the heat input of 8 kJ shows the best performance.
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Key words:
- heat input /
- weld metal /
- microstructure /
- properties
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