厚板SA508-3钢NG-SAW焊接接头的组织和性能

Microstructure and properties of NG-SAW(Narrow gap shield arc welding)joint of SA508-3 thick steel plate

针对SA508-3钢,采用窄间隙埋弧焊方法对厚度100 mm钢板进行了焊接,分析不同焊接热输入下焊接接头的低温冲击、硬度分布、抗拉强度、弯曲性能,并对接头的显微组织和断口形貌进行了观察。试验结果表明,随着焊接热输入的增加,焊接接头中焊缝的冲击韧性逐渐增加,热影响区冲击韧性不断下降。不同焊接热输入下,焊接接头均有较好的韧性储备,弯曲性能均合格,焊接热输入的变化对接头的抗拉强度没有明显影响,焊接接头硬度最低的位置出现在母材处,焊接热输入越小,焊接热影响区的硬度越高。焊接接头中焊缝显微组织为先共析铁素体+回火贝氏体,随着焊接热输入的增加,先共析铁素体减少,回火贝氏体增多;焊接热影响显微组织为粒状回火贝氏体组织,随着焊接热输入的增加,热影响区的晶粒发生粗化。

SA508-3 steel of 100 mm thickness was welded by NG-SAW method.The low-temperature impact,hardness distribution,tensile strength and bending performance of the welded joints under different welding heat input were analyzed,and the microstructure and fracture morphology of the joints were observed.The test results show that the impact toughness of the weld in the welded joint increases gradually with the increase of welding heat input,while the impact toughness of the heat-affected zone decreases continuously.Under different welding heat input,the welded joints all have good toughness reserve and qualified bending performance.The change of welding heat input has no obvious influence on the tensile strength of the joint.The position with the lowest hardness of the welded joint appears at the base material,and the smaller the welding heat input is,the higher the hardness of the welding heat affected area is.In the welded joint,the microstructure of the weld is the pre-eutectoid ferrite+tempered bainite.With the increase of welding heat input,the pre-eutectoid ferrite decreases and the temper bainite increases.The microstructure of the welding heat affected area is granular tempered bainite,and with the increase of welding heat input,the grains of the heat affected area are coarsened.