不同强度级别低合金钢焊缝金属的组织特征及其对韧性的影响

焊接区的微观组织是决定其力学性能的关键因素。为了改善低合金钢焊缝的冲击韧性,对500~1 000MPa级焊条的焊缝金属的化学组成、金相组织和力学性能进行了对比研究。采用金相显微镜和透射电子显微镜对不同强度级别的低合金钢焊缝组织进行了观察和电子衍射分析,并进行了焊缝金属拉伸强度和冲击韧性测试。结果表明,随着焊条强度级别的增加,焊缝组织由先共析铁素体、针状铁素体加珠光体变成粒状贝氏体,最后变成贝氏体加马氏体组织;当焊缝组织为粒状贝氏体时其韧性最低。

Microstructure Character and Its Effect on Toughness for Weld Metals With Different Strength Grades

Microstructure is a crucial influence factor for the mechanical properties of welded joint. In order to improve the impact toughness of weld metals for low alloy steel, chemical compositions, microstructures and mechanical properties of 500-1000MPa grade weld metals produced by shielded metal arc welding were analyzed and compared. Optical microscope and transmission electronic microscope were used for microstructure and electron-diffraction analysis. Tensile strength and impact toughness of the weld metal were tested. The results indicate that with the increase of strength grade of coated electrode, the microstructure of weld metal changes from proeutectoid ferrite+acicular ferrite+perlite to granular bainite, and then to bainite+martensite. Weld metal shows the lowest toughness when its microstructure is granular bainite.