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在无预热和焊后热处理条件下,采用熔化极气体保护焊(GMAW)对10 mm厚的调质高强钢Q690D进行三道次焊接试验,通过组织观察和硬度测试分析了该钢焊接接头组织转变特征及硬度分布规律。结果表明,Q690D热影响区组织主要为粒状贝氏体和少量下贝氏体,热影响区产生软化现象,最大失强率达到23%,粗晶区受再热作用后发生组织遗传;采用实芯焊丝CHW-70C(ER69-G)使焊缝得到90%的针状铁素体组织,硬度值比母材低;为控制软化区宽度,焊接线能量以8 kJ/cm为宜。
In the condition of no preheat and post-weld heat treatment, three-pass welding test of 10 mm-thick quenched and tempered high-strength steel Q690D was carried out by using GMAW. The microstructure and hardness of the welded joint were analyzed by means of microstructure observation and hardness test. Change characteristics and hardness distribution. The results showed that the tissue of Q690D heat-affected zone mainly consisted of granular bainite and a few of lower bainite. The softening phenomenon occurred in the heat-affected zone, with the maximum loss rate reaching 23%. The coarse grain zone was reheated and then hereditary. The core wire CHW-70C (ER69-G) made the weld get 90% acicular ferrite structure, the hardness value is lower than that of the base metal. To control the width of the softened zone, the welding wire energy is preferably 8 kJ / cm.