Q355C钢板超低温焊接接头组织与性能研究

Study on microstructure and properties of welded joint of Q355C steel plate in ultra-low temperature

为研究Q355C钢板的超低温焊接工艺,进行了-20℃超低温环境下的焊接工艺方案设计,并完成了相应的焊接工艺评定试验。对焊后Q355C钢板进行了焊接接头力学性能测试及金相组织观察分析。结果表明:25 mm厚Q355C钢板在超低温环境下,焊前进行40℃预热,层间温度控制在40~250℃之间,焊后进行250℃×2 h的加热和保温缓冷,焊接接头拉伸、弯曲等各方面力学性能满足规范要求;焊缝处金相组织为先共析铁素体(PF)+侧板条铁素体(FSP)+针状铁素体(AF);热影响区粗晶区晶粒粗大、硬度较高,但没有出现淬硬组织。

In order to study the ultra-low temperature welding process of Q355 C steel, the welding process scheme was designed at-20 ℃ and the corresponding welding process qualification test was completed. The mechanical properties and metallographic structure of welded joint of Q355 C steel were tested and analyzed. The results showed that Q355 C steel plate with thickness of 25 mm was preheated at 40 ℃ before welding, the interpass temperatu was controlled at40~250 ℃, and heated at 250 ℃×2 h after welding. The tensile, bending and mechanical properties of welded joints met the requirements of the specification. The metallographic structure of the weld was proeutectoid ferrite(PF) +side lath ferrite(FSP) +acicular ferrite(AF). The coarse grain zone in HAZ was coarse in grain size and high in hardness, but there was no hardened structure.