Abstract: The manual welding on 7 mm plate of ultra-fine-grained steel SS400 (/% : 0.18C, 0.04Si, 0.43Mn, 0.022Al, 0.002Ca) has been carried out by using J442 (/% : ≤0.12C, 0.3-0.6Mn) , J506 (/% :≤0.12C, 1.6Mn) and J507 (/% : ≤0.12C, ≤1.25Mn) welding rod with heat input 6-14 kJ/cm, and the structure and microhardness of welded joint are observed and measured by optical microscope and microhardness tester. Results show that with increasing alloy element content in welding rod, the amount of acicular ferrite in welded zone increases； as heat input ≤10 kJ/cm, the change of size of coarse grain in heat affected zone is minor, and as heat input is larger than 10 kJ/cm, the size of coarse grain in heat affected zone increases obviously ； the microhardness of welded joint with different welding process is all higher than the microhardness of base metal, there is no soften zone in welded joint.

Key words: Ultra-fine-grained Steel, SS400, Welded Joint, Heat Input, Structure, Hardness

摘要： 分别采用J442(/%:≤0.12C、0.3~0.6Mn)、J506(/%:≤0.12C、≤1.6Mn)和J507(/%:≤0.12C、≤1.25Mn)焊条对7 mm SS400钢板(/%:0.18C、0.04Si、0.43Mn、0.022Al、0.002Ca)在热输入6~14 kJ/cm下进行手工电弧焊实验,并通过光学显微镜和显微硬度计观察和测试焊接接头的组织和硬度。结果表明,随焊条合金元素含量的增加,焊缝组织中针状铁素体量增加,当热输入≤10 kJ/cm时,焊接热影响区粗晶尺寸变化不大,当热输入大于10 kJ/cm时,粗晶尺寸明显增大;不同焊接工艺焊接接头的显微硬度均高于母材的显微硬度,没有接头软化现象。

关键词: 超细晶粒钢, SS400, 焊接接头, 热输入, 组织, 硬度