400 MPa级超细晶粒钢板焊接热影响区的组织和力学性能

超细晶粒钢的强度和韧性比普通晶粒钢有大幅度的提高，其焊接性是该钢能否获得广泛应用的关键。通过采用实际焊接和焊接热模拟方法，研究了焊接热输入对超细晶粒钢组织和力学性能的影响。研究结果表明，超细晶粒钢的奥氏体晶粒长大倾向与普通晶粒钢相近，在热影响区和母材之间存在一再结晶软化区，板厚小于3mm时，粗晶热影响区的裂纹扩展吸收能大于母材，板厚大于5mm时，粗晶热影响区韧性比母材有较大幅度降低。对影响粗晶热影响区韧性的机理进行了探讨。

Microstructures and mechanical properties of welding HAZ of 400 MPa ultra-fine grained steel

The strength and toughness of ultra-fine grained steel areraised a great deal compared to the normal grain steel. Weldability of ul-tra-fine grained steel is important for application of the steel. In this paperwelding and thermal simulation are conducted to study the effect of weld-ing heat input on the microstructures and mechanical properties of thesteel. Experimenal results indicate that the tendency of austenite graingrowth of ultra-fine grained steel is almost the same as normal grain steel.There is a softened zone between heat affected zone and base metal be-cause of recrystallization. For the steel plate thinner than 3 mm, the ab-sorption energy of crack propagating in coarse grain HAZ is higher thanthat of base metal. For the steel plate thicker than 5 mm,the toughness ofcoarse grain HAZ is nmch lower than that of base metal. The mechanismthat affects the toughness of coarse grain HAZ is studied.