超细化低碳贝氏体钢焊接性能的研究

Study on Weldability of Low-Carbon Bainitic Steel With Ultrafine Microstructure

针对超细化低碳贝氏体钢，采用裂纹敏感性指数Pcm斜Y坡口接头裂纹率和模拟粗晶热影响区（CGHAZ）的硬度等参数评价了焊接冷裂纹倾向，研究了不同线能量下模拟CGHAZ和气体保护焊（MIG）接头的组织结构和力学性能。实验结果表明：钢的焊接淬硬倾向低，预热温度50℃以上可完全避免焊接冷裂纹产生；采用14～25kJ／cm的小线能量焊接时，CGHAZ由原奥氏体晶内不同位向的贝氏体铁素体板条束和少量粒状组织构成，具有较高的抗冲击脆断性；与YS800焊丝配套的气体保护焊接头力学性能优异。

The weldability of a low-carbon bainitic steel with ultrafine microstructure was evaluated using calculated cracking susceptibility index Pcm, restrained Y-groove depositing test and microstructure and mechanical examination of simulated coarse-grain heat-affected zone （CGHAZ） and the gas-metal-arc-welded （MIG） joint. It was shown that the steel has low hardenability and cold-cracking susceptibility during welding with preheating temperature of 50 ℃ or above and a large restraint. When the energy input as low as 14-25 kJ/cm is used, the CGHAZ is mainly composed of lath-like bainitic ferrite with different directions and a small amount of granular islands in the prior austenite grain, which result in a tough microstructure with high resistance to brittle cracking. Excellent mechanical properties can be obtained by using YS800 welding wire as the filler metal.