夹杂物对Ti,Zr微合金钢中针状铁素体形成的影响

Effect of Inclusions on Formation of Acicular Ferrite in Ti and Zr Micro-alloying Steel

采用实验室真空感应炉,炼制了3炉35 kg钢锭.利用MMS-300型热模拟机对实验钢进行线能量为100 kJ/cm,峰值温度为1 400℃的大热输入焊接模拟实验.借助金相显微镜（OM）、扫描电子显微镜（SEM）、能谱分析仪（EDS）和电子探针显微镜（EPMA）对粗晶热影响区（CGHAZ）组织进行观察;研究了热循环后夹杂物的数量、大小、分布和组成对焊接热影响区（HAZ）中针状铁素体形成的影响.结果表明：在粗晶热影响区中针状铁素体的数量随小尺寸氧化物夹杂的数量和面积分数的增加而增加;针状铁素体在Ti,Zr为主的复合夹杂物上形核,这些夹杂物多以Ti,Zr氧化物为核心,表面析出MnS,尺寸在0.5~3μm之间.

The 35 kg ingot was refined with vacuum induction furnace in laboratory. The high heat input welding thermal simulation test was conducted in 100 kJ/cm heat input at 1 400℃ top temperature by using thermal simulator MMS-300. The microstructure was observed, and the effect of number, size, distribution and composition of oxide inclusions on the formation of acicular ferrite in coarse grain heat affected zone （CGHAZ） was studied with optical microscope （OM）, scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS） and electron probe micro-analyzer （EPMA）. The results showed that the fraction of acicular ferrite in CGHAZ increases with the number and area fraction of oxide inclusions. Acicular ferrite forms on Ti, Zr complex inclusions, the inclusions are mostly Ti, Zr oxide as the core, and MnS precipitates on the surface of oxide inclusions, with size in the range of 0.5-3μm.