钛稀土复合处理对C--Mn钢粗晶热影响区组织及韧性的影响

利用Gleeble-1500D热模拟机进行焊接热影响区热循环模拟实验,研究了在焊接热输入为65 kJ·cm-1时稀土单独处理和钛稀土复合处理对C-Mn钢粗晶热影响区组织及冲击韧性的影响,并利用扫描电镜观察和分析了实验钢中的夹杂物和冲击断口形貌,利用光镜观察了热循环模拟后实验钢中的微观组织.实验结果表明:稀土单独处理和钛稀土复合处理的试样微观组织分别主要是晶界铁素体+块状铁素体+针状铁素体和晶界铁素体+晶内针状铁素体.经稀土单独处理的试样中夹杂物为La₂O₂S+锰铝硅酸盐+MnS复合夹杂;钛稀土复合处理的试样中的夹杂主要是La₂O₂S+TiO_x+锰铝硅酸盐+MnS复合夹杂.钛稀土复合处理钢中的复合夹杂更细小,有利于形成细小的晶内针状铁素体.钛稀土复合处理极大地改善了实验钢的焊接热影响区低温冲击韧性,比稀土单独处理对试样的冲击性能提升效果更好. 

Influence of Ti-rare earth addition on microstructure and toughness of coarse grain heat-affected zone in C-Mn steel

The influences of rare earth (RE) and Ti-RE complex treatment on the microstructures and toughness in the coarse grain heat-affected zone (CGHAZ) of C-Mn steel were investigated using a Gleeble-1500D thermal simulator with input heat energy of 65 kJ·cm-1. The inclusions and impact fracture morphology were observed and analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX), and the microstructure was characterized using an optical microscope (OM). The results show that the microstructures in the CGHAZs of RE-and Ti-RE-treated samples are mainly grain boundary ferrite (GBF) + polygonal ferrite (PF) + intragranular acicular ferrite (IAF) and grain boundary ferrite + intragranular acicular ferrite, respectively. Inclusions in the RE-treated specimen are La₂O₂S + Mn-Al-Si-O + MnS, while those in the Ti-RE-treated specimen are La₂O₂S + TiO_x + Mn-Al-Si-O + MnS. The complex inclusions in Ti-RE-treated steel are smaller than those in RE-treated steel, and the size of IAF in Ti-RE-treated steel is smaller. The impact properties of the CGHAZ in Ti-RE-treated C-Mn steel is improved significantly, and the material is tougher than RE-treated steel.