钙处理对稀土在大线能量焊接HAZ中作用的影响

 为了探明钙处理对稀土改善C-Mn钢焊接HAZ韧性作用的影响,利用Gleeble模拟了热输入为339 kJ/cm的焊接热循环过程,对比研究了稀土处理钢和Ca-稀土处理钢焊接HAZ中夹杂物、显微组织和低温冲击韧性差异,分析了钙对稀土在HAZ中作用的影响规律,发现钙处理能促进稀土改善HAZ低温冲击韧性。钙能使稀土处理钢HAZ中的夹杂物从稀土氧化物复合夹杂转变为稀土-Ca的复合夹杂,平均尺寸从1.5增大到2.2 μm,长宽比从1.5减小到1.4,夹杂物总量降低。虽然钙对稀土处理钢HAZ中晶内针状铁素体的含量影响不大,但钙能增强稀土对HAZ原奥氏体晶粒粗化的抑制作用,Ca-稀土处理钢HAZ原奥氏体晶粒尺寸比稀土处理钢小。热输入为339 kJ/cm时,钙处理能使稀土处理钢HAZ低温冲击韧性明显提高。

Influence of Ca treatment on application of rare earth in HAZ during high heat input welding progress

To make clear the influence of Ca treatment on the effect of Rare Earth (RE) to improve the toughness of Heat Affected Zone (HAZ) in C-Mn steel,Gleeble was used to simulate the welding thermal cycle process with a heat input of 339 kJ/cm. The differences in inclusion,microstructure and low-temperature impact toughness in HAZ between RE treated steel and Ca-RE treated steel were compared. At last,the influence of Ca on the role of RE in HAZ was studied. It was found that Ca can promote the function of RE to improve the low temperature impact toughness in HAZ. The inclusions in HAZ of RE treated steel transformed from complex inclusions containing RE_xO_y to that of RE and Ca when treated with Ca,thereby decreasing the total amount of inclusions. Ca treatment also resulted in the increase in the mean size of the inclusions from 1.5 to 2.2 μm,while a decrease in the aspect ratio from 1.5 to 1.4. Although Ca had little effect on the content of acicular ferrite in HAZ of RE-treated steel,however,the inhibition of RE on prior austenite grain coarsening in HAZ was enhanced by Ca treatment,with a smaller grain size than that of the RE treated steel. The low-temperature impact toughness in HAZ of RE treated steel was obviously improved by Ca treatment When the heat input was 339 kJ/cm.