TiN粒子在焊接热循环过程中的溶解、粗化及再析出行为

DISSOLUTION,COARSENING AND PRECIPITATION OF TiN PARTICLE IN Ti MICROALLOYED STEEL DURING WELDING THERMAL CYCLE

采用萃取复型技术 ,对经受焊接热循环不同阶段的试样进行研究 ,分析了TiN粒子在焊接热循环不同阶段的溶解、粗化及再析出行为。结果表明 ,在焊接热循环加热过程的低温阶段 (12 0 0℃以下 ) ,粒子的溶解以粒子的尺寸减小为主要特征 ,粒子数量变化不大。在焊接热循环加热过程的高温阶段 (12 0 0～ 135 0℃ ) ,大量小尺寸粒子消失 ,粒子平均尺寸显著增大。研究发现 ,TiN粒子的溶解存在很大的滞后效应 ,在冷却过程的高温阶段 (135 0～ 130 0℃ ) ,粒子仍继续溶解 ;在冷却过程的低温阶段 (130 0℃以下 ) ,固溶状态的Ti与N结合并沉淀到残留的TiN粒子上 ,使粒子粗化。在焊接热循环过程中 。

Carbon extraction replica analysis were carried out on the specimen in Ti microalloyed steel which is subjected to different stage of the welding thermal cycle so as to study the dissolution,coarsening and precipitation of TiN particle in Ti microalloyed steel during different stage of welding thermal cycle.It is concluded that at the low heating temperature stage(lower than 1?200?℃)of thermal cycle,the dissolution was characterized by shrinkage of particles and the number of particles did not decrease noticeably, which shows that particle coarsening was very weak.At the high heating temperature stage(1?200～1?350?℃)of thermal cycle, a large number of small particles disappeared with the mean particle size increment.It is found that TiN particles dissolution still occurred due to lag effect.At high temperature zone of cooling stage,the particles are dissolved continuously.At lower temperature zone of cooling stage,free Ti and N were combined and TiN reprecipatated onto the survived particles,thus the mean size increase remarkably.The austenite grains coarsening mainly occurred in the cooling stage of the welding thermal cycle.