冷却时间对Ti微合金钢焊接粗晶区组织及韧性的影响

EFFECT OF COOLING TIME ON CGHAZ TOUGHNESS AND MICROSTRUCTURE OF Ti MICROALLOYED STEEL

利用光镜、金属薄膜电子显微分析技术、碳萃取复型电子显微分析技术、系列Charpy冲击试验等对Ti微合金钢模拟粗晶区的组织及韧性进行了研究结果表明，随着800-500℃冷却时间的增加，该区域原始奥氏体（γ）晶粒长大并不严重；二次组织由上贝氏体为主逐渐转变为针状铁素体为主；珠光体的形态由非层片相间变为层片相间；M-A组元由条状变为块状，且数量减少，因此韧性得以提高．电子衍射及EDX分析还表明，该区域中的第二相粒子主要为TIN，亦有少量MnS，Ti3Al和AlN等．

The toughness and microstructure of CGHAZ of Ti microalloyed steel were investigated by means of OM, TEM of carbon extraction replica and metal foil, and series charpy impact testing. The results showed that with the increase of cooling time (t8/5), the austenite grain coarsening was not serious, the microstructure varied from a mixture comprised mainly of upper bainite to a mixture comprised mainly of acicular ferrite, the pearlite changed from a non-lamellar structure to a lamellar structure, and the M-A constituent changed from a elongated shape to a massive shape, therefore the toughness of CGHAZ of Ti microalloyed steel increased. It was also found that the great majority of particles in the CGHAZ are TiN, and small amount are Ti3Al, AlN and MnS.