超大热输入焊接用EH40钢的模拟熔合线组织与性能

通过实验室EH40船板钢的超大热输入焊接热模拟实验,研究焊接熔合线部位的组织与性能,分析钢中夹杂物对原奥氏体晶界及晶内组织的影响规律.结果表明:实验钢在采用800 kJ/cm(t_8/5=730 s)的焊接热输入,峰值温度为1400℃（保温30 s）的条件下,-20℃的冲击功能够达到150 J以上.其金相组织由块状的晶界铁素体（GBF）、晶内多边形铁素体（IPF）、晶内针状铁素体（IAF）组成,且IAF面积分数占50%以上,无板条贝氏体和粒状贝氏体组织.实验钢中夹杂物类型合理、密度大,有效地抑制了GBF的粗化.钢中存在的直径为5—8μm的大尺寸夹杂物,也具有IGF形核能力,甚至会形成IAF组织,表现出贫Mn区的形核机制.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF SIMULATE FUSION LINE IN EH40 SHIP PLATE STEEL FOR HIGH HEAT INPUT WELDING

The microstructure and mechanical properties in simulate fusion line of EH40 ship plate steel with high heat inputs were investigated using welding thermal simulation test.The effects of inclusions on the grain size of original austenite and intragranular ferrite（IGF） were analyzed.The results indicate that impact energy of the steels at -20℃was more than 150 J with a heat input of 800 kJ/cm(t_8/5=730 s) and maximum temperature of 1400℃for 30 s.The microstructures of the steel were composed of GBF,IPF and IAF,and the fraction of IAF was over 50%.Lath bainite and granular bainite were not observed.The type and concentration of inclusions were ideal which decreased the growth of GBF.Those inclusions whose diameter were 5—8μm can also promote the formation of IGF,and sometimes IAF was also formed through the nucleation at Mn-depleted zone.