STT焊机在超细晶粒钢焊接中的试验研究

Research on ultra-fine grain steel welding with STT welder

采用STT焊接电源进行了400 MPa级超细晶粒钢焊接试验。结果表明,在表面张力过渡CO2气保焊条件下,超细晶粒钢热影响区宽度极窄约为1 mm,随着线能量增大,热影响区中过热区的晶粒尺寸随之增大,但低线能量的表面张力过渡使晶粒长大的程度得到控制。各焊接线能量下,热影响区各区平均硬度不低于母材,不存在软化现象。过热区为多相组织混合形貌,为低碳马氏体、贝氏体、珠光体、铁素体的不平衡混合组织。对线能量3.68 kJ/cm时的焊接接头进行综合力学试验,发现超细晶粒钢的热影响区硬度、强度和韧性均高于母材。

Having welded 400MPa ultrd-fine grain steel with STT welder,the result showed that under the condition of SIT CO2 Gas Metal Arc Welding, HAZ width was very narrow about 1 mm,and the grain sizes of overheated zone were increasing with the increasing of the welding line energy,but the low line energy of surface tension transfer controlled grain growth.Under all welding line energy,the average hardness of HAZ wasn＇t lower than base metal and the softening appearance didn＇t occur.The overheated zone was muhiphase texture mixed microstructure made of low carbon martensite,bainite,pearlite and ferrite.Evaluating the HAZ of E=3.68 kJ/cm with mechanics experiment,the result showed that the hardness,intensity and toughness of wltra-fme grain steel HAZ of ultra-fine grain steel were all higher than base metal.