690MPa级低合金高强钢焊接接头组织性能

Study on microstructure and properties of welded joints of a 690 MPa grade HSLA steel

为探讨690 MPa级低合金高强钢焊接接头组织与性能的关系,采用手工电弧焊(SMAW)和埋弧焊(SAW)获得成形良好的焊接接头,经过拉伸、冲击、弯曲试验及光学显微镜、扫描电镜和透射电镜分析,对两种焊接方法的接头组织性能进行研究.结果表明:两种焊接方法的焊缝组织主要为板条状贝氏体和少量针状铁素体,粗晶区为粗大贝氏体和少量马氏体;焊缝中含有大量分布均匀的微小球形夹杂物;两种焊接方法所得焊接接头都具有较高力学性能,-50℃的冲击断口形貌为韧窝、准解理混合型;埋弧焊焊缝冲击韧性低于手工电弧焊,手工电弧焊熔合线处冲击吸收功小于埋弧焊,但随距熔合线距离增加其值增加更快.显微组织和夹杂物是影响接头性能的主要因素.

To reveal the relationship between microstructures and mechanical properties of a 690 MPa grade high strength low alloyed（HSLA） steel,the welded joints without developing any defects were obtained by SMAW and SAW,and the mechanical properties（tensile strength,toughness,flexural strength） were measured,the microstructures were studied by OP,SEM and TEM.The results indicated that both microstructures of the welds from two welding processes mainly consisted of lath bainite and a little acicular ferrite,and the coarse grain heat affected zones（CGHAZ） revealed a predominately coarse bainite structure and a little martensite.Numerous spherical inclusions,small and uniformly distributed,were founded in both weld metals.The welded joints of the two welding processes had fine mechanical properties.At-50 ℃ both the fracture surfaces exhibited a mixed fractograph of dimples and quasi-cleavage.Impact energy of SMAW at weld interface was lower than that of SAW,but it increased more significantly with the increase of distance from weld interface.Microstructures and inclusions play an important role in welded joints.