690 MPa级低合金高强钢焊接接头组织性能

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.

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

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 meas- ured,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 0C both the fracture surfaces exhib- ited 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. Micro- structures and inclusions play an important role in welded joints