SUS304/Q235B双金属冶金复合螺旋管激光-CMT复合焊+埋弧焊接头组织及性能

采用激光-CMT复合焊+埋弧焊的焊接工艺对SUS304/Q235B双金属冶金复合螺旋管进行了生产试制，利用OM，EDS研究了复合管焊缝微观组织特征及合金元素分布，同时检验了焊接接头的力学性能和耐腐蚀性能。结果表明，焊缝合金成分合理，合金元素稀释率低。内焊焊缝(CMT区域)微观组织为奥氏体+铁素体+碳化物析出相，内焊焊缝(LBW区域)微观组织为奥氏体+铁素体+马氏体，Q235B基层焊缝微观组织为铁素体+珠光体；焊接接头抗拉强度平均值为451 MPa，-10 ℃下焊缝及热影响区的冲击吸收能量平均值分别为167 J和236 J，焊接接头面弯、背弯180°拉伸面无裂纹(弯轴直径45 mm)，焊缝硬度最高值为285 HV10；晶间腐蚀试验后，管体与焊缝弯曲180°拉伸面无裂纹(弯轴直径4 mm)。SUS304/Q235B双金属冶金复合螺旋管激光-CMT复合焊+埋弧焊接头的各项性能均符合相关标准的要求，能够满足饮用水输送工程的应用需求。创新点： 区别于传统螺旋焊管的双面埋弧焊，采用了激光-CMT复合焊(内焊)+埋弧焊(外焊)的工艺对SUS304/Q235B双金属冶金复合螺旋管进行焊接，形成了“Y+V”形的焊接接头形貌，减小了内、外焊缝的重合量，有效地控制了不锈钢复层一侧焊缝合金元素的稀释及碳钢基层一侧焊缝合金元素的过量裹入，避免了内、外焊缝高硬相的产生，提升了焊接接头的综合性能。

Microstructure and properties of welded joint of SUS304/Q235B bimetal metallurgical clad spiral pipe by laser-CMT hybrid welding and submerged arc welding

Trial production of SUS304/Q235B bimetal metallurgical clad spiral pipe were carried out by welding process of laser-CMT hybrid welding and submerged arc welding. Characteristics of microstructure and alloy element distribution of welded joints of the clad pipe were studied by OM and EDS, and mechanical properties and corrosion resistance of welded joints were also tested. The results showed that alloy composition of weld was reasonable and dilution rate of alloy element was low. Microstructure of the internal weld (CMT area) was austenite, ferrite and carbide precipitates, that of the internal weld (LBW area) was austenite, ferrite and martensite, and that of Q235B base weld was ferrite and pearlite. Average tensile strength of welded joints was 451 MPa, and average impact absorbed energy of weld and heat affected zone at -10 ℃ was 167 J and 236 J, respectively. There was no crack on the tensile surface of 180° forward and back bending of welded joints (bending shaft diameter was 45 mm). The maximum hardness of weld was 285 HV10. After intergranular corrosion test, there was no crack on the tensile surface of 180° bending of pipe body and weld (bending shaft diameter was 4 mm). Weld joints of SUS304/Q235B bimetal metallurgical clad spiral pipe by laser-CMT hybrid welding and submerged arc welding met requirements of relevant standards and application requirements of drinking water delivery engineering.Highlights: Different from double-sided submerged arc welding method of traditional spiral welded pipe, welding process of laser-CMT hybrid welding (internal welding) + submerged arc welding (external welding) was adopted to weld SUS304/Q235B bimetal metallurgical clad spiral pipe, and “Y+V” shape welded joint was formed, which reduced overlap between the inner and outer welds, effectively controlled dilution of alloy elements on the side of stainless steel cladding weld and excessive encapsulation of alloy elements on the side of carbon steel base weld, avoided generating high hard phases in the inner and outer welds, and improved comprehensive performance of welded joints.