不锈钢/碳钢复合板的焊接工艺及接头组织性能研究摘要金属复合板以其优良的综合性能被广泛地应用于石油化工、建筑、交通运输及日用品等许多领域中。但是由于其基层与覆层之间的化学成分及理化性能差异较大，在焊接过程中容易出现覆层焊缝被稀释、产生成分偏析或者出现其它焊接缺陷等，导致难以获得高质量的焊接接头。因此在工业生产中，为了减少焊接过程对焊缝金属的稀释作用，将基层与覆层分开焊接在之间添加过渡层焊缝。因此，对接头过渡层焊缝的工艺控制是顺利实现金属复合板焊接的关键所在，以保证复合板接头的焊接质量，基于此，本文对304LSA516G70奥氏体不锈钢复合板、405Q245R铁素体不锈钢复合板这两种不锈钢/碳钢复合板的焊接工艺及焊接性进行研究。针对不锈钢复合板的焊接特点，文中分别采用钨极氩弧焊(GTAW)和焊条电弧焊(SMAW)两种焊接方法，并分别采用Cr、N元素含量较高的ER309L焊丝、ER316焊丝、A302焊条作为填充金属，选用X型和X型开槽两种坡口型式对不锈钢/碳钢复合板进行对接焊。通过对在不同工艺条件下所获接头进行力学性能测试、微观组织分析及耐蚀性能评价等，确定试验条件下的最佳焊接工艺及参数。力学性能测试结果表明，两种不锈钢/碳钢复合板接头的抗拉强度与其母材本身的抗拉强度相当，且均断在远离熔合线的母材处，完全能够满足实际工程结构对接头的强度要求。在304L/SA516Gr70接头中，采用X型开槽坡口、SMAW焊获得接头A2的抗拉强度最高：而在405Q245R接头中，采用SMAW焊获得接头B2的抗拉强度比GTAW焊获得接头B1的高。利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)及X射线衍射仪(XRD)对不锈钢/碳钢复合板接头的过渡层焊缝(WM)、覆层不锈钢与过渡层焊缝熔合区(WMSS)及基层碳钢与过渡层焊缝熔合区(WMCS)进行组织观察、成分分析及相结构分析。结果表明，接头过度层焊缝的微观组织均为铁素体分布在奥氏体基体上。在WM-CS界面处，两种不锈钢复合板接头均存在不同程度的碳迁移现象，其中304L/SA516G70接头在WM-CS界面处还存在一个宽度为30~50m凝固过渡层。对该界面进行元素线扫描及能谱分析，发现Cr、Ni等合金元素浓度在该区域呈梯度分布，但是并未发现合金元素偏聚现象及有害相析出。采用化学浸泡法及电化学测试方法评价接头过渡层焊缝的耐点蚀性能，结果表明，对于304LSA516G70接头，采用ER316L焊丝的钨极氩弧焊接头A4的耐腐蚀性能最好：对于405O245R接头，采用焊条电弧焊获得接头B2的耐腐蚀性能要优于钨极氩弧焊接头B1。综上所述，在本文中试验条件下，采用所选择的焊接工艺均可在一定程度上实现不锈钢/碳钢复合板的高质量焊接。关键词：不锈钢复合板，焊接工艺，过渡层，力学性能，微观组织，耐蚀性ABSTRACTThe metal composite plates have excellent comprehensive properties,and they are widely used inmany industry fields such as petrochemical,construction industry,transportation and daily products,etc.Due to the great difference of chemical composition and physical and chemical propertiesbetween the cladding plate and the base plate,it can easily result in the weld dilution,compositionsegregation and the occurrence of other weld defects during welding,thus it is difficult to obtain awelded joint with good quality.In the practical application,when the composite plate is welded,thecladding plate and the base plate of composite plate are often welded respectively,and a transitionlayer is adopted between the base plate and the cladding plate,so as to decrease the weld dilutionduring welding.In order to get welded joint with good quality,the technology control of welding forthe transition layer is of great concem.Based on these,the welding technology and weldability of304L/SA516Gr70 405/Q245R stainless steel composite plate are investigated respectively in theAccording to the welding characteristics of the stainless steel composite plates,the stainlesssteel/carbon steel composite plates are welded by tungsten inert gas arc welding (GTAW)andshielded metal arc welding (SMAW)respectively,and the filler metals such as welding wire ER309L,welding wire ER316L and electrode A302 which contain high contents of Cr and Ni elements areadopted,and the groove pattem of welded joint are X-groove and slotted X-groove respectively.Inorder to optimize the welding technology and get the most suitable joint,the mechanical properties,microstructure and corrosion resistance of welded joints under different condition are evaluatedrespectively.Reasults of mechanical properties tests show that the tensile strength of both of the two compositeplates welded joints are similar with the tensile strength of base metal,and all the tensile samplesbroke at the position of base material distant from fusion line.Consequenly,it can meet therequirement of tensile strength for practical engineering structure.The tensile strength of slotted X-groove joint A2 weled by SMAW is the highest among all of the 304L/SA516Gr70 joints,while in the405/Q245R joints,the tensile strength of joint B2 weled by SMAW is higher than that of joint Blweled by GTAW.Joint microstructure analyses including the transition layer weld metal,the interface betweencladding layer stainless steel and weld metal (WM-SS),the interface between base layer carbon steel