双丝间接电弧焊堆焊工艺及堆焊层耐蚀性能研究

发布时间：2018-05-21 02:40

本文选题：双丝间接电弧焊 + 堆焊层　；参考：《山东大学》2017年硕士论文

【摘要】：双丝间接电弧气体保护焊(简称双丝间接电弧焊)是一种新型焊接技术,焊接时工件不接电极,两焊丝分别与焊接电源的正、负极相连,电弧在两焊丝间产生,双丝间接电弧焊的电弧热量主要用来熔化焊丝,相同条件下能熔化更多焊丝,熔敷速度大,具有高效、节能、熔合比小等优点。本文采用双丝间接电弧焊在Q235表面堆焊奥氏体不锈钢层,针对改善熔深问题,施加外加磁场以及TIG复合热源进行堆焊。通过高速摄像机拍摄了双丝间接电弧及熔滴过渡形态,采用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)等手段进行堆焊层的组织及形貌分析。本文研究了焊接参数、外加磁场及TIG复合热源对焊接工艺、耐晶间腐蚀性及耐点蚀性能影响。利用高速摄像机拍摄的双丝间接电弧形态呈"提篮"状,熔滴是由两串阴阳极熔滴构成,焊接电流越大,熔滴夹角越小。外加磁场可改变双丝间接电弧形态,施加X正方向磁场时,电弧有收缩的趋势,X负方向磁场可拉长电弧,有利于提高工件热输入;施加Y方向磁场时,电弧在YOZ面偏转;施加Z向磁场时,电弧在XOZ面偏转。双丝间接电弧焊堆焊后观察堆焊层成形发现,焊接电流越大或焊丝夹角越大,堆焊层成形越好。焊丝夹角30°时,焊接电流达到160A及以上,堆焊层成形较好。X负向磁场及复合TIG热源均会使堆焊层外形变好。堆焊时复合TIG热源,可有效增加堆焊层的部分熔深。分析了双丝间接电弧焊堆焊层组织及铁素体含量,结果表明对于使用奥氏体基的ER308焊丝,堆焊层的组织受双丝间接电弧焊堆焊工艺影响,焊丝夹角增大,施加X负向磁场以及复合TIG热源,铁素体含量增加。焊丝夹角30°时,堆焊层中铁素体主要以点状和蠕虫状存在;焊丝夹角70°时,堆焊层中铁素体以骨架状和板条状存在。电化学动电位再活化法测试的晶间腐蚀性试验结果表明,双丝间接电弧焊所得堆焊层耐晶间腐蚀性非常好。焊丝夹角30°时,再活化率Ra随焊接电流的增大先减小后增大,施加外加X负向磁场以及复合TIG热源,对堆焊层耐晶间腐蚀性有一定影响,但仍保持较好的耐晶间腐蚀性;焊丝夹角70°时,焊接电流增大以及焊速降低均会使Ra值略有增大。在使用同样焊丝的情况下双丝间接电弧焊堆焊层耐晶间腐蚀性比使用MIG焊堆焊的好,略低于304不锈钢母材,但远优于304不锈钢堆焊层耐蚀性。点蚀试验结果表明,焊丝夹角增大、焊速减小、焊接电流增大、外加磁场的施加或TIG热源的复合,均使点蚀电位下降,耐点蚀性能下降,这与熔敷金属的冷却速度不同影响贫铬区及焊接残余应力有关。双丝间接电弧焊堆焊层比MIG焊的耐点蚀性好。双丝间接电弧焊堆焊层发生点蚀之前,先出现亚稳蚀孔,有些亚稳蚀孔由于条件不足而再钝化,有些转化为稳态蚀孔。稳态蚀孔上面存在蚀孔盖,形状类似花边形。
[Abstract]:Double wire indirect arc gas shielded welding (double wire indirect arc welding) is a new welding technology. When welding, the workpiece is not connected to the electrode. The two wire is connected with the positive and negative electrode of the welding power. The arc is produced between the two wires. The arc heat of the double wire indirect arc welding is mainly used to melt the welding wire, and more wire can be melted under the same condition. With the advantages of high application speed, high efficiency, energy saving and small fusion ratio, this paper uses double wire indirect arc welding to weld austenitic stainless steel layer on Q235 surface. In order to improve the melting depth, the applied magnetic field and TIG composite heat source are applied to the welding. The arc and droplet transition form of double wire are taken by high speed camera, and optical microscope (O) is adopted. M), scanning electron microscopy (SEM), energy spectrum analysis (EDS) and other means to analyze the microstructure and morphology of the surfacing layer. This paper studied the welding parameters, the applied magnetic field and the TIG compound heat source on the welding process, the intergranular corrosion resistance and the pitting resistance. The double wire indirect arc form was shot by the high-speed camera, and the droplet was two series of yin and Yang. The larger the welding current is, the larger the welding current is, the smaller the angle of the droplet is, the smaller the angle of the droplet. The applied magnetic field can change the shape of the indirect arc of the double wire. When the X positive magnetic field is applied, the arc has the trend of contraction. The negative direction of the X can lengthen the arc, which is beneficial to the increase of the thermal input of the workpiece. When the magnetic field is applied in the direction of Y, the arc is deflected on the YOZ surface, and when the Z is applied to the magnetic field, the arc is partial to XOZ surface. After the surfacing welding of double wire indirect arc welding, it is found that the greater the welding current or the greater the angle of the welding wire, the better the forming of the surfacing layer. The welding current reaches 160A and above when the angle of welding wire is 30 degrees. The shape of the welding layer is better.X negative magnetic field and the compound TIG heat source will make the shape of the surfacing layer better. The composite TIG heat source can be effectively increased when the surfacing is surfacing. The weld layer structure and ferrite content of double wire indirect arc welding are analyzed. The results show that the structure of ER308 welding wire using austenite base is affected by double wire indirect arc welding process, the angle of welding wire is increased, the X negative magnetic field is applied and the TIG heat source is added, the content of ferrite is increased. The angle of welding wire is 3 At 0 degrees, the ferrite in the surfacing layer is mainly in the form of point and vermicular. When the angle of the welding wire is 70 degrees, the ferrite in the surfacing layer exists in the skeleton and strip shape. The intergranular corrosion test results of the electrochemical potential reactivation test show that the intergranular corrosion resistance of the surfacing layer obtained by the double wire indirect arc welding is very good. The reactivation of the welding wire is 30 degrees. The rate of Ra decreases and then increases with the increase of the welding current, and the added X negative magnetic field and the compound TIG heat source have a certain effect on the intergranular corrosion resistance of the surfacing layer, but still maintain a better intercrystalline corrosion resistance. When the angle of welding wire is 70 degrees, the increase of the welding current and the decrease of the welding speed will make the Ra value increase slightly. The intergranular corrosion resistance of lower double wire indirect arc welding surfacing layer is better than that of MIG welding. It is slightly lower than 304 stainless steel, but it is far superior to the corrosion resistance of 304 stainless steel. The pitting test results show that the angle of welding wire increases, the welding speed decreases, the welding current is increased, the applied magnetic field or the compound of the TIG heat source will decrease the pitting potential. The pitting performance decreases, which is related to the difference in the cooling rate of the deposited metal and the effect of the residual stress on the poor chromium zone and the welding residual stress. The double wire indirect arc welding layer has better pitting resistance than the MIG welding. The metastable corrosion hole appeared before the double wire indirect arc welding layer occurred pitting, and some metastable etched holes were passivated, and some were converted to stability. Etched holes. There is a hole cover on the steady etching hole, which is similar to the lace shape.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG455

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