SUS304不锈钢激光-MIG复合焊接工艺及机理研究

发布时间：2018-03-16 02:06

本文选题：激光-MIG复合焊　切入点：304不锈钢　出处：《江苏科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：激光-MIG复合焊作为一种新型的焊接方法,把两种热源结合在一起,结合了各自的优势,克服了各自的缺点,具有焊接熔深大、焊接速度快、变形小、焊接间隙适应性好等优点,是目前焊接研究的热点。SUS304不锈钢作为一种最常见的奥氏体不锈钢,由于其具有良好抗腐蚀性能,在工业生产中被广泛应用。本文针对8mm的SUS304不锈钢,采用激光-MIG复合焊的方法进行焊接,研究复合焊过程中的熔滴过渡行为,阐明了激光与电弧的作用机理,并在此基础上优化了焊接工艺,对复合焊接头的组织特征和力学性能进行了测试分析。采用高速摄像技术对激光-MIG复合焊的熔滴过渡行为进行拍摄观察,研究激光了不同工艺参数对激光-MIG复合焊熔滴过渡形式、熔滴过渡频率及熔滴尺寸的影响规律。激光-MIG复合焊由于激光的加入,使熔滴除了受到原有电弧焊所受到的力外,还受到金属蒸汽的反作用力和激光与电弧之间产生的电磁力。在激光-MIG焊过程中,随着激光功率的增大,熔滴的过渡方式由射滴过渡变为短路过渡,熔滴的尺寸逐渐变大,熔滴过渡频率降低;随着光丝间距的增加,熔滴过渡由短路过渡变为射滴过渡,当光丝间距为2mm时,熔滴过渡最稳定,当光丝间距大于4mm时,熔滴过渡不稳定,且激光与MIG之间协同效应变差,不能体现激光-MIG复合焊的优势;在激光-MIG复合焊不锈钢过程中,当焊接电流小于200A时,熔滴过渡为短路过渡,当焊接电流在200A到225A时熔滴过渡为射滴过渡,当焊接电流达到250A时,熔滴过渡又变为短路过渡。但熔滴过渡频率随着焊接电流的增加,在不断增大。通过平板堆焊工艺试验结果表明,激光-MIG复合焊过程中,激光与电弧存在最佳匹配关系。当电流为200A时,激光功率为3kW时,激光与电弧的耦合效果最好,可以得到最佳的焊缝成型;电弧在前时的焊缝成型要比电弧在后的焊缝成型好。当光丝间距为2mm时,焊缝成型最好。激光-MIG复合焊8mm的SUS304不锈钢的最佳工艺参数为:激光功率为5k W,焊接电流为220A,焊接速度为1.68m/min,采用电弧在前的方式,光丝间距DLA=2mm,离焦量?d=-5mm。该焊接工艺的间隙适用范围为0~1mm。激光-MIG复合焊激光区的晶粒组织要比电弧区的细小,激光区产生了细小的等轴晶。复合焊的接头抗拉强度达到了699MPa,与母材的强度相当近,且接头的塑性良好,延伸率为53.7%;激光自熔焊焊接头抗拉强度为619MPa,接头延伸率为32%。
[Abstract]:As a new welding method, laser-MIG composite welding combines two kinds of heat sources together, combines their advantages, overcomes their shortcomings, and has the advantages of high penetration, fast welding speed, small deformation, good adaptability of welding gap, etc. As one of the most common austenitic stainless steels, SUS304 stainless steel has been widely used in industrial production due to its good corrosion resistance. The laser MIG hybrid welding method is used to study the droplet transfer behavior in the process of composite welding. The mechanism of laser and arc interaction is clarified, and the welding process is optimized. The microstructure and mechanical properties of the composite welding joint were tested and analyzed. The droplet transfer behavior of laser MIG composite welding was observed by high speed camera technique. The effects of laser parameters on droplet transfer form, droplet transfer frequency and droplet size in laser-MIG composite welding were studied. During laser-MIG welding, with the increase of laser power, the transfer mode of the droplet changes from the transfer of the droplet to the short-circuit transition, and the size of the droplet becomes larger, as well as the reaction force of the metal vapor and the electromagnetic force between the laser and the arc. The droplet transfer frequency decreased with the increase of the optical fiber spacing, and the transfer of droplet changed from short circuit to emitter with the increase of optical fiber spacing. When the distance of optical wire was 2 mm, the transfer of droplet was most stable, and the transition of droplet was unstable when the distance of optical wire was more than 4 mm. The synergistic effect between laser and MIG has become worse, which can not reflect the advantage of laser-MIG composite welding, when the welding current is less than 200A, the transfer of droplet is short circuit transition in the process of laser MIG composite welding stainless steel. When the welding current is from 200A to 225A, the droplet transfer becomes a droplet transfer, and when the welding current reaches 250A, the droplet transfer becomes short circuit transfer, but the droplet transfer frequency increases with the welding current. The experimental results of plate surfacing welding show that there is an optimum matching relationship between laser and arc during laser MIG composite welding. When the current is 200A and laser power is 3kW, the coupling effect between laser and arc is the best. The best weld formation can be obtained; the welding seam at the front of the arc is better than the weld at the back of the arc. When the distance of the light wire is 2 mm, The best welding process parameters are: laser power 5kW, welding current 220A, welding speed 1.68m / min, arc in front, fiber spacing DLA2mm, defocus? The gap of this welding process is 0 ~ 1mm. the grain structure in laser zone is smaller than that in arc zone, and fine equiaxed crystal is produced in laser zone. The tensile strength of the joint of composite welding is 699MPa, which is very close to the strength of base metal. The ductility of the joint is good, the elongation is 53.7, and the tensile strength of the welded joint is 619 MPA and the elongation of the joint is 32 MPA.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.11

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