极性比对方波交流TIG-MIG复合焊接电弧物理特性及熔滴过渡影响的研究

发布时间：2018-05-23 09:51

本文选题：方波交流TIG-MIG + 电弧物理特性　；参考：《山东大学》2017年硕士论文

【摘要】：TIG焊接过程稳定,焊缝成形良好,但存在焊接效率低下的不足;传统单MIG焊接具有生产效率高,且易于实现自动化等优点,但焊接过程不够稳定。随着现代工业的发展,传统焊接工艺难以满足人们对于高效低成本焊接的需求。因此,众多高效焊接工艺出现并迅速发展。直流TIG-MIG复合焊接有效克服单独焊接工艺不足,综合焊接工艺的优点,在高效焊接领域得到广泛认同。但当设置TIG焊接为小参数焊接电流时,直流TIG-MIG复合焊接稳定性差,断弧现象严重,驼峰缺陷难以克服,并伴有严重的焊接飞溅。改变焊接工艺参数,对TIG-MIG复合焊接工艺进行优化具有十分重要的意义。方波交流具有正半波与负半波转换速度快,零点过渡区几乎为零,电弧稳定等优点。本文提出在TIG焊接参数选择上,利用方波交流代替直流进行方波交流TIG-MIG复合焊接工艺试验,为该工艺后续优化及工程应用提供理论基础。从焊接过程断弧数量、电参数波形等方面对比分析了直流TIG-MIG复合焊接工艺和方波交流复合焊接工艺焊接过程的稳定性,结合焊缝成形,客观分析两种工艺的优势与不足。小参数TIG直流TIG-MIG复合焊接整体稳定性差,断弧现象严重,焊缝成形较差,驼峰现象难以克服,并伴有大量飞溅。方波交流TIG-MIG复合焊接断弧较少,电参数波形更加稳定,焊缝成形良好,极性比为10焊接工艺最优。分析了方波交流TIG-MIG复合焊接电弧物理特性,并对极性比对该工艺电弧物理特性的影响展开研究。时间方面,极性比增大,复合电弧吸引时间增长,排斥时间缩短。电弧形态方面,极性比增大,复合电弧强度增强,两电弧电磁力作用强化,吸引和排斥形态更加明显。极性比小,复合电弧形态收缩,电弧集中,热量集中。分析了方波交流TIG-MIG复合焊接熔滴过渡特点,并探究极性比对熔滴过渡的影响机理。当TIG处于方波交流正半波时,MIG焊丝尖端熔化液态金属明.显后偏,向熔池后方过渡;负半波时,焊丝端部熔化液态金属前偏向熔池前方过渡。方波交流TIG-MIG复合焊接工艺MIG过渡熔滴主要维持后偏的过渡形态,过渡进入熔池的后方。随着极性比的增大,过渡熔滴向熔池后方过渡时间缩短,以前偏形态向熔池前方过渡时间增长。分析了方波交流TIG-MIG复合焊接熔池流动特点及驼峰缺陷机理,并对极性比对熔池流动的影响展开研究。极性比为0(直流),MIG焊丝尖端锥状液柱始终后偏过渡进入熔池尾部。尽管由于液态金属层较厚,其对后向液体流的驱动作用较小,熔池液态金属流向尾部形成壁面通道及熔池肿块,容易形成驼峰。极性比为10,波形处于负半波时,过渡熔滴进入熔池的位置在一范围内变化,不会对熔池形成持续的后推力,熔池金属的后向流速变小,不会在焊缝区域出现熔池肿块现象。极性比为40,波形处于负半波时,过渡熔滴前偏进入熔池前部,熔滴撞击弧坑前沿,后向液态金属流以较大的速度向熔池尾部流动,在后方形成液态金属凹陷,形成驼峰。
[Abstract]:The TIG welding process is stable, the weld forming is good, but the welding efficiency is low. The traditional single MIG welding has the advantages of high production efficiency and easy to realize automation, but the welding process is not stable. With the development of modern industry, the traditional welding technology is difficult to meet the people's demand for high efficiency and low cost welding. The direct current TIG-MIG composite welding has been widely recognized in the field of high efficiency welding. However, when TIG welding is a small parameter welding current, the stability of the DC TIG-MIG welding is poor, the arc breaking phenomenon is serious, and the hump defect is difficult to overcome. With serious welding spatter, it is of great significance to change the welding process parameters and optimize the TIG-MIG composite welding process. The square wave communication has the advantages of fast transition speed of positive half wave and negative half wave, almost zero transition zone in zero point, stable arc and so on. This paper proposes the use of square wave AC to replace DC in the selection of TIG welding parameters. The process test of square wave AC TIG-MIG composite welding is carried out to provide a theoretical basis for the subsequent optimization and engineering application of the process. The stability of the DC TIG-MIG composite welding process and the square wave AC composite welding process is compared and analyzed from the number of arc breaking and the waveform of electrical parameters. The objective analysis of two is to analyze the welding process of the square wave AC composite welding. The advantages and disadvantages of the technology are poor. The small parameter TIG DC TIG-MIG composite welding has poor overall stability, serious arc breaking phenomenon, poor weld formation, the hump phenomenon difficult to overcome, and a large amount of splash. The square wave AC TIG-MIG composite welding arc is less, the waveform of the electric parameters is more stable, the weld forming is good, the polarity ratio is the best welding process, and the analysis of the polarity ratio is the best. The arc physical characteristics of the square wave AC TIG-MIG composite welding are studied, and the influence of polarity ratio on the physical characteristics of the arc is studied. The time aspect, the increase of the polarity ratio, the increasing of the electric arc attraction time, the shortening of the rejection time, the increase of the arc shape, the increase of the polarity ratio, the intensification of the composite arc strength, the enhancement of the two arc electromagnetic force, the attraction and the absorption of the arc. The rejection morphology is more obvious. The polarity ratio is smaller, the compound arc shape contraction, the arc concentration, the heat concentration. The characteristics of the droplet transition in the Fang Bo AC TIG-MIG composite welding are analyzed and the influence mechanism of the polarity ratio on the droplet transition is explored. When the TIG is in the square wave alternating half wave, the MIG wire tip melts liquid metal clearly. During the negative half wave, the end of the welding wire is transferred to the front of the molten pool before the end of the welding wire is melted. The transition form of the transition droplet of the square wave AC TIG-MIG composite welding process mainly maintains the transition form after the transition, and the transition enters the rear of the molten pool. With the increase of the polarity ratio, the transition time of the transition droplet is shortened to the rear of the pool, and the former partial form is transferred to the front of the pool. The flow characteristics and hump defect mechanism of the square wave AC TIG-MIG composite weld pool are analyzed. The effect of polarity ratio on the flow of molten pool is studied. The polarity ratio is 0 (DC), and the tip of the MIG wire tip has always shifted to the rear of the molten pool. Although the liquid metal layer is thicker, its driving effect on the backward liquid flow When the liquid metal flows to the tail to form the wall channel and the pool mass, it is easy to form a hump. The polarity ratio is 10. When the wave is in the negative half wave, the position of the transition droplet into the pool is changed in one range, and the rear thrust of the molten pool will not be formed. The back flow velocity of the molten pool is smaller, and the weld pool mass will not appear in the weld zone. The polarity ratio is 40. When the waveform is in the negative half wave, the transition droplet goes into the front of the molten pool before the transition droplet, and the droplet hits the front of the arc pit. Then the liquid metal flow flows to the tail of the molten pool at a large speed, and the liquid metal sag is formed in the rear, and the hump is formed.
【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】：TG456

【参考文献】