基于低能耗高效率目标的脉冲激光诱导电弧物理机制及复合焊接工艺研究

发布时间：2018-03-11 18:51

本文选题：激光诱导电弧　切入点：低能耗高效率　出处：《大连理工大学》2015年博士论文　论文类型：学位论文

【摘要】：随着世界各国加工制造业和工程建设的不断发展,现代焊接技术正逐步向以节能、高效、优质为主要特征和要求的方向发展,这使得降低焊接能耗、提高焊接效率成为目前焊接领域亟待解决的重要问题之一。以低能耗、高效率为主要特征的低功率激光-电弧复合热源焊接技术在此背景下应运而生,本论文围绕低功率脉冲激光诱导电弧复合热、源焊接技术开展研究,总结了工艺参数与激光对电弧的诱导效率(相同激光功率和电弧电流参数的前提下,不同诱导过程中焊缝熔化深度的比值)之间的规律,通过对复合焊接过程中的现象进行分析,探讨了复合焊接低能耗高效率的物理本质,对比了复合焊接与其他焊接方法在能耗和效率方面的优势,开发特殊结构件及特殊板材的低能耗激光-电弧复合热源焊接工艺,拓宽复合焊接的应用范围。本文主要研究内容和结论如下：(1)激光诱导电弧现象分析。本部分在激光输出功率和电弧电流固定的前提下综合考察了热源位置和激光脉冲参数对热源诱导效率的影响规律,结果表明：在L-T(激光引导电弧)复合焊接过程中,激光对电弧的诱导效率随着Dla(激光与电弧的热源间距)的减小而提高,激光对电弧的诱导作用主要是稳定电弧,使得在高速焊接过程中依然能获得稳定的焊缝,适用于高速焊接；在T-L(电弧引导激光)复合焊接过程中,激光对电弧的诱导效率随着Dla的增加呈现出先增加后减小的趋势,诱导效率最大时Dla的取值随着电弧电流的增加而增大,激光对电弧的诱导作用主要是压缩电弧,增大诱导效率,使得相同电弧电流和激光功率条件下可以实现更厚板材的全熔透焊接,适用于深熔焊接；激光诱导电弧中,适当地降低激光脉冲宽度和脉冲频率,增大脉冲激发电流有利于诱导效率的提高；焊接过程中等离子体形态变化可以直观反映出热源诱导效率的变化。(2)激光诱导电弧机制分析。采用理论计算的方法对实现激光对电弧最大诱导效率参数条件下电弧等离子体的弧柱附加压力、电子动能以及等离子体弛豫时间进行了计算,结果表明：激光脉冲作用期间,电弧弧柱附加压力增大了5.2倍,电子动能增加了27.5%,能量密度也获得提高,三者的共同作用促使焊接能耗的降低和焊接效率的提高；激光脉冲作用之后,等离子体发生了弛豫现象,本实验过程中计算的弛豫时间约为7.5ms,而实际过程中弛豫时间约为8.0 ms,计算结果与实际结果比较吻合,弛豫过程在时间尺度上增强了激光对电弧的诱导作用效果；维持激光“匙孔”存在的主要作用力是蒸汽反冲压力,激光与交流电弧波峰相匹配时电弧电场方向由钨电极指向母材表面,等离子体内能量传递的电子由“匙孔”中部向“匙孔”底部以及侧壁方向运动,大量的携带高能量的电子把自身能量传递给“匙孔”底部及侧壁的液态金属,从而促使母材不断的蒸发、汽化或者电离,这相当于延长了蒸汽反冲压力的持续时间,从而导致“匙孔”维持开口状态的时间较长；“匙孔”与等离子体之间存在相互促进的作用,激光“匙孔”的开口状态与等离子体的形成之间存在着相互促进的作用,等离子体状态的变化与“匙孔”行为密切相关。(3)激光诱导电弧作用效果分析。采用电弧焊接、激光焊接和激光诱导电弧复合焊接三种方法实现了相同尺寸板材均匀全熔透的焊接效果,计算并对比了不同焊接方法在焊接能耗和焊接效率方面的差异,结果表明：激光对电弧的诱导作用显著提高了焊接效率、降低了焊接能耗；复合焊接的效率达到单独激光焊接效率的7.14倍和单独电弧焊接效率的4.29倍,能耗仅为激光焊接能耗的22.23%和电弧焊接能耗的63.85%,真正实现了低能耗、高效率的目标。(4)激光诱导电弧的应用及新工艺开发。在理论分析的指导下开发了低能耗激光-电弧复合焊接T形结构件焊接工艺和平板对接单面焊双面自由成形焊接工艺,结果表明：复合焊接实现了1.4 mm厚镁合金薄板T形结构件的优质连接,筋板与壁板连接的两侧焊角处均实现均匀的圆滑过度,焊缝余高控制在合理的尺寸范围内,接头剪切强度达到母材的89%；低能耗激光-电弧复合焊接技术对于1.4 mm厚钛合金T形结构件亦具有很强的适应性；通过激光对电弧的诱导作用提高了热源的能量密度,采用该工艺实现了2.5mm厚钛合金板材的单面焊双面自由成形,焊缝正面形成带有均匀细密鱼鳞纹的余高,没有产生宏观气孔、咬边等焊接缺陷,焊缝背面熔透程度适中、均匀连续,接头的性能达到或超过母材。
[Abstract]:With the continuous development of the construction industry and the world manufacturing processing, modern welding technology is gradually to energy saving, high efficiency, high quality as the main characteristics and requirements of the direction of development, which makes the welding to reduce energy consumption, improve the efficiency of welding has become one of important questions to be solved in the field of welding current. With low energy consumption, high efficiency and low power came into being the main feature of the laser arc hybrid welding technology under this background, this paper focuses on laser induced arc composite heat source welding low power pulse technology research, summarizes the induction efficiency of process parameters and laser on the arc weld depth ratio (melting process of different induction condition of the same laser power and arc current parameters, the) between the rules, based on the hybrid welding phenomenon in the process of analysis, discusses the physical hybrid welding with low energy consumption and high efficiency of this matter, comparison Composite welding and other welding methods in terms of energy consumption and efficiency advantages of low energy laser welding technology development special structure and special plate arc composite heat source, broaden the application scope of composite welding. In this paper, the main research contents and conclusions are as follows: (1) analysis of laser induced electric arc phenomenon. In this part of the laser output power and the arc current is fixed under the premise of a comprehensive investigation of the position of heat source and the laser pulse parameters on heat induced efficiency were investigated, the results showed that: in the L-T (laser guided arc) hybrid welding process, the laser induced efficiency of arc with Dla (heat source distance between laser and arc) decreases with the increase of arc induced by laser is mainly in high speed welding arc stability, which can still obtain a stable welding process, suitable for high speed welding; T-L (arc guided laser) in hybrid welding process, The induction efficiency between laser and arc with the increase of Dla, showing a trend of first increase and then decrease the maximum value, the induction efficiency of Dla increases with the increase of arc current, induced by laser on the arc is mainly compression arc, increase efficiency and achieve a more thick plate full penetration welding makes the same arc current and laser power conditions, suitable for deep penetration welding; laser induced arc, appropriate to reduce the laser pulse width and pulse frequency, pulse excitation current increase is conducive to improving the efficiency of induction; changes of plasma shape in the welding process can directly reflect the change of heat induced efficiency. (2) analysis of laser induced arc mechanism. The theoretical calculation of the arc column pressure arc plasma laser on arc induced maximum efficiency parameters under the condition of electron kinetic energy and plasma relaxation The relaxation time was calculated, the result showed that the laser pulses, the arc column added pressure increases by 5.2 times, the kinetic energy of the electrons is increased by 27.5%, the energy density is also improved, the three together to reduce energy consumption and improve the efficiency of welding welding; after the laser pulse, the relaxation of plasma in this experiment, in the process of calculation of the relaxation time is about 7.5ms, and the actual process of relaxation time is about 8 ms, the calculation results are consistent with the actual results, the relaxation process to enhance the effect of laser induced by arc in time scale; the main force to maintain the laser "keyhole" there is steam recoil pressure, laser and AC arc wave matching electric field direction by tungsten electrode to the surface of base material, electron plasma energy transfer from the central to the "keyhole" and "keyhole" bottom The side wall of the direction of movement, a large number of high energy electrons carry their own energy transfer to the liquid metal keyhole bottom and side wall, so as to promote the continuous evaporation of the parent material, which is equivalent to the vaporization or ionization, prolong the duration of the vapor recoil pressure, resulting in the "keyhole" to maintain the state opening time "there are long; promote the interaction between keyhole and plasma, there is mutual promotion between laser" keyhole "opening state and plasma formation is closely related to changes in plasma state and" keyhole "behavior. (3) analysis of laser induced by arc welding. The effect of arc, arc composite three kinds of welding method to achieve the same effect of uniform size of sheet metal welding full penetration laser welding and laser induced, calculated and compared the different welding method in welding welding efficiency and energy consumption The differences, the results showed that the induction effect of the laser on the arc significantly improve the welding efficiency, reducing welding energy consumption; 4.29 times the efficiency of hybrid welding to separate laser welding efficiency 7.14 times and single arc welding efficiency, energy consumption is only 22.23% of the energy of laser welding and arc welding energy consumption 63.85%, realizing a low energy consumption high efficiency, objective. (4) the application and development of new process of laser induced arc. Under the guidance of the theoretical analysis of low energy laser arc hybrid welding side welding free forming welding process, welding and butt T shaped structure developed the results show that the composite welding realized the high quality connection of 1.4 mm thick magnesium alloy thin T shaped structure, both sides are welded stiffened plate and shell connection angle are uniform smooth, the weld height control in the size of a reasonable range of joint shear strength reached The 89% parent material; low energy laser arc hybrid welding technology has strong adaptability for 1.4 mm thick titanium alloy T structure; through the induction effect of the laser on the arc heat source improves the energy density, the process of implementation of welding of 2.5mm thick titanium alloy double surface free forming, welding seam with the formation of uniform fine scales more than high, no macro porosity, undercut welding defects such as weld penetration of moderate, uniform and continuous, joint performance reach or exceed the base material.

【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG403

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