水下药芯焊丝湿法焊接熔滴过渡行为研究

发布时间：2018-07-10 02:35

本文选题：湿法焊接 + 过渡行为　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：随着海洋事业的不断发展,我国对水下焊接技术的需求日益提高。水下湿法焊接基于其操作简单、通用性强、经济性好等优势,目前已广泛应用于水下焊接领域,但由于缺少焊接防护措施,水下湿法焊接存在焊接电弧不稳定、焊接冶金损失严重、焊缝成形较差等诸多问题。水下湿法焊接中存在的问题与熔滴过渡形式密切相关,由于水环境及水下压力的存在,水下湿法焊接的熔滴过渡过程具有一定的特殊性。本研究针对水下药芯焊丝湿法焊接熔滴过渡过程展开了相关理论研究工作,不仅填补了水下湿法焊接熔滴过渡领域理论研究的空白,而且为水下湿法焊接熔滴过渡行为的控制提供理论支撑。基于X射线高速成像与电信号同步采集系统,观测了水下湿法焊接熔滴过渡行为,并根据熔滴过渡行为的不同划分了熔滴过渡形式,探索了熔滴过渡形式随焊接参数的转换条件。研究表明,根据熔滴过渡行为的不同,水下湿法焊接基本熔滴过渡形式分为排斥过渡、短路过渡以及“潜弧过渡”;根据排斥角大小的不同,排斥过渡可分为大角度排斥过渡与小角度排斥过渡,根据短路过渡阶段的不同,短路过渡可分为短路表面张力过渡与短路爆炸过渡;同一焊接参数下,熔滴过渡形式不是单一的,而是由三类基本过渡形式按一定比例组成,称为混合过渡;随着焊接参数的改变,混合过渡形式中基本过渡形式的种类及比例、熔滴直径及过渡频率均发生相应改变。基于静力学平衡理论,构建了水下湿法焊接熔滴过渡受力模型,探索了焊接参数对熔滴过渡行为的影响机理,并通过流体软件FLUENT模拟了水下湿法焊接上升气泡对熔滴过渡行为的影响。分析指出:在水下湿法焊接中,熔滴受到内部作用力和外部作用力的共同作用,内部作用力指气体动力,外部作用力包括表面张力、重力、电磁收缩力、等离子流力、斑点压力以及气体拖拽力。与陆上焊接不同,在水下湿法焊接中由于受到水环境的冷却作用,焊接电弧冷却收缩,等离子流力对熔滴过渡的促进作用减弱,电磁收缩力方向与熔滴过渡方向相反,阻碍熔滴过渡;上浮气泡与熔滴相互作用,产生气体拖拽力,该力是水下湿法焊接中特有的作用力,对熔滴过渡起到阻碍、排斥作用。焊接参数通过改变熔滴受力条件,影响熔滴的过渡行为,包括熔滴过渡形式、熔滴直径及过渡频率。通过对不同过渡形式下的焊接电信号、熔滴过渡影像、焊接飞溅及焊后试件进行分析,研究了熔滴过渡行为对焊接电弧稳定性、焊缝成形及焊接飞溅的影响,研究表明在水下湿法药芯焊丝焊接过程中,当混合过渡形式以短路过渡和小角度排斥过渡为主时,熔滴过渡平稳,焊接电弧燃烧稳定,焊接飞溅产生频率较低,焊缝成形均匀;当混合过渡形式以大角度排斥过渡或“潜弧过渡”为主时,焊接电弧燃烧不稳定,易于产生焊接飞溅,熔滴易对焊件产生冲击,焊缝两侧易于产生焊瘤缺陷,焊缝成形较差。
[Abstract]:With the continuous development of marine industry, the demand for underwater welding technology is increasing in our country. Underwater wet welding is widely used in underwater welding field based on its advantages of simple operation, strong generality and good economy. But because of lack of welding protection measures, the welding arc is unstable and metallurgical loss exists in underwater wet welding. There are many problems such as bad weld formation and so on. The problems in underwater wet welding are closely related to the form of droplet transition. Due to the existence of water environment and underwater pressure, the process of droplet transition in underwater wet welding has certain particularity. The research work not only fills the gap of theoretical research in the field of droplet transition in underwater wet welding, but also provides theoretical support for the control of droplet transition behavior in underwater wet welding. Based on X ray high-speed imaging and electrical signal synchronous acquisition system, the behavior of droplet transition in underwater wet welding is observed, and the transition behavior of droplets is different according to the droplet transition behavior. The transition form of droplet transition is divided. The transition form of droplet transition with welding parameters is explored. According to the different transition behavior of droplets, the basic droplet transition forms in underwater wet welding are divided into rejection transition, short circuiting transition and "submerged arc transition", and the rejection transition can be divided into large angle rejection according to the difference of the repulsive angle. Transition and small angle exclude transition, according to the different short circuit transition stage, short circuit transition can be divided into short circuit surface tension transition and short circuit explosion transition. Under the same welding parameters, the form of droplet transition is not single, but is composed of three kinds of basic transition forms, which are called mixed transition, and mixed with the change of welding parameters. The type and proportion of the basic transition form in the ferry form, the droplet diameter and the transition frequency are all changed correspondingly. Based on the static equilibrium theory, a model of the droplet transition under water wet welding is constructed, and the influence mechanism of the welding parameters on the droplet transition is explored, and the underwater wet welding up gas is simulated by the fluid software FLUENT. The effect of bubble on the transition behavior of droplet is analyzed. It is pointed out that in underwater wet welding, the droplet is affected by the interaction of internal force and external force, the internal force refers to the gas power, and the external forces include surface tension, gravity, electromagnetic contractile force, plasma force, speckle pressure, and gas drag force. Due to the cooling effect of water environment in the wet process welding, the welding arc is cooled and contracted, the plasma flow force promotes the droplet transition, and the direction of the electromagnetic contractile force is opposite to the droplet transition direction, which hinders the droplet transition, and the floating bubbles interact with the droplets to produce the drag force. This force is a special work in underwater wet welding. The transition behavior of droplets is affected by the force conditions of the droplet transfer, which affects the transition behavior of droplets, including the form of droplet transition, the droplet diameter and the transition frequency. Through the analysis of the welding signal, the droplet transition image, the welding spatter and the post weld specimen under different transition forms, the droplet is studied. The effect of crossing behavior on welding arc stability, weld formation and welding spatter shows that in the process of underwater wet wire welding wire welding, when the mixed transition form is dominated by short circuiting transition and small angle rejection transition, the transition of the droplet is stable, the welding arc is stable, the welding joint spatter is low, and the weld is formed evenly; when mixing, the weld is formed evenly. When the transition form is dominated by large angle rejection transition or "submerged arc transition", the welding arc combustion is unstable and easy to produce welding spatter. The droplets are prone to impact on the welding parts, and the welding defects on both sides of the weld are easy to produce, and the weld formation is poor.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG401

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