本文選題：濕法焊接 + 過渡行為��； 參考：《哈爾濱工業(yè)大學》2017年碩士論文

【摘要】：隨著海洋事業(yè)的不斷發(fā)展,我國對水下焊接技術的需求日益提高。水下濕法焊接基于其操作簡單、通用性強、經濟性好等優(yōu)勢,目前已廣泛應用于水下焊接領域,但由于缺少焊接防護措施,水下濕法焊接存在焊接電弧不穩(wěn)定、焊接冶金損失嚴重、焊縫成形較差等諸多問題。水下濕法焊接中存在的問題與熔滴過渡形式密切相關,由于水環(huán)境及水下壓力的存在,水下濕法焊接的熔滴過渡過程具有一定的特殊性。本研究針對水下藥芯焊絲濕法焊接熔滴過渡過程展開了相關理論研究工作,不僅填補了水下濕法焊接熔滴過渡領域理論研究的空白,而且為水下濕法焊接熔滴過渡行為的控制提供理論支撐�；赬射線高速成像與電信號同步采集系統,觀測了水下濕法焊接熔滴過渡行為,并根據熔滴過渡行為的不同劃分了熔滴過渡形式,探索了熔滴過渡形式隨焊接參數的轉換條件。研究表明,根據熔滴過渡行為的不同,水下濕法焊接基本熔滴過渡形式分為排斥過渡、短路過渡以及“潛弧過渡”;根據排斥角大小的不同,排斥過渡可分為大角度排斥過渡與小角度排斥過渡,根據短路過渡階段的不同,短路過渡可分為短路表面張力過渡與短路爆炸過渡;同一焊接參數下,熔滴過渡形式不是單一的,而是由三類基本過渡形式按一定比例組成,稱為混合過渡;隨著焊接參數的改變,混合過渡形式中基本過渡形式的種類及比例、熔滴直徑及過渡頻率均發(fā)生相應改變。基于靜力學平衡理論,構建了水下濕法焊接熔滴過渡受力模型,探索了焊接參數對熔滴過渡行為的影響機理,并通過流體軟件FLUENT模擬了水下濕法焊接上升氣泡對熔滴過渡行為的影響。分析指出:在水下濕法焊接中,熔滴受到內部作用力和外部作用力的共同作用,內部作用力指氣體動力,外部作用力包括表面張力、重力、電磁收縮力、等離子流力、斑點壓力以及氣體拖拽力。與陸上焊接不同,在水下濕法焊接中由于受到水環(huán)境的冷卻作用,焊接電弧冷卻收縮,等離子流力對熔滴過渡的促進作用減弱,電磁收縮力方向與熔滴過渡方向相反,阻礙熔滴過渡;上浮氣泡與熔滴相互作用,產生氣體拖拽力,該力是水下濕法焊接中特有的作用力,對熔滴過渡起到阻礙、排斥作用。焊接參數通過改變熔滴受力條件,影響熔滴的過渡行為,包括熔滴過渡形式、熔滴直徑及過渡頻率。通過對不同過渡形式下的焊接電信號、熔滴過渡影像、焊接飛濺及焊后試件進行分析,研究了熔滴過渡行為對焊接電弧穩(wěn)定性、焊縫成形及焊接飛濺的影響,研究表明在水下濕法藥芯焊絲焊接過程中,當混合過渡形式以短路過渡和小角度排斥過渡為主時,熔滴過渡平穩(wěn),焊接電弧燃燒穩(wěn)定,焊接飛濺產生頻率較低,焊縫成形均勻;當混合過渡形式以大角度排斥過渡或“潛弧過渡”為主時,焊接電弧燃燒不穩(wěn)定,易于產生焊接飛濺,熔滴易對焊件產生沖擊,焊縫兩側易于產生焊瘤缺陷,焊縫成形較差。
[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.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG401

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