發(fā)布時(shí)間：2018-07-10 02:35

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

【摘要】：隨著海洋事業(yè)的不斷發(fā)展,我國(guó)對(duì)水下焊接技術(shù)的需求日益提高。水下濕法焊接基于其操作簡(jiǎn)單、通用性強(qiáng)、經(jīng)濟(jì)性好等優(yōu)勢(shì),目前已廣泛應(yīng)用于水下焊接領(lǐng)域,但由于缺少焊接防護(hù)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(yán)重、焊縫成形較差等諸多問(wèn)題。水下濕法焊接中存在的問(wèn)題與熔滴過(guò)渡形式密切相關(guān),由于水環(huán)境及水下壓力的存在,水下濕法焊接的熔滴過(guò)渡過(guò)程具有一定的特殊性。本研究針對(duì)水下藥芯焊絲濕法焊接熔滴過(guò)渡過(guò)程展開(kāi)了相關(guān)理論研究工作,不僅填補(bǔ)了水下濕法焊接熔滴過(guò)渡領(lǐng)域理論研究的空白,而且為水下濕法焊接熔滴過(guò)渡行為的控制提供理論支撐�；赬射線高速成像與電信號(hào)同步采集系統(tǒng),觀測(cè)了水下濕法焊接熔滴過(guò)渡行為,并根據(jù)熔滴過(guò)渡行為的不同劃分了熔滴過(guò)渡形式,探索了熔滴過(guò)渡形式隨焊接參數(shù)的轉(zhuǎn)換條件。研究表明,根據(jù)熔滴過(guò)渡行為的不同,水下濕法焊接基本熔滴過(guò)渡形式分為排斥過(guò)渡、短路過(guò)渡以及“潛弧過(guò)渡”;根據(jù)排斥角大小的不同,排斥過(guò)渡可分為大角度排斥過(guò)渡與小角度排斥過(guò)渡,根據(jù)短路過(guò)渡階段的不同,短路過(guò)渡可分為短路表面張力過(guò)渡與短路爆炸過(guò)渡;同一焊接參數(shù)下,熔滴過(guò)渡形式不是單一的,而是由三類(lèi)基本過(guò)渡形式按一定比例組成,稱(chēng)為混合過(guò)渡;隨著焊接參數(shù)的改變,混合過(guò)渡形式中基本過(guò)渡形式的種類(lèi)及比例、熔滴直徑及過(guò)渡頻率均發(fā)生相應(yīng)改變�；陟o力學(xué)平衡理論,構(gòu)建了水下濕法焊接熔滴過(guò)渡受力模型,探索了焊接參數(shù)對(duì)熔滴過(guò)渡行為的影響機(jī)理,并通過(guò)流體軟件FLUENT模擬了水下濕法焊接上升氣泡對(duì)熔滴過(guò)渡行為的影響。分析指出:在水下濕法焊接中,熔滴受到內(nèi)部作用力和外部作用力的共同作用,內(nèi)部作用力指氣體動(dòng)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(diǎn)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(duì)熔滴過(guò)渡的促進(jìn)作用減弱,電磁收縮力方向與熔滴過(guò)渡方向相反,阻礙熔滴過(guò)渡;上浮氣泡與熔滴相互作用,產(chǎn)生氣體拖拽力,該力是水下濕法焊接中特有的作用力,對(duì)熔滴過(guò)渡起到阻礙、排斥作用。焊接參數(shù)通過(guò)改變?nèi)鄣问芰l件,影響熔滴的過(guò)渡行為,包括熔滴過(guò)渡形式、熔滴直徑及過(guò)渡頻率。通過(guò)對(duì)不同過(guò)渡形式下的焊接電信號(hào)、熔滴過(guò)渡影像、焊接飛濺及焊后試件進(jìn)行分析,研究了熔滴過(guò)渡行為對(duì)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(guò)程中,當(dāng)混合過(guò)渡形式以短路過(guò)渡和小角度排斥過(guò)渡為主時(shí),熔滴過(guò)渡平穩(wěn),焊接電弧燃燒穩(wěn)定,焊接飛濺產(chǎn)生頻率較低,焊縫成形均勻;當(dāng)混合過(guò)渡形式以大角度排斥過(guò)渡或“潛弧過(guò)渡”為主時(shí),焊接電弧燃燒不穩(wěn)定,易于產(chǎn)生焊接飛濺,熔滴易對(duì)焊件產(chǎn)生沖擊,焊縫兩側(cè)易于產(chǎn)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(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TG401

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