本文選題：AZ31鎂合金 + 直流MIG焊　； 參考：《中北大學(xué)》2017年碩士論文

【摘要】：AZ31鎂合金由于具備良好的綜合性能,現(xiàn)已廣泛應(yīng)用于各行各業(yè),正成為結(jié)構(gòu)鎂合金材料領(lǐng)域的研究熱點。鎂合金結(jié)構(gòu)件在使用過程中,必不可少需要對鎂合金進行補焊或連接,因而探究鎂合金焊接具有重要的現(xiàn)實意義。目前鎂合金焊接并不成熟,鎂合金焊接依然面臨著諸多問題,鎂合金的焊接問題茲待人們進一步解決。本論文基于MIG焊接方法,研究焊接工藝對AZ31鎂合金焊接過程的影響,試驗中通過改變工藝參數(shù)(焊接電流、干伸長度、保護氣流量),添加不同的活性劑(KCl、Zn Cl2、Ca Cl2、Cd Cl2、Mg Cl2)進行多組實驗,采集焊接過程中電弧及熔滴過渡的圖片,獲得不同工藝下焊后的焊縫接頭,對實驗結(jié)果進行觀察、測量、計算、并研究分析相關(guān)機理,本文可得出以下結(jié)論:(1)焊接電流對電弧及熔滴影響顯著,采集的圖片顯示電流從小到大的過程中,熔滴依次經(jīng)歷了滴狀過渡、噴射過渡、射流過渡,其中滴狀過渡的可調(diào)參數(shù)范圍廣,臨界電流值在220A左右,此時電弧穩(wěn)定,熔滴尺寸與焊絲直徑相近。電流從125A逐漸增大的過程中,電弧形態(tài)發(fā)生了顯著的變化,弧長由長變短,弧寬逐漸增大,熔滴過渡尺寸也發(fā)生了變化,熔滴尺寸由大變小,過渡頻率加快。電流通過影響電弧及熔滴過渡作用到焊縫成形上,熔寬增寬,熔深加深,余高增高。(2)實驗結(jié)果表明干伸長度會影響熔滴過渡中的臨界電流,干伸長度增加,臨界電流變大。在其他條件一定的情況下,干伸長度增大,焊絲的電阻值增加,電壓增大,熔滴尺寸變大,弧長變長。對焊縫的研究發(fā)現(xiàn)干伸長度過小,會造成焊縫過高,成形不良。干伸過大,電弧不穩(wěn),產(chǎn)生大量飛濺,焊縫成形性差。(3)在一定的范圍內(nèi),保護氣流量增大,電弧會發(fā)生收縮,電弧越來越穩(wěn)定,熔滴尺寸有所減小。氣流量過小,會卷入空氣,電弧紊亂,造成飛濺,且保護效果不良,造成焊縫氧化;氣流量過大,電弧吹力加劇,易造成飛濺。(4)添加不同的活性劑對電弧及熔滴過渡會產(chǎn)生不同的影響,Ca Cl2活性劑使得弧寬增大,熔滴尺寸明顯增大,熔滴過渡周期延長,阻礙了熔滴的過渡,熔深變淺,余高稍有減小。Cd Cl2活性劑和Zn Cl2活性劑收縮了電弧,使熔滴尺寸變小,焊縫的余高和熔寬大大減小。添加KCl活性劑后,電弧擴展很大,變?yōu)閭銧?電弧寬度變寬,熔滴尺寸變小,沿豎直軸向方向過渡,過渡周期減小,過渡平穩(wěn),由滴狀過渡轉(zhuǎn)變?yōu)閲娚溥^渡,KCl活性劑促進了熔滴過渡,余高熔深均增大,熔寬的增加幅度很大。Mg Cl2活性劑對熔滴過渡影響不大,電弧稍有收縮,焊縫熔深加深,但加深幅度不大。
[Abstract]:AZ31 magnesium alloy has been widely used in various industries due to its good comprehensive properties, and is becoming a research hotspot in the field of structural magnesium alloy materials. In the process of using magnesium alloy structure, it is necessary to weld or connect magnesium alloy, so it is of great practical significance to explore the welding of magnesium alloy. At present, magnesium alloy welding is not mature, magnesium alloy welding is still facing many problems, magnesium alloy welding problems need to be further solved. Based on the MIG welding method, the effect of welding process on the welding process of AZ31 magnesium alloy is studied in this paper. Different kinds of active agents (KCl-Zn Cl2Ca-CaCl2Cd-Cl2Mg-Cl2) were added to the experiments. The images of arc and droplet transfer during welding were collected, and the weld joints after welding under different processes were obtained. The experimental results were observed, measured and calculated. The results are as follows: (1) the welding current has a significant effect on the arc and droplet. The collected pictures show that the droplet has experienced droplet transition, jet transition and jet transition. The adjustable parameters of the droplet transition are wide, the critical current is about 220A, the arc is stable and the droplet size is close to the wire diameter. In the process of increasing the current from 125A to 125A, the arc shape changed significantly, the arc length became shorter, the arc width gradually increased, the size of droplet transfer changed, the size of droplet changed from large to small, and the transition frequency was accelerated. Through the influence of arc and droplet transfer on the weld formation, the weld width widens, the penetration deepens, and the residual height increases. (2) the experimental results show that the dry elongation will affect the critical current in the droplet transfer, the dry elongation will increase, and the critical current will become larger. Under certain other conditions, the dry elongation increases, the wire resistance increases, the voltage increases, the droplet size becomes larger, and the arc length becomes longer. It is found that the weld is too high and badly formed if the dry elongation is too small. When the dry extension is too large, the arc is unstable, a large amount of spatter is produced, and the welding seam formability is poor. (3) in a certain range, the flux of protective gas increases, the arc shrinks, the arc becomes more and more stable, and the droplet size decreases. If the gas flow rate is too small, it will be involved in the air and the arc will be disordered, causing spatter, and the protective effect is not good, resulting in the oxidation of the weld; if the gas flow rate is too large, the arc blowing force will be aggravated. It is easy to cause spatter. (4) addition of different active agents to the arc and droplet transfer will have different effects on arc width, droplet size and droplet transfer cycle. The residual height decreases slightly. CD Cl 2 active agent and Zn Cl 2 active agent shrink the arc, which makes the droplet size smaller, and the residual height and weld width greatly decrease. With the addition of KCl active agent, the arc expands greatly, becomes umbrella-like, widens the arc width, decreases the droplet size, and transitions along the vertical axis. The transition period is reduced and the transition is stable. The transition from dripping to jet transfer promoted the transfer of droplet, and the remaining high penetration increased. The increase of melting width was very large. The flux of MgCl _ 2 had little effect on the transfer of droplet, the arc contracted slightly, and the weld penetration deepened. But the depth is small.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG444.74

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