【摘要】：非熔化極電弧焊接具有無飛濺,焊接質(zhì)量好等優(yōu)點,但是焊接效率低,熔敷效率慢等制約了其發(fā)展。鎢極氬弧焊接與等離子弧焊作為非熔化極電弧焊,其焊接電弧卻有著較大的能量密度差距。等離子弧焊電弧是在鎢極氬弧焊接的基礎(chǔ)上發(fā)展起來的,具有較高的能量密度、等離子流力,可以實現(xiàn)單面焊雙面成形,具有較高的焊接效率、熔敷效率,因此具有廣泛的前景。由于穿孔型等離子弧焊焊接過程中的小孔難以控制,使得其應用受到約束。焊接電弧作為焊接過程中的熱源與力源,對焊接過程中小孔的形成與熔池的形貌有著重要的作用,所以對等離子弧焊過程中電弧的傳熱及傳質(zhì)影響的研究非常必要。本文對自由電弧與等離子弧焊電弧進行數(shù)值模擬,同時利用高速攝像技術(shù)對電弧形態(tài)與熱絲下熔滴過渡分析,以確定其傳熱及傳質(zhì)情況。根據(jù)流體力學中的質(zhì)量連續(xù)、動量守恒、能量守恒及磁矢量分量方程,建立二維軸對稱自由電弧數(shù)學模。對自由電弧的溫度場、電磁場、流場等進行了分析,與采用麥克斯韋方程組文獻結(jié)果進行對比,結(jié)果表明二者分布趨勢較吻合。建立二維約束型等離子弧焊電弧數(shù)學模型,確立其邊界條件,采用SIMPLE算法,對等離子弧焊電弧特性進行計算。在相同焊接電流140A下等離子弧焊電弧與自由電弧比較發(fā)現(xiàn),等離子弧焊電弧在陽極工件附件更是高達15000K比自由電弧陽極處高5000K左右;等離子弧焊電弧軸向上最大等離子流速是自由電弧的2倍;作用在陽極工件上的電弧壓力更是自由電弧的20倍。同時改變焊接電流、等離子氣流量、鎢極內(nèi)縮量、噴嘴孔徑等參數(shù),對等離子弧焊電弧的溫度場、電磁場、流場等情況進行了分析模擬,結(jié)果表明焊接電流增大120A,等離子弧焊電弧溫度可以提高1000K以上,等離子流速提高了13.6%-19%,陽極電弧壓力提高近200Pa。等離子氣流量的增加主要是等離子流速和電弧壓力影響較大。在提高單位體積流量的等離子氣流量后可以使其流速提高20%以上,陽極工件電弧壓力更是提高300Pa以上。同時鎢極內(nèi)縮量的增大、噴嘴孔徑的縮小均可以提高電弧溫度、等離子流速及陽極工件電弧壓力,有利于焊接效率提高。對等離子弧焊的電弧壓縮狀態(tài)與流動狀態(tài)研究,與假設(shè)一致。利用高速攝像技術(shù)研究焊接電流、等離子氣流量等參數(shù)的改變對等離子弧焊的電弧形態(tài)與數(shù)值計算形態(tài)對比,兩者在形態(tài)上吻合度較好。同時對熱絲填充K-PAW的電弧與熔滴過渡情況進行分析,結(jié)果表明熱絲電流可以提高焊接熔敷效率。本文所建立的模型與采用高速攝像對熱絲填充等離子弧焊的電弧研究建立了一定的基礎(chǔ)。
[Abstract]:Non-melting electrode arc welding has the advantages of no spatter and good welding quality, but its development is restricted by its low welding efficiency and slow deposition efficiency. Argon tungsten arc welding and plasma arc welding as non-melting electrode arc welding, its welding arc has a large gap in energy density. Plasma arc welding is developed on the basis of tungsten argon arc welding. It has high energy density and plasma flow force, and can be formed on both sides of single side welding, and has high welding efficiency and deposition efficiency. Therefore, there is a wide range of prospects. Because the holes in the perforated plasma arc welding are difficult to control, its application is restricted. Welding arc, as the heat source and force source in welding process, plays an important role in the formation of holes and the appearance of weld pool, so it is very necessary to study the effect of heat and mass transfer of arc in plasma arc welding process. In this paper, the numerical simulation of free arc and plasma arc welding arc is carried out. At the same time, the arc shape and droplet transfer under hot wire are analyzed by high speed camera technology to determine the heat and mass transfer. According to the mass continuity, momentum conservation, energy conservation and magnetic vector component equations in hydrodynamics, a two-dimensional axisymmetric free arc mathematical model is established. The temperature field, electromagnetic field and flow field of free arc are analyzed and compared with the results of Maxwell equations. The mathematical model of two dimensional confined plasma arc welding arc is established and its boundary conditions are established. The arc characteristics of plasma arc welding are calculated by SIMPLE algorithm. In the same welding current 140A plasma arc welding and free arc comparison found that plasma arc welding arc in the anode workpiece accessories is as high as 15 000 K than the free arc anode about 5 000 K. The maximum plasma velocity in the axial direction of plasma arc welding is 2 times that of the free arc, and the arc pressure acting on the anode is 20 times higher than that of the free arc. The temperature field, electromagnetic field and flow field of plasma arc welding arc are analyzed and simulated by changing the welding current, plasma gas flow rate, tungsten electrode shrinkage, nozzle aperture and so on. The results show that the welding current increases 120A, and so on. The arc temperature of plasma arc welding can be increased by more than 1000K, the plasma flow rate is increased by 13.6- 19, and the anode arc pressure is increased by nearly 200Pa. The increase of plasma flow rate is mainly influenced by plasma velocity and arc pressure. The flow rate of plasma gas can be increased by more than 20% with increasing the flow rate of plasma gas per unit volume flow, and the arc pressure of anode workpiece can be increased by more than 300Pa. At the same time, the arc temperature, plasma flow rate and arc pressure of anode workpiece can be increased by increasing the shrinkage of tungsten electrode and reducing the aperture of nozzle, which is beneficial to the improvement of welding efficiency. The research on the arc compression and flow state of plasma arc welding is consistent with the hypothesis. The arc shape of plasma arc welding is compared with that of numerical calculation with the change of welding current and flow rate of plasma gas by using high speed camera technology. The results show that the two parameters are in good agreement with each other in shape. At the same time, the arc and droplet transfer of K-PAW filled with hot wire is analyzed. The results show that the hot wire current can improve the welding deposition efficiency. The model established in this paper is based on the research of hot wire filled plasma arc welding with high speed camera.
【學位授予單位】：江蘇科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG44

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本文編號：2353646