非熔化极焊接电弧仿真研究
发布时间：2018-11-24 12:06
【摘要】：非熔化极电弧焊接具有无飞溅,焊接质量好等优点,但是焊接效率低,熔敷效率慢等制约了其发展。钨极氩弧焊接与等离子弧焊作为非熔化极电弧焊,其焊接电弧却有着较大的能量密度差距。等离子弧焊电弧是在钨极氩弧焊接的基础上发展起来的,具有较高的能量密度、等离子流力,可以实现单面焊双面成形,具有较高的焊接效率、熔敷效率,因此具有广泛的前景。由于穿孔型等离子弧焊焊接过程中的小孔难以控制,使得其应用受到约束。焊接电弧作为焊接过程中的热源与力源,对焊接过程中小孔的形成与熔池的形貌有着重要的作用,所以对等离子弧焊过程中电弧的传热及传质影响的研究非常必要。本文对自由电弧与等离子弧焊电弧进行数值模拟,同时利用高速摄像技术对电弧形态与热丝下熔滴过渡分析,以确定其传热及传质情况。根据流体力学中的质量连续、动量守恒、能量守恒及磁矢量分量方程,建立二维轴对称自由电弧数学模。对自由电弧的温度场、电磁场、流场等进行了分析,与采用麦克斯韦方程组文献结果进行对比,结果表明二者分布趋势较吻合。建立二维约束型等离子弧焊电弧数学模型,确立其边界条件,采用SIMPLE算法,对等离子弧焊电弧特性进行计算。在相同焊接电流140A下等离子弧焊电弧与自由电弧比较发现,等离子弧焊电弧在阳极工件附件更是高达15000K比自由电弧阳极处高5000K左右;等离子弧焊电弧轴向上最大等离子流速是自由电弧的2倍;作用在阳极工件上的电弧压力更是自由电弧的20倍。同时改变焊接电流、等离子气流量、钨极内缩量、喷嘴孔径等参数,对等离子弧焊电弧的温度场、电磁场、流场等情况进行了分析模拟,结果表明焊接电流增大120A,等离子弧焊电弧温度可以提高1000K以上,等离子流速提高了13.6%-19%,阳极电弧压力提高近200Pa。等离子气流量的增加主要是等离子流速和电弧压力影响较大。在提高单位体积流量的等离子气流量后可以使其流速提高20%以上,阳极工件电弧压力更是提高300Pa以上。同时钨极内缩量的增大、喷嘴孔径的缩小均可以提高电弧温度、等离子流速及阳极工件电弧压力,有利于焊接效率提高。对等离子弧焊的电弧压缩状态与流动状态研究,与假设一致。利用高速摄像技术研究焊接电流、等离子气流量等参数的改变对等离子弧焊的电弧形态与数值计算形态对比,两者在形态上吻合度较好。同时对热丝填充K-PAW的电弧与熔滴过渡情况进行分析,结果表明热丝电流可以提高焊接熔敷效率。本文所建立的模型与采用高速摄像对热丝填充等离子弧焊的电弧研究建立了一定的基础。
[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.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG44
本文编号：2353646
[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.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG44
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