镁合金薄板焊接成型研究

发布时间：2018-01-18 23:59

本文关键词： AZ31B镁合金铜电极焊缝成形显微组织结构显微硬度　出处：《南昌大学》2016年硕士论文　论文类型：学位论文

【摘要】：本文在DE-GMAW(Double Electrode Gas Metal Welding,以下简称DE-GMAW)焊的基础上,对其进行了一定的改进,设计了一款以铜合金为电极的焊枪替换DE-GMAW焊接系统的旁路TIG焊枪,对AZ31B镁合金薄板进行堆焊焊接实验。首先,使用单一变量法,保持其它焊接参数不变,改变某一焊接参数,进行焊接实验,分析该参数对焊缝成形的影响,通过对比,获得该参数的最优值。依次对焊接电压、旁路电流、焊枪几何位置、焊接速度使用该方法进行实验,分析焊缝成形和焊缝尺寸,得出了各个焊接参数对焊缝成形及焊缝尺寸影响的规律,最终获得了各个焊接参数的最优值和良好的焊缝成形。然后,利用光学显微镜观察焊缝的显微组织。发现当各个焊接参数较小时,焊缝熔合区含有部分柱状晶,晶粒尺寸较大,晶粒内部和晶界处含有较多的析出相。随着焊接参数的增大,熔合区的柱状晶逐渐消失,晶粒尺寸减小,析出相减少。最后,使用显微硬度计测试焊缝的显微硬度。发现焊缝熔合区的显微硬度最小,母材区较大,焊缝中心区最大,在中心线附近达到最大值。随着焊接参数的增大,焊缝熔合区和中心区的显微硬度逐渐增大,但熔合区的显微硬度始终小于母材区。利用万能试验机对试样进行拉伸实验,发现焊缝的抗拉强度随着焊接参数的增大而增大,但始终小于母材的抗拉强度,并且断裂处位于焊缝熔合区。经过分析,最终获得的焊接参数为:焊接电压U=20V,总电流I=220A,旁路电流Ibp=140A,焊接速度V=2.9m/min,焊丝末端至工件距离d=3mm,铜电极末端至焊丝的距离d1=2mm,铜电极末端至工件距离d2=4mm,MIG焊枪导电嘴至工件距离d3=18mm,MIG焊枪与旁路焊枪夹角θ=55°,氩气流量为25L/min。
[Abstract]:This paper is based on DE-GMAW(Double Electrode Gas Metal Welding (hereinafter referred to as DE-GMAW) welding. Some improvements have been made and a by-pass TIG welding torch with copper alloy electrode is designed to replace the DE-GMAW welding system. The surfacing welding experiment of AZ31B magnesium alloy sheet was carried out. Firstly, the single variable method was used to keep the other welding parameters unchanged, and the welding experiment was carried out by changing a certain welding parameter. The influence of this parameter on weld forming is analyzed, and the optimum value of the parameter is obtained by comparison. The welding voltage, bypass current, welding torch geometry position and welding speed are tested by this method in turn. The influence of welding parameters on weld formation and weld size is analyzed, and the optimal value of each welding parameter and good weld forming are obtained. The microstructure of the weld was observed by optical microscope. It was found that when the welding parameters were small, there were some columnar crystals in the fusion zone of the weld, and the grain size was larger. With the increase of welding parameters, the columnar crystals in the fusion zone gradually disappear, the grain size decreases, and the precipitated phase decreases. The microhardness of weld is measured by microhardness meter. It is found that the microhardness of weld fusion zone is the smallest, the base metal area is larger, and the weld center area is the largest, which reaches the maximum near the center line. With the increase of welding parameters. The microhardness of the fusion zone and the center zone of the weld increases gradually, but the microhardness of the fusion zone is always smaller than that of the base metal zone. It is found that the tensile strength of the weld increases with the increase of welding parameters, but is always smaller than the tensile strength of the base metal, and the fracture is located in the fusion zone of the weld. The welding parameters obtained are as follows: welding voltage U20 V, total current I 220A, bypass current Ibp 140A, welding speed V2. 9 m / min. The distance from the end of the wire to the workpiece is 3 mm, the distance from the end of the copper electrode to the wire is 1 mm to 2 mm, and the distance from the end of the copper electrode to the workpiece is 4 mm. The distance from the conductive nozzle to the workpiece of the MIG welding torch is 318mm, the angle between the torch and the bypass torch is 55 掳, and the argon flow rate is 25L / min.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG457.19

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