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  本文關(guān)鍵詞： AZ31B鎂合金 銅電極 焊縫成形 顯微組織結(jié)構(gòu) 顯微硬度　出處：《南昌大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：本文在DE-GMAW(Double Electrode Gas Metal Welding,以下簡稱DE-GMAW)焊的基礎(chǔ)上,對其進(jìn)行了一定的改進(jìn),設(shè)計(jì)了一款以銅合金為電極的焊槍替換DE-GMAW焊接系統(tǒng)的旁路TIG焊槍,對AZ31B鎂合金薄板進(jìn)行堆焊焊接實(shí)驗(yàn)。首先,使用單一變量法,保持其它焊接參數(shù)不變,改變某一焊接參數(shù),進(jìn)行焊接實(shí)驗(yàn),分析該參數(shù)對焊縫成形的影響,通過對比,獲得該參數(shù)的最優(yōu)值。依次對焊接電壓、旁路電流、焊槍幾何位置、焊接速度使用該方法進(jìn)行實(shí)驗(yàn),分析焊縫成形和焊縫尺寸,得出了各個焊接參數(shù)對焊縫成形及焊縫尺寸影響的規(guī)律,最終獲得了各個焊接參數(shù)的最優(yōu)值和良好的焊縫成形。然后,利用光學(xué)顯微鏡觀察焊縫的顯微組織。發(fā)現(xiàn)當(dāng)各個焊接參數(shù)較小時,焊縫熔合區(qū)含有部分柱狀晶,晶粒尺寸較大,晶粒內(nèi)部和晶界處含有較多的析出相。隨著焊接參數(shù)的增大,熔合區(qū)的柱狀晶逐漸消失,晶粒尺寸減小,析出相減少。最后,使用顯微硬度計(jì)測試焊縫的顯微硬度。發(fā)現(xiàn)焊縫熔合區(qū)的顯微硬度最小,母材區(qū)較大,焊縫中心區(qū)最大,在中心線附近達(dá)到最大值。隨著焊接參數(shù)的增大,焊縫熔合區(qū)和中心區(qū)的顯微硬度逐漸增大,但熔合區(qū)的顯微硬度始終小于母材區(qū)。利用萬能試驗(yàn)機(jī)對試樣進(jìn)行拉伸實(shí)驗(yàn),發(fā)現(xiàn)焊縫的抗拉強(qiáng)度隨著焊接參數(shù)的增大而增大,但始終小于母材的抗拉強(qiáng)度,并且斷裂處位于焊縫熔合區(qū)。經(jīng)過分析,最終獲得的焊接參數(shù)為:焊接電壓U=20V,總電流I=220A,旁路電流Ibp=140A,焊接速度V=2.9m/min,焊絲末端至工件距離d=3mm,銅電極末端至焊絲的距離d1=2mm,銅電極末端至工件距離d2=4mm,MIG焊槍導(dǎo)電嘴至工件距離d3=18mm,MIG焊槍與旁路焊槍夾角θ=55°,氬氣流量為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 擄, and the argon flow rate is 25L / min.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TG457.19

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本文編號：1441709