6022铝合金薄板的冷金属过渡焊接工艺研究

发布时间：2018-05-06 04:14

本文选题：冷金属过渡焊(CMT) + 铝合金薄板　；参考：《中国民航大学》2017年硕士论文

【摘要】：汽车的车身板件多采用电阻点焊工艺进行焊接,为了能够保证车身结构的整体气密性,对于焊点之间的缝隙应进行焊接处理以获得密封性。国产汽车生产制造厂家多运用熔化极活性气体保护焊(Metal Active-gas Arc Welding,MAG)的技术来实现点焊焊点之间的缝隙焊接。传统焊接方式进行作业时无控制、粗犷式的热输入方式往往产生大量飞溅,严重损坏车身铝合金板材。同时,熔滴过渡时过大的短路电流会向熔池传入过多热量,引起车身铝合金板材多度受热变形。焊缝成型不均匀,局部可能出现烧穿、焊漏。有时需要对缝隙进行二次焊接,大幅度降低车身生产效率。基于以上生产加工实际情况,本文采用冷金属过渡焊接技术(Cold Metal Transfer,CMT)进行铝合金薄板对接形式的焊接。CMT冷金属过渡焊接工艺是一种新型的熔化极气体保护焊接方式,相对于普通的焊接方式,CMT焊接的特点是热输入量更低、焊接过程无飞溅、熔滴过渡方式温和的特点。本文选取1mm厚度的6022牌号铝合金薄板作为母材,以直径Φ=1.2 mm ER4043铝硅焊丝作为焊接的焊缝填充材料,来研究CMT铝合金板件的对接焊接性。通过单因素水平对比试验,研究了主要的焊接参数:送丝速度、弧长修正系数、焊接速度对焊接接头力学性能和微观组织的影响。利用激光共聚焦显微镜、蔡斯显微镜、扫描电子显微镜(SEM)观察微观形貌;采用能谱扫描仪分析接头成分组成;通过万能拉伸试验机,和显微硬度仪确定了焊缝熔合区,热影响区(HAZ,Heat-affected Zone)的范围。1.试验表明,铝合金薄板CMT焊缝表面成型均匀,没有明显的可见缺陷,焊后母材平整几乎无变形,焊缝熔合区域组织致密。2.铝合金薄板对接焊缝成型良好。母材硬度高于焊缝区硬度,铝合金薄板对接接头截面不同位置的显微硬度结果的峰值标示了热影响区的范围。对接接头的拉伸强度比焊接母材低20%,观察拉伸试验断口,主要为热影响区HAZ韧断模式。3.焊缝宏观形貌参数主要包括熔深、熔宽和深宽比。焊缝宏观形貌参数与焊丝输送速度、弧长修正系数成正相关,与焊枪行走速度数值成负相关。焊接送丝速度、弧长修正系数和焊接速度共同决定了焊接线能量大小。4.冷金属过渡焊接工艺(CMT)代替传统焊接方式,铝合金薄板焊接接头的宏观成型和力学性能达到要求。经过试验数据统计分析,得到6022牌号1mm铝合金薄板CMT焊接的最佳工艺参数:送丝速度为8m/min.、弧长修正系数为5%、焊接速度为540mm/min.。
[Abstract]:In order to ensure the overall airtightness of the body structure, the welding of the cracks between the solder joints should be carried out in order to obtain sealing. Domestic automobile manufacturers often use metal Active-gas Arc welding technology to realize gap welding between spot welding joints. The traditional welding method has no control, and the rough heat input often produces a lot of spatter, which seriously damages the aluminum alloy plate of the body. At the same time, the excessive short circuit current will transmit too much heat to the molten pool during droplet transfer, which will cause many thermal deformation of aluminum alloy sheet. Weld formation is not uniform, local may be burn-through, welding leakage. Sometimes it is necessary to weld the cracks twice, which greatly reduces the production efficiency of the body. Based on the actual production and processing, the cold metal transfer welding technology, Cold Metal transfer (CMT), is a new type of gas shielded welding process for aluminum alloy sheet welding. Compared with conventional welding method, CMT welding is characterized by lower heat input, no spatter and mild droplet transfer mode. In this paper, 6022 grade aluminum alloy sheet with 1mm thickness is selected as base metal, and diameter 桅 1.2mm ER4043 aluminum silicon wire is used as weld filling material to study the butt weldability of CMT aluminum alloy plate. The effects of main welding parameters, such as wire feeding speed, arc length correction coefficient and welding speed, on the mechanical properties and microstructure of welded joints were studied by single factor horizontal contrast test. Laser confocal microscope, Chase microscope, scanning electron microscope (SEM) were used to observe the microstructure, energy spectrum scanner (EDS) was used to analyze the composition of the joints, and the weld fusion zone was determined by universal tensile tester and microhardness tester. The range of HAZA Heat-affected Zone1. The results show that the CMT weld surface of the aluminum alloy sheet is uniform, without obvious visible defects, the base metal is flat and almost no deformation after welding, and the microstructure of the weld fusion zone is dense. 2. The butt weld of aluminum alloy sheet is well formed. The hardness of base metal is higher than that of weld zone. The peak value of microhardness of aluminum alloy sheet butt joint at different positions indicates the range of heat affected zone. The tensile strength of the butt joint was 20% lower than that of the welding base metal. The tensile test fracture was observed mainly in the heat affected zone (HAZ) HAZ fracture mode. 3. The macroscopic morphology parameters of weld include penetration width and aspect ratio. The macroscopic appearance parameters of the weld are positively correlated with the wire conveying speed and arc length correction coefficient, and negatively correlated with the walking speed of the welding torch. Welding wire feeding speed, arc length correction coefficient and welding speed together determine the welding line energy. 4. Cold metal transition welding process (CMT) instead of conventional welding method, aluminum alloy sheet welding joint macro forming and mechanical properties meet the requirements. Through statistical analysis of test data, the optimum technological parameters for CMT welding of 6022 grade 1mm aluminum alloy sheet are obtained: wire feeding speed is 8 m / min., arc length correction coefficient is 5 and welding speed is 540 mm / min.
【学位授予单位】：中国民航大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.14;U466

【参考文献】