镁合金TIG-MIG复合焊研究

发布时间：2019-05-23 19:34

【摘要】：本文采用TIG-MIG复合焊对AZ31镁合金型材进行了焊接研究,主要研究了焊缝成形、微观组织、力学性能。首先,进行了 TIG-MIG复合焊系统搭建,主要包括两个部分:两焊枪的夹持装置设计和控制系统设计。其次是两焊枪的相对位置关系的确定。适合本次试验的两焊枪的位置关系是:两焊枪在同一直线上,TIG焊枪在前,MIG焊枪在后,TIG焊枪垂直与工件,MIG焊枪与TIG焊枪成45°夹角。然后研究了工艺参数(TIG焊电流、MIG焊电流、MIG焊电压、焊接速度、TIG焊电弧与MIG焊电弧的中心距离)对焊缝成形的影响规律,最终获得成形良好的接头。对成形良好的焊接接头进行了拉伸试验,得出抗拉强度达到215MPa,约为母材的79.63%,接头的断裂形貌主要呈现为韧窝断裂与解理断裂的混合型断裂。对焊接接头进行了硬度试验,得出焊缝硬度的平均值为57.78HV、热影响区硬度的平均值为52.81HV、母材硬度的平均值为56.14HV。对焊接接头进行了微观组织研究,研究结果表明焊接接头由母材区、热影响区、焊缝区组成。母材的微观组织为较均匀,晶粒细小,主要由α-Mg相组成。热影响区的微观组织呈现晶粒粗大而又不规则,有少量的β-Mg17Al12金属间化合物。焊缝为细小均匀的等轴晶,主要由α-Mg相和β-Mg17Al12金属间化合物两个部分组成。β-Mg17Al12金属间化合物主要分布在晶粒和晶界上,呈现条状和粒状。最后对比分析了 TIG-MIG复合焊高速焊与低速焊的接头宏观、微观、硬度。从宏观上比较,高速焊接的焊缝表面鱼鳞纹更细和熔宽更宽。从微观上比较,高速焊接的热影响区与焊缝晶粒比低速焊接的相应区域更细小。从接头硬度比较,高速焊接的热影响区硬度和焊缝硬度比低速焊接的相应区域大。
[Abstract]:In this paper, TIG-MIG composite welding was used to study the welding of AZ31 magnesium alloy profiles. The weld forming, microstructure and mechanical properties were mainly studied. Firstly, the TIG-MIG composite welding system is built, which mainly includes two parts: the clamping device design and the control system design of the two welding guns. Secondly, the relative position relationship of the two welding guns is determined. The position relationship between the two welding guns is as follows: the two welding guns are in the same straight line, the TIG welding torch is in front of the MIG welding torch, the TIG welding torch is perpendicular to the workpiece, and the MIG welding torch is 45 掳angle with the TIG welding torch. Then the influence of process parameters (TIG welding current, MIG welding voltage, welding speed, center distance between TIG welding arc and MIG welding arc) on weld forming is studied, and finally the well formed joint is obtained. The tensile test of the well-formed welded joint shows that the tensile strength is 215 MPA, which is about 79.63% of that of the base metal, and the fracture morphology of the joint is mainly the mixed fracture of dimple fracture and cleavage fracture. The average hardness of the welded joint is 57.78 HV. the average hardness of the heat affected zone is 52.81 HV. the average hardness of the base metal is 56.14 HV. the average hardness of the welded joint is 57.78 HV. the average hardness of the heat affected zone is 52.81 HV. the average hardness of the base metal is 56.14 HV. The microstructure of the welded joint is studied. The results show that the welded joint is composed of base metal zone, heat affected zone and weld zone. The microstructure of the base metal is uniform and the grain size is fine, which is mainly composed of 伪-Mg phase. The microstructure of the heat affected zone is coarse and irregular, and there are a small amount of 尾-Mg17Al12 intermetallic compounds. The weld is a fine and uniform equiaxed crystal, which is mainly composed of 伪-Mg phase and 尾-Mg17Al12 intermetallic compound. 尾-Mg17Al12 intermetallic compound is mainly distributed on grain and grain boundary, showing strip and grain shape. Finally, the macro, micro and hardness of high speed welding and low speed welding of TIG-MIG composite welding are compared and analyzed. From a macro point of view, the fish scale lines on the weld surface of high speed welding are thinner and wider. Compared with the corresponding area of low speed welding, the heat affected zone and grain size of high speed welding are smaller than those of low speed welding. Compared with the hardness of the joint, the hardness of the heat affected zone and the hardness of the weld in the high speed welding are larger than those in the low speed welding.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG456

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