镁合金双弧活性焊接微观组织及性能分析

发布时间：2018-12-09 18:54

【摘要】：本文对2mm厚AZ31B镁合金DE-GMAW(双电极气体保护焊)焊接进行研究,分析旁路电流、焊接电压、焊接速度三个不同焊接参数对焊缝性能的影响,得出一个相对合适的焊接参数搭配。在这一焊接参数的基础上,通过在母材表面涂覆一层活性剂SiC,研究SiC涂覆量对AZ31B镁合金焊接性能的影响。实验中通过分析焊缝的形貌和焊缝尺寸来研究各个参数对焊缝成型的影响,通过对接头的金相组织、显微硬度和抗拉强度等性能的分析,结果表明各个参数对接头性能具有一定的影响。(1)在其他焊接参数一定的情况下,旁路电流从150A增加到180A过程中,焊缝熔宽和熔深都是在减小,而余高增加。通过测量得到焊缝熔合区中晶粒尺寸减小。焊接接头显微硬度在旁路电流逐渐增加的过程中呈现出逐渐增加的规律。通过对不同旁路电流所得的焊接接头进行拉伸可知,接头的抗拉强度从旁路电流为150A增加到180A过程中一直增加,当旁路电流为180A时,抗拉强度急剧增加。(2)焊接电压的增加使得焊缝熔宽增加,熔深和余高减小,在焊接电压为23V时,焊缝成型最好。同时晶粒尺寸也增加,但增加量很小,可以认为基本不受影响。焊缝熔合区显微硬度基本保持不变,接头抗拉强度缓慢减小,而当电压为24V时焊缝未熔透,抗拉强度有所增加。(3)焊接速度从2.3m/min到2.9m/min焊接过程中,焊缝熔宽和熔深逐渐减小,而余高从焊接速度为2.3m/min开始增加到焊接速度为2.7m/min达到最大,焊缝熔合区晶粒尺寸变化规律同旁路电流时的变化规律相同。显微硬度测试和拉伸实验结果显示,随着焊接速度的增加,焊接头显微硬度和抗拉强度增加。(4)最终得出最优焊接参数搭配为:主路电流I主=230A,旁路电流I旁=170A,焊接电压U=23V,焊接速度V=2.7m/min。(5)焊缝熔深和余高随SiC增加到ρ=5.64 mg/cm2的过程中逐渐增大,随着SiC涂覆量进一步增加而减小,而熔宽的变化规律刚好相反。当SiC添加量小于ρ=5.64 mg/cm2时,可以起到细化晶粒的作用,同时SiC颗粒可以使β-Mg17Al12在焊缝中弥散分布。SiC颗粒的添加有效的提高了焊接接头的显微硬度,并且随着SiC涂覆量的增加接头的显微硬度逐渐增加。随着SiC涂覆量的增加,接头的抗拉强度增加。但当SiC涂覆量大于ρ=5.64 mg/cm2时,焊接接头抗拉强度明显降低。
[Abstract]:In this paper, the welding of 2mm thick AZ31B magnesium alloy DE-GMAW (double electrode gas shielded welding) is studied. The influence of three welding parameters such as bypass current, welding voltage and welding speed on the weld performance is analyzed. A relatively suitable welding parameter is obtained. On the basis of these welding parameters, the effect of SiC coating amount on the welding properties of AZ31B magnesium alloy was studied by coating a layer of active agent SiC, on the base metal surface. In the experiment, the influence of various parameters on weld formation was studied by analyzing the morphology and size of the weld, and the metallographic structure, microhardness and tensile strength of the joint were analyzed. The results show that each parameter has a certain effect on the performance of the joint. (1) when the by-pass current increases from 150A to 180A, the weld penetration width and penetration depth decrease, while the residual height increases. The grain size in the weld fusion zone is reduced by measurement. The microhardness of welded joints increases gradually with the increasing of bypass current. By drawing the welded joints with different bypass currents, the tensile strength of the joints increases from 150A to 180A, and when the bypass current is 180A, (2) with the increase of welding voltage, the weld width increases, the weld depth and residual height decrease, and the weld formation is the best when the welding voltage is 23V. At the same time, the grain size also increases, but the increase is very small, which can be considered as basically unaffected. The microhardness of weld fusion zone remains basically unchanged, and the tensile strength of the joint decreases slowly, while when the voltage is 24V, the weld does not melt through and the tensile strength increases. (3) during the welding process from 2.3m/min to 2.9m/min welding, The weld width and penetration decreased gradually, while the residual height increased from the welding speed of 2.3m/min to the maximum of the welding speed of 2.7m/min, and the variation law of grain size in the weld fusion zone was the same as that of the by-pass current. The results of microhardness test and tensile test show that the microhardness and tensile strength of welded joints increase with the increase of welding speed. (4) the optimal welding parameters are as follows: main circuit current I = 230 A, bypass current I = 170 A. (5) the weld penetration depth and residual height increase gradually with the increase of SiC to 蟻 = 5.64 mg/cm2, and decrease with the further increase of SiC coating amount, but the variation of weld width is just the opposite. When the content of SiC is less than 蟻 = 5.64 mg/cm2, the grain size can be refined, and the 尾-Mg17Al12 can be dispersed in weld seam by SiC particle. The microhardness of welded joint can be improved effectively by adding SiC particles. The microhardness of the joint increases with the increase of coating amount of SiC. With the increase of SiC coating amount, the tensile strength of the joint increases. However, when the coating amount of SiC is greater than 蟻 = 5.64 mg/cm2, the tensile strength of welded joint decreases obviously.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG444.72

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