7075超硬铝合金焊接性及焊接接头组织研究

发布时间：2018-06-19 12:45

本文选题：超硬铝合金 + 焊丝　；参考：《沈阳工业大学》2017年硕士论文

【摘要】：铝及其合金已经广泛地应用于工业领域,产量仅次于钢铁的第二大类金属材料。目前,7075铝合金由于具有比强度高、加工性能优良等特点,在航空航天发展中占有十分重要的地位。但是,7075超硬铝合金其焊接性较差,焊接接头常出现热裂纹、气孔和接头软化等焊接性缺陷,影响其广泛应用。因此,通过使用不同焊接材料,调整焊接工艺参数与工艺措施,研究分析其对7075超硬铝合金焊接性及接头组织影响规律。本课题对7075超硬铝合金采用ER4043和ER5356两种焊丝在不同焊接工艺条件下获得的焊接接头进行性能检测和组织分析,从而确定适合7075超硬铝合金焊接性的焊接材料和工艺参数。外加纵向交流磁场进行正交试验,研究磁场参数和焊接工艺对焊接性及接头组织性能的影响,实验结果表明:(1)采用ER5356焊丝焊接接头(简称ER5356焊接接头)力学性能及组织比采用ER4043焊丝焊接接头(简称ER4043焊接接头)好。随着焊接电流的增加,焊接接头的力学性能呈先增大后降低的变化趋势。当焊接电流增加至120A时,ER4043焊接接头力学性能达到最大:σb=287.4MPa、δ=3.85%,焊缝硬度为96.7HV,焊缝中Si产生低熔点共晶可降低裂纹敏感性;当焊接电流增加至130A时,ER5356焊接接头力学性能达到最大:σb=310.0MPa、δ=4.44%,焊缝硬度为106.3HV,Mg元素形成强化相,提高组织性能,改善7075超硬铝合金焊接性。(2)采用ER5356焊丝进行正交试验确定最佳焊接工艺及磁场参数。当焊接电流为130A,磁场电流为3.0A,磁场频率为40Hz时,焊接接头的力学性能最大:σb=342.5MPa、δ=5.63%,焊缝硬度为112.2HV。与相同焊接工艺下未施加磁场的焊接接头性能相比,组织得到改善,7075超硬铝合金焊接接头性能提高。(3)外加纵向交流磁场使电弧中的带点粒子产生运动,一方面带电粒子运动使电弧发生旋转,产生电磁搅拌作用,焊缝晶粒细化;另一方面带电粒子运动改变焊接电弧形貌,平衡熔池温度,减少偏析,从而改善7075超硬铝合金焊接性及焊接接头组织性能。
[Abstract]:Aluminum and its alloys have been widely used in industrial fields, the second largest category of metal materials after iron and steel. At present, due to its high specific strength and excellent processing properties, the alloy plays an important role in the development of aeronautics and astronautics. However, the weldability of super hard aluminum alloy is poor, such as hot cracks, porosity and softening of joints, which affect its wide application. Therefore, by using different welding materials and adjusting welding process parameters and technological measures, the influence of welding parameters and process measures on the weldability and joint microstructure of 7075 superhard aluminum alloy is studied and analyzed. In this paper, the mechanical properties and microstructure of 7075 superhard aluminum alloy welded joints obtained by ER4043 and ER5356 wires under different welding process conditions were tested and analyzed, and the welding materials and process parameters suitable for the weldability of 7075 superhard aluminum alloy were determined. The effects of magnetic field parameters and welding process on the weldability and microstructure and properties of the joints were studied by orthogonal experiments with external longitudinal alternating magnetic field. The experimental results show that the mechanical properties and microstructure of ER5356 wire welded joint are better than that of ER4043 wire welded joint (ER4043 welding joint). With the increase of welding current, the mechanical properties of welded joints increase first and then decrease. When the welding current is increased to 120A, the mechanical properties of the welded joints reach the maximum: 蟽 _ (b) 287.4MPa, 未 ~ (3.85), the hardness of the weld is 96.7HV.The low melting point eutectic produced in the weld can reduce the crack sensitivity. When the welding current is increased to 130A, the mechanical properties of the welded joints reach the maximum: 蟽 _ (b) 310.0 MPa, 未 _ (4.44), the hardness of weld is 106.3 HVN mg, and the microstructure and properties of the welded joints are improved. To improve the weldability of 7075 superhard aluminum alloy, the best welding process and magnetic field parameters were determined by orthogonal test with ER5356 wire. When the welding current is 130 A, the magnetic field current is 3.0 A, and the magnetic field frequency is 40 Hz, the mechanical properties of the welded joint are maximum: 蟽 _ (b) 342.5 MPA, 未 ~ (5.63) and the hardness of weld is 112.2 HV. Compared with the welded joints without magnetic field applied in the same welding process, the microstructure improves the properties of the welded joints of the superhard aluminum alloy, I. e., the effect of longitudinal alternating magnetic field on the movement of the strip-point particles in the arc. On the one hand, the motion of charged particles causes the arc to rotate and produce electromagnetic stirring, and the grain of weld is refined. On the other hand, the motion of charged particles changes the shape of welding arc, balances the temperature of molten pool, and reduces segregation. So as to improve the weldability of 7075 super hard aluminum alloy and the microstructure and properties of welded joint.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG457.14

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