6061-T6铝合金DP-MIG焊轧复合成形接头组织与力学性能

宋刚; 董孝南; 程继文; 王泽力; 刘黎明

doi:10.12073/j.hjxb.20220511001

6061-T6铝合金DP-MIG焊轧复合成形接头组织与力学性能

大连理工大学, 辽宁省先进连接技术重点实验室, 大连, 116024

基金项目: 国家自然科学基金资助项目(U1960111)；中央高校基本科研业务费专项资金资助项目(DUT21LAB133).

详细信息

作者简介:
宋刚，博士，教授，博士研究生导师；主要研究方向为轻量化材料先进焊接理论及方法； Email: songgang@dlut.edu.cn

中图分类号: TG 441.8
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出版历程
- 收稿日期: 2022-05-10
- 网络出版日期: 2023-03-30
- 刊出日期: 2023-04-24

Microstructure and mechanical properties of DP-MIG welding-rolling composite forming joints of 6061-T6 aluminum alloy

Key Laboratory of Advanced Connectivity Technology of Liaoning Province, Dalian University of Technology, Dalian, 116024, China

摘要

摘要: 为解决6061-T6铝合金焊后热影响区软化导致力学性能下降的问题，基于焊接接头余高大变形强化过时效软化区的思想，采用双轧辊系统对6061-T6薄板铝合金直流双脉冲熔化极气体保护焊(DC double pulse metal inert gas welding，DP-MIG焊)接头进行同步双面轧制，并分析了焊轧复合成形接头组织与力学性能. 结果表明，焊缝晶粒受到竖直方向的轧制力发生大塑性变形，内部气孔消失，焊缝区域变宽，邻近焊缝的热影响区受到来自焊缝的挤压力发生协同宏观变形，远离焊缝的过时效软化区组织受到来自焊缝处的压应力，从沿垂直焊缝方向产生部分协同形变强化；接头的硬度明显提升，过时效软化区的硬度由60 ~ 70 HV提升至80 ~ 90 HV，过时效软化区的拉伸性能也有所提升，当焊接速度为800 mm/min时，抗拉强度最佳可达到母材的83.6%，相较于焊接接头提升19.4%，进而实现了对过时效软化区的强化效果.
- 铝合金 /
- 热影响区软化 /
- 直流双脉冲熔化极气体保护焊 /
- 焊轧复合成形
Abstract: To solve the problem of degrading of mechanical properties of as welded 6061-T6 aluminum alloy joint caused by softening of the heat-affected zone, this study applied a double-roller system to perform simultaneous double-sided rolling on 6061-T6 thin aluminum alloy DC double pulse metal inert gas (DP-MIG) welded joints, based on the idea of utilizing welding residual height and large deformation to strengthen the over-aging softened zone. The microstructure and mechanical properties of the welding-rolling composite forming joints were analyzed. The results are as follows: the weld grain is subjected to large plastic deformation by the vertical rolling force; The internal pores disappear, thus the weld area widens. The heat-affected zone adjacent to the weld is subjected to co-macro deformation by the extrusion force from the weld, and the over-aging softened zone far from the weld is subjected to compressive stress from the weld, resulting in partial co-deformation strengthening along the vertical weld direction. The overall hardness of the joints is significantly improved with the hardness of the over-aging softened zone, which increased from 60 − 70 HV to 80 − 90 HV. The tensile properties of the over-aging softened zone are improved. When the welding speed is 800 mm/min, the best tensile strength can reach 83.6% of that of the base metal, 19.4% higher than that of the welded joint, which is a notable improvement to the over-aging softened zone.
- aluminum alloy /
- softened zone in heat-affected zone /
- DC double pulse metal inert gas welding /
- welding-rolling composite forming

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图 1 母材的微观组织

Figure 1. Microstructure of base material

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图 2 DP-MIG焊焊接电流波形示意图

Figure 2. Schematic diagram of DP-MIG welding current waveform

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图 3 焊缝几何形貌示意图

Figure 3. Schematic diagram of weld geometry

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图 4 轧制过程示意图

Figure 4. Schematic diagram of rolling process

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图 5 接头的表面宏观形貌

Figure 5. Surface macro morphology of the joints

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图 6 接头的横截面形貌

Figure 6. Cross-section morphology of the joints

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图 7 焊接速度400 mm/min下接头的微观组织

Figure 7. Microstructure of joints at welding speed 400 mm/min. (a) welding, weld; (b) welding, fusion zone; (c) welding, over-aging softened zone; (d) welding-rolling, weld; (e) welding-rolling, fusion zone; (f) welding-rolling, over-aging softened zone

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图 8 硬度分布

Figure 8. Hardness distribution

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图 9 接头的抗拉强度和断后伸长率

Figure 9. Tensile strength and elongation of the joints

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图 10 轧制过程DP-MIG焊接头各部分受力情况

Figure 10. Force on each part of DP-MIG welding joints during rolling. (a) high heat input; (b) low heat input

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表 1 母材与焊丝的化学成分(质量分数，%)

Table 1 Chemical compositions of base metal and welding wire

材料	Mg	Si	Fe	Cu	Mn	Cr	Zn	Ti	Al
6061-T6	1.074	0.635	0.397	0.268	0.082	0.205	0.003	0.003	余量
ER5356	4.900	0.050	0.120	0.005	0.120	0.120	0.090	0.090	余量

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表 2 DP-MIG焊焊接电流波形基本参数

Table 2 Corresponding parameters of DP-MIG welding current waveform

平均焊接电流 I/A	基值电流 I_b /A	峰值电流 I_P /A		基值时间 t_b /ms		峰值时间 t_P /ms
平均焊接电流 I/A	基值电流 I_b /A	弱脉冲	强脉冲	弱脉冲	强脉冲	弱脉冲	强脉冲
80	28	310	336	0.8	0.6	1.0	0.8

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表 3 焊接工艺参数

Table 3 Welding parameters

焊接电流I/A	焊接速度v/(mm·min⁻¹)	脉冲频率f/Hz	热输入E/(kJ·mm⁻¹)	焊丝伸出长度l/mm	保护气体流量Q/(L·min⁻¹)
80	400	3	1.78	15	16
80	600	3	1.19	15	16
80	800	3	0.90	15	16

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表 4 不同焊接速度下焊缝尺寸

Table 4 Weld size at different welding speeds

焊接速度v/(mm·min⁻¹)	余高h/mm	熔宽w/mm
400	2.88	8.54
600	1.98	7.80
800	1.52	6.16

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