Repair process of magnesium alloy casting by He-Ar mixed gas TIG welding
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摘要: 镁合金因其较高的比强度而在诸多领域发挥重要的减重作用，且多为铸造构件，但镁合金铸件的缺陷问题成为制造瓶颈. 对镁合金铸件修复工艺进行研究，采用非熔化极惰性气体保护焊(TIG焊)探究此工艺下不同保护气体对TIG焊修复焊道的成形、组织特征及性能的影响，并通过不同氦-氩含量的保护气体下TIG焊电弧形态及电弧电压的研究，分析氦气含量对修复焊道熔深的影响. 结果表明，调整镁合金铸件TIG焊修复工艺保护气体中的氦气比例，会改善焊道形貌；增加保护气体中的氦气比例，将有效提高焊道熔深和深宽比；保护气体中氦气含量的改变对修复焊道组织、硬度无显著影响. 模拟缺陷修复试验结果表明，镁合金铸件氦-氩保护TIG修复工艺可以满足铸件浅层缺陷修复需求，增加保护气体中氦气含量可提高熔深，提高此工艺的适用性.Abstract: Magnesium alloy plays an important role in weight-loss because of its high specific strength, most of magnesium alloy components are casting. The defects of magnesium alloy castings become a manufacturing bottleneck issue. The repair process of magnesium alloy castings by tungsten inert gas (TIG) welding was studied, the effects of protect gas on the form, microstructure and properties of TIG repair beads were examined. The effects of helium content on the penetrations of welding beads were analyzed through the arc shape and arc voltage of TIG welding under different helium content. The results showed that the form of the weld bead could be improved by changing the helium content, the penetration and the penetration to width ratio could be improved by increasing the helium content, with no obvious effect on the microstructure and the hardness. The results of the simulating defect repair experiments showed that, the He-Ar mixed gas TIG welding repair process could repair shallow defects of magnesium alloy castings, increasing the helium content in the protect gas could increase the penetration and the suitability of this repair process.
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Keywords:
- magnesium casting /
- defects repair /
- helium /
- arc characteristics
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图 2 不同氦气含量的焊道形貌
Figure 2. Weld appearance of different helium content. (a) helium content 0%; (b) helium content 12.5%; (c) helium content 25%; (d) helium content 37.5%; (e) helium content 50%; (f) helium content 62.5%; (g) helium content 75%; (h) helium content 87.5%; (i) helium content 100%
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图 3 焊道宏观形貌
Figure 3. Macroscopic metallographic of weld. (a) helium content 0%; (b) helium content 12.5%; (c) helium content 25%; (d) helium content 37.5%; (e) helium content 50%; (f) helium content 62.5%; (g) helium content 75%; (h) helium content 87.5%; (i) helium content 100%
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图 4 焊道熔深、深宽比与氦气含量关系曲线
Figure 4. Relationship between weld penetration, penetration-to-width ratio and helium content
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图 5 焊道和部分熔化区组织
Figure 5. Microstructure of weld and PMZ. (a) microstructure of weld; (b) helium content 0%; (c) helium content 25%; (d) helium content 50%; (e) helium content 75%; (f) helium content 100%
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图 8 不同氦气含量保护气下电弧形态
Figure 8. Arc shape with different helium content. (a) helium content 0%; (b) helium content 25%; (c) helium content 50%; (d) helium content 75%; (e) helium content 100%
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图 9 电弧形态示意图
Figure 9. Schematic diagram of arc shape. (a) helium content 0%; (b) helium content 100%
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图 11 凹槽深度1 mm时模拟缺陷修复
Figure 11. Simulated defect repair of groove depth 1 mm. (a) hole depth 2 mm; (b) hole depth 3 mm
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图 12 凹槽深度3 mm时模拟缺陷修复
Figure 12. Simulated defect repair of groove depth 3 mm. (a) hole depth 2 mm; (b) hole depth 3 mm
表 1 焊接工艺参数
Table 1 Welding process parameters
焊接电流I/A 焊接速度v/(mm·s−1) 电弧长度a/mm 保护气体流量Q/(L·min−1) 钨极伸出长度l/mm 160 4 1.5 14 11 
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