铸造镁合金的焊接修复技术研究现状及发展方向

A Review and Development Tendency of Welding Repair Technology for Cast Magnesium Alloy

镁的密度为1.74 g/cm^3,是铝密度的2/3,具有铸造性好、比强度高的特点,可以在减轻结构质量方面发挥重要作用,铸造镁合金被广泛应用于航空航天、汽车等领域的重要机械零件。尤其是在铸造镁合金中添加稀土元素,可进一步提升镁合金的室温强度和高温蠕变性能,以满足更多领域的应用需求,进一步扩大镁合金的应用。镁合金在铸造过程中不可避免会产生铸造缺陷,为保障铸造镁合金构件的可靠性,针对铸造镁合金缺陷的焊接修复技术具有切实的工程意义。从铸造镁合金缺陷修复的实际需求出发,结合镁合金独特的物理特性及焊接性,国内外学者针对铸造镁合金缺陷的焊接修复技术展开了研究。钨极氩弧焊具有成本低、操作简单、适用性强的特点,在铸造镁合金的焊接修复中应用最广,为保证焊接质量,需要从缓慢冷却、控制热输入等方面制定严格的焊接工艺;冷金属过渡焊接可实现焊接过程的精确控制,从而提高熔化极气体保护焊焊接镁合金的焊缝质量;激光焊具有能量密度高度集中的特点,获得的焊接接头具有较小的热影响区,但需制定合理的工艺参数以避免焊接缺陷的产生;搅拌摩擦焊可较好地完成铸造缺陷修复,但由于构件复杂结构的影响,在铸造镁合金焊接修复中的应用受限。另外,脉冲激光焊、电子束焊、钎焊、扩散焊及复合焊接方法均在镁合金的焊接中有所应用,但在铸造镁合金的焊接修复中尚未见实际应用。然而,由于铸造镁合金特殊的物理性质和焊接性,以及待修复构件的复杂结构,已进行的铸造镁合金缺陷焊接修复技术仍存在许多局限性,亦缺乏深入系统的理论研究。为了有效解决铸造镁合金的实际修复工程问题,无论是该类铸造镁合金焊接修复技术,还是关于修复技术的系统化研究,都需要大量的探索性工作。本文简述了铸造镁合金的应用及其焊接性,重点介绍了钨极氩弧焊、冷金属过渡焊接、激光焊、搅拌摩擦焊在铸造镁合金焊接修复中的应用,讨论了目前铸造镁合金焊接修复技术存在的问题和未来的发展,为实现焊接修复区组织与性能更加可控的智能修复技术提供参考。

The density of magnesium is 1.74 g·cm^-3,which is 2/3 of aluminum s density.Magnesium alloys with good castability and high specific strength play an important role in reducing structural weight.Therefore,cast magnesium alloys are widely used in aerospace and automobile.In particular,the addition of rare earth elements in cast magnesium alloys enhances the room temperature strength and the high temperature creeps properties of magnesium alloys,expanding the application of magnesium alloys.However,some inevitable defects exist in casting magnesium alloys.In order to ensure the reliability of cast magnesium alloys components,welding repair technology for the defects of casting magnesium alloys has practical engineering significance.Considering the actual requirements of the repair of magnesium alloys defects,some researchers have studied the welding repair technology of cast magnesium alloys defects,combined with the unique physical properties and weldability of magnesium alloys.Tungsten argon arc welding has the widest application in the welding repair of cast magnesium alloys because of the characteristics of low cost,easy operation,and good applicability.In order to ensure the welding quality,it is necessary to make strict welding process,such as cooling slowly and restricting the heat input.Cold metal transfer welding can achieve precise control of the welding process and improve the weld quality of the magnesium alloys welded by the gas shielded welding.Laser welding has high-density energy and smaller heat affected area,but it has requirement to develop a reasonable process to avoid welding defects.Friction stir welding can better complete the repair of casting defects,but it is li-mited in the welding repair of cast magnesium alloys for the complex structure of the components.Pulsed laser welding,electron beam welding,brazing,diffusion welding and hybrid welding technologies are applied in the welding of magnesium alloys,but have not yet been applied in the welding repair of casting magnesium alloys.Due to the special physical properties and weldability of cast magnesium alloys,as well as the complex structure of the components to be repaired,existing magnesium alloys defects welding repair technology has many limitations,deeper systematic theoretical research is still needed.In order to effectively solve the actual repair engineering problems of cast magnesium alloys,both the casting magnesium alloy welding repair technology and the systematic research on the repair technology require a lot of exploratory work.This paper briefly describes the application and weldability of cast magnesium alloys,and introduces the application of tungsten argon arc wel-ding,cold metal transfer welding,laser welding and friction stir welding in the welding repair of cast magnesium alloys emphatically.Then it discusses the existing problems and the future development prospects,and provides a research reference for the realization of intelligent repair technology with better controllable organization and performance of the welding repair zone.