摘要
摘 要
高强铝合金在航空航天、汽车、轻型轨道交通等工业部门得到了广泛应用。
由于高强铝合金很难用一般的熔焊方式来焊接,用来做结构件时通常用螺栓、铆
钉来连接,但这些连接方法会增加结构重量和增加经济消耗。激光束具有很高的
能量密度,所以用激光进行焊接不仅速度快,而且变形小,但是激光焊接铝合金
同样会遇到一般熔焊方法焊接铝合金时出现的气孔、裂纹等缺陷。为了消除这些
缺陷,在激光焊接过程中加入焊丝是一种非常实用的方法,国际上有关此方面的
研究已很深入并开始走向工业应用。与焊丝相似,金属粉末同样可以作为填充材
料,而且更具柔性化,但有关此方面的研究极少,本文的主要研究内容就是从机
理和实验两方面研究采用填充粉末的方式对铝合金进行激光焊接。
为达到送粉焊接的目的,我们在对现有喷粉头进行了深入地研究分析后,
设计出了一种自汇聚同轴三层结构送粉头,它不仅可以将粉末汇聚到焊接要求的
束径,同时能对焊缝进行有效地的保护。经实验证实,此送粉头完全能满足送粉
焊接的要求。
对填粉焊接过程进行的高速摄像和金相分析表明,焊接过程比未加粉稳定,
金属蒸汽和等离子体被有效压缩,使用成分为 AlSi12 的填充粉末可以有效地消
除热裂纹和气孔。
利用优化的焊接工艺参数,我们在 YAG 激光器上成功地对 7075 为主的几种
高强铝合金成功地进行了激光填粉焊接,焊缝整齐美观,无咬边、下陷、不连续
等宏观缺陷。拉伸实验证实,7075 焊后的平均拉伸强度为 370Mpa,为母材的 80%
左右。
High strength aluminum alloys are used in a wide range of engineering
applications, which include aerospace, automobile, light railway etc. Since these
alloys are not easy to weld, they must be joined by bolts and rivets when assembled as
structures. Such mechanical joints are disadvantageous for reduce weight and
construction cost. Laser beam has very high power intensity, there is an increasing
interest in applying laser beam welding to aluminum alloys since it offers advantages
such as high welding speeds and low distortion. However, porosity and hot crack are
often encountered in laser welding as well as in conventional processes. To minimize
this problem, filler wire are used in laser welding. Just like filler wire ,powder metal
have the same effect, otherwise, it is more flexible than wire in the weld. In this paper,
we do some theoretical and experimental studying on aluminum powder welding.
To meet the specialty of laser powder welding, we designed a three-ply
self-bundling coaxial powder injecting head which can both feed the powder metal
and provide shielding gas. Its function has been approved in experiments is good.
High speed camera shoot show the moving of the welding pool is steady and
uniform. By metallographic analyzing of the welded seam, the conclusion can be
made that it can well eliminate the hot crack and porosity when the weld adopt AlSi12
powder alloy metal.
Adopting optimized processing parameters we have welded 7075 aluminum
successfully by injecting powder filler metal to the welding pool with high power
YAG laser. Both sides of the welded seam is full filled and without defect such as
undercut, excessive penetration, discontinuous etc on the surface of seam .the porosity
is low and the hot crack is eliminated also. The tension experiment shows that the
tensile strength of the 7075(T73)Al alloy can reach 370MPa.
引文
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