Ａｌ‐Ｍｇ‐Ｓｉ系合金のＣＯ２レーザ溶接 １ Ａｌ‐Ｍｇ‐Ｓｉ系合金レーザ溶接部における凝固割れ防止に関する検討

Abstract

Al-Mg-Si alloys are widely used for industrial components because of those excellent extrudability, high corrosion resistance, and relatively high strength within the various aluminium alloys. However, welds of Al-Mg-Si alloys are known to have high crack susceptibility and to be softened due to weld heat input.Laser welding process has significant advantages in terms of low heat input, low distortion, high welding speed, and ease to automation compared with the conventional welding process. In particular, there is considerable interest in welding heat treated alloy, such as Al-Mg-Si alloy, since low heat input makes softened region of welds minimize.This paper describes the results of welding efforts of Al-Mg-Si alloys, mainly A6063-T5 with 5 kW CO2 laser. Wel-dabilities, solidification crack susceptibilities were studied in bead-on plate tests. Solidification crack susceptibilities were estimated by using a crater cracking test and a self-restraint cracking test, a modified form of Houldcroft test. After that, welding with filler materials were performed in order to prevent the solidification cracking in weld metal. Microstructure, alloying element distributions, and mechanical properties were studied. Effects of groove geometry and Si contents of weld metals on properties have been established. Solidification cracking in weld metal has been prevented by using high Si content Al-Si alloy, such as A4047, and getting Si content of all the weld metal more than 2%.