高エネルギーX線を利用した異種材料レーザー溶接部内部ひずみ評価

Evaluation of internal strain distribution of dissimilar laser welding using high energy X-rays

菖蒲 敬久  ; 城 鮎美*; 村松 壽晴*

Shobu, Takahisa; Shiro, Ayumi*; Muramatsu, Toshiharu*

レーザー溶接は、照射領域が非常に小さく、制御も簡便であることから様々な金属材料に対してすでに実用化されている。本研究では実用化が期待されている異種材料レーザー溶接の課題の1つである、加工影響部付近のひずみ・応力・変形等について高エネルギー放射光X線回折法により評価した。銅と鉄の異材接合に関して内部変形測定を行った結果、線膨張係数が高い銅側はほとんど変形しておらず、鉄側に強い引張ひずみと熱影響部に塑性変形領域が確認された。加えて、鉄の塑性変形領域には銅が混ざったことが原因と思われる残留オーステナイト相が観測され、混在する金属材料中の材料強度評価にさらなる課題が明らかなとなった。

Laser welding has already been put into practical use for various metal materials because the irradiation area is very small and the control is easy. In this study, we evaluated strain, stress, deformation, etc. near the processing affected area by high-energy synchrotron radiation X-ray diffraction method, which is one of the problems of laser welding of different materials that are expected to be put into practical use. As a result of internal deformation measurement of the bonding of dissimilar materials of copper and iron, it was confirmed that the copper side with a high coefficient of linear expansion was hardly deformed, strong tensile strain on the iron side, and a plastic deformation region on the heat-affected zone. In addition, a retained austenite phase, which is thought to be caused by the mixture of copper, was observed in the plastic deformation region of iron, and further problems were clarified in the evaluation of material strength in the mixed metallic materials.