Comparison of residual stress distributions of similar and dissimilar thick butt-weld plates

同材及び異材の厚板突合せ溶接の残留応力分布の比較

鈴木 裕士  ; 勝山 仁哉  ; 森井 幸生*

Suzuki, Hiroshi; Katsuyama, Jinya; Morii, Yukio*

中性子回折法により厚さ35mmのA533B-SUS304異材突合せ溶接及びSUS304同材突合せ溶接の残留応力分布を測定するとともに、それら残留応力分布の比較から、溶接残留応力に及ぼす熱膨張係数や材料強度の影響を検討した。同材突合せ溶接では、溶接線を挟んで対称な残留応力分布となるなど、厚板突合せ溶接における典型的な残留応力分布を示した。一方、異材突合せ溶接においては、母材及び溶接金属間の熱膨張係数や降伏強度の差により、ルート部付近において非対称な残留応力分布が見られた。溶接線直交方向には熱膨張係数差の影響を受けにくいため、異材突合せ溶接と同材突合せ溶接の溶接線直交方向の残留応力は、同じ分布傾向を示した。また、ルート部近傍における溶接線直交方向の残留応力の大きさは、材料の降伏強度に依存した。溶接線法線及び溶接線方向の残留応力は、熱膨張係数差の影響を受けるため、溶接線を挟んで非対称な分布傾向を示した。

Residual stress distributions of 35 mm thick dissimilar butt-weld between A533B ferritic steel and Type 304 austenitic stainless steel (304SS) with Ni alloy welds and similar metal butt-weld of 304SS were measured using neutron diffraction. Effects of differences in thermal expansion coefficients (CTEs) and material strengths on the weld residual stress distributions are discussed by comparison of the residual stress distributions between the similar and dissimilar metal butt-welds. Residual stresses in the similar metal butt-weld exhibited typical distributions found in a thick butt-weld and they were distributed symmetrically on either side of the weld line. Meanwhile, asymmetric residual stress distributions were observed near the root of the dissimilar metal butt-weld, which was caused by differences in CTEs and yield strengths between parent and weld metals. Transverse residual stress distribution of the dissimilar metal butt-weld was similar trend to that of the similar metal butt-weld, since effects of differences in CTEs are negligible, while magnitude of the transverse residual stress near the root depended on the yield strengths of each metal. In contrast, the normal and longitudinal residual stresses in the dissimilar metal butt-weld distributed asymmetrically on either side of weld line due to influence of differences in CTEs.