抄録
A study had been conducted to establish the precise method estimating the creep rupture life of welded steam pipe joints. Firstly, basic creep data of 2. 25Cr1Mo low alloy steel, such as rupture time, minimum creep strain rate, and creep crack growth rate, had been obtained on mother material, fine-grained heat affected zone (HAZ) , coarse-grained HAZ, and weld metal. Secondly, creep rupture tests had been conducted on the internally pressurized pipe specimens of mother material, seam welded joint and girth welded joint. Whereas girth welded pipe joints showed longer lives than those of mother material pipes, seam welded pipe joints showed shorter rupture lives. To clarify the effect of fine-grained HAZ on the rupture life of the seam welded pipe joint, an analytical study had been performed taking the difference of creep deformation between fine-grained HAZ and mother material into account. The analytical creep rupture lives agreed quite well with the experimental results. Finally, creep rupture test had been conducted on the specimens of the internally pressurized seam welded pipe joints with a half elliptic notch introduced along the outer HAZ of weld line. Creep rupture life of these specimens was calculated as the sum of crack incubation time and crack growth time. It was shown that the calculated creep rupture life agreed quite well with the experimental results.
