Bolts for use in high temperature steamturbines require good elevated temperature strengthand ductility. The development and enhancement of1%CrMoV based bolting alloys for use in UK designedsteam turbines is described. Initial ductilityproblems encountered over 30 years ago were solved bythe addition of Ti and B to the base alloy.Subsequent developments have concentrated on reducingthe residual levels (P, Sn, Sb, As, Cu). Currentmaterials made to low residual practice show excellentductility and tests in progress indicate that the lowresidual material shows notch strengthening.
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