Creep crack growth in P22 and P91 welds - overview from SOTA and HIDA projects

摘要

Creep crack growth (CCU) tests on two pressure vessel steels, P22 (2.25Cr1Mo) and P91 (9CrMoVNb) were carried out in two European Commission supported projects: SMT 2070 'SOTA' and BE1702 'HIDA'. Tests in the SOTA project were conducted on the all-weld and cross-weld compact tension (CT) specimens; in the case of cross-weld specimens the electrical discharge machined (edm) notches were placed at various positions inside the HAZ to study the effect of notch position on CCG characteristics. These tests were conducted at 550℃ (P22) and 600℃ (P91). Tests in the HIDA project were carried out on the base metal and cross-weld CT specimens; in the case of cross-weld specimens the edm notches were placed in the centre of the HAZ. These tests were carried out at higher temperatures than those in the SOTA project i.e. at 565℃ (P22) and 625℃ (P91). In this project CCG tests were also carried out on large seam-welded pipes (feature specimens) with edm notches positioned in the base metal and in the centre of HAZ. The base and weld metals used in both projects were from the same cast/pedigree. This paper discusses the findings of the two projects and implications for crack growth in the weldments of these two steels.