Fracture toughness tests of 9 Cr type steels at elevated temperature; 2 nd. Report

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A series of high temperature fracture toughness tests of 9Cr type steels was put in practice on a three-years scheme in 1988. In this experimental study, Mod.9Cr-1Mo steel, 9Cr-2Mo steel and 9Cr-1Mo-Nb-V steel are tested, and these fructure toughness are investigated on the basis of J integral. In a first year, high temperature fracture toughness test method was established using R-curve method and unloading compliance method, and J values of Mod. 9Cr-1Mo steel were measured at RT, 400C, 500C, 550C and 600C. In a second year, fracture toughness tests of 9Cr-2Mo steel, 9Cr-1Mo-V-Nb steel and these aged materials were performed, and several factors which affected fracture toughness values of 9Cr type steels were clarified. In this report, the test results in a second year are summarized. In a last year, fracture toughness tests of weldment and thick plate of 9Cr type steel are going to be carried out. Furthermore, an effect of crack direction on J value will be studied.