PREDICTION OF FRACTURE-TOUGHNESS KIC TRANSITION CURVES OF PRESSURE-VESSEL STEELS FROM CHARPY V-NOTCH IMPACT TEST-RESULTS

A single and generalized prediction method of fracture toughness K(IC) transition curves of pressure vessel steels has been greatly desired by engineers in the petrochemical and nuclear power industries, especially from the viewpoint of life extension of reactor pressure vessels. In this paper, the toughness degradation of Cr-Mo steels during long-term service was examined and the two prediction methods of fracture toughness K(IC) transition curves were studied using the data of 54 heats. 1) The toughness degradation of 2 1/4 Cr-1Mo steels levels off within around 50,000 h service. 2) The FATT versus J-factor (= Si + Mn) (P + Sn) x 10(4)) and/or XOBAR (= (10P + 5Sb + 4Sn + As) x 10(-2)) relationships to estimate the maximum embrittlement of Cr-Mo steels were obtained. 3) A master curve method developed by authors et al.; that is, the method using a K(IC)/K(IC-US) versus excess temperature master curve of each material was presented for 2 1/4 Cr-1Mo, 1 1/4Cr-1/2Mo, 1Cr and 1/2Mo chemical pressure vessel steels and ASTM A508 C1.1, A508 C1.2, A508 C1.3 and A533 Gr.B C1.1 nuclear pressure vessel steels, where K(IC-US) is the upper-shelf fracture toughness and excess temperature is test test temperature minus FATT. 4) A generalized prediction method to predict the K(IC) transition curves of any low-alloy steels was developed. This method consists of K(IC)/K(IC-US) versus T - T0 master curve and temperature shift DELTAT between fracture toughnes and CVN impact transition curves versus yield strength relationship, where T0 is the temperature showing 50 percent K(IC-US) of the material. 5) The K(IC) transition curves predicted using both methods showed a good agreement with the lower bound of measured K(JC) values obtained from J(C) tests.