Fracture toughness requirements for ASME section VIII vessels for temperatures colder than 77K

Earlier research work conducted at MIT and NIST indicated that CVN specimen s with an initial temperature at or near 4K (-452 degreesF) actually fractu re at temperatures significantly above 4K due to adiabatic heating. As a re sult of this work, ASTM E-23 test method on CVN testing was revised to inco rporate a restriction that CVN tests are valid only at 77K (-320 degreesF) and warmer. ASME requested PVRC to assess the above CVN issue and provide a n appropriate recommendation for the Code change or for a further Code chan ge, if needed for vessels with MDMT colder than 77K. PVRC formed a Task Gro up under the Committee on Failure Modes. The TG undertook a program which i ncluded a review of the existing data and an experimental program to develo p new K-1c (J) data at 4K and 77K and CVN data at 77K. In the experimental program, a total of four 1-in-thick weldments were prepared from SA 240, Ty pe 304 stainless steel plate using the SMAW process and E316L-15 electrodes . The electrodes purchased permitted the preparation of the weldments with four progressively higher levels of ferrite. The PVRC data and existing dat a were utilized in developing the recommendations to ASME. The recommendati ons are: use CVN tests (with 316L S.S. weld filler metal with FN less than or equal to5) at 77K with increased acceptance criterion of 21 mils lateral expansion; for welds not meeting the foregoing requirements, use ASTM E182 0 J(1c) tests at MDMT and the acceptance criterion for K-1c (J) has been se t at 120 ksi root in. This paper presents the test data, analysis and techn ical basis for the PVRC recommendations to ASME.