DETERMINATION OF CPF STEEL FRACTURE TOUGHNESS

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Authors
  1. Hull, D.A.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN);Engineering Material Research, Downsview ONT (CAN)
Abstract
The material specificaton for the steels (CSA 350WT and ASTM A517) used in the Halifax class frigates, was primarily based on tensile strength and Charpy impact energy. There is a need to demonstrate adequate damage tolerance in the welded hull, but the data from Charpy tests cannot be used rigorously to describe the fracture of larger components or in structural calculations. A quantitative assessment of the resistance to cracking is needed to determine the risk of brittle fracture under service conditions. This requires laboratory toughness testing at the minimum service temperature and at loading rates equivalent to hull impact events such as wave slamming and minor collisions. Impact tests have previously provided comparative rankings of plate, weld, and heat affected zone toughness. The results indicated that the 350WT heat affected zone had lower toughness than plate, as did both the weld and HAZ of the high strength ASTM A517. Lower bound transition temperatures for these limited toughness materials were estimated to be close to 0C. The report describes a further series of welded plate tests to quantify the fracture resistance of the 350WT HAZ and of the A517 weld and HAZ. The results confirm that that the A517 weld has the highest transition temperature. Although the 350WT HAZ is more rate sensitive, even under impact loading it has a transition temperatue below that expected in service.
Keywords
350WT steel;A517 steel;HAZ
Report Number
DREA-CR-98-417 — Contractor Report
Date of publication
01 Jan 1998
Number of Pages
211
DSTKIM No
98-01843
CANDIS No
508283
Format(s):
Hardcopy;Document Image stored on Optical Disk

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