AN ASSESSMENT OF WELD MIS-MATCHING

A large data bank of information related to welded offshore structural steels has been used to assess the influence of weld metal strength m is-matching on the fracture resistance of these weldments, based on Ch arpy impact test results, crack tip opening displacement CTOD values a nd wide plate results, along with supporting welding details, metallog raphy and mechanical properties. The advantage of this approach is tha t there are sufficient tests for the values to be assessed against a n ormal statistical distribution, enabling trends to be identified despi te appreciable scatter inherent in a smaller number of tests. The prac tical results are contrasted with the guidelines given in the British Standards Institution publication PD6493:1991 for initially assessing flaws in fusion welded joints in the as welded and post weld heat trea ted conditions. The important difference between specifying a required toughness K-mat and a required CTOD value delta(mat) has been demonst rated by considering the Level 1 assessment procedure. The improvement in toughness on post weld heat treating these joints has been quantif ied and distinguished from the practical benefits from weld metal stre ngth overmatching.