TWI Industrial Member Report Summary 324/1986
By I S Matharu
The procedures for the avoidance of HAZ hydrogen cracking predicted by The Welding Institute nomograms were derived from work carried out in the 1960s and '70s on C-Mn steels with carbon equivalents in the range 0.40-0.54CEIIW. Since then, significant changes have occurred in steel compositions and manufacturing processes, and current steels may differ appreciably from those used in the determination of the original HAZ cracking data. These changes may require modifications to the existing nomograms, and indeed recent work at The Welding Institute and British Gas Corporation has indicated that the cracking behaviour of some low C steels was not adequately described by The Welding Institute nomograms, nor by the derivative BS 5135: 1984. Accordingly, a programme has been undertaken to generate data on the basis of which revised prediction procedures may ultimately be derived. A previous report considered the cracking behaviour of some 30mm thick modern steels when tested without preheat. In the present work the cracking behaviour of a series of 50mm thick steels has been investigated using CTS tests with and without preheat. Manual metal arc welding was used together with a weld metal diffusible hydrogen level of 12.2mlH2/100g of deposited metal. Two 30mm thick steels were also investigated with preheat, the results from tests without preheat having been reported earlier. The cracking data are presented with reference to The Welding Institute nomograms and BS 5135:1984.