TWI Industrial Member Report Summary 655/1998
A J Kinsey
Weld tests define the boundary conditions for avoidance of weld metal hydrogen cracking in multipass welds made using cored-electrodes.
Guidelines which enable a fabricator to select safe preheat levels to prevent fabrication hydrogen cracking in the heat affected zones (HAZ) of welded joints have been established for some time. With the introduction of modern steels of low hardenability, necessary preheat levels to avoid HAZ cracking can be substantially reduced such that the sensitivity of the weld metal to hydrogen cracking may now dictate the selection of preheat to produce crack free welded joints. Existing standards provide limited guidelines to avoid weld metal cracking. Previous work at TWI has led to a reasonable understanding of the parameters which affect cracking in carbon manganese steels up to 450 N/mm 2 yield strength. This work was based mainly on the submerged arc (SAW) process. In view of the increasing use of tubular-cored electrodes, the present study was aimed at expanding the current TWI weld metal cracking database to enable guidelines to be applied to this process. In addition, the conversion of diffusible hydrogen to residual hydrogen upon reheating in multipass rutile MMA welds has been noted. The effect is anticipated to be of benefit in avoiding weld metal hydrogen cracking. Therefore, this aspect was addressed with respect to rutile tubular-cored electrodes in the present work.
- To assess existing schemes to prevent weld metal hydrogen cracking in multipass welds made with cored electrodes in steel of 450 N/mm 2 yield strength.