SUSCEPTIBILITY OF LOW STRENGTH RUTILE FLUX-CORED WELD METAL TO HYDROGEN ASSISTED COLD CRACKING

摘要

This paper presents the results of an investigation into hydrogen assisted cold cracking (HACC) susceptibility of seamless and seamed low strength rutile flux cored wires, with nominal diffusible hydrogen (H{sub}D) levels of 5 and 10 ml/100 g, respectively. The objective was to assess the influence of key welding parameters on susceptibility of weld metal to cold cracking. Parameters investigated were the welding current, the contact-tip to work-piece distance (CTWD), the shielding gas and the preheat temperature. The gapped bead-on-plate (G-BOP) test was used to examine the effects of these parameters on the extent of weld metal transverse cracking at a range of preheat temperatures. The overall results indicate that the weld metal susceptibility to cold cracking correlates with diffusible hydrogen content, H{sub}D. It was found that, without preheat, the seamless wire weld deposits (< 5 ml/100 g) did not crack, whereas all those weld metals produced using the seamed wire (> 5 ml/100 g) exhibited cold cracking. Weld metal deposited using 75Ar-25CO{sub}2 shielding gas resulted in a higher H{sub}D levels than for CO{sub}2 shielding gas and, consequently, a higher susceptibility to cold cracking for no or low temperature preheat conditions. Preheating was found to have a strong effect on crack susceptibility, substantially decreasing the amount of cold cracking in the seamed wire welds.