CONTROL OF HYDROGEN ASSISTED CRACKING IN HIGH STRENGTH STEEL WELDS

Abstract

The cracking that may occur near the fusion zone of a steel weldment can oflen be attributed to the embrittlement of the microstructure by hydrogen induced during the welding process. The modified implant test was used in this case to evaluate the hydrogen assisted cracking susceptibility of two different plates i.e. (i) AIS! 8620. and (ii) AlSI 304. The diffusible hydrogen content (Ho) was measured using the Glycerine method for both the materials. Welding was accomplished by SMAW process using basic type electrodes. The hydrogen was intentionally introduced for the plate of the material 304 by using an oil of grade SAE 10, which is of very low viscosity. The low viscous oil has smaller molecules as compared with high viscous oil due to which hydrogen pickup is faster with low viscous oil. The fractured as well as un-fractured implant assembly were examined and studied to reveal the fracture morphology. The l-IAZ susceptibility is to be quantified by finding the critical level of stress for a measured IlD. Cracking in the plate was observed to initiate and propagate in an area near the weld interface. The exact location of the fractures varied according to the type of'materials being tested. The effect of stress intensity together with hydrogen content on the mode of fracture present is addressed in detail.