2014 Volume 100 Issue 10 Pages 1306-1314
To standardize the evaluation technique of hydrogen embrittlement properties of ultra high-strength steel sheets, hydrogen embrittlement properties of SCM435 and V added steel sheets with tempered martensitic matrix were investigated and compared by using 4-Point Bending Cathode Charging Technique, 4-point Bending Constant Displacement Compression Technique and Conventional Strain Rate Technique which was tensile tests. In the SCM435 and the V added steels, it was confirmed that little deterioration of maximum stress was observed at a low diffusible hydrogen concentration region while rapid deterioration of maximum stress was indicated at a high diffusible hydrogen region in all of the testing techniques. Similar hydrogen embrittement properties of the both steels evaluated by 4-Point Bending Cathode Charging Technique and 4-Point Bending Constant Displacement Compression Technique were obtained when maximum tensile stress and accumulated diffusible hydrogen concentration of outside at the center in length of specimens were estimated by FEM analysis. Hydrogen embrittlement properties obtained by both of 4-Point Bending Technique of SCM435 and V added steels were higher than those properties evaluated by Conventional Strain Rate Technique. This might be caused by the difference in the fracture morphologies between 4-Point Bending Technique and Conventional Strain Rate Technique. In 4-Point Bending Technique, intergranular fracture with plastic deformation was occurred in the prior austenite grain near initiation point of cracks, even though intergranular fracture without plastic deformation was observed in the prior austenite grain near the edge of specimen in Conventional Strain Rate Technique.
