1994 Volume 80 Issue 3 Pages 243-248
Medium carbon steels added 2.0% Si or 1.5% Si-30ppm Ca with 1400N/mm2 tensile strength show high resistance to delayed fracture. It is important to clarify the hydrogen occlusion behavior to delayed fracture of steels with high resistance to delayed fracture. The hydrogen diffusion coefficient and hydrogen content were measured by electrochemical permeation technique, and hydrogen evolution content after accelerated delayed fracture test was directly measured by hydrogen thermal analysis. It is found that high resistance to delayed fracture of 2.0% Si steel is due to the high hydrogen content needed for fracture, in spite of its high hydrogen occlusion rate. Also the high resistance to delayed fracture of 1.5% Si-30ppm Ca steel is found to be due to the low hydrogen occlusion rate and the low hydrogen content needed for fracture.