鋼の水素脆化に関する研究(第1報)

Abstract

The discontinuity-migration theory on hydrogen brittleness of steels has been published and supported by researchers. The purpose of this investigation is to reconsider this theory on hydrogen brittleness and, if possible, to establish the new theory.In this paper, authors report the results of a few experiments on hydrogen brittleness of mild steel. Hydrogen was charged in mild steel specimens by cathodic electrolysis method (5%H2SO4, 0.08-0.09A/cm2, carbon tube anode used). The volumes of hydrogen in specimens were regulated with change the charging hours and were measured using other specimens before mechanical tests.On mechanical tests, tensile test, V-notched slow bend test and V-notched charpy impact test were used.(1) In the case that the specimens were tested soon after charging; Yield strengths and maximum stresses on tensile test were almost same value, in spite that the volumes of hydrogen in specimens were different.But the elongation was remarkably decrease in accordance with increase of the volume of hydrogen in specimen.Energy of crack initiation and propagation on V-notched slow bend test were also remarkably decrease. The decrease of ductility on V-notched charpy impact test with increase the hydrogen in specimen was considerably remarkable, in spite that the test was carried out under very high speed and atomic hydrogen in specimen could not consider to migrate through the gap of Fe-atom.(2) In the case that specimens were aged up 4 days after charging before test; Ductility was remarkably recovered nearly equal to that of virgin specimen.From these experimental results and consideration, authors obtain the guiding-star of the new theory of hydrogen brittleness.