On Hydrogen Brittleness of Steel (Report 2)

The Effect of Testing Speed on Hydrogen Brittleness

Abstract

In the previous paper, authors reported the results of a few experiments on hydrogen brittleness of mild steel. In this paper, authors reported mainly the effect of testing speed on hydrogen brittleness.
(1) Hydrogen was charged in mild steel specimens by cathodic electrolysis (5% H₂SO₄ and with catalyser a few drops of P+CS₂ solution were used).
(2) Partially charged specimens were tested for the depth and the degree of brittle part in the specimens.
(3) Tensile and bending tests were carried out in accordance with the three kinds of testing speed, i.e., statically (6mm/min, 150mm/min) and dinamically (Charpy Impact).
In consequency of these tests, ratio of reduction in area and elongation on tensile test, and lateral contraction and absorbed energy on bending tests were remarkably decreased inaccordance with increase of charging hours, and in the case that charging hour was more than two hours (about 7ccH2/100gr-Fe), testing results were almost settled. It is interested that under high testing speed, these decreases of reduction in area and etc. were not so remarkable. The degree of hydrogen brittleness becomes remarkably when slower testing speed was used.
(4) In the case that the specimens were aged up 4 days after charging, the ductility of the specimens was almost recovered to that of virgin specimen when pre-strain had not given, besides the ductility was hardly recovered when suitable pre-strain was given.