The results of studies with respect to hydrogen embrittlement phenomenan have been reported by many workers and many hypotheses of that mechanism are advanced, but it seems that any unified opinion is not published.
Then, in the study of that mechanism, it is significant to discuss about hydrogen-occluded steels under various stresses.
From this point of view, this paper deals with the hydrogen embrittlment of commercial steels which are subjected to the constant load rupture test.
Hydrogen was charged into steels cathodically under given constant loads (bath; 5% sulphric acid in poison phosphorus, charging temperature; R.T., current density; 0.08-0.09 amp/cm
2, anode; platinum coil).
The steels examined were carbon steels, chromium steels, stainless steels, 60 kg/mm
2 class and 80 kg/mm
2 class high tension steels, all commercial.
This work discusses, using base material specimens and weld joint specimens of each steel, their susceptibility to hydrogen embrittlement.
The results are summarized as follows:
(1) The gradient of hydrogen embrittlement lines (relations between given stress and fracture time) for 80kg/mm
2 class high tension steels are very steep and the stress range in which a hydrogen-delayed fracture occurs is very wide: 60 kg/mm
2 class, carbon steels and chromium steel show in this order gentler slope and narrower stress range in which a delayed fracture occurs. Therefore, 80 kg/mm
2 class high tension steels suffered most embrittlement and carbon steel did less embrittlemt. Stainless steel did not fracture by hydrogen.
(2) High tension steel being affected by hydrogen, in the construction of high tension steels close attention must be paid to the problem of hydrogen embrittlement.
(3) The susceptibility to hydrogen embrittlement of weld joint specimens was very different from that of each steel. High tension steel onffered most embrittlement which was more remarkable than in base material specimens. The fractured part mostly falls on bond and H.A.Z., for the welded part is affected easily by hydrogen.
(4) When hydrogen-occluded steels were placed in a certain stress field, hydrogen cracks initiate at the defect and inclusion which exist already in steels and propargate. Propagation of hydrogen cracks is affected by the structure of matrix and the distribution of the lamination, but it needs more detailed microscopic analysis.
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