Keizo Ohnishi1, Ryuichi Chiba1, Kunio Teshirogi1 and Hisashi Kaga1
1Research Laboratory Muroran Plant, The Japan Steel Works, Ltd., Muroran
The embrittlement tests of high strength steels with yield strength of 116 to 150 kg/mm2 were performed under a high pressure gaseous hydrogen atmosphere at a room temperature.
The results obtained are summarized as follows:
(1) The high strength steels such as Medium C-Ni-Cr-Mo Steel obviously shows embrittlment under gaseous hydrogen atmosphere at room temperature. The extent of embrittlement increased with hydrogen pressure in such that the notch tensile strength decreased remarkably with increasing hydrogen pressure up to 50 kg/cm2, while the degradation became rather smaller in the pressure range of 50 to 100 kg/cm2.
\noindent (2) The degradation of the notch tensile strength due to gaseous hydrogen appeared to be closely associated with the stress concentration factor; that is, with its increase, the notch tensile strength was reduced.
(3) The fracture pattern that failed under high pressure gaseous hydrogen was varied with the depth; quasi-cleavage fracture beneath the notch, then intergranular fracture and finally to ductile fracture. Intergranular fractured area increased with embrittlement.
(4) Hydrogen analysis for the failed test pieces showed that the residual hydrogen content in the embrittled materials was larger than that for the non-embrittled.
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