PURPOSE: To obtain a steel for a high temp. and presure hydrogen vessel having desired resistance to hydrogen attack by forcing a Cr-Mo steel having a specified composition to be cooled from a temp. in the austenite range, regulating the amounts of C, Mn and Si, and carrying out tempering under regulated conditions.
CONSTITUTION: A steel contg. 2.0W2.5% Cr and 0.9W1.1% Mo is cooled from a temp. in the austenite range at a cooling rate above the air cooling rate, and it is tempered to manufacture a 2 1/4Cr-1Mo steel for a high temp. and pressure hydrogen vessel. At this time, the amounts of C, Mn and Si and conditions during the tempering are regulated so as to control the amount of carbides having low thermodynamic stability. By this control, the resistance of the resulting steel to hydrogen attack is contolled.
TSUKADA KOSHIRO
SUZUKI HARUO
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