| ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ KAWASAKI STEEL TECHNICAL REPORT No.20 ( June 1989 ) Information Systems ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ |
| High Strength 2-1/4 and 3% Cr-1% Mo Steels
with Excellent Hydrogen Attack Resistance Jun-ichi Shimomura, Hidefumi Tani, Takeshi Kooriyama, Shingo Sato, Syuzo Ueda |
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Synopsis : To develop 300-mm thick alloy-modified 2-1/4 Cr-1 Mo steels for pressure vessels to be operated at 900F and a hydrogen pressure of 3 ksi, laboratory study and factory-scale production trial were carried out. The main results obtained follow: (1) The addition of 0.25`0.30%V, 0.015`0.020 Nb and a small amount of B, and the reduction of Si content to less than 0.1% realizes the modified 2-1/4 Cr-1 Mo Steel. The steel satisfies the target values of strength and toughness as proposed by MPC and API after PWHT whose tempering parameter is 20.6~103, and also gives good resistivity to hydrogen attack. (2) The addition of 0.20%V and 0.020% Nb and the reduction of Si to less than 0.1% improve creep rupture strength and resistivity to hydrogen attack of the 3 Cr-1 Mp stress, though both properties are inferior to the modified 2-1/4 Cr-1 Mo Steel. (3) These modified Cr-Mo steels give low susceptibility to reheat cracking during PWHT and good properties of narrow gapped SAW joints. |
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