SEDL / STP / STP755-EB / STP28413S

A 2¼Cr-1Mo Pressure Vessel Steel with Improved Creep Rupture Strength

Ishiguro, T
Material Research Laboratory, The Japan Steel Works, Ltd., Muroran,

Murakami, Y
Research Laboratory, Muroran Plant, The Japan Steel Works, Ltd., Muroran,

Ohnishi, K
Material Research Laboratory, The Japan Steel Works, Ltd., Muroran,

Watanabe, J
Material Research Laboratory, The Japan Steel Works, Ltd., Muroran,

Pages: 19    Published: Jan 1982

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Abstract

In the ASME Boiler and Pressure Vessel Code, Sec. VIII, Div. 1, design allowable stress-intensity values are influenced by the creep rupture strength at temperatures higher than 450°C. Pressure vessels for such high-temperature service inevitably tend to be thickwalled unless a steel with high creep strength is used. In the case of a coal liquefaction reactor, for instance, a possible wall thickness would be approximately 300 mm or even greater with the use of conventional 2¼Cr-1Mo steel (SA336 F22).

The objective of the present work was to develop a heavy-section 2¼Cr-1Mo steel with better creep strength by conducting a set of experiments with regard to the effect of microalloying elements. The best composition to obtain improved creep-rupture properties was found to be low Si-0.10C-2¼Cr-1Mo-¼V-Ti-B. With this composition, remarkable reduction in temper embrittlement susceptibility was also achieved. Other properties, such as weldability, low temperature toughness, and hydrogen embrittlement resistance, were similar to those of conventional 2¼Cr-1Mo steel.