STP755

    Design Properties for Steels Used in Coal Conversion Vessels

    Published: Jan 1982


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    Abstract

    A fracture-mechanics related approach was used to evaluate the performance of 2¼Cr-1Mo in simulated coal conversion environments. Two heats of ASTM A 387 and ASTM A 542 were prepared in the form of commercially produced weldments on 178-mm (7-in.)-thick plate. Base metal, weld metal, and heat-affected zone (HAZ) were investigated. In addition, a simulation of Type 347 stainless steel weld overlay was prepared.

    The sensitivity to environmentally enhanced crack growth was evaluated by rising load test for exposure in 6 percent H2S-Balance H2. The temperature range covered was from room temperature to 727 K (850°F), and pressures were from 5.5 to 24.1 MPa (800 to 3500 psi). Fixed-displacement wedge-loaded specimens were exposed in 100 percent H2 at 24.1 MPa for six months.

    Results indicate that 2¼Cr-1Mo in all metallurgical conditions will be sensitive to environmental cracking in 6 percent H2S-Balance H2 at room temperature. At 588 K (600°F) effects due to 6 percent H2S-Balance H2 are minimal, but at 727 K significant environmentally assisted plasticity develops.

    Fixed-displacement specimens in high-pressure hydrogen were found to have severely degraded postexposure toughness. The mechanism of degradation is believed to be hydrogen-assisted cracking. It also was found that highly preloaded and cracked specimens of 2¼Cr-1Mo will develop creep at temperatures as low as 727 K.

    Keywords:

    coal conversion, pressure vessels, chromium-molybdenum steels, environment, hydrogen, hydrogen sulfide, liquefaction, fracture, testing, plasticity


    Author Information:

    Landes, JD
    Advisory Engineer and Senior Engineer, Westinghouse R&D Center, Pittsburgh, Pa.

    McCabe, DE
    Advisory Engineer and Senior Engineer, Westinghouse R&D Center, Pittsburgh, Pa.


    Paper ID: STP28410S

    Committee/Subcommittee: A01.06

    DOI: 10.1520/STP28410S


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