The design of low alloy steels for thick wall pressure vessels

The steels required for second generation coal conversion vessels must be fabricated in section sizes up to 400 mm thick and must withstand chemically hostile environments containing elevated temperature and high pressure hydrogen. Compositonal modifications of 2.25Cr-1Mo and 3Cr-1Mo steels have been developed to provide improved hardenability, strength, impact toughness, creep strength, resistance to hydrogen attack and reduced temper embrittlement susceptibility. The alloy design criteria which were applied to develop a new class of weldable, heavy section pressure vessel steels are reviewed in this paper