HEAT-RESISTANT CAST STEEL EXCELLENT IN AGED DUCTILITY AND CREEP RUPTURE STRENGTH FOR HYDROGEN PRODUCING REACTION TUBES

摘要

A heat-resistant cast steel excellent inhigh-temperature strength, aged ductility and creep rupturestrength for use as a material for steam reforming reactiontubes in fuel cell hydrogen generation systems and the like.The cast steel has a chemical composition comprising, in mass %,0.1 to 0.5% of C, up to 2.5% of Si, up to 2.5% of Mn, 15 to26% of Cr, 8 to 23% of Ni, 0.1 to 1.2% of Nb, 0.01 to 1.0% ofTi, 0.001 to 0.15% of Ce, up to 0.06% of N and the balancesubstantially Fe, the cast steel being 20 to 45 in the parametervalue P calculated from the expression:P = 89.3 - 78.4C + 0.1Si - 5.7Mn - 1.7Cr+ 0.01Ni + 2Nb + 5.3Ti - 36.5N - 50.8Ce.When desired, the steel contains at least one of 0.001 to 0.05%of B, 0.01 to 0.5% of Zr and 0.001 to 0.15% of La, and/or 0.01to 0. 3% of Al. Further when desired, the C, Cr and Ni contentsare limited to 0.1 to 0.3% of C, 15 to 20% of Cr and 8 to 18%of Ni.