Patent ID: 7442265

Claim:
A hydrogen producing reaction tube excellent in aged ductility and creep rupture strength, said tube being formed of a cast steel comprising, in mass %, 0.13 to 0.5% of C, up to 2.5% of Si, up to 2.5% of Mn, 15 to 26% of Cr, 8 to 23% of Ni, 0.1 to 1.2% of Nb, 0.01 to 1.0% of Ti, 0.001 to 0.15% of Ce, up to 0.06% of N and the balance substantially Fe, the cast steel being 20 to 45 in the parameter value P represented by the following expression: P= 89.3−78.4C+0.1Si−5.7Mn−1.7Cr+0.01Ni+2Nb+5.3Ti−36.5N−50.8Ce.