Abstract: A substrate steel of the comprising from 0.01 to 0.60 wt. % of La, from 0.0 to 0.65 wt. % of Ce; from 0.06 to 1.8 wt. % of Nb up to 2.5 wt. % of one or more trace elements and carbon and silicon may be treated in an oxidizing atmosphere to product a coke resistant surface coating of MnCr2O4 having a thickness up to 5 microns.

Abstract: A thermal cracking tube is adapted to suppress pressure losses while maintaining heat transfer promoting effect on the fluid inside the tube. The tube has a plurality of projections rows extending circumferentially along inner surface of the tube orthogonal to or as inclined with respect to the axis of tube, each of the projection rows including a plurality of projections provided on the tube inner surface. The tube is defined by S/10?D=0.2?0.7, h/D=0.02?0.05 and L/?D=0.04?0.5. D is inner diameter of the tube, h is height of projection A arbitrarily chosen in a projection row ?, L is length of circular arc of projection A in a direction orthogonal to tube axis, and S is area of a region R surrounded by projection A, phantom lines L1 and L2 (extending respectively from circumferentially opposite ends of projection A in parallel to tube axis) and projection row ? downstream from projection row ?.

Abstract: A heat resistant alloy comprising, in % by weight, over 0.6% to not more than 0.9% of C, up to 2.5% of Si, up to 3.0% of Mn, 20 to 28% of Cr, 8 to 55% of Ni, 0.01 to 0.8% of Ti and 0.05 to 1.5% of Nb, the balance being Fe and inevitable impurities, the value of (Ti+Nb)/C being 0.12 to 0.29 in atomic % ratio. When the alloy further contains up to 0.5% of Zr, the value of (Ti+Nb+Zr)/C is 0.12 to 0.29 in atomic % ratio. When the alloy is heated at a temperature of at least about 800 degrees C., a fine Ti—Nb—Cr carbide or Ti—Nb—Zr—Cr carbide precipitates within grains to thereby retard creep deformation and give an improved creep rupture strength. The alloy is therefore suitable as a material for hydrogen production reforming tubes.

Abstract: A thermal cracking tube is provided which is adapted to suppress pressure losses to the greatest possible extent while maintaining a heat transfer promoting effect on the fluid inside the tube. The tube passes a fluid therethrough from one end thereof toward the other end and has a plurality of rows of projections extending circumferentially along an inner surface of the tube orthogonal to or as inclined with respect to the axis of tube, each of the projection rows including a plurality of projections provided on the tube inner surface. The tube is defined by S/10?D=0.2-0.7, h/D=0.02-0.05 and L/?D=0.04-0.

Abstract: A heat resistant alloy comprising, in % by weight, over 0.6% to not more than 0.9% of C, up to 2.5% of Si, up to 3.0% of Mn, 20 to 28% of Cr, 8 to 55% of Ni, 0.01 to 0.8% of Ti and 0.05 to 1.5% of Nb, the balance being Fe and inevitable impurities, the value of (Ti+Nb)/C being 0.12 to 0.29 in atomic % ratio. When the alloy further contains up to 0.5% of Zr, the value of (Ti+Nb+Zr)/C is 0.12 to 0.29 in atomic % ratio. When the alloy is heated at a temperature of at least about 800 degrees C., a fine Ti—Nb—Cr carbide or Ti—Nb—Zr—Cr carbide precipitates within grains to thereby retard creep deformation and give an improved creep rupture strength. The alloy is therefore suitable as a material for hydrogen production reforming tubes.

Abstract: A heat-resistant cast steel excellent in high-temperature strength, aged ductility and creep rupture strength for use as a material for steam reforming reaction tubes 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 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 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 0.01 to 0.3% of Al. Further when desired, the C, Cr and Ni contents are limited to 0.1 to 0.3% of C, 15 to 20% of Cr and 8 to 18% of Ni.

Abstract: A heat-resistant cast steel excellent in high-temperature strength, aged ductility and creep rupture strength for use as a material for steam reforming reaction tubes 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 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 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 0.01 to 0.3% of Al. Further when desired, the C, Cr and Ni contents are limited to 0.1 to 0.3% of C, 15 to 20% of Cr and 8 to 18% of Ni.