| 摘要 |
PURPOSE:To develop the titled plate having excellent workability and high temp. oxidizing resistance by using a steel plate contg. Cr, having decreased contents of C and S and contg. specific ratios of Ti, B, Ni, etc., as a fin material for a boiler tube attached with a helical-fin. CONSTITUTION:The thin steel plate contg., by weight, <0.015% C, <0.50% Si, 0.05-0.40% Mn, <0.030% P, <0.010% S, 0.50-5.0% Cr, 0.03-0.20% Ti, 0.0003-0.0015% B and <0.0060% N or furthermore contg. 0.15-0.30% Ni is used as the fin material for a boiler tube attached with a helical-fin. The high temp. oxidizing resistance is improved by the addition of Cr and the rise of the strength of the steel plate more than necessity and the generation of cracks caused by MnS inclusions are suppressed by the decrease of the amounts of C and S. The irregular growth of ferrite grains at the time of stress relief annealing is furthermore suppressed by the addition of Ti, B or B and Ni, by which the excellent cold workability of the titled plate is improved.
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