| 摘要 |
PURPOSE:To obtain steel pipe superior all in normal temp. and high temp. short time strengths, and high temp. long time creep strength, without deteriorating workability, weldability and toughness, by specifying the final heat treating condition of steel pipe made of Cr-Mo low alloy steel for high temp. service. CONSTITUTION:Low alloy steel as stock composed of, by weight 0.02-0.15% C, 0.10-1.00% Si, 0.10-0.70% Mn, 0.70-1.30% Cr, 0.10-0.70% Mo and the balance Fe is worked to pipe. Thereafter, the pipe is normalizing treated by austenitization at 920-980 deg.C at the final heat treatment. Further, the pipe is tempered at 600-700 deg.C for the time in which a parameter P obtd. by a formula [T; holding temp. ( deg.K), (t); holding time (hr)] becomes to 17,000-19,500. Thereby, the aimed steel pipe is obtd., further since addition of special alloying elements is not needed, steel pipe having sufficient workability, weldability and toughness and most suitable for heat transfer pipe, etc., of boiler and heat exchanger is obtd.
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