| 摘要 |
PURPOSE:To obtain a titled steel pipe contg. a limited amt. of delta-ferrite, having high strength and toughness and having excellent resistance to stress corrosion cracking by combining centrifugal casting and cold working in producing said pipe. CONSTITUTION:This method is a production method for a small diameter long sized corrosion resistant cast steel pipe consisting of two phase cast stainless steel contg. 5-30% (area rate) ferrite phase. The molten cast steel is subjected to centrifugal casting and after the steel solidifies, the steel is cooled at the average cooling rate controlled to >=20 deg.C/min. down to 600 deg.C. The resulted casting pipe is subjected to a solution heat treatment then to cold working, and is thus worked to an intended small bore long sized pipe. The pipe is subjected to a recrystallization fining treatment prior to cold working or in the mid-way of the cold working according to need. The crystal grains of the casting pipe are fined by the above-described control of the cooling rate, whereby the sufficient processability to make the pipe withstand the succeeding cold working is provided. Otherwise the processability is further improved by the refining treatment, whereby the working to the small bore long sized pipe is accomplished easily and smoothly. |
