| 摘要 |
PURPOSE:To prevent deterioration in intergranular corrosion-resisting property at the internal surface of a seamless steel tube after mandrel mill rolling, by incorporating, in particular, specific amounts of Sb and Sn into an austenitic stainless steel. CONSTITUTION:The steel has a composition which consists of, by weight, <=0.15% C, <=1.5% Si, <=2.0% Mn, 16.0-26.0% Cr, 6.0-22.0% Ni 0.001-0.024% Sb and/or Sn, and the balance essentially Fe and to which, if necessary, 2.0-3.0% Mo is incorporated and also at least either of Ti and Nb is incorporated by the amounts in the ranges satisfying Ti=4X(C%)-0.6% and Nb=8X(C%)-1.2%, respectively. Even if this austenitic stainless steel is used as a stock and a mandrel bar to which a graphite-type lubricant is applied is inserted into the above stock to carry out mandrel rolling, carburizing does not occur to the internal surface of the stock. Accordingly, the intergranular corrosion-resisting property at the internal surface of the rolled seamless steel tube can be improved.
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