To provide a method of manufacturing a martensitic stainless steel tube having high strength of which the yield stress exceeds 650 MPa and also having excellent toughness at a low temperature.
After martensitic stainless steel which has a composition consisting of, by weight, 0.10-0.18% C, ≤0.5% Si, 0.1-1.5% Mn, ≤0.02% P, ≤0.01% S, 12-14% Cr, 1-3% Ni, ≤0.3% Al, 0.001-0.08% N and the balance Fe with inevitable impurities and further, containing, if necessary, one or ≥2 kinds among ≤0.5% Mo, ≤1.5% Cu, 0.001-0.05% Ti and 0.001-0.01% Ca, is formed into a tube by hot rolling, is if necessary, heated up to a temperature region between an Ac3 point and 950°C and successively cooled down to a room temperature at a velocity not lower than an air cooling velocity, heated up to a temperature between the Ac1 point and the Ac3 point, successively cooled down to the room temperature and then, tempering-treated at a temp. not higher than the Ac1 point.
SAKAMOTO TOSHIHARU
MARUYAMA KAZUSHI
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