| 摘要 |
PURPOSE:To manufacture the titled steel pipe, by working low alloy steel having a specified compsn. to stainless steel pipe, quenching inner and outer surfaces thereof simultaneously, then temper treating it at specified temp. and time. CONSTITUTION:Steel contg. by weight, 0.20-0.50% C, 0.50-1.50% Mn, 0.20-0.35% Si, <0.015% P, <0.005% S, 0.8-2.0% Cr, <0.2% Cu, <1% Ni, 0.5-1.5% Mo, 0.01-0.1% Nb, 0.005-0.1% Al, and having component controlled so that value D1 defined by a formula (I) satisfies a formula (II) corresponding to a wall thickness (t)mm of seamless steel pipe made of this, is hot worked to manufacture seamless steel pipe. Inner and outer surfaces of the steel pipe are quenched simultaneously, then held at 650 deg.C - Ac1 transformation point range for T(min) satisfying a formula (III) corresponding to the thickness (t). Seamless steel pipe having superior sour resistance, strength of 65-85kgf/mm<2> yield strength or 0.5% proof stress, and >=5mm wall thickness is obtd.
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