| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive seawater resistant steel which shows adequate corrosion resistance with a few kinds and a few quantities of alloy elements, and the seawater resistant steel showing more adequate corrosion resistance, and to provided a manufacturing method therefor. SOLUTION: The seawater resistant steel comprises 0.04% or less C, 1.5% or less Si, 5.0% or less Mn, 1.0 to 5.0% Cr, 0.003 to 0.05% sol. Al, the balance substantially Fe, and 0.003% or less S, 0.008% or less N, and 0.005% or less O, in the impurities. The steel may include one or more among predetermined quantities of P, Cu, Ni, Mo, W, Nb, V, B, Ti, Ca, Mg and REM. The surface layer part of the steel at least 0.5mm deep from the surface preferably has a fine grain structure having a bainite phase of 50% or more by area rate and an average grain size of 8μm or less. The method for stably obtaining the steel comprises heating the raw steel to 1,000 to 1,200°C hot-rolling it with a cumulative rolling reduction of 10% or higher in a temperature range of Ar<SB>3</SB>or higher, once cooling it down to 600°C or lower at surface temperature of the steel with a cooling rate of 15°C/second or higher, recuperating the surface temperature of the steel to 750°C or higher, and finish-rolling it at a finishing temperature of 700°C or lower. COPYRIGHT: (C)2004,JPO
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