PURPOSE: To produce a dull-worked, temper-colored alloy steel for building material, excellent in coloring uniformity and corrosion resistance, without using complicated stages.
CONSTITUTION: At the time of producing an iron-chromium (Fe-Cr) alloy steel containing 5-60wt.% chromium (Cr), ≤30ppm carbon (C), ≤50ppm sulfur (S), ≤50ppm nitrogen (N), and ≤50ppm oxygen (O), rolling is done, at the time of cold rolling, by using a dull roll to which dull working of ≥1.0μm average surface roughness Ra is applied. Subsequently, in an atmospheric gas consisting of 1-25% hydrogen gas and the balance inert gas, the steel is held for 1-200sec at 500-1000°C annealing temp. in a furnace where, dew point is regulated to -50 to -10°C, to undergo finish annealing, by which an alloy steel with tempering coloring is produced. By this method, the Fe-Cr alloy steel usable for building material can be obtained.
SATO SUSUMU
FUJISAWA MITSUSACHI
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