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Black Annealed zitsulo coils
Cold rolled black annealed coils (CRBA), yomwe imadziwikanso kuti "Blue Steel".CRBA ndiozizira adagulung'undisa zitsulo koyilokuti akhala oxidized ndi annealing mu unsembe wapadera kuti apange wosanjikiza woonda kwambiri magnetite (Fe304) padziko (zosakwana 1 μm wandiweyani) chitetezo kwambiri.