| 摘要 |
PROBLEM TO BE SOLVED: To establish a method for correctly and quantitatively evaluating hard inclusions affecting remarkable the cold workability such as wire drawability and wire twisting properties of a steel and to produce a steel capable of stably and surely showing excellent cold workability. SOLUTION: This high clarity steel excellent in cold workability is the one in which a steel is dissolved in an aq. soln. of mixed acid of [60% (by mass) nitric acid by 250ml+96% sulfuric acid by 10ml+pure water by 550ml] heated at 90 to 95 deg.C, and in which, among inclusions detected by subjecting insoluble inclusions to EPMA analysis, the number of the inclusions composed of >=80% Al2 O3 and having >=30μm dimension is regulated to 10 pieces per 50g of the amt. of the steel to be dissolved and the number of the inclusions composed of 50 to <80% Al2 O3 and having >=20μm dimension is regulated to <=5 pieces per 50g of the amt. of the steel to be dissolved.
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