| 摘要 |
PROBLEM TO BE SOLVED: To provide a ferritic free-cutting stainless steel capable of remarkably improving the machinability and corrosion resistance of a small-diameter bar steel and wire rod of <=30mm diameter as compared with those of the conventional SUS430F (17Cr-S added). SOLUTION: This steel has a composition consisting of, by weight, <=0.10% C, 0.05-2.00% Si, <=2.00% Mn, <=0.20% P, <=2.00% Ni, 20.0-30.0% Cr, <=1.0% Mo, 0.05-0.45% S, 0.05% Se, <=0.020% O, 0.03-0.30% Pb, and the balance Fe. Moreover, as to relatively large-size sulfide inclusions of >=5μm major axis among the sulfide inclusions existing in the steel, at least 80% of them have <=8 ratio of major axis to minor axis, and further, Mn/(S+Se) and S/Se are regulated to >3.5 and >1.5-<5.0, respectively.
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