| 摘要 |
PROBLEM TO BE SOLVED: To stably produce a strengthened steel by specifying particle size and the content of oxide/sulfide particles to be incorporated into the steel and dispersing combined particles, which precipitate a copper sulfide on the surface of oxide particles thereby preventing oxide particles to be added in a molten steel from aggregating and coarsing. SOLUTION: Oxide/sulfide particles of 0.01-0.06μm particles are incorporated into the steel by a volume % of 0.05-2%. Oxide/sulfide particles are dispersed in the steel by using combined particles which precipitate a copper sulfide on a surface of oxide particles as taking an oxide particle for a nucleus. In the case a fine oxide is dispersed in a steel, because sulfur is an element having an activated surface, the sulfur is stuck to a surface of the oxide. The sulfur stuck to surface reacts with copper in a steel to produce a sulfide. Boundary energy of a copper sulfide with a molten metal is small, the oxide particles coated, a surface of which is coated with sulfide copper, are not flocculated. The method, by which a combined oxide is dispersed in the molten steel, is used for dispersing the fine oxide in the molten steel.
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