超低硫微合金钢中稀土元素的作用

Effect of Rare Earths on Extra low Sulfur Microalloy Steel

稀土在超低硫（Ｓ＜０．００３％）铌钛微合金钢中仍然有净化钢质、变质夹杂的作用。钢中ｃＲＥ／ｃＯ＋Ｓ控制在４左右，可获得最佳效果。超低硫钢中稀土固溶量可达到１０－５～１０－４数量级，显著减少晶界Ｓ、Ｐ的偏聚，推迟钢的动态再结晶，细化晶粒和沉淀相，促进铌钛碳氮化物析出。稀土在钢中还有微合金化的作用。

In Nb Ti microalloy steel with extra low sulfur(<0 003%), rare earths(RE) show effects on purfying the molten steel and controlling sulphide morphology. The optimum value for RE treatment is about c RE / c O+S =4 The amount of RE in solid solution is the order of 10 -5 to 10 -4 in extra low sulfur steel. The results indicate that RE in solid solution reduces the segregation of both S and P on grain boundaries, delay the dynamic recrystallization, refine grain and precipitation size, and promote(Nb, Ti) (C, N) precipitation. Obviously, the RE has micro alloy effect in the steel.