Study on the formation behavior of sulfides in free-cutting steel by unidirectional solidification
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摘要: 通過定向凝固實驗研究了易切削鋼中硫化物的生成過程,并建立了枝晶臂間距、硫化物的平均直徑與凝固條件之間的關系.實驗結果表明:隨著溫度梯度和拉速的增大,MnS的平均直徑減小,數量增多;定向凝固過程中硫化物的完全析出溫度大約在固相線溫度下100℃左右,MnS形態的改變,主要受其組成元素的活度影響,即MnS形態的改變受其界面自由能的影響;對定向凝固實驗中鋼的枝晶臂間距、硫化物的平均直徑與凝固條件的關系進行了擬合,擬合結果與前人研究結果相吻合.Abstract: The formation behavior of sulfides in free-cutting steel was investigated under unidirectional solidification.The relations of the dendrite arm spacing and sulfides' average diameter to solidification conditions were established.Experimental results show that the average diameter of MnS inclusions decreases with increasing temperature gradient around the solid/liquid zone and casting speed,but the number of MnS inclusions increases.The complete precipitation temperature of MnS is about 100℃ lower than the solidus temperature.The morphological changes of MnS are mainly effected by the activities of constituent elements,in other words,they are mainly influenced by interfacial energy.The relations of the dendrite arm spacing and sulfides' average diameter to solidification conditions were regressed,and the regression results are basically in agreement with the ones of previous researchers.
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Key words:
- free-cutting steel /
- inclusions /
- manganese sulfide /
- dendrites /
- unidirectional solidification
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