低碳低硫钢中MnS析出行为分析

Precipitation behavior of MnS in low-carbon low-sulfur steel

本文研究铝含量、硫含量、冷却速率等对低碳低硫钢中MnS夹杂物的成分、形貌和析出量的影响,并利用Scheil凝固方程及FactSage 6.1软件对MnS析出行为进行了理论计算。结果表明,冷却速率较低(5K/min)时,钢中夹杂物为双层结构,核心氧化物为Al2O3-SiO2和Al2O3-SiO2-MnO,MnS在氧化物表面局部或包裹析出;冷却速率较高(900K/min)时,钢中夹杂物主要为Al2O3-SiO2-MnO,高铝钢样中没有MnS析出,而低铝钢样中有极少量MnS析出;MnS在夹杂物上的析出率随着冷却速率的降低、钢中铝含量的减少(硫含量随之增加)而提高;复合氧化夹杂中的MnO+SiO2对MnS的析出影响较大,MnO+SiO2含量越高,MnS越容易在氧化物上析出;在低硫(w[S]<0.0050%)条件下,MnS不能在液相中单独析出,但能在夹杂物上复合析出。

The effects of aluminum content,sulfur content and cooling rate on the composition,morphology and amount of MnS inclusion in low-carbon low-sulfur steel were studied and the precipitation behavior of MnS was theoretically calculated by using Scheil equation and Factsage 6.1software.The results show that,at the low cooling rate of 5 K/min,the inclusions have bilayer structure whose cores are mainly composed of Al2O3-SiO2 and Al2O3-SiO2-MnO,and MnS wraps the oxide cores or locally precipitates on them;at the high cooling rate of 900K/min,the inclusions are mainly composed of Al2O3-SiO2-MnO,with no MnS precipitating in high-aluminum steel samples and few MnS precipitating in low-aluminum steel samples;ratio of MnS precipitating on the inclusions increases with the decrease of cooling rate and Al content（S content increases accordingly）in the steel;MnO＋SiO2content in the composite oxide inclusions has greater effect on MnS precipitation,and the more MnO＋SiO2content is,the easier it is for MnS to precipitate on the oxides;under the condition of low sulfur（w[S]〈0.0050%）in molten steel,MnS can＇t precipitate alone in the liquid phase,but can precipitate on the complex inclusions.