材料期刊网

采用无水有机溶液电解法分离提取重轨钢中的MnS夹杂物，采用扫描电镜观察铸坯内和钢轨中MnS夹杂物的三维形貌，并结合能谱仪分析其成分。铸坯被轧制成钢轨后，相应的MnS夹杂物都沿着轧制方向被轧制成长条状。基于热力学和动力学模型，分析重轨钢中MnS夹杂物析出行为以及在钢液凝固过程中锰元素和硫元素偏析的程度。热力学分析表明，MnS夹杂物在凝固末期凝固分数为0.94时开始析出，其析出量由初始w([Mn])和初始w([S])决定，且在凝固过程受到冷却速率的影响，对比发现，热力学的计算析出结果与Thermo-Calc和FactSage6.4的计算结果有较好的一致性；动力学分析表明，在钢液凝固过程增加冷却速率，凝固析出的MnS颗粒尺寸将减小。通过调整钢中w([Mn])和w([S])以及改变冷却速率，可以控制MnS的析出时机和形态，减小其对钢性能的有害影响。

The three-dimensional morphologies of MnS inclusions in continuous casting blooms and rolled rails of U75V steel were obtained by electrolytic extraction method using non-aqueous electrolytes combined with SEM method. However,MnS was elongated along the rolling direction during rolling process,and the morphology of MnS inclusions presents an elongated shape in rail. Precipitation of MnS inclusions was studied on the basis of thermodynamics and ki-netics model in heavy rail steels,and the amount of segregation behavior of w([Mn]) and w([S]) elements in molten steel was quantified during solidification. The calculated results show that MnS inclusions were generated due to the initial concentration product of manganese and sulfur equaled to the equilibrium concentration product,i.e.,MnS inclusions started to precipitate in the solid which fraction was 0.94. In comparison,the thermodynamic calculation results were in good agreement with that of the results by Thermo-Calc and FactSage6.4. Effect of the initial concentration of Mn and S in molten steel and cooling rate during solidification on the amount of MnS inclusions was calculated using micro-segre-gation model. In addition,the size of MnS inclusions decreased obviously with increasing cooling rate through the dy-namic calculation. Therefore,the influences of the content of w([Mn]) and w([S]) in molten steel and the cooling rate on the characteristics of MnS inclusions in heavy rail steel were analyzed,including precipitation size,time and amount of the MnS particles. Thus,it would be helpful for decreasing detrimental factors on the properties of steel.