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采用无水有机溶液电解法分离提取重轨钢中的Mn S夹杂物,采用扫描电镜观察铸坯内和钢轨中Mn S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Mn S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Mn S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,Mn S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Fact Sage6.4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Mn S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Mn S的析出时机和形态,减小其对钢性能的有害影响。
The MnS inclusions in heavy rail steel were separated and extracted by anhydrous organic solution electrolysis. The three-dimensional morphology of MnS inclusions in the slab and rail was observed by scanning electron microscope. The composition of MnS inclusions was analyzed by energy dispersive spectroscopy. After the slab is rolled into rails, the corresponding MnS inclusions are rolled into strips along the rolling direction. Based on the thermodynamic and kinetic models, the precipitation behavior of MnS inclusions in heavy rail steel and the degree of segregation of manganese and sulfur during the solidification of molten steel were analyzed. Thermodynamic analysis shows that MnS inclusions begin to precipitate at a solidification fraction of 0.94 at the end of the solidification. The amount of precipitation is determined by the initial w ([Mn]) and the initial w ([S]) and is influenced by the cooling rate during solidification. The results show that there is a good agreement between the results of thermodynamic calculation and those calculated by Thermo-Calc and Fact Sage 6.4. The dynamic analysis shows that when the cooling rate is increased during the solidification of molten steel, the size of precipitated Mn S particles will decrease small. By adjusting w ([Mn]) and w ([S]) in the steel and varying the cooling rate, the timing and morphology of MnS precipitation can be controlled to reduce its detrimental effect on steel performance.