过共析钢中TiN夹杂形成热力学分析

Thermodynamics analysis of TiN inclusion formation in hypereutectoid steel

根据过共析钢（特别是碳质量分数为0.90%~0.95%的钢种）凝固过程氮钛元素的溶质再分配机制,对钢中TiN夹杂的形成进行热力学计算。结果表明：随着钢中碳质量分数的增加,在凝固前沿液相形成TiN夹杂所需的氮钛浓度积逐渐降低,同时各钢种都是在凝固后期（固相分数在90%以上）达到形成TiN夹杂的热力学条件。在最后凝固区域,由于钢液补缩不充分,钢的组织出现不同程度的疏松,造成TiN夹杂与钢坯疏松共存的现象。为控制碳质量分数为0.90%~0.95%的钢种中的TiN夹杂,需要进一步降低凝固前沿液相中氮钛浓度积。

The TiN inclusion formation in steel is thermodynamics calculated according to hypereutectoid steel,especially for steel grade with 0.90% to 0.95% carbon content,N and Ti solute redistribution mechanism during solidification.Results show： the Ti and N solute concentration product in molten steel required for the formation of TiN inclusion decreases with increasing of carbon content in steel,and the thermodynamics condition of formation TiN inclusion is formed in the later solidification stage,solid phase fraction over 90%.In the last solidification area,there is different degree porosity due to insufficient feeding of liquid steel,which leads to coexistence of TiN inclusion and porosity.Ti and N solute concentration product in molten steel before solidification should be decreased further for controlling TiN inclusion in carbon mass fraction from 0.90% to 0.95% steel.