高锰高铝钢中溶质元素与非金属夹杂物控制的基础研究

High Mn-high Al steel not only has broad application prospects in automotive industry, but also has great values in machinery industry because of excellent mechanical properties such as high strength and good ductility due to the feature of Twinning Induced Plasticity (TWIP). While the production of this steel grade, such as refining and casting is very difficult due to high Mn and Al concentration. Although the mechanical properties and fracture mechanisms of High Mn-high Al steel has garnered the most attention, the detailed and key techniques in metallurgy have seldom been reported yet. Thus, the fundamental techniques related to metallurgy of High Mn-high Al steel will be investigated in current study, aiming to provide the theoretical guidance for the production. The main works can been described as following: (1) Calculation and measurement of the thermo physical properties of High Mn-high Al steel, such as the liquidus and solidus temperature, thermal expansion coefficient, viscosity and surface tension. (2) The concentration control of solute elements, such as [Al], [Mn], [O] and [N], in molten steel without top slag and the interaction relationship. (3) The effects of reaction between refining slag and molten steel on the following changes as the compositions in the steel and slag phases, as well as non-metallic inclusions in steel. The effect factors include reaction time, [Al] and [Mn] in the steel, and slag compositions. Through present study, the content of solute elements in molten steel and the relationship among them, as well as the effects of refining slag/molten steel reaction on the composition changes in the steel and slag phases, and non-metallic inclusions are expected understood and mastered.

具有孪晶诱导塑性特点的高锰高铝钢因高强度、高塑性的特性不仅在汽车工业有广阔的应用前景，在机械行业也有重要的价值。但因为锰、铝含量高等特点，冶炼和浇注的难度很大，已成为国内外关注的热点，而关于冶金方面的细节和核心技术公开报道的极少。本项目拟对高锰高铝钢生产的相关冶金技术进行基础研究，为该材料的制造工艺提供理论指导。主要工作有：（1）高锰高铝钢的热物性参数的测定，包括液/固相线温度、热膨胀系数、粘度、表面张力等；（2）无渣条件下高锰高铝钢的成分控制及脱氧规律，包括钢中的[Al]、[Mn]、[O]、[N]含量，及[O]、[N]含量与[Al]、[Mn]溶质元素的关系；（3）精炼渣-高锰高铝钢之间反应对炉渣、钢液组元及非金属夹杂物的影响，因素包括渣/钢反应时间、钢中溶质元素含量和炉渣组成。掌握高锰高铝钢中溶质元素含量及相互关系，渣/钢反应对炉渣和钢液组元的影响规律，钢中的夹杂物及影响因素等。

具有孪晶诱导塑性特点的高锰高铝钢因高强度、高塑性的特性不仅在汽车工业有广阔的应用前景，在机械行业也有重要的价值。但因为锰、铝含量高等特点，冶炼和浇注的难度很大，而关于该钢种冶金方面的细节和核心技术公开报道的极少。. 本项目通过热力学计算和实验的方法系统开展了以下研究内容：(1)高锰高铝钢的热物性参数，如液固相线温度、密度、导热系数等；(2)精炼用CaO-SiO2-Al2O3-MgO四元渣系、CaO-SiO2-Al2O3-MgO-MnO五元渣系的冶金特性；(3) 高[Mn]、[Al]含量的Fe-Mn系、Fe-Mn-Al系的制备及钢中溶质元素的平衡关系；(4) CaO-SiO2-Al2O3-MgO渣系与高锰钢的平衡反应。. 结果表明：(1) 与常规钢种相比，高锰钢的液、固相线温度和导热系数较低，且随着钢中[Mn]、[C]溶质元素含量的增加而进一步降低。(2) 适用于高锰钢精炼的炉渣组成位于CaO-SiO2-Al2O3-8%MgO-5%MnO相图的中部位置，随渣中MnO含量的增加，液相区域的面积增大；渣中Al2O3含量对精炼渣冶金特性有很大影响。(3) 1873K下，随着钢中[Al]含量增加，Fe-10Mn-xAl的[O]含量呈先降低后增加的趋势；一定温度下，对于Fe-Mn-Al-N体系和Fe-Mn-C-Al-N体系，当钢中[%N]•[%Al]超过一定数值时，将会析出AlN；当温度和钢中[Al]含量一定时，钢中[Mn]含量越低，[C]含量越高，AlN析出越容易。(4) 1873K和高纯Ar保护气氛下，CaO-SiO2-Al2O3-MgO精炼渣（B=4，Al2O3=20%）与高锰钢（Mn=9%, 19%）反应平衡后，渣中MnO含量在1%左右；钢中夹杂物主要为类球状、微米级的Al2O3-MgO-SiO2-CaO-MnO系；钢中的合金含量和炉渣组成对渣/钢反应有很大影响。. 以上研究结果初步掌握了高锰高铝钢的冶金特性，为该钢种的冶炼生产，如冶炼温度、精炼渣系、浇铸温度和拉速等方面的确定提供了理论依据和数据支撑。