电渣连铸钢坯洁净化基础研究

Electroslag continuous casting can produce high quality steel as conventional electroslag metallurgy, and meanwhile avoid the problems of low productive efficiency and low metal yield. It is with good prospect in special steel production. Both inclusion capture during solidification and inclusion removal are crucial factors for product cleanliness of electroslag continuous casting. However, for electroslag continuous casting, neither mechanism of inclusion removal and process simulation of it have been sufficiently studied..Mechanism of inclusion removal and numerical simulation of electroslag continuous casting will be studied with the combination of thermodynamic calculation, laboratory experiment, numerical simulation and industrial trial. Thermodynamic calculation of inclusion formation will be carried out with various slag compositions and steel compositions. Wetting behavior among slag-steel-inclusion and modification effect of slag on inclusion are to be studied. Thereby, the mechanism of formation, modification and adsorption of inclusions can be revealed and effective control of inclusions in electroslag continuous casting billet can be realized. Solidification model of steel and capture model of inclusion during electroslag continuous casting process will be developed. Based on accurate simulation of fluid flow and temperature field, prediction of inclusion distribution during electroslag continuous casting will be achieved using FLUENT and self-writing UDF. Experiments will be carried out for model modification. Results of this study can provide fundamental basis for steel cleanliness improvement of electroslag continuous casting and give important guidance for high quality steel production.

电渣连铸既保持了电渣冶金产品高品质的特点，又解决了传统工艺生产效率和金属收得率低的问题，在特殊钢冶炼方面具有良好的前景。夹杂物去除和凝固捕捉都是电渣连铸产品洁净度的决定性因素，目前夹杂物去除机理研究和生产过程模拟尚待提高。.本项目结合热力学计算、实验室实验、数值模拟和工业实验多种研究手段，对电渣连铸夹杂物控制和过程数值模拟两方面进行研究。调整渣系配比和钢液成分，对夹杂物生成热力学进行计算，并研究渣-钢-夹杂物间的润湿行为和渣系对夹杂物的改性效果，从而揭示电渣连铸过程夹杂物生成、改性和吸附规律，实现对电渣连铸钢坯夹杂物的有效控制。建立电渣连铸钢坯凝固模型和电渣连铸过程夹杂物捕捉模型，利用模拟软件FLUENT和自编UDF，在电渣连铸流场、温度场模拟的基础上，实现对电渣连铸钢坯中夹杂物分布的预测，并通过实验进行模型优化。研究结果可为电渣连铸钢坯洁净化生产提供理论基础，为高端金属冶炼提供重要指导。

电渣连铸既保持了电渣冶金产品高品质的特点，又解决了传统工艺生产效率和金属收得率低的问题，是实现高端金属熔炼的重要手段。影响电渣连铸产品洁净度的夹杂物去除和凝固捕获机理尚需探究，同时高温合金及电热合金生产过程中加入的贵重金属元素收得率低的问题也有待解决。本研究结合热力学计算、实验室实验、数值模拟和工业实验多种研究手段，对电渣连铸钢坯洁净化进行了基础研究。.针对FeCrAlYHfZr高温合金，采用优化后的渣成分30%Y2O3-20CaO%-50%CaF2，可以将[Y]的收得率稳定提高到35%左右。以(Y,Zr,Hf)xO为核心、外层为(Zr,Hf)xC的近立方体复合夹杂物和树枝晶状(Zr,Hf)xC在合金中析出，在加入适量的Zr和Hf时，可以完全阻止Cr的碳化物析出，有助于提升合金的高温强度和抗氧化性。针对Cr20Ni80Ce合金进行了夹杂物分析，电渣重熔能够较为有效地减少铸锭中夹杂物的个数及尺寸，夹杂物数密度从电渣前的14.98 #/mm2降低至6.80 #/mm2，夹杂物平均直径由2.74 μm降低至1.06 μm。.通过数值模拟研究发现，渣池区域温度在1838~2007 K之间，渣池温度最高区域位于焦耳热最大位置下方。熔滴当量直径与界面张力的二分之一次方成正比，与落下频率成反比。接近熔池附近时，熔滴的速度逐渐降低，随着界面张力的增大，熔滴直径对滴落速度的影响更为显著。为提高电渣重熔铸锭中La元素的收得率，可适当增大电极插入深度以及改变渣成分增大钢渣界面张力，在界面张力为1.0 N·m-1时，La元素收得率达54.95%。夹杂物初始速度越大、初始速度角与界面角越小，越有利于夹杂物的穿越行为。将电渣过程分为电极熔化至熔滴形成、熔滴穿过渣池滴落、夹杂物在熔池上浮去除阶段，考虑界面阻力时夹杂物在0.8 s内的脱除率约为54%。.本研究实现了对电渣连铸钢坯夹杂物的预测和控制。研究结果为进一步提高电渣连铸产品洁净度、提高特殊钢生产水平以满足我国经济建设和国防工业需求提供了一定理论指导。