基于电炉立式连铸工艺制备特种合金的关键基础问题研究

The slab fabrication of nickel-based alloy and special stainless steel based on electric arc furnace-vertical continuous casting process by instead of the traditional casting ingot process can greatly reduce the production cost, improve the product quality and the metal yield, which is the frontier technology owned by a few developed countries in the world. In this project, the key basic problems and key technologies of Incoloy825 nickel-based corrosion resistant alloy with high content of Al and Ti and duplex stainless steel are mainly investigated in the process of melting, refining and continuous casting. The control conditions of inclusions composition and morphology in their refining process is confirmed. The new technologies of controlling inclusion morphology are proposed for Fe-Ni-Cr corrosion resistant alloy based on magnesium treatment process with a low magnesium and molybdenum master alloy and for duplex stainless steel based on rare earth treatment. A new type of continuous casting mold flux is designed and developed for the nickel-based alloy with high content of Al and Ti. A new method for controlling the initial solidification behavior of slab in continuous casting mold is proposed to improving the surface quality and subsurface quality of slab, it is called the method with a thermal barrier coating in meniscus of mold. The mechanism of the thermal barrier coating method to suppress the formation of oscillation marks in continuous casting slab is investigated, and the new technology of controlling the solidification structure, inclusions distribution and crack formation of slab based on electromagnetic field is also developed. The continuous casting slab of Incoloy825 nickel-based alloy with excellent inside and outside quality will been fabricated and form a series of innovative technologies with independent intellectual property on the fabrication of special alloys based on electric arc furnace-vertical continuous casting process.

以电炉-立式连铸工艺替代传统模铸工艺制备镍基合金和特种不锈钢连铸坯，可大幅度降低生产成本，提高产品质量和金属收得率，是当今个别发达国家所掌握的前沿关键技术。本项目以Al、Ti元素含量高的Incoloy825镍基耐蚀合金和双相不锈钢为研究对象，重点研究其在冶炼、精炼和连铸等过程中的关键基础问题和关键技术。研究确定精炼过程中夹杂物成分及形态控制条件；提出开发低镁含钼中间合金处理Fe-Ni-Cr系耐蚀合金、稀土处理双相不锈钢等夹杂物控制新工艺；设计开发高钛高铝的镍基合金用新型连铸保护渣；提出了控制板坯连铸结晶器初始凝固行为，改善铸坯表面质量和皮下质量的的新方法—弯月面热障涂层法。研究弯月面热障涂层方法抑制连铸坯振痕形成的机制，电磁场控制铸坯凝固组织、夹杂物分布和裂纹形成的新技术，制备出内外质量优良的Incoloy825镍基合金连铸坯，形成具有自主知识产权的电炉立式连铸制备特种合金的系列性创新技术

本项目针对宝钢特钢电炉-立式连铸生产工艺流程，以Fe-Ni-Cr合金为研究对象，开展精炼渣与合金渣金反应、镁处理和稀土处理、结晶器保护渣开发、以及电磁搅拌和热障涂层结晶器控制铸坯内外质量的基础研究。揭示了含TiO2精炼渣对合金中Al和Ti烧损率、夹杂物形态等的影响规律。揭示了不同Ce添加量对2101双相不锈钢微观组织、夹杂物形态力学性能和耐蚀性能的影响规律。揭示了不同Mg含量对Incoloy825合金微观组织、夹杂物形态、力学性能和耐蚀性能的影响规律。自主研发了新型镍镁钼合金脱硫剂，显著提高镁的收得率。揭示了连铸保护渣与Incoloy825合金中Al、Ti元素的反应机理，不同含量Al2O3、TiO2和TiN等夹杂物对保护渣理化性能的影响规律。自主研发了新型含稀土氧化物的连铸保护渣，抑制钢渣界面化学反应，且保证了保护渣的润滑性能。提出新型立式线性电磁搅拌方法，促进铸坯内熔体产生纵向大环流运动，强化铸坯上部高温熔体与下部低温熔体的温度混合与成分均匀化，促进了Incoloy 825合金的柱状晶向等轴晶转变，显著减轻和消除连铸坯中心缩孔、疏松和偏析缺陷，提高Incoloy 825合金中TiN夹杂物的去除效果。建立了三相等轴晶凝固模拟模型，数值模拟揭示了电磁搅拌作用下连铸方坯流场、固相分数和溶质分布的演变过程与形成规律，验证了立式电磁搅拌驱动熔体产生纵向大环流运动，促进铸坯散热和溶质均匀化，显著减轻连铸坯中心宏观偏析的作用机理与效果。揭示了热障涂层方法抑制连铸坯振痕形成的作用机制。研究开发了热障涂层结晶器用涂层材料，设计制造了连铸热障涂层结晶器。本项目发表期刊论文21篇，会议论文12篇、做会议报告16次（其中，国内外会议大会报告4次和主题报告1次）。申请和授权中国发明专利8项，申请国际PCT专利1项。培养毕业博士和硕士研究生10人，其中1名硕士生学位论文获2020辽宁省优秀硕士学位论文。