基于氮气压力动态调节的电渣重熔制备高氮高速钢梯度材料的基础研究

Based on the urgent needs of performance improvement and development of new varieties of high speed steel, the new idea and technology that “Fundamental research on manufacturing high nitrogen high speed steel gradient material by electroslag remelting based on dynamic regulation of nitrogen pressure” is innovatively proposed. It is proposed to improve the morphology and distribution of eutectic carbides by comprehensive means of pressure enhanced cooling, nitrogen gas phase alloying and substituting nitrogen for carbon to improve the performance of high speed steel. The new concept of gradient structure is introduced to make the hardness and toughness matching of high speed steel with nitrogen gradient distribution more reasonable. Base on gas phase nitriding mechanism, the relationship between pressure and nitrogen content will be quantified, the prediction model of nitrogen content will be established and the gradient distribution and precise control of nitrogen will be achieved by electroslag remelting based on dynamic regulation of nitrogen pressure. The mechanism of improving the morphology and distribution of eutectic carbides by pressure enhanced cooling will be clarified. The occurrence of nitrogen in high speed steel will be elucidated, the synergistic effect mechanism of alloying elements and nitrogen on the microstructure and properties of high speed steel will be revealed, and then the alloy composition optimization of high speed steel with substituting nitrogen for carbon as the core and the design method of gradient nitrogen content will be established. The effect mechanism of heat treatment process on the microstructure and properties of high nitrogen high speed steel gradient material will be revealed, and the theory and method for precisely controlling its microstructure and properties using heat treatment method will be mastered. The research results will enrich and develop the process and theory of manufacturing high speed steel with high performance and gradient material, and promote the development and application of the new varieties of high speed steel in China.

基于高速钢性能提升和新品种研发的迫切需求，项目创新性地提出了“基于氮气压力动态调节的电渣重熔制备高氮高速钢梯度材料”新思路和新工艺，拟采用加压强化冷却、气相氮合金化及以氮代碳的综合手段改善共晶碳化物形态与分布以提升高速钢性能，引入梯度结构新理念，使氮梯度分布的高速钢硬度和强韧性匹配更合理。基于气相渗氮机理，量化压力与氮含量之间的关系，构建氮含量预测模型，基于氮气压力动态调节的电渣重熔实现氮梯度分布和精确调控。阐明加压强化冷却改善共晶碳化物形态与分布的机理。揭示氮在高速钢中的赋存状态，阐明合金元素与氮的协同作用影响其组织和性能的机制，建立“以氮代碳”为核心的高速钢合金成分优化和梯度氮含量设计方法。揭示热处理工艺对高氮高速钢梯度材料组织和性能的影响机理，掌握利用热处理工艺精确调控其组织与性能的理论和方法。研究成果将丰富和发展制备高性能高速钢及梯度材料的工艺理论，促进我国高速钢新品种研发和应用。

本项目研究了凝固压力对铸态M42高速钢枝晶组织、莱氏体组织以及共晶碳化物的影响规律，阐明了增加凝固压力细化铸态组织和改善共晶碳化物形态与分布的机理；开展了加压电渣重熔制备高氮高速钢实验研究，基于渣系物性参数的检测优化了气相渗氮渣系，明确了渣系、冶炼压力、熔速等工艺参数对增氮效果的影响规律，量化了压力与氮含量之间的关系，构建了氮含量预测模型，成功制备了高氮M42高速钢材料，掌握了基于氮气压力动态调节的加压电渣重熔制备高氮高速钢梯度材料的关键技术；研究了氮、铈和镁对铸态M42高速钢枝晶组织、莱氏体组织以及共晶碳化物的影响规律，揭示了氮、铈和镁在铸态组织中的赋存状态，明晰了氮、铈和镁细化铸态组织的作用机理以及对共晶碳化物形成、转变和分布的影响机制；同时，探讨了铈和镁处理对夹杂物特征的影响规律；研究了高温退火处理对铸态高氮M42高速钢微观组织和热加工性能的影响，分析了M2C共晶碳化物的高温分解行为，揭示了高温退火处理显著改善热加工性能的作用机理；研究了合金元素对M42高速钢相变温度、相类型及析出量的影响规律；研究了氮和热处理工艺对M42高速钢热处理组织和性能的影响规律，揭示了合金元素与氮的协同作用以及热处理工艺对其组织和性能的作用机制，掌握了利用热处理手段精确调控高氮M42高速钢材料组织与性能的方法。本项目研究成果丰富和发展了制备高性能高速钢以及梯度材料的工艺和理论，促进了高性能高速钢新品种的研发及应用。