铸造高硼高速钢硼碳化物调控及其耐磨性研究

In rolling steel production, roll is the important consumption spare parts. At present, the high-speed steel roll is widely used. However, high-speed steel roll contains many expensive V, W, Co etc. alloy elements, which leads to the increase of production cost. This project takes cheap boron as the main elements, and calculates the phase diagram of high boron high-speed steel containing 0.2~0.8wt%C, 4.0~8.0wt%Cr, 1.0~3.0wt%B, 2.0~4.0wt%Mo, 0.5~1.5wt%Al, 0.5~1.5wt%Si and 0.5~1.5wt%V by using Thermo-Calc thermodynamic calculation software. By studying the solidification process of high boron high-speed steel and nucleation and growth behavior of borocarbide, the nucleation and growth mechanism of borocarbide are investigated. Moreover, the effect of interaction between Ce, Mg, K, N and Ti etc. modification and solidification cooling rate of high boron high-speed steel on the nucleation and growth of borocarbide is studied, and the contron of size, morphology and distribution of borocarbide in cast high boron high-speed steel boron is achieved. We also investigte the effect of Cr, Mo, Ce etc. trace atoms doping on the toughening of borocarbide, and reveal the mechanism of toughening. At last, the mechanism that the regulation of size, morphology, distribution of borocarbide and its toughening improve mechanical properties and wear resistance of high boron high-speed steel is put forward, and the wear mechanism of high boron high-speed steel is opened out. The ultimate goal of this project is to provide a theoretical basis for the development of cheap high boron high-speed steel roll material having better strength and toughness and wear resistance.

轧辊是轧钢生产中重要消耗备件，目前应用的高速钢轧辊含有较多昂贵的钒、钨、钴等元素，增加了生产成本。本项目以廉价硼为主要元素，采用Thermo-Calc热力学计算软件，对含1.0~3.0wt%B、0.2~0.8wt%C、4.0~8.0wt%Cr、2.0~4.0wt%Mo、0.5~1.5wt%Al、0.5~1.5wt%Si和0.5~1.5wt%V高硼高速钢相图进行计算，研究其凝固过程，探讨硼碳化物形核和生长机制；研究铈、镁、钾、氮、钛等变质处理和凝固冷却速度交互作用对硼碳化物形核和生长的影响，实现高硼高速钢硼碳化物尺度、形态及分布调控；研究铬、钼、铈等微量原子掺杂对硼碳化物韧化影响并揭示韧化机理。在此基础上提出硼碳化物尺度、形态和分布调控及韧化对改善高硼高速钢力学性能和耐磨性的作用机制，揭示高硼高速钢磨损机理。本项目最终目标是为开发具有更好强韧性和抗磨性的廉价高硼高速钢轧辊材料提供理论依据。

在轧钢生产中，轧辊是重要耗材之一。高钒高速钢轧辊虽然具有优越的性能，但价格昂贵。使用硼元素制备出高硼高速钢，能够在组织中形成高硬度的硼碳化物，且硼元素价格低廉。高硼高速钢中的硼碳化物呈连续网状结构，且脆性大，严重恶化了高硼高速钢的性能。因此改变高硼高速钢组织中硼碳化物的原始形貌，使之呈细小、弥散的团球状分布于基体中，从而提高材料性能，是确保其能够用于轧辊制备的关键，具有重大的研究意义。.本项目研究了不同B含量的高硼高速钢组织形貌、力学性能及两体磨损性能；通过定向凝固-液淬试验，研究了高硼高速钢的凝固过程，揭示了不同成分硼碳化物的生长机理；还研究了不同Al含量高硼高速钢的组织形貌、力学性能及抗回火软化特性；还以Mo元素作变量，研究了不同Mo含量高硼高速钢中硼碳化物形貌、力学性能及两体磨损性能的变化规律；以Ca、Ti作为变质元素，研究了Ca、Ti单一变质及复合变质处理对高硼高速钢组织形貌、力学性能的影响，及不同凝固速率对Ca-Ti复合变质效果的影响，同时研究了Ca-Ti复合变质高硼高速钢的高温干滑动摩擦磨损性能。.研究表明，高硼高速钢具有极好的淬透性，B含量增加，合金硬度提高，耐磨性增加。高硼高速钢凝固时的物相析出顺序为：初生奥氏体、共晶奥氏体、富Mo硼碳化物、富Cr硼碳化物；奥氏体以非小平面机制生长，富Cr硼碳化物以小平面机制生长，富Mo硼碳化物以“六边形”机制生长。Al元素能显著提高其抗回火软化性能。Mo元素以置换固溶的方式存在于硼碳化物中，改变了硼碳化物晶胞的电子环境，使晶胞热力学稳定性、化学键强度增加，从而提高了硼碳化物的韧性。Ca、Ti元素能够改变硼碳化物的生长方式，使硼碳化物尺寸细化，显著提高了合金韧性。Ca-Ti复合变质高硼高速钢中硼碳化物尺寸细小且弥散分布，且具有良好的高温抗氧化性，使其在室温和高温下均具有良好的抗摩擦磨损性能。.