45Cr9Si3气阀钢电渣锭、轧制及退火过程中碳化物析出行为

Precipitation Behavior of Carbides in 45Cr9Si3 Valve Steel During ESR, Rolling and Annealing Process

摘要: 通过X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、电解实验、热力学理论计算，对比研究了45Cr9Si3气阀在电渣锭、轧制及退火三种状态下所析出碳化物的类型、尺寸、形貌及析出条件。结果发现，45Cr9Si3气阀钢中的碳化物类型主要为Cr₇C₃，尺寸较大，最大尺寸大于20 µm，形貌呈条棒状；含有少量的TiC和NbC，尺寸较小，最大尺寸不超过5 µm，形貌以三角形、方形和小颗粒为主；同时含有少量小颗Cr₂₃C₆型碳化物。根据热力学理论计算，TiC和NbC在固液两相区开始析出，析出温度分别为1627.5 K和1619.7 K。Cr₇C₃和Cr₂₃C₆在固相中析出，析出温度分别为1395.4 K和1193.1 K。为下一步45Cr9Si3气阀钢中碳化物细化和性能提升奠定理论基础。

Abstract: By means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), elec-trolysis experiment, thermodynamic calculation, the type, size, morphology and precipitation conditions of carbide precipitated from 45Cr9Si3 valve under electroslagremelting (ESR), rolling and annealing are compared and studied. The results show that the main type of carbides in 45Cr9Si3 valve steel is Cr₇C₃, with larger size and the maximum size is more than 20 μm, and the morphology is bar-shaped. It contains a small amount of TiC and NbC, the maximum size is less than 5 μm, and the morphology is mainly triangular, square and small particles. At the same time, it contains a small amount of small Cr₂₃C₆ carbides. According to calculations based on thermody-namic theory, it is concluded that TiC and NbC begin to precipitate in the solid-liquid two-phase zone, and the precipitation temperatures are 1627.5 K and 1619.7 K, respectively. Cr₂₃C₆ and Cr₇C₃ precipitate in the solid phase, and the precipitation temperatures are 1395.4 K and 1193.1 K, re-spectively. It lays a theoretical foundation for further refinement of carbides and improvement of properties in steel.