超超临界机组转子FB2钢630℃长期时效稳定性研究

An Investigation on 630℃ Long-term Aging Stability for FB2 Rotor Steel Used in Ultra-Supercritical Units

摘要:

本文以FB2转子钢为研究对象,利用冲击实验、硬度测试、扫描电镜、透射电镜及X射线衍射仪等测试方法研究了630℃长期时效中FB2转子钢组织和性能的变化,结果表明：随着时效时间延长,冲击功和硬度都呈下降趋势,冲击韧性在2000 h后下降较为明显,后逐渐趋于稳定。而硬度总体处在较高水平(253 HBW)。M₂₃C₆碳化物尺寸及含量有所增长,但未见明显粗化；Laves相尺寸增长更明显并在晶界处聚集,但未形成链状。Laves相的析出长大与聚集是导致冲击韧性下降的主要原因。研究结果认为630℃时效至5000 h FB2钢能够保持较高的高温稳定性。

Abstract:

In present work the 630℃ long-term aging stability of FB2 rotor steel are investigated by impact test, hardness test in combine with SEM, TEM and XRD analysis. The investigation shows that impact toughness and hardness decrease with proloning aging time. The impact ductility decreases apparently after 2000 h aging and then keeps stable. The hardness stays in a high level (253 HBW). The size and amount of M₂₃C₆ carbide increases slightly during aging without apparent coarsen. The size increase of Laves phase is more obvious and Laves phase tends to gather at grain boundary. While no chain of Laves phase is observed. The coarsen and gathering of Laves phase at grain boundary is the major reason for impact toughness degeneration. Bases on the research, it can be concluded that FB2 rotor steel keeps stable at 630℃ for up to 5000 h.