Precipitation behavior of P550 steel for non-magnetic drill collars was investigated by microstructure characterization as well as thermodynamic calculation. The results demonstrate that the main precipitate formed at 650–900 °C was cellular Cr₂N, and its precipitation depended heavily on the aging temperature. The most sensitive precipitation temperature of cellular Cr₂N was 750 °C. At 750 °C, the cellular Cr₂N exhibited fast-slow precipitation kinetics with the aging time prolonging. The initial precipitation of cellular Cr₂N was governed by the short-range intergranular diffusion of Cr. During long-term aging, its growth was controlled by the long-range bulk diffusion of Cr. In addition, cellular Cr₂N induced the precipitation of σ phase ahead of the cell after long period of aging. Increasing the nitrogen content resulted in the increment of both the nucleation site and the driving force for the cellular Cr₂N, which jointly promoted its precipitation.

通过显微组织表征和热力学计算研究了P550钢在非磁性钻collar中的析出行为。结果表明，在650–900°C时形成的主要沉淀物是蜂窝状Cr ₂ N，其沉淀物在很大程度上取决于时效温度。Cr ₂ N胞中最敏感的沉淀温度为750°C。在750°C时，随着时间的延长，细胞中的Cr ₂ N表现出快速的沉淀动力学。细胞Cr ₂ N的初始沉淀是由Cr的短程晶间扩散控制的。在长期时效过程中，其生长受Cr的远距离本体扩散控制。另外，细胞Cr ₂长时间老化后，N诱导了σ相在细胞之前的沉淀。氮含量的增加导致细胞Cr ₂ N形核位点和驱动力的增加，共同促进了其沉淀。