Abstract: The study of P80 on-line solid solution process was tested by Gleeble 3800 thermal simulation testing machine， and the results showed that the open cooling temperature ranged from 870 ℃ to 930 ℃， the lower the temperature， and the higher the hardness， the higher the variance and the lower the hardness fluctuation after the on-line solid solution and aging. Under the premise of ensuring that obtaining single-phase structure and uniform hardness， the process parameters such as open cooling temperature and cooling speed were determined： the open cooling temperature was 860 - 880 ℃， cooling speed was 10 ℃/s， and the re-reddening temperature not greater than 400 ℃. Applying the above process parameters to P80 production practice， the results showed that the on-line solid solution P80 steel plate after 520 ℃ / 3 hours of aging treatment， the microstructure was transformed from bainite and martensitic to granular bainite and lath bainite， hardness was 40.1 HRC， which could meet the technical requirements， and could replace the off-line solid solution process.

Key words: P80 Steel, Plastic Mold Steel, On-line Solid Solution, Aging, Hardness

摘要： 采用Gleeble 3800热模拟试验机进行了P80在线固溶工艺试验研究，发现开冷温度在870 ℃～930 ℃范围内，温度越低，在线固溶再经过时效后，硬度越高，方差减少，硬度波动降低。在保证获得单相组织，且硬度均匀的前提下，确定了开冷温度与冷却速度等工艺参数：在线固溶工艺为开冷温度860～880 ℃、冷却速度10 ℃/s，返红温度≤400 ℃。利用上述工艺参数进行生产实践，发现在线固溶后的P80钢板经过520 ℃/3 h时效处理后，组织由贝氏体+马氏体转变为粒状贝氏体+板条贝氏体，硬度为40.1 HRC，满足技术要求，可以实现对离线固溶工艺的替代。

关键词: P80钢, 塑料模具钢, 在线固溶, 时效, 硬度