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采用SEM、EBSD和高温拉伸试验等方法研究了长期时效对一种隔热油管钢显微组织和力学性能的影响。结果表明:无论在350℃还是400℃长期时效,在时效2000 h时,显微组织中的马氏体特征仍很明显,时效5000 h后,马氏体板条特征基本消失。随时效时间的延长,碳化物颗粒尺寸略有增加。抗拉强度Rm、屈服强度Rt0.5,在长期时效2000 h前不仅不降低,反而略有增加,长期时效5000 h后明显降低。N80-Q钢的断后伸长率A,在350℃长期时效时,随时间的延长变化不大,在400℃长期时效时有略微降低的趋势。
The effects of long-term aging on the microstructure and mechanical properties of an insulated tubing steel were studied by means of SEM, EBSD and high temperature tensile tests. The results show that the martensite features in the microstructure are still obvious at the aging time of 2000 h, no matter at the long-term aging of 350 ℃ or 400 ℃. The martensite lath disappears after 5000 h aging. With the extension of aging time, the size of carbide particles increased slightly. Tensile strength Rm, yield strength Rt0.5, long-term aging in 2000 h before not only does not reduce, but slightly increased, long-term aging significantly reduced after 5000 h. The elongation at break (A) of N80-Q steel changed little with the extension of time at 350 ℃ for long-term aging, and slightly decreased at 400 ℃ for long-term aging.