Super304H管材高温服役过程组织与性能的变化

Microstructure and Mechanical Properties of Domestic Super304H Tubes During High-temperature Services

通过室温拉伸、冲击试验、硬度测试、金相组织分析、扫描电镜及能谱分析等,对600℃超超临界锅炉用国产Super304H管材高温服役过程的微观组织和力学性能进行了试验分析.结果表明:与国产原始钢管相比,高温服役后国产Super304H管材的室温强度和硬度升高、塑性和韧性下降,焊接接头的强度、硬度、冲击韧性不断降低且明显低于同一服役时间的母材.服役30 000h以上后,管材的力学性能仍处于较高水平,基体组织稳定,晶粒未见长大,微观组织开始出现M23C6沿晶界呈链状分布的老化迹象.可见,国产Super304H管材组织状态良好,在目前600℃超超临界机组设计条件下可稳定运行,建议加强对国产Super304H管材焊接接头的金属监督.

The microstructure and mechanical properties of domestic Supre304H tubes used for 600℃ ultra-supercritical boilers during high-temperature services were investigated by room-temperature tensile test, impact test, hardness test, metallographic inspection, scanning electronic microscopy and energy spectrum analysis. Results show that the strength and hardness of domestic Supre304H tubes increase with the time during high-temperature services, while their plasticity and toughness decrease. The strength, hardness and impact toughness of domestic Super304H welded joints decrease with the time during high-temperature services, which are obviously lower than the properties of base metal at same service time. After more than 30 000 hours of service, the mechanical properties of domestic Super304H tubes are still in high level with stable matrix and uhchanged sizes of grains, but the microstructure indicates aging phenomenon in the form of chain-like precipitation of M23 C6 along grain boundary. In general, domestic Super304H tubes have good microstructure and mechanical properties, which are able to operate stably under the conditions designed for 600℃ ultra supercritical units. It is suggested to strengthen the supervision on the welded joints of domestic Super304H tubes.