630℃长期时效对FB2转子钢组织和力学性能的影响

Effect of long-term aging at 630 ℃ on structure and mechanical properties of FB2 rotor steel

通过冲击性能试验、硬度测试、扫描电镜和透射电镜观察等方法对630℃不同时效时间后的FB2转子钢样品进行组织观察和力学性能分析。结果表明,FB2转子钢在630℃时效过程中能够保持较好的高温稳定性; FB2转子钢的冲击断口表现为准解理脆性断裂;在时效前期,位错回复,冲击韧性提高;在时效中后期,由于析出相M_(23)C_6和Laves相在晶界位置聚集粗化,引起应力集中,冲击性能下降,时效5000 h后转子钢的冲击吸收能量为17 J;在长时时效过程中,FB2转子钢的强度下降趋势与析出相M_(23)C_6的尺寸变化趋势相一致,当析出相M_(23)C_6进入尺寸稳定期后FB2转子钢的硬度也基本稳定为253. 4 HBW(5/750),析出相M_(23)C_6是维持FB2转子钢服役性能的重要影响因素。

The effect of long-term aging at 630 ℃ on microstructure and mechanical properties of FB2 rotor steel was studied though impact property test,hardness test,SEM,TEM. The results shows that the FB2 rotor steel has a good high temperature stability after aging at 630 ℃.The impact fracture of FB2 rotor steel is quasi cleavage brittle fracture. The recovery of dislocation enhances the impact toughness at the early time. In the later stage of aging,the decrease of impact toughness is due to the aggregation and coarsening of M23C6 and Laves phases at the grain boundary and the final impact absorbed energy is 17 J after aging 5000 h. In the long-term aging process,the trend of the strength declining of FB2 rotor steel is in accordance with the trend of the precipitation phase M23C6. When the precipitated phase M23C6 enters the period of dimensional stability,the hardness of the FB2 rotor steel is also basically stable to keep at 253. 4 HBW( 5/750). The precipitated phase M23C6 is an important factor in maintaining the service performance of FB2 rotor steel.