1Mn18Cr18N护环钢高温低周疲劳特性研究

High Temperature Low-cycle Fatigue Properties of 1Mn18Cr18N Austenitic Stainless Steel Applied on Retaining Ring

为了研究超超临界汽轮发电机护环钢1Mn18Cr18N在工作温度100℃的低周疲劳特性,本文采用应变控制法对其进行温度为100℃下的低周疲劳试验,并对试验结果进行分析讨论。拟合出循环应力应变曲线和应变寿命曲线,得到了护环钢1Mn18Cr18N在100℃时的低周疲劳特性参数,包括Rambeg-Osgood参数和Manson-Coffin公式,推导出该材料的转变寿命NT。结果表明:1Mn18Cr18N护环钢低周疲劳特性表现为循环软化,循环软化程度随应变幅值的增加而增大,软化速率随应力下降幅值增加而增大;1Mn18Cr18N护环钢的过渡寿命为2177周次,小于2177周次时,塑性应变高于弹性应变成为影响疲劳断裂的主要因素,大于2177周次时,弹性应变主导疲劳断裂。

1Mn18Cr18N is one typical austenitic stainless steel which is generally applied on the retaining ring of ultra-supercritical turbo-generator at working temperature of 100℃. In this paper, strain control method has been utilized to investigate the low-cycle fatigue properties of 1Mn18Cr18N at testing temperature of 100℃. Furthermore, the low-cycle fatigue characters of 1Mnl8Crl8N have also been discussed to provide technical references for designing and application of retaining rings. Low-cycle fatigue characteristic parameters including Rambeg- Osgood parameter and Manson-CotTm equation of 1Mn18Cr18N at 100℃ and material transform life Nr have been derived from the cyclic stress strain curves and strain life curves. The results indicate that the low-cycle fatigue of 1Mn18Cr18N material is characterized by cyclic softening, which was strengthened as the strain amplitude increased. The transition fatigue life of 1Mn18Cr18N retaining ring material is about 2177 cycles. Plastic strain tends to be the main parameter which affects the fatigue fracture of retaining ring when Nr is less than 2177 cycles, otherwise, elastic strain would play the leading role.