Research on Remaining Life Evaluation Method of T92 Steel for Superheater Tube Based on Oxide Layer Growth
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TECHNICAL ARTICLE—PEER-REVIEWED
Research on Remaining Life Evaluation Method of T92 Steel for Superheater Tube Based on Oxide Layer Growth Jiansan Li . Haitong Wei . Zhou Yuan
Submitted: 29 October 2018 / in revised form: 9 May 2019 / Published online: 10 June 2019 ASM International 2019
Abstract T92 steel is widely used in high-temperature superheater of supercritical power station boiler, and the researches on its remaining life have always been the hot spot of scholars around the world. In this paper, based on the analysis of high-temperature creep rupture strength data, the optimum C value of Larson–Miller parameter formula for T92 steel is obtained by using isothermal extrapolation method. On this basis, combining the relationship between the thickness of the oxide layer and the operating time, the relationship between the thickness of the oxide layer and the temperature of the tube wall and the relationship between the thickness of the oxide layer and the stress of the tube wall, a new remaining life evaluation formula is deduced. Finally, based on the cumulative creep damage life evaluation method, the service life of superheater tube is divided into three stages, which provides a new reference for the service life evaluation of superheater tube of ultra-supercritical boiler. Keywords Larson–Miller parameter Superheater Oxide layer growth Remaining life evaluation Cumulative creep damage
Introduction Due to the large heat transfer resistance of the oxide layer, the heat exchange between the steam medium and the wall metal is blocked, which leads to the increase in the
J. Li H. Wei (&) Z. Yuan School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510641, Guangdong, People’s Republic of China e-mail: [email protected]
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temperature of the wall metal. Relevant calculations show that for every 0.025 mm oxide increase, the superheater wall temperature increases by about 1.67 C. At the same time, exfoliated oxide skin will block the steam flow and cause superheater tube over-temperature explosion. This has become the second major cause of boiler tube failure in the world [1]. T92 steel is widely used in high-temperature superheater of supercritical power station boiler. Therefore, it is of great significance to evaluate the remaining life of T92 steel for superheater tubes. Rolf Sandstro¨m et al. [2] combined the precipitation hardening model to derive the life assessment model for ductile fracture of austenitic heat-resistant steel. Purbolaksono et al. [3] found that the major contributor which results in the failure of the tube was interaction between the excessive scale formation on the inner surface and outer wall thinning due to coal-ash corrosion. Kapayeva et al. [4] presented the method that considers a combined effect of overheating and wall thinning. They used LMP method for creep evaluation, while adding the effect of wall thinning. The actual data for the thickness of tube wall and thickness of internal oxide layer were taken from measureme
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