Aging behavior of 60Si2MnA spring steel shims for steam turbine in nuclear power plant

doi:10.13251/j.issn.0254-6051.2020.10.045

Abstract

Abstract: The 60Si2MnA spring shims locating at the bottom of the roots of steam turbine blades subject to various aging effects such as potential corrosion, fatigue, and stress relaxation during service.Thus the aging effects caused by corrosion, wear and fatigue during service were comprehensively analyzed for the spring shims at roots of the last blade and the secondary blade in the low-pressure rotors in a nuclear power plant, and the aging behavior and service life of the shims were studied.The results show that the surface of the spring shims after service for 10 years has wearing traces formed by fretting wear, however, no obvious corrosion products or morphology have been found,which implies that the corrosion effect has a limited impact on the service life of the spring shims in the course of long service. Besides,certain differences exist between the disassembled spring shim and the original state because the material shows obvious strengthening and hardening characteristics during the initial cycles.Therefore,it should be explicited by the power plant that the installation instructions for new shims are not applicable for the installed ones.Moreover, the used spring shim after service for 10 years is estimated conservatively to serve for at least another 5 years based on the practical operating state, in consequence, the existing maintenance and replacement cycle can be extended to save the overhaul period and economic cost.

Key words: 60Si2MnA steel, spring shim, corrosion, fatigue, service life evaluation

CLC Number:

TG142.41

Jia Wenqing, Liu Siwei, Yuan Shuai, Xu Yingjun, Jia Kaili, Chen Mingya, Lai Yunting. Aging behavior of 60Si2MnA spring steel shims for steam turbine in nuclear power plant[J]. Heat Treatment of Metals, 2020, 45(10): 236-240.

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