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Martensite Microstructure of Austenitic Stainless Steel after High Temperature Stress Aging

Time:2016-10-19 15:48:22

ASMESA213S30432 steel by the Japanese Sumitomo Metal Co., Ltd. and Mitsubishi Heavy Industries in the TP304H on the basis of Mn plus copper, niobium and nitrogen obtained an oxidation and strength grade higher austenitic heat-resistant stainless steel, is the manufacture of ultra-supercritical boiler Superheater and reheater tube of choice material, and a large number of applications in the USC unit. In this work, the type, shape, distribution and quantity of martensite transformation of S30432 austenitic stainless steel after high temperature stress aging were investigated. The influence of martensite structure on magnetic properties of S30432 steel was analyzed.

 
The chemical composition (mass fraction,%) of the sample is: C0.09, Si0.27, Mn0.82, S0.0005, P0 (the standard is Φ44.5mm × 9mm) made by standard heat treatment. .009, Cr18.57, Ni8.60, N0.07, Nb0.38, Al0.013, B0.014, Cu2.78. The aging samples were a high-temperature superheater tube of a 1000MW boiler with aging time of 1.9 × 104h. The temperature and pressure of the aging tube steam were 650 ℃ and 51MPa, respectively.
 
The samples were analyzed by X - ray diffraction (XRD). The martensite phase was observed by X - ray diffraction (XRD). The results of SEM and JEM2010 transmission electron microscopy (TEM) (TEM). The microstructural analysis was carried out with EDS (TEM) and the phase structure analysis was carried out by EBSD (Aztec EDS + EBSD). The phase structure of the martensite phase was analyzed by electron diffraction analysis (TEM) And quantitative, with VersaLab type integrated physical measurement system (VSM) for the measurement of magnetic parameters, high temperature aging samples of carbide extraction using electrolysis method.
 
The results show:
 
(1) α-martensite occurs in the austenitic stainless steel S30432 after aging at 650 ℃ / 51MPa / 19000 hours, and is located near the grain boundary in the poor chromium region. The substructure is high-density dislocation.
 
(2) The depletion of chromium element in S30432 high temperature stress aging samples induced martensitic transformation.
 
(3) S30432 high temperature stress aging samples of carbide with a magnetic, 0.234emu / g (external magnetic field strength 1000Oe); martensite and carbide co-induced high temperature aging S30432 magnetic, of which the former accounted for the main part.
stainless steel 304 coil,coil stainless steel 201,alloy stainless 316 steel
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