Open AccessFormation Causes and Preventive Measures of the Scale of 600MW Unit High Temperature Reheater Tubes
Author(s) -
Zhenliang Li,
Ke Huang,
Xi Wang
Publication year - 2019
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/677/3/032044
Subject(s) - spall , materials science , metallurgy , austenite , microstructure , oxide , boiler (water heating) , austenitic stainless steel , ultimate tensile strength , indentation hardness , tensile testing , composite material , corrosion , waste management , engineering
It was found obvious accumulation of scale at the elbow of a high temperature reheaters, by measuring scale accumulation of boiler high temperature reheater SA213-TP347H steel pipe of a power plant. By hardness test, tensile test, optical microscopy and spectroscopy analysis of the pipe sample, it was showed that hardness test results meet DL / T 438-2009 standard requirements; mechanical properties test results meet GB 5310-2008 standards. The microstructure of cross-sectional sample is austenite. EDS analysis result shows that the scale mainly composed of Fe, Cr, Ni oxide. There is obvious stratification in the scale of austenitic stainless steel, the inner layer scale has higher levels of Cr and Ni, Fe and O content is relatively low, which has antioxidant. Fe and O content of the outer layer of skin is relatively high, low Cr and Ni content, leading to its outer oxide does not have the ability of anti-oxidation. There are gathered holes between the inner and outer layers. Temperature change process will produce stress, resulting in oxidation of the outer layer of skin off. Finally, a few precautions to prevent the scale spalling are proposed.