The oxide exfoliation is one of the main problems that cause the explosion of superheater or reheater, which threaten the safety of power plant units, but there is no direct test method of the particle concentration of the scales in high temperature steam. Based on the study of ferromagnetic and optical characteristics of scales, the technology and equipment were developed for on-line measurement based on magnetic sensitivity and granularity behavior. Through numerical simulation and dynamic simulation experiments of scale movement under high temperature and high pressure steam, calculating method of the particle concertation of scales in the main steam or reheated steam pipeline was retrieved by local sampling concentration.

The delivery state of austenitic heat resistant steel boiler tubes is paramagnetic, such as TP304H, TP347H and S30432, the material state, however, appears obviously magnetic after long-time high-temperature service. Vibrating Sample Magnetometer (VSM) has been employed to test the magnetism difference after high-temperature service, and XRD, SEM, TEM, SAED and EDS has been adopted to observe and analyze their microstructure, phase structure and composition. The research results show that compared with the delivery state, the lath α´-Martensite and sometimes the lamellar ε-Martensite will occur in areas adjacent to grain boundaries due to martensite transformation in the microstructure of austenitic heat resistant steel boiler tube after high temperature service. There are high density dislocations tangled together in the substructure of α´-Martensite, and lamellar stacking faults arrayed orderly by a large number of dislocations in the substructure of ε-Martensite. The magnetism of α´-Martensite, its internal stress and carbides is the reason why the austenitic heat resistant steel boiler tubes appear obviously magnetic after high temperature service, and the α´-Martensite plays a major role.