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Study on Ultrasonic Non-destructive Evaluation for the Microstructure of Ultra-Supercritical (USC) Steel

Author: ZhouHongWei
Tutor: LiPing
School: Dalian University of Technology
Course: Material non-destructive testing and evaluation
Keywords: Ultrasonic nondestructive evaluation Ultra-supercritical steel Aging Creep Microstructure
CLC: TG142.11
Type: Master's thesis
Year: 2011
Downloads: 38
Quote: 1
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Abstract


Are typical Super304H steel and HR3C steel ultra-supercritical boiler superheater and reheater steel. Both steel long-term service in the harsh environment of high temperature and pressure and alternating loads, which cause material changes in the organizational structure so as to affect the mechanical properties of the material, which will lead to reduced service life of such equipment. There is an urgent need for materials worker organizations in its service nondestructive evaluation, thereby ensuring the safe operation of equipment, extending its life. The use of non-destructive method to study ultra-supercritical stainless steel, to understand the process of transformation of the microstructure in the service process, thereby ensuring the good mechanical properties of the service components, becoming the focus of the study of materials scholars. Paper uses ultrasound flooding focusing method get the aging time Super304H steel time domain waveform. Using the speed of sound different aging time Super304H steel organization the nondestructive identification, combined with the means to carry out the analysis of the differences in the organization of the metallurgical microscope, electron probe. The study found that the ultrasonic longitudinal wave velocity is reduced with the increase of the aging treatment time. The differences in these laws and microstructure analysis found corresponding relation to the application of ultrasound parameters the Super304H steel aging organizations identify feasible. The article also applied velocity method to evaluate Super304H steel circumferential and axial microstructure results found no differences in the speed of sound in the two directions, also corresponding to the consistency of this microstructure in both directions. In this paper, wavelet band energy nondestructive identification of HR3C steel under different stress creep organization, First focusing method using ultrasound flooding obtained the creep stress HR3C steel bottom echo signal, and a bottom echo feature extraction. Found: 3.91 ~ 7.81MHz frequency range, with the improvement of the creep stress, wavelet energy is gradually reduced, thereby effectively to the tissue under HR3C steel creep stress identification; binding microstructure of this phenomenon. were analyzed and found HR3C steel at 750 ℃, respectively, in 70MPa, 80MPa, 90MPa creep stress insulation microstructure after 500 hours there are differences, i.e. with the increase of stress, the organization of large grains and precipitates occupied The ratio gradually increases, so that is enhanced scattering attenuation effects of the ultrasonic waves, also manifested as wavelet frequency energy reduction. The experimental results are consistent with the theoretical analysis. This study also measured using velocity method HR3C steel creep tissue elasticity modulus, the study found that as the creep stress is the increase in elastic modulus that is a generally downward trend, the creep stress is a modulus of elasticity of the sample 90MPa after treatment decline compared to the other two stress too obvious, reason needs further analysis.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Steel > Microstructure and properties of steel > Steels
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