A numerical simulation method is used to predict the depth distribution of martensite and hardness in the case layer of carburizing (carbonitriding)-quenched 20CrMnTi steel. Microstructure and mechanical properties of 20CrMnTi steel after carbonitriding and subsequent induction hardening is investigated. The results show that the microstructure after nitriding and subsequent induction hardening is main tempered martensite and nitrides; after carbonitriding and subsequent induction hardening is main martensite and a small amount nitrides. The simulation results were a little different from experimental results. According to the results, the factors of reducing the accuracy of the numerical simulation method have been discussed.
By the ultrasonic preventing and removing fouling test-bed, study on the effect of velocity on ultrasonic propagation characteristics by experiment. Keep the liquid temperature, ultrasonic emission frequencies and power constant. In the heat exchange tube, measure the ultrasonic sound intensity at the inlet and outlet of the pipeline, when the liquid velocity changed. The results show that, at normal temperature (25°C), the input power and ultrasonic frequency keeping constant, the ultrasonic sound intensity decreased gradually firstly and then increased with the change of the liquid velocity changed from 0m/s to 2m/s. The ultrasonic sound intensity attain minimum when the liquid velocity about 0.45m/s.
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