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Tian-Liang Fu,Xiang-Tao Deng,Guo-Huai Liu,Zhao-Dong Wang,Guo-Dong Wang 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.11
The quenching temperature drop curve for Q345B steel plate with 84 mm and 170 mm thickness was tested to analyze the distributing regularities and influencing factors of cooling speed for ultra-thick steel plate during the jet impinging and quenching process. The influences for temperature drop, temperature gradient and cooling speed were analyzed under the conditions of 60~100 m3/h water amount, 0.4~1.0 MPa water pressure, transient switching of quenching mode and the distribution of heat exchanger. Threedimensional heat anti transfer model, surface heat transfer coefficient model and thermal physical parameter model were built up by finite element and optimization. The results showed that the deviation of calculated and measured values was less than 4% for temperature drop curve model. The cooling speed of vertical section for 84 mm-thick steel plate was approximately proportional to surface heat transfer coefficient. The influence of surface heat transfer to cooling speed became weak when the thickness was increased. The influences of temperature effect when switching different quenching modes and temperature gradient of vertical section to cooling speed were stronger. The minimum value of cooling speed was about 1.0~1.8oC/s, between H/6 and H/3 region. These data provide the key information for increasing the cooling speed and uniformity.
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Interaction between Barium Oxide and Carbon Film in BaO/C/Mo System under High Temperature
Yue Hui Lu,Xue Mei Wu,Lan Jian Zhuge,Xiang Huai Liu 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Carbon ¯lm, used as the coating of the Mo grid in pulsed-controlled grid traveling wave tubes, can eectively suppress electron emission from the Mo grid contaminated by the emission material of the hot cathode, i.e. BaO or Ba, so that the lifetime of the tubes can be prolonged signi¯cantly but the reasons for it have not been well understood. To study the eect of it on the BaO/Mo system under high temperature, carbon ¯lms were prepared on Mo substrate at room temperature by a dual-ion-beam sputtering deposition system, and post-annealing was conducted to know their microstructure under high temperature. In our experiments, BaO layers were coated on Mo and carbon-coated Mo substrates by the chemical method to compare with each other, and the prepared BaO/Mo and BaO/C/Mo samples were annealed at two dierent temperatures of 973 K and 1223 K in order to investigate the interaction between barium oxide and carbon ¯lm under high temperature. The results show that the BaO/C/Mo changes into C/Mo after the exhaustion of BaO at 1223 K, nevertheless, This does not happen at 973 K. In this paper, the mechanism whereby the addition of carbon ¯lm can suppress the grid emission under its operating condi-tion is discussed according to the experimental results and the calculation of the reaction free energy.
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