A better understanding of droplet formation and dripping behavior would be useful in the efficient removal of impurity elements and nonmetallic inclusions from liquid metals. In the present work, we developed a transp...A better understanding of droplet formation and dripping behavior would be useful in the efficient removal of impurity elements and nonmetallic inclusions from liquid metals. In the present work, we developed a transparent experimental apparatus to study the mechanisms of droplet formation and the effects of filling ratio on droplet behavior during the electroslag remelting（ESR） process. A high-speed camera was used to clearly observe, at small time scales, the droplet formation and dripping phenomenon at the slag/metal interface during a stable ESR process. The results illustrate that a two-stage process for droplet formation and dripping occurs during the ESR process and that the droplet diameter exhibits a parabolic distribution with increasing filling ratio because of the different shape and thermal state of the electrode tip. This work also confirms that a relatively large filling ratio reduces electricity consumption and improves ingot quality.展开更多
Current-conductive mold was recently developed to extend electroslag remelting(ESR)functions to overcome some solidification defects by changing the current path.The macrostructures,microstructures,macrosegregation,an...Current-conductive mold was recently developed to extend electroslag remelting(ESR)functions to overcome some solidification defects by changing the current path.The macrostructures,microstructures,macrosegregation,and microsegregation of the Inconel 718 ingots produced by the custom laboratory-scale ESR furnace under different current paths(the classical ESR and the single power,and two circuits ESR process with current-conductive mold(ESR-STCCM))with the same power input were compared and investigated.The results indicate that when the ingot was produced during ESR and ESR-STCCM processes,at the same power input,the pool depth was 104 and 90 mm,respectively.A flatter and shallower molten pool was obtained during ESR-STCCM process.Moreover,compared with a classical ESR ingot,the cooling rate of the centerline of ESR-STCCM ingot was increased from 12.7 to 16.7 K min^(−1).The increased cooling rates caused by decreased melting rate and thinner slag skin reduced the growth angle of columnar crystal to the vertical axis and the secondary dendrite arm spacing.Furthermore,the macrosegregation and microsegregation of segregation elements for ESR-STCCM process were dramatically reduced compared with ESR process.The average volume fraction of Laves phase was reduced from 7.39%to 6.14%,and the segregation of Nb in Laves phase was significantly reduced.展开更多
The composition of a slag system has been shown to be particularly important and influential for the new technology of electroslag remelting withdrawal process.The oxidation of the GH984G alloy elements,in contact wit...The composition of a slag system has been shown to be particularly important and influential for the new technology of electroslag remelting withdrawal process.The oxidation of the GH984G alloy elements,in contact with different contents of CaF_(2)–CaO–Al_(2)O_(3)–MgO–TiO_(2)–SiO_(2)in various slag systems,has been investigated in the present study by performing slag–metal equilibrium experiments and ion and molecule coexistence theory analysis.The results show that CaF_(2)and MgO have only a minor effect on the oxidation rates of Al and Ti in the GH984G superalloys.However,it was found that SiO_(2)would intensify the oxidation degree of Al and Ti,and Al was found to become easier oxidized than Ti.Moreover,CaO was found to reduce the activity of SiO_(2)and,thereby,also the oxidation degree of Al and Ti.Also,TiO_(2)was found to reduce the oxidation rate of Ti and instead increase the oxidation rate of Al.Finally,the effect of Al_(2)O_(3)on the oxidation of Al and Ti was observed to be opposite to that of TiO_(2).The calculated results were found to be in good agreement with experimental measurements.Moreover,viscosity experiments showed that CaO would rapidly increase the viscosity of the slag at low temperatures,and that the viscosity of the slag would increase with an increase in SiO_(2)content.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 51274266)the Joint Research Fund of National Natural Science Foundation of China and Baosteel Group Corporation (No. U1360103)the Fundamental Research Funds for Central Universities of China (No. N150202003)
文摘A better understanding of droplet formation and dripping behavior would be useful in the efficient removal of impurity elements and nonmetallic inclusions from liquid metals. In the present work, we developed a transparent experimental apparatus to study the mechanisms of droplet formation and the effects of filling ratio on droplet behavior during the electroslag remelting（ESR） process. A high-speed camera was used to clearly observe, at small time scales, the droplet formation and dripping phenomenon at the slag/metal interface during a stable ESR process. The results illustrate that a two-stage process for droplet formation and dripping occurs during the ESR process and that the droplet diameter exhibits a parabolic distribution with increasing filling ratio because of the different shape and thermal state of the electrode tip. This work also confirms that a relatively large filling ratio reduces electricity consumption and improves ingot quality.
基金This project was supported by the National Natural Science Foundation of China(Grant Nos.51674070,51874085,and U1435205)Also,this project was supported by the Transformation Project of Major Scientific and Technological Achievements in Shenyang(Grant No.Z17-5-003)and the"Innovation&Entrepreneurship Talents”Introduction Plan of Jiangsu Province in 2018.
文摘Current-conductive mold was recently developed to extend electroslag remelting(ESR)functions to overcome some solidification defects by changing the current path.The macrostructures,microstructures,macrosegregation,and microsegregation of the Inconel 718 ingots produced by the custom laboratory-scale ESR furnace under different current paths(the classical ESR and the single power,and two circuits ESR process with current-conductive mold(ESR-STCCM))with the same power input were compared and investigated.The results indicate that when the ingot was produced during ESR and ESR-STCCM processes,at the same power input,the pool depth was 104 and 90 mm,respectively.A flatter and shallower molten pool was obtained during ESR-STCCM process.Moreover,compared with a classical ESR ingot,the cooling rate of the centerline of ESR-STCCM ingot was increased from 12.7 to 16.7 K min^(−1).The increased cooling rates caused by decreased melting rate and thinner slag skin reduced the growth angle of columnar crystal to the vertical axis and the secondary dendrite arm spacing.Furthermore,the macrosegregation and microsegregation of segregation elements for ESR-STCCM process were dramatically reduced compared with ESR process.The average volume fraction of Laves phase was reduced from 7.39%to 6.14%,and the segregation of Nb in Laves phase was significantly reduced.
基金supported by the National Key Research and Development Program(2017YFB0305201)the National Natural Science Foundation of China(Grant Nos.51674070,51874085)"Innovation&Entrepreneurship Talents"Introduction Plan of Jiangsu Province in 2018.
文摘The composition of a slag system has been shown to be particularly important and influential for the new technology of electroslag remelting withdrawal process.The oxidation of the GH984G alloy elements,in contact with different contents of CaF_(2)–CaO–Al_(2)O_(3)–MgO–TiO_(2)–SiO_(2)in various slag systems,has been investigated in the present study by performing slag–metal equilibrium experiments and ion and molecule coexistence theory analysis.The results show that CaF_(2)and MgO have only a minor effect on the oxidation rates of Al and Ti in the GH984G superalloys.However,it was found that SiO_(2)would intensify the oxidation degree of Al and Ti,and Al was found to become easier oxidized than Ti.Moreover,CaO was found to reduce the activity of SiO_(2)and,thereby,also the oxidation degree of Al and Ti.Also,TiO_(2)was found to reduce the oxidation rate of Ti and instead increase the oxidation rate of Al.Finally,the effect of Al_(2)O_(3)on the oxidation of Al and Ti was observed to be opposite to that of TiO_(2).The calculated results were found to be in good agreement with experimental measurements.Moreover,viscosity experiments showed that CaO would rapidly increase the viscosity of the slag at low temperatures,and that the viscosity of the slag would increase with an increase in SiO_(2)content.
