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Wang L.,University of Science and Technology Beijing | Yang S.,University of Science and Technology Beijing | Li J.,University of Science and Technology Beijing | Wu T.,University of Science and Technology Beijing | And 2 more authors.
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science

Industrial experiments were performed to improve the cleanliness of 95CrMo drill rod steel by slag refining. Higher steel cleanliness, lower corrosion, and small inclusions were obtained using the optimal slag composition (pctCaO/pctSiO2 = 3.7 to 4, pctCaO/pctAl2O3 = 6 to 8). Layered composite inclusions formed during vacuum decarburizing refining. CaS first precipitated around the spinel and subsequently formed inclusions in which solid CaS-CaO wrapped around the Al2O3-MgO-SiO2-CaO system as the modification and diffusion progressed. The thermodynamic equilibrium between slag and liquid 95CrMo steel at 1873 K (1600 °C) was also studied to understand the effect of slag composition on the oxygen content and absorption capacity for Al2O3. A mathematical model based on an investigation of slag viscosity and the interfacial tension between slag and inclusions was used to predict the size of critical inclusions for different slags. The evolution of typical inclusions is discussed in terms of the study of reactions between slag and steel. © 2015, The Minerals, Metals & Materials Society and ASM International. Source

Wang L.,University of Science and Technology Beijing | Li J.,University of Science and Technology Beijing | Xiong J.,Shougang guiyang special steel co. | Yang S.,University of Science and Technology Beijing | And 2 more authors.
Materials Science and Technology Conference and Exhibition 2014, MS and T 2014

This paper mainly studied the behavior of titanium in production process of 95CrMo hollow steel. Thermodynamics calculation of titanium oxide and TiN inclusions formation in 95CrMo was carried out in this paper, considering the relationship between ejTi, ejO, ejN and temperature respectively. Some second-order interaction parameters were searched and used in the calculation which was based on the different composition and temperature of molten steel at every step during the process of Consteel-LF-VD-CC. By the theoretical calculation, it's found that Ti2O3 generated stably from VD refining when the content of oxygen reached 12-15ppm. Ti3O5 may generate during tundish metallurgy. TiN started to precipitate when the temperature reached 1617-1663K which was in the range of solidus-liquidus zone (1613K-1735K) and the pure TiN inclusions size was large. To obtain fine TiN inclusions, the content of [N] needed to be controlled at least lower than 66ppm and it should be less than 43ppm as [Ti] was 0.006%. The thermodynamic calculation conclusions coincided with the detected results and it had guiding significance for the production of 95CrMo. Copyright © 2014 MS&T14®. Source

Yang C.-L.,Guiyang University | Liu-Qun,Guizhou University | Liu-Qun,Xian Jiaotong University | Ou M.-G.,Guizhou University | And 3 more authors.
Advanced Materials Research

Effect of subcritical quenching temperature on microstructure and mechanical properties of 22SiMnCrNi2Mo steel was studied. Conventional quenching was performed for tested steel to compare with subcritical quenching. The results show that morphology and number of ferrite change with the increase of subcritical quenching temperature. The shape of ferrite evolved from block to thin strip, and the number decreased. Ferrite and martensite formed strips spaced parallelly at subcritical quenching temperature 800℃.Steel presented good strength and ductility, while hardness is lower than conventional quenching. © (2014) Trans Tech Publications, Switzerland. Source

Zhang B.,Shougang guiyang special steel co. | Li G.,University of Science and Technology Beijing | Xiong J.,Shougang guiyang special steel co. | Yu W.,University of Science and Technology Beijing
Jinshu Rechuli/Heat Treatment of Metals

In order to improve the strength and ductility of high carbon steel 95CrMo and increase the service life of the hollow steel, the effects of controlled rolling and cooling on microstructure and mechanical properties were investigated. The results show that in case of air cooling, with the increasing of finish rolling temperature, the recrystallization of austenite is improved, the secondary cementite decreases and the strength and ductility increase. As a result, the experimental steel obtain a good combination of strength and ductility at the finish rolling temperature between 870 ℃ and 900 ℃. The spray cooling increases the amount of secondary cementite but decreases the interlamellar spacing of pearlite. The secondary cementite is decreased as the finish cooling temperature decreasing. Ductility of the experimental steel is preferable when the finish rolling temperature at 870 ℃ and the finish cooling temperature at 650 ℃. © 2016, Chinese Mechanical Engineering Society of Heat Treatment. All right reserved. Source

Liu Q.,Guizhou University | Ou M.,Guizhou University | Wang P.,Guizhou University | Xiong J.,Shougang guiyang special steel co. | Long Q.,Shougang guiyang special steel co.
Jinshu Rechuli/Heat Treatment of Metals

Effects of tempering temperature on microstructure and mechanical properties of 22SiMnCrNi2Mo steel were investigated by use of microstructure observation, tensile and impact test, hardness measurement, determination of retained austenite and impact fracture analysis. The results show that the microstructure of the steel tempered below 300°C is composed of tempered martensite+bainite+retained austenite, tempered at 400-500°C, is tempered troostite and tempered at 600°C, is tempered sorbitic. With tempering temperature increasing, the strength and hardness of 22SiMnCrNi2Mo steel reduce gradually, the retained austenite decreases gradually, the impact properties falls first and then rapidly increases. Temper brittleness appears at 400-500°C and impact absorbed energy reaches to maximum at 600°C. Comprehensive comparison, the strength, hardness, plasticity and toughness has a better match when tempered at 200°C. Source

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