Investigation on evolution of inclusions in bearing steel during secondary refining
WANG Kun-peng1, WANG Ying2, XU Jian-fei1, CHEN Ting-jun1, XIE Wei1, JIANG Min3
1. Technology Center, Zenith Steel Group Co., Ltd., Changzhou 213011, Jiangsu, China; 2. Zenith Special Steel Co., Ltd., Changzhou 213011, Jiangsu, China; 3. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
Abstract:Composition, type and quantity of inclusions in bearing steel during LF refining and RH vacuum treatment were studied. The experimental results were analyzed and discussed in combination with thermodynamic calculation and interface parameters between inclusions and liquid steel. The inclusion analysis results showed that the deoxidization product Al2O3 disappeared after 25 min refining, and the inclusions in steel were mainly pure spinel, spinel containing small amount of CaO, CaO·2Al2O3 and CaO·Al2O3. Pure spinel, spinel containing small amount of CaO, CaO·2Al2O3 and CaO·Al2O3 were still the main inclusions in steel after 65 min refining to the end of LF refining. After RH vacuum treatment for 25 min, the total number of inclusions in steel was reduced by 75% compared with that after LF refining. The removal efficiency of pure spinel and spinel containing small amount of CaO inclusions was 99.5% and 93.2%, respectively, and that of CaO·2Al2O3 inclusion was 67%. The inclusions after RH treatment were mainly liquid calcium aluminate CaO·Al2O3 and 12CaO·7Al2O3. The size of spinel inclusions in the refining process was concentrated below 10 μm, and the inclusions above 20 μm were mainly calcium aluminates in the liquid phase, which had appeared in the early stage of LF refining. Solid inclusions pure spinel, spinel containing small amount of CaO and CaO·2Al2O3 whose contact angle with molten steel was greater than 90° were easy to remove in RH vacuum treatment, while liquid inclusions CaO·Al2O3 and 12CaO·7Al2O3 whose contact angle with molten steel was less than 90° were not easy to remove. Therefore, controlling the inclusions into solid inclusions after LF refining was beneficial to the high efficient removal of inclusions in RH vacuum treatment. The thermodynamic calculation results show that when the w(T[O])is 0.001 0% and w([Mg]) in steel exceeds 0.000 18%, the deoxidization product Al2O3 cannot be stable in thermodynamics. It is difficult to obtain solid Al2O3 inclusions under the condition of Al deoxidation and high basicity slag refining. To obtain fully solid spinel or high melting point calcium aluminate inclusions, w([Ca]) in steel should be controlled below 0.000 1%。When w([Ca]) in steel exceeds 0.000 2%, it will achieve the thermodynamic conditions for formation of liquid inclusions.
王昆鹏, 王郢, 徐建飞, 陈廷军, 谢伟, 姜敏. 轴承钢二次精炼过程夹杂物演变规律[J]. 钢铁, 2022, 57(6): 42-49.
WANG Kun-peng, WANG Ying, XU Jian-fei, CHEN Ting-jun, XIE Wei, JIANG Min. Investigation on evolution of inclusions in bearing steel during secondary refining[J]. Iron and Steel, 2022, 57(6): 42-49.
[1] Sato K, Takasu I,Unigame Y. Development of evaluation method for nonmetallic inclusions in steel through 15MHz ultrasonic test[J]. Sanyo Technical Report, 2006, 13(1): 25. [2] 王坤, 胡锋, 周雯, 等. 轴承钢研究现状及发展趋势[J]. 中国冶金, 2020, 30(9): 119.(WANG Kun, HU Feng, ZHOU Wen, et al. Research status and development trend of bearing steel[J]. China Metallurgy, 2020, 30(9): 119.) [3] Sato Y, Masuda T, Kawakami K, et al. Recent improvements in cleanliness in high carbon chromium bearing steel[J]. ISIJ International, 1996, 36 (s): S82. [4] 冯路路, 吴开明, 乔文玮, 等. 轴承钢珠光体球化的研究现状及发展趋势[J]. 中国冶金, 2020, 30(9): 110. (FENG Lu-lu, WU Kai-ming, QIAO Wen-wei,et al. Research status and developing tendency of bearing steel spheroidization of pearlite[J]. China Metallurgy, 2020, 30(9): 110.) [5] 李明,王新成,段加恒,等. 轴承钢中D类夹杂物的形成与控制[J]. 工程科学学报,2018, 40 (增刊1): 31. (LI Ming, WANG Xin-cheng, DUAN Jia-heng, et al. Formation and controlling of type-D inclusions in bearing steel[J]. Chinese Journal of Engineering,2018, 40 (s1): 31.) [6] 姜敏,王昆鹏,侯泽旺,等. 低氧特殊钢中Ds类夹杂物生成机理[J]. 工程科学学报,2016, 38(6): 780. (JIANG Min, WANG Kun-peng, HOU Ze-wang, et al. Formation mechanism of oversized Ds-type inclusions in low oxygen special steel[J]. Chinese Journal of Engineering, 2016, 38(6):780.) [7] 朱雷敏, 李莉娟, 罗坤坤, 等. PMO对GCr15轴承钢连铸坯中MnS夹杂物的影响[J]. 中国冶金, 2021, 31(12): 32. (ZHU Lei-min, LI Li-juan, LUO Kun-kun,et al. Effect of PMO on MnS inclusions in continuous casting billet of GCr15 bearing steel[J]. China Metallurgy, 2021, 31(12): 32.) [8] 徐迎铁,陈兆平,杨宝权. 轴承钢Ds类大颗粒夹杂物研究[J]. 炼钢,2016, 32(4): 49.(XU Ying-tie, CHEN Zhao-ping, YANG Bao-quan. Study of large size Ds type inclusions in bearing steel[J]. Steelmaking, 2016, 32(4): 49.) [9] Nagao M, Hiraoka K, Unigame Y. Influence of nonmetallic inclusion size on rolling contact fatigue life in bearing steel[J]. Sanyo Technical Report, 2005, 12(1): 38. [10] 史智越,徐海峰,许达,等. 冶金工艺对GCr15高周旋转弯曲疲劳性能的影响[J]. 钢铁,2018, 53(11): 85.(SHI Zhi-yue, XU Hai-feng, XU Da, et al. Effects of metallurgical craftwork on high bending fatigue performance of GCr15 steel during high cycle rotation[J]. Iron and Steel, 2018, 53(11):85.) [11] Frank L A. Castability-From alumina to spinels[J]. Iron and Steelmaker, 1999, 26(4): 33. [12] 徐林红, 罗海文. 广义帕累托分布在轴承钢夹杂物评价方面的应用[J]. 中国冶金, 2021, 31(6): 19. (XU Lin-hong, LUO Hai-wen. Application of generalized Pareto Distribution in evaluation of inclusions in bearing steels[J]. China Metallurgy, 2021, 31(6): 19.) [13] Verma N, Pistorius P C, Fruehan R J, et al. Calcium modification of spinel inclusions in aluminum-killed steel: Reaction steps[J]. Metallurgical and Materials Transactions B, 2012, 43(8): 830. [14] Ohta H, Kimura S, Mimura T, et al. Behavior of CaO containing inclusions during ladle refining of ultraclean bearing steel[J]. Kobe Steel Engineering Reports, 2011, 61(1): 98. [15] Piva S P T, Pistorius P C. Ferrosilicon-based calcium treatment of aluminum-killed and silicomanganese-killed steels[J]. Metallurgical and Materials Transactions B, 2021, 52(1): 6. [16] 刘浏,范建文,王品,等. 轴承钢精炼中大型夹杂物来源的示踪[J]. 钢铁,2017, 52(9): 34. (LIU Liu, FAN Jian-wen, WANG Pin, et al. Generation mechanism of large inclusions during bearing steels refining process by tracer method[J]. Iron and Steel,2017, 52(9): 34.) [17] 刘浏. 高品质特殊钢关键生产技术[J]. 钢铁, 2018, 53(4): 1. (LIU Liu. Key production-technology for high-quality special steels[J]. Iron and Steel,2018, 53(4): 1.) [18] 杨光维,初仁生,王新华,等. X70管线钢RH真空脱气过程夹杂物的去除行为[J]. 钢铁,2014, 49(1): 34. (YANG Guang-wei, CHU Ren-sheng, WANG Xin-hua, et al. Removal behavior of inclusion during RH vacuum treatment of X70 pipeline steel[J]. Iron and Steel,2014, 49(1): 34.) [19] Matsuno H, Kikuchi Y. The origin of MgO type inclusion in high carbon steel[J]. Tetsu-to-Hagane, 2002, 88(1): 48. [20] Matsumoto T, Watanabe Y, Yamauchi T. Recent development to decrease spinel-type inclusions by modification of slag composition at ladle furnace[C]//AISTech Proceedings. Philadelphia: Association for Iron and Steel Technology, 2018: 1273. [21] Liu C Y, Gao X, Ueda S, et al. Change in composition of inclusions through the reaction between Al-killed steel and the slag of CaO and MgO saturation[J]. ISIJ International, 2019, 59 (2): 268. [22] Liu C Y, Gao X, Kim S J, et al. Dissolution behavior of Mg from MgO-C refractory in Al-killed molten steel[J]. ISIJ International, 2018, 58 (3): 488. [23] Cramb A W, Jimbo I. Calculation of the interfacial properties of liquid steel-slag systems[J]. Steel Research International, 1989, 60(3/4), 157. [24] Shinozaki N, Echida N, Mukai K. Wettability of Al2O3-MgO, ZrO2-CaO, Al2O3-CaO substrates with molten iron[J]. Tetsu-to-Hagane, 1994, 80(10), 748.