Influence of RH vacuum treatment on spinel inclusions of high carbon chromium bearing steel
WANG Kun-peng1, WANG Ying2, XIE Wei3, XU Jian-fei1, CHEN Ting-jun3, JIANG Min4
1. Steelmaking Factory, Zenith Special Steel Co., Ltd., Changzhou 213011, Jiangsu, China; 2. Zenith Special Steel Co., Ltd., Changzhou 213011, Jiangsu, China; 3. Technology Center, Zenith Steel Group Co., Ltd., Changzhou 213011, Jiangsu, China; 4. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
Abstract：Spinel inclusions in steel not only deteriorate the castability of steel, but also may lead to macroscopic inclusions in finished products, and RH vacuum treatment is an important step to remove the inclusions in steel. The number, composition and types of inclusions of high carbon chromium bearing steel in RH vacuum treatment were studied, and the influence of vacuum pressure on the stability of spinel inclusions in high carbon chromium bearing steel was discussed through thermodynamic calculation. The experimental results show that when the vacuum pressure is 30 Pa, the total amount of liquid steel circulation reaches 200-400 t after 10 min of vacuum treatment, and all the spinel inclusions disappear. After 15 min of vacuum treatment, the total number of inclusions decreased from 480/(200 mm2) to 97/(200 mm2), and the total number of inclusions decreased by 80%. After vacuum treatment, the number of liquid inclusions in steel increases and inclusions become highly liquid. Compared with that before vacuum treatment, the number of liquid inclusions increases from 44/(200 mm2) to 71/(200 mm2), an increase of 61%, and the proportion of liquid inclusions increases from 9% to 73%. The spinel inclusions were single granular throughout the whole process, and no collision or aggregation was found. Thermodynamic calculation shows that the spinel inclusions in high carbon chromium bearing steel can be reduced and decomposed by C in the steel under vacuum condition. At 1 600 ℃, the critical decomposition pressure is 16 000-22 000 Pa. The higher the vacuum degree, the more conducive to the reduction and decomposition of spinel inclusions. When the vacuum pressure is 4 900 Pa, the total amount of liquid steel circulation reaches 511-1 022 t after 7-14 min of vacuum treatment, and the spinel inclusion disappears completely. When the vacuum degree is 20 400 Pa, spinel inclusions still exist even when the treatment time is extended to 40 min and the total circulating volume of liquid steel is increased to 2 360 t. Compared with the view that inclusions are physically removed, the reduction and decomposition of spinel inclusions by Cin steel under vacuum can better explain the spinel inclusions change characteristics during vacuum process.
王昆鹏, 王郢, 谢伟, 徐建飞, 陈廷军, 姜敏. RH真空处理对高碳铬轴承钢尖晶石夹杂物的影响[J]. 钢铁, 2023, 58(1): 108-115.
WANG Kun-peng, WANG Ying, XIE Wei, XU Jian-fei, CHEN Ting-jun, JIANG Min. Influence of RH vacuum treatment on spinel inclusions of high carbon chromium bearing steel[J]. Iron and Steel, 2023, 58(1): 108-115.
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2023, Vol. 58 
