Heat Treatment of Metals ›› 2023, Vol. 48 ›› Issue (7): 84-90.DOI: 10.13251/j.issn.0254-6051.2023.07.015

• PROCESS RESEARCH • Previous Articles     Next Articles

Heat treatment of high performance rolled steel balls for large ball mills

Zhang Laichao1, Jin Yunxue1, Zhu Xuwei1, Wang Bingsheng2, Jia Boshan2   

  1. 1. School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang Jiangsu 212000, China;
    2. Shandong Zhaojin Grinding Media Co., Ltd., Zhaoyuan Shandong 265400, China
  • Received:2023-01-06 Revised:2023-05-26 Online:2023-07-25 Published:2023-09-04

Abstract: The influence of heating temperature, quenching temperature and tempering process on the microstructure and properties of B3 steel balls during the production process were studied, and the impact resistance test was carried out on the trial steel balls. The results show that at 980-1080 ℃ heating temperature, the quenched structure of the B3 steel is martensite+retained austenite, and when the heating temperature reaches 1080 ℃, the martensite structure size exceeds 20 μm, and the hardness and impact properties of the steel balls are reduced. Under the same heating conditions, as the quenching temperature increases, the content of retained austenite in the steel ball decreases, and the internal lamellar martensite of the steel ball gradually increases. For quenching temperature of 750-780 ℃, lamellar martensite + lath martensite mixture appears in the steel ball, and both the hardness and the impact properties are the best. After cooling and low-temperature tempering treatment, the microstructure of the steel ball is tempered martensite, with almost no hardness difference from the surface to the core, while the impact properties are substantially improved compared to that of the untempered. The most suitable heat treatment process for large diameter ?125 mm rolled steel balls is: heating temperature of 980-1030 ℃, quenching temperature of 750-780 ℃, after the surface of the steel ball cooled to 50 ℃ then low temperature tempering treatment. The surface of the steel ball is still in good condition after a 9 m high, 29 000 times ball drop test, which meets the requirements of large ball mills.

Key words: B3 steel balls, heat treatment, microstructure, properties

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