金属热处理 ›› 2021, Vol. 46 ›› Issue (2): 178-181.DOI: 10.13251/j.issn.0254-6051.2021.02.032

• 工艺研究 • 上一篇    下一篇

不同冷速对700 MPa级汽车大梁钢过冷奥氏体转变的影响

赵楠1, 薛峰1, 潘进1, 郭维超1, 李建朝2   

  1. 1.河钢集团钢研总院, 河北 石家庄 050000;
    2.河北工业职业技术学院, 河北 石家庄 050000
  • 收稿日期:2020-07-23 出版日期:2021-02-25 发布日期:2021-05-08
  • 通讯作者: 李建朝,副教授,E-mail:316043240@qq.com
  • 作者简介:赵楠(1991—),女,助理工程师,硕士,主要研究方向为金属材料的物理性能,E-mail:15122306691@163.com。

Effect of cooling rate on undercooling austenite transformation of 700 MPa automotive beam steel

Zhao Nan1, Xue Feng1, Pan Jin1, Guo Weichao1, Li Jianchao2   

  1. 1. Hesteel Group Technology Research Institute, Shijiazhuang Hebei 050000, China;
    2. Hebei College of Industry and Technology, Shijiazhuang Hebei 050000, China
  • Received:2020-07-23 Online:2021-02-25 Published:2021-05-08

摘要: 在DIL805L型淬火膨胀仪上测定了一种700 MPa级汽车大梁钢(700L)的连续冷却转变曲线(CCT曲线),结合金相-硬度法分析其相变规律、相变组织及影响因素。结果表明:试验钢的临界点Ac3=898 ℃,Ac1=772 ℃;当冷速小于0.5 ℃/s时,过冷奥氏体的转变产物为铁素体、珠光体和少量贝氏体;当冷速大于0.5 ℃/s时,珠光体消失;当冷速为5 ℃/s时,铁素体消失,转变产物全部为贝氏体;当冷速为10 ℃/s时,转变产物中出现少量马氏体组织,随着冷速增大,马氏体逐渐增多,贝氏体逐渐减少直至完全消失;随着冷速的提高,试验钢的硬度逐渐增大,当冷速为10 ℃/s时,硬度值有明显大幅度的增加。

关键词: 汽车大梁钢, 连续冷却转变曲线, 临界点, 显微组织, 硬度

Abstract: The continuous cooling transformation (CCT) curves of 700 MPa automotive beam steel 700L were determined by using DIL805L quenching dilatometer. Combined with metallography-hardness method, the phase transformation rules and microstructure as well as the influence factors were analyzed. The results show that the critical point of 700L steel is Ac3=898 ℃, Ac1=772 ℃. The transformation product of undercooling austenite is ferrite, pearlite and bainite when the cooling rate is less than 0.5 ℃/s, then pearlite disappears when the cooling rate is more than 0.5 ℃/s, ferrite disappears and the transformation product is all bainite when the cooling rate is 5 ℃/s. A few martensite appears in the transformation products when the cooling rate is 10 ℃/s, and with the increase of cooling rate, martensite increases and bainite decreases gradually until totally disappears. The hardness of the steel gradually increases with the increase of cooling rate, and increases significantly at 10 ℃/s.

Key words: automotive beam steel, continuous cooling transformation (CCT) curve, critical point, microstructure, hardness

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