金属热处理 ›› 2022, Vol. 47 ›› Issue (8): 34-39.DOI: 10.13251/j.issn.0254-6051.2022.08.005

• 材料研究 • 上一篇    下一篇

Mn-Cr-Mo系贝氏体轨钢连续冷却转变的原位观察

张迪1, 包喜荣1, 陈林1, 王晓东1, 赵文倩2, 宋冉1   

  1. 1.内蒙古科技大学 材料与冶金学院(稀土学院), 内蒙古 包头 014010;
    2.北京北冶功能材料有限公司 材料研究所, 北京 100192
  • 收稿日期:2022-03-04 修回日期:2022-06-20 出版日期:2022-08-25 发布日期:2022-09-19
  • 通讯作者: 包喜荣,教授,博士, E-mail:bxrwty@126.com
  • 作者简介:张 迪(1994—),男,硕士研究生,主要研究方向为贝氏体钢轨的热处理工艺优化及综合性能,E-mail:1782130440@qq.com。
  • 基金资助:
    国家自然科学基金(51461034);内蒙古自治区自然科学基金(2019MS05046,2019LH05013)

In situ observation of continuous cooling transformation of Mn-Cr-Mo bainite rail steel

Zhang Di1, Bao Xirong1, Chen Lin1, Wang Xiaodong1, Zhao Wenqian2, Song Ran1   

  1. 1. School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou Inner Mongolia 014010, China;
    2. Materials Research Institute, Beijing Beiye Functional Materials Company Limited, Beijing 100192, China
  • Received:2022-03-04 Revised:2022-06-20 Online:2022-08-25 Published:2022-09-19

摘要: 采用原位观察法研究不同奥氏体化温度1250、950 ℃及不同相变冷速0.8、1.5 ℃/s对Mn-Cr-Mo系贝氏体轨钢连续冷却转变的影响。结果表明,贝氏体板条形核长大在晶界处以有序同时或不同时生长、晶粒内部无序不同时生长的特点;晶界、晶粒内形核的贝氏体板条都以近似相等的恒定速率生长,不同位向板条遇晶界或预先形成的贝氏体板条停止生长而形成“交叉”板条组织。板条生长速率主要受相变驱动力控制,而奥氏体晶粒大小及强度是影响最终贝氏体板条长度的主要因素。降低奥氏体化温度、加快相变冷速,可加快板条生长并缩短相变时间,减少贝氏体转变量,并获得细小均匀稳定的贝氏体板条组织。Mn-Cr-Mo系贝氏体轨钢中贝氏体板条平均生长速率为4.053 μm/s,支持贝氏体扩散控制相变机制。

关键词: 原位观察, 奥氏体化温度, 冷却速度, 生长速率

Abstract: Effects of austenitizing temperature of 1250 ℃, 950 ℃ and cooling rate of 0.8 ℃/s, 1.5 ℃/s on continuous cooling transformation of Mn-Cr-Mo bainite rail steel were studied by in-situ observation. The results show that the bainite plates nucleate and grow up orderly on grain boundaries simultaneously or non-simultaneously, but disorderly non-simultaneously in grain. The nucleated bainite plates on grain boundaries and in the grains grow at approximately the same constant rate, and the plates with different orientation stop growing when colliding grain boundaries or the preformed bainite plates and form a "cross-like" bainite structure. The growth rate of the plates is mainly controlled by the driving force of phase transformation, and the size and strength of austenite are the main factors affecting the length of the final bainite plates. It is concluded that lowering the austenitizing temperature and accelerating the cooling rate of bainite transformation can speed up the growth of the plates, shorten the transformation time and reduce the amount of transformed bainite. As a result, a fine, uniform and stable bainite plate structure can be obtained. Further, the average growth rate of bainite plates in Mn-Cr-Mo bainite rail steel is calculated to be 4.053 μm/s, which supports the diffusion-controlled phase transformation mechanism.

Key words: in situ observation, austenitizing temperature, cooling rate, growth rate

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