贝氏体钢轨钢组织控制的研究

发布时间：2018-02-01 21:06

  本文关键词： 贝氏体钢轨 再结晶 马氏体 贝氏体　出处：《内蒙古科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：作为国民经济发展的重要组成，铁路的发展对国家的工业化进程有着重要的作用。贝氏体钢轨与其他钢轨相比具有更优越的塑性和韧性，因而此类钢轨的研发与制备成为各国争相研究的重点。但是贝氏体钢轨在使用过程中仍会出现裂纹伤损等问题。因此在充分利用贝氏体钢轨优点的同时，解决此类问题是根据试验钢的CCT图，钢轨的终轧温度，钢轨精轧后的冷却速度等参数制定生产工艺，控制贝氏体钢轨钢的组织变化。从热轧过程中的再结晶行为、相变行为、冷却控制行为三方面着手，研究不同的轧后余热淬火工艺对贝氏体钢轨钢组织变化的影响。 本课题是以某钢厂贝氏体钢轨为研究对象主要从这两个方面进行分析，首先通过ZEISS金相显微镜和Zeiss SUPRA55型扫描电子显微镜对热处理后的组织进行观察与分析。另一方面采用Gleeble-1500D热模拟实验机研究了贝氏体钢轨在不同条件下热变形时的再结晶行为，多道次压缩实验分析了变形工艺参数对再结晶行为的影响。 结果表明：不同的冷却方式的热处理工艺对试验钢的组织有很大的影响。贝氏体钢轨油冷时，得到的组织为板条马氏体+残余奥氏体。缓慢冷却时，得到的组织为铁素体加粒状贝氏体。在盐浴炉350℃等温淬火15min，30min，60min时得到的是条片状贝氏体。在回火时得到的是无碳贝氏体加残余奥氏体。在热模拟单道次实验中贝氏体钢轨在1100℃时发生动态再结晶，900℃-1050℃只是发生了少量的动态回复，没有发生动态再结晶；在间隔时间为20s时，就可以辨别出900℃为未再结晶区，950℃为部分再结晶区，1000℃-1050℃为完全再结晶区。多道次压缩中，方案一二是在第一道次发生了动态再结晶，二三道次之间是应变积累的过程，第四道次是在910℃发生了18%的压下，有再结晶的趋势。压下量较大时就容易发生动态再结晶。方案三中前两道次是在完全再结晶区域内进行轧制，后两道次在未再结晶区域内进行轧制，避开部分再结晶区可以使晶粒更加细化。研究发现：贝氏体钢中存在冶金缺陷，存在明显的带状组织及MnS夹杂物；在冷却过程中易于产生马氏体组织，，这些是引起钢轨开裂的原因。
[Abstract]:As an important component of national economic development, the development of railway plays an important role in the industrialization process of the country. Bainite rail has better plasticity and toughness than other rails. Therefore, the research and preparation of this kind of rail has become the focus of many countries. However, the bainitic rail will still have crack damage in the process of use. Therefore, the advantages of bainite rail can be fully utilized at the same time. To solve this problem, the production process is determined according to the CCT diagram of the test steel, the final rolling temperature of the rail, and the cooling rate of the rail after finishing rolling. In order to control the microstructure of bainitic rail steel, the recrystallization behavior, transformation behavior and cooling control behavior during hot rolling are discussed. The effect of different afterheat quenching processes on the microstructure of bainitic rail steel was studied. In this paper, the bainitic rail in a steel plant is taken as the research object, which is mainly analyzed from these two aspects. First, through ZEISS metallographic microscope and Zeiss. The microstructure after heat treatment was observed and analyzed by SUPRA55 scanning electron microscope. On the other hand, the bainite rail under different conditions was studied by Gleeble-1500D thermal simulation machine. Recrystallization behavior during hot deformation. The effect of deformation parameters on recrystallization behavior was analyzed by multi-pass compression experiment. The results show that different cooling processes have great influence on the microstructure of the test steel. When the bainite rail oil is cooled, the microstructure obtained is lath martensite retained austenite. The microstructure obtained is ferrite with granular bainite and isothermal quenching at 350 鈩

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