高碳纳米珠光体钢轨钢组织与性能的研究

发布时间：2018-04-18 05:24

本文选题：珠光体 + 钢轨钢　；参考：《燕山大学》2015年硕士论文

【摘要】：高碳珠光体钢以其高强度、高耐磨性在钢轨中得到广泛应用。本文以八种高碳钢作为研究对象,采用Gleeble 3500热力模拟试验机对试验钢进行轧后欠速冷却模拟处理,最终得到珠光体组织。利用扫描电镜进行组织观察并统计珠光体片间距,应用透射电镜分析拉伸塑性变形机理,并采用三维原子探针设备分析合金元素在铁素体相与渗碳体相中的分布,研究了Al、Mn、Cr、Si对纳米珠光体的形成与性能的影响。研究结果表明,提高Al含量或降低Mn含量,珠光体片间距得到显著细化。在100 oC/min的冷却速度下,钢的珠光体片间距达到了80 nm左右,珠光体钢的抗拉强度达到了1670 MPa,延伸率达到了11.2%。在珠光体相变过程中,Al增加,Mn降低促进珠光体团的形核,同时Al增加,Mn降低会增大珠光体转变自由能,使得珠光体片间距得到细化。Al和Si为非碳化物形成元素,不溶于渗碳体,向铁素体相中偏聚,Mn和Cr为碳化物形成元素,向渗碳体相中偏聚,合金元素的配分过程减慢了珠光体长大的过程。珠光体组织形态与力学性能受冷却速度的影响,冷却速度较慢时,过冷度小,珠光体形核数量较少,珠光体组织片间距较为粗大,渗碳体片规则排列,硬度与强度较低;当冷速增大时,过冷度也随之增大,珠光体形核较多,珠光体片间距得到细化,渗碳体片层呈断续状,钢的硬度与强度升高。
[Abstract]:High carbon pearlite steel is widely used in rail because of its high strength and high wear resistance.In this paper, eight kinds of high carbon steel were used as the research object, and the pearlite microstructure was obtained by using Gleeble 3500 thermal simulator to simulate the undercooling of the tested steel after rolling.The microstructure of pearlite was observed by scanning electron microscope, the tensile plastic deformation mechanism was analyzed by transmission electron microscope, and the distribution of alloy elements in ferrite phase and cementite phase was analyzed by three-dimensional atomic probe equipment.The effect of Al _ (mn) _ (mn) Cr-Si on the formation and properties of nanocrystalline pearlite was studied.The results show that the interlamellar spacing of pearlite is significantly refined by increasing Al content or decreasing mn content.At the cooling rate of 100 oC/min, the distance between pearlite sheets reaches about 80 nm, the tensile strength of pearlite steel reaches 1670 MPA, and the elongation reaches 11.2%.In the process of pearlite transformation, the increase of Al and the decrease of mn promote the nucleation of pearlite, and the decrease of Al increases the free energy of pearlite transition, which makes the spacing of pearlite thin. Al and Si are non-carbide forming elements and insoluble in cementite.The segregation of mn and Cr in ferrite phase and carbides in cementite phase and the segregation of alloying elements in cementite phase slowed down the process of pearlite growth.The microstructure and mechanical properties of pearlite are affected by cooling rate. When cooling rate is slow, the undercooling degree is small, the number of pearlite nucleation is less, the spacing of pearlite tissue is coarse, the cementite slice is arranged regularly, and the hardness and strength are low.When the cooling rate increases, the degree of undercooling also increases, the pearlite nucleation is more, the spacing of pearlite is refined, the cementite lamellae is intermittent, and the hardness and strength of the steel increase.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.1

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