微量Ce对65Mn显微组织和力学性能的影响

发布时间：2018-09-04 16:33

【摘要】：随着航天航空、铁路、汽车、工程机械和电子等行业的快速发展，国内弹簧钢的需求量日益增多。虽然我国弹簧钢的生产工艺技术和产能已与国内消费量匹配，但中高级别弹簧钢的进口量仍居高不下，严重阻碍我国弹簧钢产业、钢铁企业品种结构和国内经济的可持续、健康发展。弹簧钢在特殊环境（如长期承受拉、压、弯、扭和冲击等载荷作用）下工作，不仅要具有稳定的化学成分、纯净的钢质，而且需具备微细的基体组织和优异的力学性能。根据目前国际、国内弹簧钢的生产实际和冶金理论前沿研究成果，本研究围绕“提高钢液洁净度、控制夹杂物性状与钢材组织、提高弹簧钢使用性能”等子课题，以应用广泛的65Mn钢为研究对象，进行较为系统的基础理论研究。为改善65Mn弹簧钢微观组织、夹杂物性状和力学性能，通过冶金热力学理论计算和实验室规模研究，在定量表征弹簧钢显微组织、夹杂物性状和力学性能等随微量Ce变化规律的基础上，分析、探讨精炼过程中Ce含量在0.65%C-0.35%Si-1.20%Mn系钢液中夹杂物变性机理、含Ce夹杂物颗粒性状对钢材组织和力学性能的作用机理。为稀土元素在高碳类弹簧钢中的应用提供基础实验数据，对于开拓钢铁材料细晶化方法、调整钢铁品种结构和开发低成本制造高强韧性钢材的生产工艺技术具有重大意义。通过实验研究、分析计算和归纳整理，本研究得出以下结论：（1）在[Ce]含量为0.0046%时，[O]、[S]含量分别降低至0.0017%，0.0012%的水平，，其脱[O]率为81.5%，脱[S]率为76.9%。（2）当[Ce]含量在0~0.0046%时，钢材中大尺寸、长条状的MnS夹杂物变为1~2μm的椭球形或类球形的MnS与Ce3S4的复合夹杂物，大尺寸、不规则的氧化物变为1~2μm的椭球形（或类球形）氧化物+Ce2O2S（Ce2O3）的复合夹杂物。（3）随[Ce]含量增加，钢中夹杂物密度增大；但＞2μm的夹杂物数目显著减少，可异质形核的1~2μm的夹杂物数目显著增大。（4）钢中加入微量Ce元素后，钢基体晶粒组织细化，珠光体片层间距变小。在[Ce]含量为0~0.0046%的范围内，珠光体晶粒尺寸由21.65μm减小至13.74μm，钢基体晶粒度增加1.34倍，珠光体片间距由264nm减小至116.77nm。（5）随[Ce]含量增加，65Mn钢的力学性能显著提高。当[Ce]含量为0.0046%时，σs=714.38MPa，σb=864.7MPa、δ=22.75%和Ak=37J，分别比不加Ce时提高4.00%、11.47%、68.52%和45.10%。
[Abstract]:With the rapid development of aerospace, railway, automobile, construction machinery and electronics, the domestic spring steel demand is increasing day by day. Although the production technology and production capacity of spring steel in China are in line with domestic consumption, the import of spring steel of middle and high grade still remains high, which seriously hinders the spring steel industry, the variety structure of iron and steel enterprises and the sustainability of domestic economy. Develop healthily. Spring steel works under special conditions (such as long term load such as tension, compression, bending, torsion and impact). It must not only have stable chemical composition, pure steel, but also fine matrix structure and excellent mechanical properties. According to the current international and domestic production practice of spring steel and the frontier research results of metallurgical theory, this study revolves around the sub-topics of "improving the cleanliness of molten steel, controlling the character of inclusions and the structure of steel, improving the performance of spring steel", etc. Taking the widely used 65Mn steel as the research object, the systematic basic theory research was carried out. In order to improve the microstructure, inclusions and mechanical properties of 65Mn spring steel, the microstructure of spring steel was quantitatively characterized by the theoretical calculation of metallurgical thermodynamics and the study of laboratory scale. Based on the analysis of the variation of inclusions and mechanical properties with trace amount of Ce, the mechanism of inclusion denaturation of Ce content in the molten steel of 0.65%C-0.35%Si-1.20%Mn series during refining and the mechanism of the effect of particle properties of inclusions containing Ce on the microstructure and mechanical properties of steel are discussed. The basic experimental data are provided for the application of rare earth elements in high-carbon spring steels. It is of great significance to develop the method of fine crystallization of iron and steel materials, to adjust the structure of steel varieties and to develop the production technology of high-strength and toughness steels at low cost. Through experimental research, analysis, calculation and induction, the following conclusions are obtained: (1) when [Ce] content is 0.0046, the [O] and [S] contents are reduced to 0.001717 ~ 0.0012%, respectively, with 81.5 [O] removal rate and 76.9% [S] removal rate. (2) when [Ce] content is between 0 and 0.0046, the content of [O] and [S] decrease to 0.0012%, respectively. (2) when the content of [Ce] is 0 ~ 0.0046, the content of [O] and [S] decrease to 0.0017% and 0.0012%, respectively. Large size, long MnS inclusions in steel become ellipsoidal or spherical MnS and Ce3S4 complex inclusions of 1 2 渭 m, large size, Irregular oxides become ellipsoidal (or spherical) oxide Ce2O2S (Ce2O3) complex inclusions with 1 ~ 2 渭 m. (3) the inclusion density increases with the increase of [Ce] content, but the number of inclusions > 2 渭 m decreases significantly. The number of inclusions at 1 ~ 2 渭 m of heterogeneous nucleation increases significantly. (4) the grain structure of the steel matrix is refined and the lamellar spacing of pearlite is reduced with the addition of a small amount of Ce element into the steel. The grain size of pearlite decreases from 21.65 渭 m to 13.74 渭 m, the grain size of steel matrix increases by 1.34 times, and the interlamellar spacing of pearlite decreases from 264nm to 116.77 nm in the range of 0 ~ 0.0046% of [Ce] content. (5) with the increase of [Ce] content, the mechanical properties of the steel increase significantly. When the content of [Ce] was 0.0046, the contents of 蟽 _ (sn) _ (714.38) MPA, 蟽 _ (B) _ (864.7) MPA, 未 ~ (22. 75%) and Ak=37J, were increased by 4.00% and 45.10%, respectively, compared with those without Ce (11.47%, 68.52% and 45.10%, respectively).
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG142.1

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