【作者】 杨佳林；

【导师】 王社斌；

【作者基本信息】 太原理工大学 ， 冶金工程， 2015， 硕士

【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%。更多还原

【Abstract】 The demand of domestic spring steel largely increased with the rapiddevelopment of aerospace, automotive, railway, engineering machinery andelectronics industry. Although the technology level and production of domesticspring steel has been matched with domestic consumption, the import of highquality spring steel is still great, which largely hinder the sustainable andhealthy development of domestic spring steel industry, product structure ofenterprises and domestic economy. Due to its special working conditions suchas stretch, extrusion, bend, impact, the steel is necessary to have not only astable chemical composition and high steel cleanness, but also fine matrixorganization and excellent mechanical properties. According to the currentinternational and domestic process of spring steel and metallurgy theoryfrontier research results, wide application of65Mn steel is as the researchobject, the research around the project of raising molten steel cleanliness,controlling inclusions characteristic and organization, improving theperformance of spring steel, then taking a basis and systematic theory research.In order to control the microstructure, inclusions characteristic andmechanical of65Mn steel. By metallurgical thermodynamics calculation andscale research, on the basis of the influence of trace rare earth Ce on springsteel microstructure, inclusions characteristic and mechanical properties were studied. Quantitative research the change of microstructure, metamorphicinclusions and mechanical properties of0.65%C-0.35%Si-1.20%Mn steel withCe content were analyzed and discussed. The basic experiment data wasprovides for the application of rare earth elements in high carbon spring steel.It has a great significance for developing fine crystallization method of steelmaterials, adjusting the varieties of steel and low cost manufacturing hightoughness steel produce technology.The conclusions can be drawn as followings through experimentalresearch, analysis and calculation.(1) When the Ce content was0.0046%, the content of oxygen and sulfurwere reduced to0.0017%and0.0012%. The content of oxygen and sulfur werereduced by81.5%and76.9%, respectively.(2) When Ce content was within0~0.0046%, large size, long strips MnSinclusions were metamorphosed into1~2μm ellipsoid or spherical MnS andrare earth sulfide inclusions, irregular large size of oxide inclusions weremetamorphosed into1~2μm ellipsoid or spherical with Ce2O2S and Ce2O3composite inclusions.(3)With Ce content increasing, the total density of inclusions increased,the number of inclusions which diameter were more than2μm is greatlyreduced. The number of inclusions which diameter were1~2μm significantlyincreased, which could be used as heterogeneous nucleation of ferrite.(4) With the trace element Ce adding into steel, the matrix grainorganization largely refined, the spacing of pearlite lamellar is smaller. WithCe content was within0~0.0046%, the pearlites grain size decreased from21.65μm to13.74μm, matrix grain size increased1.34times, pearlite spacingdecreased from264nm to116.77nm.(5) The mechanical properties of steel were improved significantly withthe Ce content increasing. When the Ce content reched0.0046%, the specimens’ yield strength, tensile strength, elongation and impact toughnessreach to714.38Mpa,864.70Mpa,22.75%and37J, which respectivelyincreased by4.00%、11.47%、68.52%and45.10%compared with0%specimen.更多还原