低碳微合金化含硼冷镦钢的冲击性能

通过对不同B含量的低碳硼钢和Nb、V微合金化低碳硼钢的冲击实验,研究了B含量及Nb、V微合金化对低碳硼钢冲击性能的影响. 结果表明:0.0006%～0.0015%的B将提高热处理状态钢的冲击韧性,B质量分数超过0.003%将降低钢的冲击韧性. Nb、V复合微合金化同时加入适量Al可显著提高热处理状态低碳硼钢的冲击韧性. Ti质量分数超过0.03%对低碳硼钢和微合金硼钢的冲击性能不利.     

(V,Nb)C溶解规律及其对奥氏体晶粒粗化的影响

应用物理化学相分析法定量测定了V,Nb 复合微合金化钢中V,Nb 复合碳化物在不同奥氏体化温度下的溶解量,以及V,Nb 在溶解过程中的相互影响。通过对奥氏体晶粒的直接腐蚀显示,测出了不同 V,Nb 含量对奥氏体晶粒粗化的影响,为 V,Nb 复合的微合金化钢在轧制时奥氏体化温度的合理选择提供了依据。同时,得出了使奥氏体晶粒细化的 V,Nb 含量和 V,Nb 最佳化学配比。     

一种核级316LN钢的相图计算与微合金化设计

用热力学方法计算了一种核级316LN钢及其在Nb、V微合金化条件下的伪二元平衡相图,研究了不同温度下钢的平衡相组成。结果表明,316LN钢中的主要析出相为Cr2N、M23C6、和相,Nb微合金化316LN钢中会形成含C的MX,有望提高材料的力学性能和耐晶间应力腐蚀性能,V微合金化316LN钢中会形成VN,但对稳定C的作用不大。     

Nb微合金化对低合金高强钢耐海水腐蚀性能的影响

利用室内模拟海水加速腐蚀试验及电化学分析,研究了Nb微合金化对Cu-Cr-Ni-P系低合金高强钢耐海水腐蚀性能的影响。结果表明,含Nb钢与不含Nb钢组织均由铁素体和珠光体构成,但Nb微合金化后钢中珠光体组织减少且晶粒细化明显,其在模拟海水介质中的平均腐蚀速率与不含Nb钢相比,降低了约12%,阳极腐蚀电流密度也有所降低。由此可见,在Cu-Cr-Ni-P系低合金高强钢中加入Nb元素有助于提高其耐海水腐蚀性能。     

Nb微合金化对大规格GCr15钢球化组织的影响

为了提高大规格GCr15钢球化退火组织合格率,进行不同Nb含量微合金化试验,采用ICAP6300等离子光谱分析仪及蔡司光学显微镜进行检验分析。结果表明:采用0.022%Nb微合金化,网状碳化物明显改善,球化退火效果提高,球化退火后获得了碳化物颗粒细小均匀的球化组织。GCr15钢冶炼过程中采用0.022%Nb微合金化,可提高球化退火组织合格率。     

铌微合金化对高Al冷轧TRIP钢组织与力学性能的影响

采用二段式盐浴热处理、金相显微镜(OM)、扫描电镜(SEM)、X射线衍射(XRD)和拉伸实验等方法,研究了添加0.025%微合金元素Nb对高Al(1.5%Al)冷轧相变诱导塑性钢(TRIP)组织与性能的影响规律. 结果表明:Nb微合金化使高Al冷轧TRIP钢在连续退火后组织得到细化,残余奥氏体含量及其碳含量比无Nb钢均有所升高. 含Nb钢在370 ℃和400 ℃等温后抗拉强度均大于650 MPa,且总伸长率达到35%,具有优异的综合力学性能. Nb微合金化,将本实验所研究的高Al冷轧TRIP钢的最优贝氏体区等温温度由400 ℃左右扩大到370～400 ℃,提高了生产的工艺稳定性.     

Mn-V-Nb重轨钢组织与性能的研究

以研制特级耐磨重轨钢为目的,在 U 74普碳耐磨重轨钢化学成分的基础上,加入微量V,Nb 元素并适当提高 C,Mn 元素的含量,设计并冶炼出 Mn-V-Nb 重轨钢。研究了该钢的组织及性能。结果表明:Mn-V-Nb 钢的常规力学性能达到了特级耐磨轨钢的要求。在实验室条件下,抗磨损性能和抗接触疲劳性能分别较 U74 钢提高3.7 倍和 4.6倍。提高的原因在于珠光体片间距的细化及 V,Nb 元素的沉淀强化作用。     

14MnNbq钢中Nb的作用

14MnNbq钢是为满足我国制造大跨度桥梁而开发的新型微合金化用钢。文中通过对14MnNbq钢板进行模拟控轧控冷试验，利用光学显微镜、透射电子显微镜、电化学萃取分析等检测分析技术和手段，分析了Nb及其碳氮化物在控制轧制和控制冷却各阶段的作用及其对钢材微观组织和性能的影响；分析指出，为了充分发挥Nb的作用，在精轧阶段未再结晶区应尽可能增加变形量，轧后冷速以及终冷温度可按现场条件进行适当控制，以保证Nb（CN）的充分析出，证明Nb具有较强的细晶强化作用和中等的沉淀强化作用。     

铌对65Cr4W3Mo2V钢显微组织及机械性能的影响

通过改变65Cr4W3Mo2V钢中Nb的含量,研究了Nb对不同温度淬火回火钢的显微组织和机械性能的影响.结果表明:当加热温度超过1100℃时,随加热温度升高和Nb含量的增加,Nb对晶粒的细化作用越明显;随着Nb含量的增加,钢的机械性能提高,当Nb含量为0.25%(质量百分数,下同)时,作用最明显.     

纤维双相钢的组织形成及对性能的影响

研究了纤维双相15Mn2Nb钢组织的形成及对性能的影响.结果表明,纤维双相钢具有优异的强塑性匹配,是一种天然的复合材料.其纤维组织的获取主要取决于合金化和热处理工艺规程,而合金元素Nb阻碍铁素体再结晶是形成纤维组织的关键.     

稀土轨钢过冷奥氏体转变机理及CCT曲线的预测方法

通过金相观察、扫描电镜分析、能谱分析、电化学萃取定量相分析等方法,研究了稀土和铌元素对稀土微合金重轨钢热处理性能的影响机理．结果表明,铌影响碳的扩散是铌提高轨钢淬透性的主要机理;稀土通过在晶界偏聚和影响碳的扩散而对过冷奥氏体产生一定的影响;而稀土轨钢淬透性提高的主要原因在于硅锰含量的增加．在机理分析的基础上,建立了该钢种过冷奥氏体等温转变和连续冷却转变曲线的预测方法．     

Hot deformation mechanism and microstructure evolution of an ultra-high nitrogen austenitic steel containing Nb and V

The flow curves of an ultra-high nitrogen austenitic steel containing niobium (Nb) and vanadium (V) were obtained by hot compression deformation at temperatures ranging from 1000℃ to 1200℃ and strain rates ranging from 0.001 s-1 to 10 s-1. The mechanical behavior during hot deformation was discussed on the basis of flow curves and hot processing maps. The microstructures were analyzed via scanning electron microscopy and electron backscatter diffraction. The relationship between deformation conditions and grain size after dynamic recrystallization was obtained. The results show that the flow stress and peak strain both increase with decreasing temperature and increasing strain rate. The hot deformation activation energy is approximately 631 kJ/mol, and a hot deformation equation is proposed. (Nb,V)N precipitates with either round, square, or irregular shapes are observed at the grain boundaries and in the matrix after deformation. According to the discussion, the hot working should be processed in the temperature range of 1050℃ to 1150℃ and in the strain rate range of 0.01 to 1 s-1.     

铜丝除钒精制四氯化钛废弃物中铌钽资源研究

铜丝除钒精制四氯化钛所排废弃物中含有丰富的钒、铜、钛等资源。进一步研究结果表明,该废弃物中铌、钽含量也很高。其中铌含量可达到2.66%,钽含量可达到0.29%,远高于铌钽的工业品位,是一种新型的铌钽资源。该废弃物中的铌钽应为钛铁矿伴生稀有元素,在四氯化钛制备过程中,经过钛铁矿选冶、富钛料高温氯化、粗四氯化钛精制等工艺过程富集而形成。     

Effects of Nb on the microstructure and mechanical properties of 38MnB5 steel

The effects of the microalloying element niobium (Nb) on the microstructure and mechanical properties of the hot stamped steel 38MnB5 were investigated. The impact of Nb addition on the microstructure was studied through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The experimental results indicated that the microstructures of the steel containing Nb were finer than those of the steel without Nb. Moreover, Nb mainly presented as a second-phase particle in 38MnB5 steel, and the particles included Nb carbonitrides. In addition, the tensile strength and elongation of the hot rolled and hot stamped steels were also measured, and they demonstrated that the appropriate addition of Nb was beneficial to the mechanical properties of 38MnB5. Under the same conditions, the tensile strength of 38MnB5Nb was higher than that of 38MnB5, which increased from 2011 to 2179 MPa. The yield strength also increased from 1316 to 1476 MPa, and the elongation increased from 5.92% to 6.64%. Overall, Nb had a positive effect on the performance of the hot stamped steel.     

Ti和Nb对18Cr-2Mo铁素体不锈钢韧脆转变温度的影响

通过真空冶炼、锻造、热轧和退火试验制备出18Cr-2Mo铁素体不锈钢,结合其冲击试验和透射电子显微镜、扫描电子显微镜及电子背散射衍射等分析结果探讨了Ti和Nb微合金化对其韧脆转变温度的影响.结果表明：在C和N含量较低的条件下,添加微量元素Ti和Nb可以显著降低18Cr 2Mo铁素体不锈钢的韧脆转变温度（降低约40 °C）,并改变热轧后的织构类型而形成(001)和(111)复合织构;通过合适的退火工艺处理,可进一步提高其冲击韧性;在热轧过程中,产生细小弥散的Ti（N, C）和Nb（C, N）相是复合织构形成的主要原因.     

中碳铸钢微合金化的研究

中碳铸钢微合金化的研究董寅生苏华钦梅建平刘传博（东南大学机械工程系，南京２１００１８）（东南大学材料科学与工程系，南京２１００１８）钢的微合金化，就是利用合金成分的微小调整，在工艺性能不受影响或稍有改善、生产成本不显著增加的条件下，使钢的性能得到较...     

Mo和变质处理对高钒高速钢耐磨性的影响

为讨论Mo元素和变质处理对高钒高速钢耐磨性的影响,制备高钒钼高速钢.通过金相法、X射线衍射和摩擦磨损实验对高钒高速钢的显微组织、物相组成和耐磨性能进行分析.结果表明：热处理后的未变质高钒高速钢、变质高钒高速钢和变质高钒钼高速钢的组织主要由马氏体、Fe3C和V2C组成;Mo元素和变质处理使高钒高速钢的碳化物明显细化,大量颗粒状碳化物弥散分布;变质高钒钼高速钢在室温下干磨损60 min,失重量为0.0119 g.该研究为高钒高速钢的发展提供了理论依据.     

Effect of Nb and V on the continuous cooling transformation of undercooled austenite in Cr–Mo–V steel for brake discs

The increasing speed of trains necessitates the development of brake-disc materials that meet more stringent requirements. Therefore, Nb and V have been added to Cr–Mo–V steel to improve its thermal fatigue performance when used in brake discs. In this paper, the influences of Nb and V on the static continuous cooling transformation (CCT) behaviors of undercooled austenite were studied. The microstructures, hardness, and dislocation densities at different cooling rates and with the addition of different alloying elements were also investigated. The results show that the transformation products of ferrite, granular bainite, lower bainite, and martensite form under different cooling conditions. With increasing Nb and V contents, the CCT curves are shifted to the left, ferrite and bainite transformations are promoted, and the critical cooling rate of total martensite formation is increased. The added V mainly forms V-rich M₈C₇ precipitates and reduces the dissolved C content; therefore, the A_c1, A_c3, and M_s-point temperatures increase. Moreover, the stability of retained austenite is also reduced; its content therefore decreases. Compared with V, the effect of added Nb is weaker because of its smaller content. However, the addition of Nb improves the hardness at lower cooling rates because of the precipitation of fine NbC particles and refining of the microstructure.     

Electronic properties and stabilities of methoxy-substituted Lindqvist polyoxometalates [Nb2W4019CH3]3- by DFT

The electronic properties and stabilities of five [Nb2W4O18OCH3]3-isomers have been investigated using a density functional theory method.The results show that the isomer with the methoxy group occupying a bridging position between two tungsten atoms(two tungsten atoms in the plane that contains two niobium atoms) in the [Nb2W4O18OCH3]3-framework is the most stable isomer in acetonitrile.The stability of the one-electron-reduced isomers changes little.The most stable one-electron-reduced isomer has the methoxy group occupying a bridging position between niobium atoms in the [Nb2W4O18OCH3]4-framework.The M-Ob(M = Nb,W;b denotes bridging) bond lengths in anions in which the metal atoms are connected by a methoxy group are longer than those in [Nb2W4O19]4-.The highest occupied molecular orbitals(HOMO) in [Nb2W4O19]4-mainly delocalize over the bridging oxygen atoms of two niobium atoms and two tungsten atoms located in the equatorial plane,and the bridging oxygen atoms on the axial surface.The lowest unoccupied molecular orbitals(LUMO) of [Nb2W4O19]4-are mainly concentrated on the tungsten atoms and antibonding oxygen atoms.Methoxy substitution modifies the electronic properties of the [Nb2W4O18OCH3]3-isomers.The HOMOs in the five isomers formally delocalize over the bridging oxygen atoms,which are distant from the surface containing the methoxy group and four metal atoms.The LUMOs delocalize over the d-shells of the four metal atoms that are close to the methoxy group,and the p-orbitals of oxygen.One-electron reduction occurred at the tungsten atoms,not the niobium atoms.