微合金化对高碳钢成分偏析影响的实验室研究

以铬微合金化为基础,主要研究钒、铌、钛及其交互作用对高碳铸坯宏观组织、凝固偏析的影响,为微合金元素应用于高碳钢提供实验依据。实验表明,铌在加入量范围内对枝晶有强烈的细化作用,显著影响碳偏析,随铌量的增加则碳偏析减小;钒一元微合金化,钒、铌二元微合金化,钒、铌、钛三元微合金化,随钒量的增加则碳偏析明显减小;钛在加入量范围内对碳偏析影响不明显,但却能明显减轻锰的偏析;钒、铌、钛在不同程度上均可减轻锰、硅、硫的偏析。     

鞍钢钒、钛、铌微合金钢的应用与开发

对钒、钛、铌在钢中的微合金化作用作了全面阐述,并介绍了鞍钢在开发钒、钛、铌微合金钢方面所进行的工作及前景。     

鞍钢含钒低合金钢研制概况及今后发展设想

前言目前,世界各国钒、钛、铌微合金化钢发展很快,已成为低合金钢发展的一个重要途径。由于钒、钛、铌是我国富有的合金元素,我国从1959年就开始应用钒、钛、铌研制低合金钢新钢号,目前已取得了可喜的成果,有了一个良好的开端,今后应该加快发展速度。过去,低合金钢发展主要是靠锰、硅等固溶强化途径达到的。由于固溶强化的潜力有限,不得不提高碳的含量,因此恶     

钢中铌、钒、钛微合金化的主要作用

<正>微合金化理论被誉为20世纪物理冶金学领域所取得的最重要进展,极大地推动了微合金化钢的研究、生产与应用,钢中最常用的微合金化元素是铌、钒和钛等,其主要作用是细化晶粒与沉淀强化。钢中添加微合金铌元素可显著提高再结晶温度、细化晶粒,有利于提高钢的工艺性能及使用性能,但降低钢的高温塑性,恶化钢的焊接性能。     

薄板坯直轧微合金钢

对国外研究用薄板坯直接轧制生产钒一铌和钛一钒一铌系统微合金钢的情况做了介绍。这种实验模拟将厚度为50mm板坯轧制成7mm厚的钢带，使原始奥氏体晶粒度降至16～28μm，转变后的铁素体晶粒度达到4．5～5．9μm。在热轧过程中，立方形状的、颗粒度大（20～60nm）的钒一铌一碳氮化物沿原始奥氏体晶界析出，对钢基体起弥散强化作用的颗粒度不大于15nm的钒一铌碳氮化物在轧后模拟卷板过程中（500700℃）沉淀析出。钒一铌系统微合金钢中加入微量钛，在轧制过程中将在奥氏体中提前沉淀析出大颗粒（50～300nm）的钛一钒一铌碳氮化物，从而降低了可在卷板过程中沉淀析出的碳和氮量，同时减少了弥散强化钢基体的细颗粒钛一钒一铌碳氮化物的量，钢的屈服强度也随之下降。这次试验轧制获得了高屈服强度YS487～632MPa并有良好韧性和延伸性能匹配的微合金高强度钢板。论述了我国对美国NUCOR钢厂连铸薄板坯直轧的X65管线钢的质量分析情况，并同具有类似化学成份的传统热连轧管线钢做了比较。对美国用这种X70X80强度级管钢板制造卷曲（挠性）油管情况做了介绍。     

优化生产高强钢筋的工艺技术

<正>目前中国高强钢筋生产主要采用微合金化、超细晶粒和余热处理等3种工艺。微合金化钢筋主要是指通过在钢水中添加微量钒、铌、钛等合金元素,通过这些微量元素的碳化物、氮化物在钢中的沉淀析出,达到细化晶粒和沉淀析出强化的目的,从而改善钢筋性能。通过微合金化工艺生产的钢筋,具有强度高、焊接性能好、抗震性能强的特点,是产品综合性能较好的高强钢筋生产工艺,但由于需要添加钒、铌、钛等合金元素,相应会在一定程度增加生产成本。     

Nb-Ti-N微合金化生产HRB400E的实践

介绍了采用铌钛氮微合金化技术研制开发HRB400E钢筋的生产工艺和产品性能。实践证明,采用铌钛氮复合合金替代钒氮合金生产HRB400E钢筋,不仅其力学性能良好,而且具有低成本优势。     

充分利用我国MAE资源大力发展HSLA钢

概述微合金化元素钒、钛、铌在生产低合金高强度结构钢中的重要作用。这些元素虽加入量不多,但能明显改善钢材的多种性能(如提高其强度、硬度、韧性,相应减轻结构重量等),以适应制作各种不同用途构件的需要。结合我国攀钢、包钢丰富的钒、钛、铌资源,指出大力发展低合金高强度结构钢的有利条件、必要性与前景。     

A572Gr65高强钢板的生产实践与研究

根据成分及性能要求,采用中碳、高锰、添加少量的铌、钒、钛微合金化元素的低成本成分设计,通过强化冶炼控制、连铸操作、轧钢温度控制等措施,济钢厚板厂批量生产了A572Gr65高强钢板。检验结果表明,钢板强度、低温冲击韧性等性能指标优良,满足用户要求。     

铌钒复合微合金化400MPa级钢筋的研制与生产

介绍了采用铌钒复合微合金化技术研制开发HRB400钢筋的工艺和产品性能,分析了冶炼、轧制工艺及合金元素对钢筋性能的影响规律,并应用回归分析方法确定了铌、钒元素对性能影响的经验公式,对开发铌钒微合金钢具有很好的指导意义。实践证明,采用铌钒复合技术生产HRB400钢筋,不仅其机械性能良好,而且具有低成本优势。     

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The beneficial effects of the elements Nb, V, Ti and N in microalloyed forging steels was reviewed. Among these elements, the vanadium is the most effective and commonly used strengthening element for non-quenched and tempered steels due to its high solubility in the steels. The effects of grain refinement and precipitation strengthening can be achieved in non-quenched and tempered steels through micro-alloying elements Nb, V and Ti inhibiting the recrystallization of deformed austenites and grain growth, and enchancing strain induction precipitation during hot processing. Although the Nb, V and Ti are all strengthening elements, their strengthening effect and strengthening mechanism vary with the C and N content of these steels. Therefore, it would be the most effective way to improve strength and toughness of the ferrite-pearlite non-quenched and tempered steels through making use of the microalloying characteristics of the elements Nb, V, Ti and N and meanwhile applying the proper forging process.     

Effect of Ti and Ti+B additions on the creep properties of 1.25 Cr-0.5 Mo steels

An investigation of the effect of Ti additions with and without B on the mechanical properties of normalized and tempered 1.25 Cr-0.5 Mo Steels has been completed. Concentrations of impurities P, Sb and Sn were also varied to obtain insight into possible interactions between alloy additions and impurities. Results show that by a combined addition of Ti and B, appreciable improvements can be achieved in tensile strength, creep strength and rupture strength at 538°C, regardless of the nature and the amount of other impurity species present in the steel. Effects of Ti in the absence of B are complex. With P as the major impurity Ti additions reduced the tensile, creep and rupture strength. In presence of large amounts of P+Sb+Sn, however, improved strength levels are achieved due to Ti additions. Rupture ductilities are higher for all the steels containing Ti, independent of the presence or absence of B and the nature of the impurity species. The work reported here was conducted at the Westinghouse Research Laboratories, Pittsburgh, PA.     

铌、钒、钛在微合金钢中的作用

微合金化元素Nb、V、Ti在钢中的作用,主要表现在在热加工过程中抑制奥氏体的形变再结晶并阻止其晶粒的长大,并通过它们的碳氮化合物的应变诱导析出,对钢进行沉淀强化。这3个元素虽然都是通过细化晶粒和沉淀强化来提高强度,但它们在钢中的作用机理及强化程度并不同,Nb在钢中具有最强的晶粒细化强化效果,而V在钢中具有最强的沉淀强化效果,Ti则介于Nb和V两者之间。     

Laser Keyhole Welding of Dissimilar Ti-6Al-4V Titanium Alloy to AZ31B Magnesium Alloy

Laser keyhole welding of Ti-6Al-4V titanium alloy to AZ31B magnesium alloy was developed, and the correlations of process parameters, joint properties, and bonding mechanism were studied. The results show that the offset from the laser beam center on AZ31B side to the edge of the weld seam plays a big role in the joint properties by changing the power density irradiated at the Ti–Mg initial interface. The optimal range of the offset is 0.3 to 0.4mm in the present study. Some lamellar and granular Ti-rich mixtures are observed in the fusion zone, which is formed by intermixing melted Ti-6Al-4V with liquid AZ31B. The maximum ultimate tensile strength of the joints reaches 266 MPa. Furthermore, the fracture surface consists of scraggly remaining weld metal and smooth Ti surface. The higher the failure strength, the smaller the proportion of smooth Ti surface to whole interface is. Finally, the bonding mechanism of the interfacial layer is summarized by the morphologies and test results of fracture surfaces.     

Shear Strength of Reactive Resistance Welded Ti6Al4V Parts with the Use of Ni(V)/Al Multilayers

The Ti6Al4V/(Ni/Al)/Ti6Al4V joints were obtained through reactive resistance welding which takes advantage of electric current heating to initiate the rapid exothermic reaction of Ni(V)/Al multilayers and activate diffusion of elements across the Ni/Al-Ti6Al4V interfaces. Simulations of temperature distribution, carried out using COMSOL^® software, showed temperature gradient in the joint being a result of differences in resistivity of the Ti6Al4V alloy and the (Ni/Al)/Ti6Al4V interface. Shear tests revealed that extending duration of the process from 2 to 6 minutes helped to improve the shear strength from ~?240 to ~?335 MPa. The microstructure observations of the samples after those tests showed that de-cohesion of the joint occurred along the filler material/base material interface. A microcrack network characteristic for reacted Ni/Al foil with small ridges was found on the flat surfaces of fractured samples.     

Effect of Ti Addition on Yield Strength of Low-Mo Fire-Resistant Steel at Elevated Temperatures

Herein, a series of low-Mo (0.2 wt%) fire-resistant steels with varying amounts of Ti (0.008–0.13 wt%) are investigated to study the effects of Ti on yield strength at elevated temperatures. At room temperature (RT), precipitation strengthening by nanoscale TiC precipitates is found to be the major factor for the enhanced strength. The amount of TiC precipitates and both the yield and tensile strengths increase monotonically with the Ti content. However, the yield strength ratio (YS at 600 °C divided by YS at RT) of the steel with the highest Ti content (0.13 wt%) is significantly reduced to 0.6. In contrast, the YS ratio of the steels with Ti content in the range of 0.008–0.087 wt% remains above 0.7 and increases with Ti content. The difference between the steels lies in the B content and the resultant bainite volume fraction. The steel with 0.13 wt% Ti does not contain B and has only 4% bainite, whereas the other steels contain 20 ppm B and approximately 60% bainite. Hence, a microstructure with a sufficient fraction of bainite is required to ensure strength at elevated temperatures. The properties can be further improved by Ti precipitation strengthening.     

热变形对钒、氮合金钢77B性能的影响

 对未微合金化高碳钢77B和V、N微合金化高碳钢钢77B进行了620℃盐浴等温和920℃热变形后再进行620℃等温处理。结果表明：盐浴等温后微合金化钢比未微合金化钢77B强度显著增加,韧性略有下降, V（CN）的沉淀析出提高了组织的强度,但对珠光体团几乎无细化作用;经热变形等温处理后,两种试验钢的强度和韧性与盐浴等温相比,均得到了有效提高,加V、N的77B钢珠光体团发生了显著的细化,计算表明这与大量V(CN)形变诱导析出抑制奥氏体再结晶有关。     

Sintering behaviour and mechanical characterisation of Ti64/xTiN composites and bilayer components

Ceramic particle reinforcement can be used to improve the surface properties of Ti6Al4V (Ti64) alloy. Powder metallurgy route is a promising method to fabricate such reinforced Ti64 components. To assess the relevance of this technique, this work investigates the effect generated by the addition of TiN particles in Ti64 powder during free sintering. TiN reinforcement particles were randomly distributed in the Ti64 matrix with three different concentrations in two configurations: completely reinforced and unreinforced–reinforced bilayer. Dilatometry was used to obtain the shrinkage kinetics of samples at 1200, 1300 and 1400°C under inert atmosphere and to investigate the impact of reinforced particles on the sintering behaviour. The microstructure of sintered materials was shown to be lamellar in the unreinforced material and equiaxed in reinforced materials. Finally, the Vickers microhardness measurement showed the huge benefit of adding TiN particles to increase the mechanical strength of the Ti64 alloy.     

Effects of Coiling Temperature on Strength,Yield Ratio and Precipitation Behaviors of Hot Rolled High Strength Microalloyed Steel for Cold Forming

Various hot rolling schedules were applied to a Nb,V,Ti contained HSLA steel.Coiling temperature had crucial effects on not only yield strength,but also yield ratio and precipitation behavior.600Mpa yield strength is achieved when coiled at 450℃,which is 100Mpa higher than those coiled at 570℃.However,the low coiling temperature had adverse effect to increase yield ratio,which increased from 0.78 to 0.88 as coiling temperature dropped from 570℃ to 450℃.High resolution SEM analysis shows that sizes of Nb,V,Ti precipitates are affected by coiling temperature.Coarse (Nb,Ti)(C,N) precipitates up to 5μm are observed at higher coiling temperature and to decrease tensile strength,where high coiling temperature corresponds to low cooling rate.With strong cooling and coiling capacity of Shasteel’s 1450mm width hot rolling mill,these results indicate that strength and formability of the steel can be balanced when coiling temperature has been optimized.Alloying and microalloying costs can be reduced by efficiently utilizing the capacity of rolling mill.Alumina inclusions are found to act as nucleus for Nb,V,Ti precipitates,contributing to coarsening of precipitates.     

Effects of aluminum, silicon, and boron on the dissolution rate of nitrogen into molten iron

An isotope exchange technique is employed as a method for measuring the nitrogen dissolution rate into molten iron alloys, and the effects of Al, Si, and B addition have been studied at temperatures ranging from 1873 to 2023 K. The results are compared with those of other elements such as Ti, Zr, V, and Cr. The rate of nitrogen dissolution into molten iron is shown to decrease by the addition of Al, Si, and B due to a weaker affinity for nitrogen than Fe, which is contrary to the case of Ti, Zr, V, and Cr. Among them, B shows the largest effect when their contents are lower than 1 mass pct. A reasonable correlation of the rate constant with an interaction parameter between nitrogen and each element has been observed, which can be explained by the change in the activity of the vacant site on the surface of the molten alloy. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.