An evaluation of vanadium oxycarbide as ladle addition to molten steels

The present paper deals with a process involving carbothermic reduction of vanadium trioxide to produce vanadium oxycarbide. The vanadium, oxygen and carbon constituents of the oxide-carbon reaction product of the present work satisfy the empirical formula VO_(0.67-0.44)C_(0.20-0.70). The paper also presents results of additions of the various grades of vanadium oxycarbide to steel melts. Results of additions have been compared with those obtained with vanadium carbide and ferro-vanadium additions. Such studies have pointed towards the suitability of VO_(0.52-0.46)C_(0.23-0.37) for introducing negligible amounts of additional carbon into steel melts. An attempt has also been made on the electroextraction of vanadium using vanadium oxycarbide as soluble anode.     

莫来石和氧化铝对高锰高铝钢用铬质引流砂烧结的影响

为了提升高锰高铝钢的自动开浇率,将莫来石和氧化铝等颗粒加入铬质引流砂中,研究揭示了高锰高铝钢对铬质引流砂烧结行为的影响规律.研究发现,铬质引流砂添加莫来石后,莫来石会熔解并与铬铁矿砂反应,从而生成SiO2-Al2O3-FeO-MgO系液相.无钢液作用下,提高引流砂中Al2O3含量有利于铬质引流砂的烧结,但超过一定范围反...     

Carbonization of steel by molten pig iron in the ladle

Soviet Ministry of Ferrous Metallurgy. Dneprodzerzhinsk Metallurgical Combine. Translated from Metallurg, No. 4, p. 26, April, 1989.     

钢包耐火材料与钢液反应的研究现状

随着国家工业的快速发展,对高品质钢的需求增大,侵蚀的耐火材料作为钢中外来夹杂物的主要来源受到广泛关注.基于此,阐述了耐火材料与钢液的反应机制、不同耐火材料与钢液的相互作用以及对钢液质量造成的影响.耐火材料会向钢中溶解并与钢中成分发生反应,之后形成界面层,当界面层是高熔点物质时,会阻碍耐火材料的溶解扩散,当界面层是低熔点...     

Structure of continuously cooled low-carbon vanadium steels

The structures of four 0.15 pct carbon steels containing vanadium, nitrogen, and aluminum separately and together were studied systematically, with the help of transmission electron microscopy, by cooling suitable steels at four different rates ranging from 120 °C/min to 3.6 °C/ min from temperatures giving a common austenite grain size of 35 μm. Except for the steel containing only vanadium and that containing only aluminum and nitrogen cooled at the fastest rate used, the observed microstructures were all essentially mixtures of polygonal ferrite and expected amounts for pearlite. For all the steels studied, except the one containing aluminum and nitrogen, it was found that general precipitation was more common than interphase precipitation, although the extent of the latter increased at lower cooling rates. Moreover, in some cases, both general and interphase precipitation were present in the same area. The presence of aluminum was observed to enhance the formation of interphase precipitates at all cooling rates, and the spacing between parallel rows of precipitates increased as the cooling rate was decreased. The dislocation density was high at all cooling rates in all the steels, but it was found to decrease with decreasing cooling rates. Very fine precipitates were found in all the steels, except the steel containing aluminum and nitrogen. At the fast cooling rates, the segregation of vanadium and interstitial elements, which led to locally lower transformation temperatures and higher supersaturations, resulted in clusters of fine particles of vanadium carbonitride, V(C, N). At the slower cooling rates, all the steels showed severe heterogeneity in precipitate morphology which was more pronounced in the steel containing aluminum and nitrogen, while a needlelike morphology of V(C, N) precipitate was occasionally found in steels containing either vanadium and nitrogen or vanadium, nitrogen, and aluminum. As the cooling rate decreased, particle coarsening and growth occurred, causing a reduction in the number of particles/unit area. The coarsening rate of V(C,N) in the presence of aluminum is considerably lower than that of vanadium carbide, VC, or of V(C, N) in the absence of aluminum. Because of the unfavorable precipitation kinetics, any aluminum nitride (A1N) formed during cooling did not nucleate separately but was deposited on the pre-existing A1N particles, thus causing them to be coarsened very rapidly with decreasing cooling rate. Formerly with the Department of Metallurgy, The University of Sheffield, Sheffield, England     

210t钢包钢水温降规律的数值模拟

通过建立钢包有限元传热数学模型,模拟钢包传热过程的瞬态温度场.分别采用代表值法和能量守恒法分析重庆钢铁股份公司炼钢厂210 t钢包不同烘烤温度、不同绝热层材质对钢水温降的影响,预测了不同工况的钢水温降速率,并与实测值进行了对比.结果表明:钢包烘烤温度对钢水温降影响很大;钢水浇铸过程中温降速率比静置时要大;实测的温降速率...     

Effect of vanadium and molybdenum addition on high temperature recovery,recrystallization and precipitation behavior of niobium-based microalloyed steels

The effects of multiple microalloy additions on the dynamic recovery and recrystallization behavior of austenite were investigated in a series of 0.05% C-l.25% Mn steels. The steels contained one or more of 0.30% Mo, 0.035% Nb or 0.115% V, and a reference plain carbon steel was also tested. Constant strain rate compression tests were conducted in the temperature range 1150°–875°C, that is, above and below the relevant carbonitride solution temperatures (T_sol). Dynamic recrystallization-time-temperature (RTT) curves were developed from the flow curves at 5.6 × 10⁻³ and 3.7 × 10⁻²s⁻¹. At the higher strain rate, only the solute retardation of recrystallization was detected for the vanadium, Nb-V, Nb-1.9 Mn and No-Mo steels. An additional delay due to the dynamic precipitation of Nb(CN) was observed in the Nb-1.25 Mn steel, where there was a break to the right in the RTT curve. These breaks were seen in the results for all the steels at the lower strain rate. They appeared about 50°–100°C below the calculated T_sol for the particular carbonitride, and coincided with the intersection of the RTT and PTT (precipitation-time-temperature) curves. The solute retarding potential of each element was normalized to 0.1 at.% with a solute retarding parameter (SRP). The SRP for niobium, molybdenum and vanadium when added singly, was 63, 10 and 3% respectively. In the multiply alloyed steels, the SRP attributable to each element was smaller than when it was present alone. Possible explanations for this negative interaction are advanced. Dynamic PTT curves for the precipitation of carbonitrides are presented for the Nb-1.25 Mn, Nb-1.9 Mn, Nb-Mo, Nb-V and Nb-Mo-V steels. The addition of molybdenum, vanadium or manganese is seen to retard the dynamic precipitation of Nb(CN). These delays are explained in terms of the decrease in T_sol resulting from the reduction in the carbon and nitrogen activity coefficients in the joint presence of the former elements. An empirical formulation for the effect of manganese on NbC solubility is deduced from results reported in the literature which is consistent with the present observations.     

Diffusion interaction of vanadium carbide with powdered steels

Conclusions The processes of diffusion interaction of vanadium carbides with cast and powdered steels are largely analogous. Differences are mainly due to unequal diffusional mobility of the components in cast and powdered materials.In cast and powdered steels equal boundary concentration of vanadium are established on the boundary with the carbides, and these concentrations are determined by the carbon content of the steel and by the temperature.The interdiffusion coefficient in ferrite does not depend on the carbon content, and it is the same for cast and powdered steels. The interdiffusion coefficient in austenite increases with increasing carbon content, and it is noticeably larger in powdered steels than in cast steels.The activation energy of interdiffusion in the austenite of powdered steels (220–230 kJ/mole) is noticeably lower than in cast steels (260–270 kJ/mole); this is due to the substantial contribution of the processes of surface diffusion to the overall mass transfer in porous materials.Translated from Poroshkovaya Metallurgiya, No. 11(323), pp. 40–45, November, 1989.     

A mass transport theory for interphase precipitation with application to vanadium steels

A mass transport theory is developed for interphase precipitation reactions in binary and pseudobinary systems where constant concentrations of solute are maintained at the interphase boundary. The theory presents exact solutions to the problem of diffusion-controlled growth involving the coupled motion of two boundaries. It is generally applicable to interphase pre-cipitation in both solid-solid and solid-liquid systems. Aspects of the theory are discussed with reference to the interphase precipitation reaction in model iron-carbon-vanadium alloys.     

Studies on addition of inclusions to molten aluminum using a novel technique

Considerable initiatives have often been taken to introduce specific solid particles directly into molten metals in a desirable quantity, but little success has been achieved, particularly in the case of reactive particles. Therefore, alternative routes such as production of solid particles through chemical reactions within the melt are often used. While these methods are capable of producing solid particles within the melt, the chemistry of the melt changes and control of particle size and chemistry is difficult. In the present study, a direct addition technique has been used to introduce many types of inclusions into liquid aluminum and Al-Si alloys, irrespective of their wettability and chemical reactivity, while preserving the surface characteristics and melt chemistry. A uniform particle distribution can be obtained even at low volume fraction of addition and with particle sizes of the order of 2 to 5 μm. This technique allows valuable information regarding the behavior of many inclusions, such as TiB₂, TiC, SrO, and Sr(OH)₂, in liquid aluminum to be studied. Several such examples are presented.     

Application of a new model to the interphase precipitation reaction in vanadium steels

A new model has been applied to the precipitation of vanadium carbide (VC) particles in sheets at austenite/ferrite interphase boundaries during the isothermal transformation of Fe-C-V steels. Linear relationships between the intersheet spacings, the VC particle sizes, and the square root of the vana-dium diffusivity in ferrite have been identified. The model establishes predictive correlations be-tween the interphase precipitate sheet widths, intersheet spacings, and boundary migration speeds as a function of isothermal transformation temperature, and shows that the time associated with the in-terphase precipitate repeat period is a constant for each alloy over the temperature ranges studied. From a single measurement of interphase boundary velocity in a volume where the intersheet spac-ing is known, it is possible to predict the intersheet spacing and width as a function of temperature.     

钢包耐火材料对钢中氧含量及钢水温降的影响

利用氧势指数分析了钢包耐火材料组成、配比以及加热温度对耐火材料分解和向钢中传氧的影响,并利用热传导理论计算了钢包包衬耐火材料的绝热性能对钢水温降的影响.结果表明:随着耐火材料材质由碱性向中性和酸性的顺序变化及温度的升高,耐火材料的氧势指数增大,由耐火材料向钢中的传氧能力增加;通过使用绝热性能良好的耐火材料,可以显著降低...     

基于不同保温措施下的铁水包热状态模拟分析

在铁钢界面现有模式下的铁水运输过程中,由于铁水包运行周期及保温效果不够理想,导致在高炉接铁时铁包耐材温度低,热状态差,使得铁水在铁水包内的热量损失较大.减小铁水温降能有效防止铁水包结壳结瘤,降低离线烘烤频率,间接提高铁水包周转率;同时在转炉冶炼过程中,低温铁水将严重影响废钢的加入量和吹氧等操作.由此可见,铁水温度控制是钢铁企业节能降耗和高效有序生产的关键因素之一.为了减小铁水温降,本文建立了多种不同保温措施情况下的铁水包传热模型,通过fluent软件对各模型在不同空包时间情况下的温度场进行数值计算,分析不同保温措施及空包时间下热状态对铁水温降的影响规律.分析结果表明：无保温措施的情况下空包时间由5 h缩短至3 h能降低下一周期铁水温降2.2 K·h^-1;空包阶段最合理的保温措施为增设6 mm左右绝热层并加包盖,能提高工作层平均温度约155 K,在空包3~5 h内能减小铁水温降3.4~3.7 K·h^-1.该结论为铁水包空包阶段采取合理保温措施及不同保温情况下空包运行时间控制提供了理论指导.     

Research on molten flow simulation of 30t VOD ladle smelting stainless steel

30tVOD ladle smelting stainless steel was used as the process background, and the numerical and physical simulations were applied to investigate the flow and mixing characteristics of molten steel during the 30tVOD refining process. The cold experiment was employed to investigate the mixing behaviors of molten steel under the bottom and combined blowing systems. The flow features of molten steel were analyzed by numerical simulation with different blowing conditions. The results show that when the plug position of the ladle is located on 1/4R(R is the radius of ladle bottom), whether top- bottom blowing or bottom blowing, the molten steel is mixed well, and mixing time compared to the central position is reduced by 46% and 14% respectively. In addition, the comparison of flow field and turbulent kinetic energy of the molten steel show that when the bottom blowing position is 1/4R, the flow direction of the molten steel caused by the top blowing and the bottom blowing is better near the bath surface, and active volume ratio of molten steel is higher than that of other blowing positions. Current results were validated in industrial VOD furnace, which indicates that 1/4R is regarded as the optimum injection position for combined stirring.     

钢包钢水温降及其影响因素的模拟

通过有限元方法建立了120 t钢包的传热模型,计算分析了钢包在使用过程中的传热行为,研究了钢包内衬及厚度对钢水温降的影响.结果表明:使用导热系数较低的保温材料,在传统钢包内衬中添加绝热层能显著提高钢包的保温效果,减低钢水温降速率;改变工作衬厚度对钢水温降速率的影响较小.     

Technology for chemical preheating of automotive-grade and tube steels in the ladle

The converter shop at the Severstal’ Metallurgical Combine has developed and introduced a unit for the chemical preheating of steel in pouring ladles. When the filled ladle arrives at the steel-finishing unit, the steel is blown with argon in accordance with existing procedures. Measurements of temperature are then used to evaluate the need for chemical heating of the steel. The mass of aluminum to be used for this purpose and the total consumption of oxygen are calculated based on the steel’s temperature and aluminum content. The chemical heating technology can be used in the production of ordinary steels, automobile sheet 08Yu, and tube steel 22GYu. When IF-type automobile sheet is being made, the amount of oxygen used for chemical preheating should be limited to 100 m³. __________ Translated from Metallurg, No. 2, pp. 45–47, February, 2007.