低碳TWIP钢AOD氧化精炼过程数学模型

依据AOD精炼反应前期为供氧控速、后期为碳扩散控速的机理建立了低碳TWIP钢AOD氧化精炼过程数学模型.对8t AOD冶炼TWIP钢氧化过程钢液中碳、硅和锰含量变化进行了计算,碳含量变化与实测数据偏差小于5%.研究表明,8t AOD冶炼TWIP钢脱碳的临界碳含量处于0.33%~0.38%之间.     

A simplified resistance model for reversible multicomponent ion exchange

Ion exchange resins have found increasing application in the metallurgical sector over the last few decades through resin-in-column (RIC) technology. These processes are usually simulated by using some form of resistance model. Furthermore, of these, a dual resistance approach incorporating both film and pore-wall diffusion is the most popular and widely used technique for simulations involving ion exchange and adsorption processes. This procedure assumes that equilibrium exists at the solid/liquid interface, an assumption easily applied to single-component systems. However, in multicomponent systems, this assumption makes the simulation procedure cumbersome. In addition, the inability of frequently used isotherms to accurately describe equilibrium conditions over a wide range of solution concentrations results in significant errors. This study investigates the use of a simple film-diffusion mechanism to describe mass transfer kinetics. Furthermore, a simplified Fritz and Schleunder isotherm was used to overcome complex iterative techniques in order to obtain equilibrium conditions at the solid/liquid interface. The procedure was evaluated using a chelating resin in a ternary system and proved to be very effective with reversibility well explained. Moreover, it has been shown that the effect of the counter-ion may be ignored in batch operations but not in column configurations because of the significant increase of the counter-ion in solution.     

A computational model for the prediction of steel hardenability

A computational model is presented in this article for the prediction of microstructural development during heat treating of steels and resultant room-temperature hardness. This model was applied in this study to predict the hardness distribution in end-quench bars (Jominy hardness) of heat treatable steels. It consists of a thermodynamics model for the computation of equilibria in multicomponent Fe-C-M systems, a finite element model to simulate the heat transfer induced by end quenching of Jominy bars, and a reaction kinetics model for austenite decomposition. The overall methodology used in this study was similar to the one in the original work of Kirkaldy. Significant efforts were made to reconstitute the reaction kinetics model for austenite decomposition in order to better correlate the phase transformation theory with empiricism and to allow correct phase transformation predictions under continuous cooling conditions. The present model also expanded the applicable chemical composition range. The predictions given by the present model were found to be in good agreement with experimental measurements and showed considerable improvement over the original model developed by Kirkaldy et al.     

A model for the silicon-manganese deoxidation of steel weld metals

From an analytical and theoretical study of flat and out-of-position gas metal arc (GMA) C-Mn steel welds containing varying additions of silicon and manganese, we conclude that the buoyancy effect (flotation obeying Stokes’ law) does not play a significant role in the separation of oxide inclusions during weld metal deoxidation. Consequently, the separation rate of the particles is controlled solely by the fluid flow pattern in the weld pool. A proposed two-step model for the weld metal deoxidation reactions suggests that inclusions formed in the hot, turbulent-flow region of the weld pool are rapidly brought to the upper surface behind the arc because of the high-velocity flow fields set up within the liquid metal. In contrast, those formed in the cooler, less-turbulent flow regions of the weld pool are to a large extent trapped in the weld metal as finely dispersed particles as a result of inadequate melt stirring. The boundary between “hot” and “cold” parts for possible inclusion removal is not well defined, but depends on the applied welding parameters, flux, and shielding gas composition. As a result of the intricate mechanism of inclusion separation, the final weld metal oxygen content depends on complex interactions among the following three main factors: (1) the operational conditions applied, (2) the total amount of silicon and manganese present, and (3) the resulting manganeseto-silicon ratio. The combined effect of the latter two contributions has been included in a new deoxidation parameter, ([pct Si][pct Mn])^−0.25. The small, negative exponent in the deoxidation parameter indicates that control of the weld metal oxygen concentrations through additions of silicon and manganese is limited and that choice of operational conditions in many instances is the primary factor in determining the final degree of deoxidation to be achieved.     

取向硅钢板坯高温抗氧化涂料

为了提高取向硅钢板坯的抗高温氧化性能,采用浆料法制备MgO-Cr₂O₃系的取向硅钢用高温抗氧化涂料.通过氧化增重、X射线衍射和电子扫描电镜等测试方法,研究涂层保护下的取向硅钢在不同温度下的氧化增重规律以及1400℃下氧化产物截面形貌、元素分布特征.结果表明,该涂料对于取向硅钢具有良好的高温防护功能,且具有宽泛的抗氧化区域.     

A thermodynamic model for deoxidation equilibria in steel

For relattively dilute solutions of oxygen and a deoxidizer M (M=Al, Cr, Ca, Mg, ...) in molten Fe, a thermodynamic model is proposed wherein the dissolved species are M*O associates as well as unassociated M and O atoms. At higher metal concentrations, a small amount of M ₂*O associates also form. Experimental deoxidation equilibria for 15 deoxidizers M are quantitatively reproduced at all temperatures, with only a constant, temperature-independent and composition-independent empirical parameter for the Gibbs energy of formation of each associate. The deoxidation behavior of Mg, Ca, and Ba is elucidated for the first time. The parameters are stored in a database, which can be used to predict complex deoxidation equilibria in multicomponent steels.     

A simplified model of heat generation during the uniaxial tensile test

The temperature rise in a sheet tensile specimen has been calculated by the finite difference method for a plain-carbon steel at various strain rates and in several environments. Prior to necking, a uniform heat generation function is used with the governing flow equation while during the post-uniform strain, an empirical heat generation function is used. The empirical function is based on a strain distribution equation generated by curve fitting of experimental data. The effect of heat transfer conditions on the temperature increase has been discussed. The maximum temperature rise in air may reach 42 K at the center of an I.F. steel specimen at a strain rate of 10^-2/s. The instability strain during tensile testing has been predicted by taking into account strain hardening, strain-rate hardening, and deformationinduced heating. The results show that significant deformation heating can occur during tensile testing in air at “normal” strain rates near 10^-2/s, and that the uniform elongation can be affected markedly. Predictions for other alloys based on tabulated data are also presented.     

A simplified model of heat generation during the uniaxial tensile test

The temperature rise in a sheet tensile specimen has been calculated by the finite difference method for a plain-carbon steel at various strain rates and in several environments. Prior to necking, a uniform heat generation function is used with the governing flow equation while during the post-uniform strain, an empirical heat generation function is used. The empirical function is based on a strain distribution equation generated by curve fitting of experimental data. The effect of heat transfer conditions on the temperature increase has been discussed. The maximum temperature rise in air may reach 42 K at the center of an I.F. steel specimen at a strain rate of 10^-2/s. The instability strain during tensile testing has been predicted by taking into account strain hardening, strain-rate hardening, and deformationinduced heating. The results show that significant deformation heating can occur during tensile testing in air at “normal” strain rates near 10^-2/s, and that the uniform elongation can be affected markedly. Predictions for other alloys based on tabulated data are also presented.     

A simplified model of heat generation during the uniaxial tensile test

Metallurgical and Materials Transactions A - The temperature rise in a sheet tensile specimen has been calculated by the finite difference method for a plain-carbon steel at various strain rates...     

A model for calculating solubility of hydrogen in steel

Abstract

A model has been developed for calculating the hydrogen solubility in steel on the basis of composition (S, Ti, B) and grain size, with the objective of improving the control of hydrogen content in steel products. The effects of sulphur are in agreement with previous experience, but complex effects have been observed with variations in titanium and boron contents. The model defines trap sites in crystallographic terms for the various phases and features of interest. Segregation effects have been studied using laboratory casts and with composites using continuously cast slab from which the natural segregation has been removed. Segregated regions absorb large amounts of hydrogen, but the crack threshold is reduced such that the composites have much lower safe hydrogen levels than unsegregated material. The effects of assumptions in the model on number of traps and binding energies are considered.     

A collision model for fume formation in metal oxidation

During the oxidation of copper at high temperatures, two simultaneous mechanisms are observed in the hot stage environmental scanning electron microscope: the nucleation and growth of solid cuprous oxide crystals and the formation of a solid fume composed of very small copper and copper oxide particles. A collision model for fume formation in metal oxidation is presented. By calculating the collision frequency between evaporated copper atoms and oxygen molecules in the gas phase, the amount of fume formed can be estimated. Although the effect of Van der Waals forces between particles has not been quantified, the temperature difference between the two gases was taken into account and yielded a multiplying factor of 4 in the collision frequency for copper oxidation at 950 °C. Unoxidized copper particles were formed from unsuccessful elastic collisions between Cu(v) and O₂. These copper particles are composed of interpenetrating icosohedra and possess a high crystalline perfection. Formerly Graduate Student, Department of Metallurgical Engineering, The Ohio State University, Columbus, OH 43210.     

A novel technique for isolation of pure sperm heads from disintegrated mammalian spermatozoa

The phenomenon of differential charge distribution on sperm surface membrane has been utilised here in a low e.m.f. (electro motive force) capillary electrophoresis system to effect separation of sperm heads from disintegrated mixed spermatozoal subfractions. Washed caudal sperm of goat (Black Bengal variety) and ejaculated washed human sperm were fractionated by sonication into head, mid-piece and tail portions. Routine techniques of density gradient centrifugation on Percoll and/or sucrose were performed with sonicated spermatozoa for separation into their respective subfractions. The products obtained were not free of contamination in either case. Mixed sperm fractions when subjected to the afore mentioned modified capillary electrophoresis technique only the head pieces exhibited high affinity for migration towards the cathode terminal. With this method around 50% of the total sperm heads were separated and collected in absolutely pure form at the cathode side within 2 hrs. at 150 volts (V) and 1.5 milliampere (mA) current at 37.5 degrees C. A 4 cm. long capillary tube with a bore size 1.2 mm. was used for this purpose.     

A model for the strength of the As-deposited regions of steel weld metals

Metallurgical and Materials Transactions A - The strength of as-deposited steel weld metal, as a function of temperature, strain rate, microstructure, and alloy chemistry, has been factorized into...     

Reducing the degree of oxidation of low-carbon steel

Krivorozhstal Combine. Translated from Metallurg, No. 8, p. 37, August, 1989.     

一种建筑用耐火钢变形抗力模型的建立

利用Gleeble-1500热模拟试验机对一种建筑用耐火钢进行了压缩试验,分析了变形温度、变形速率以及变形量对变形抗力的影响;在变形抗力σ与温度T的关系中,考虑了应变ε和应变速率ε的影响;在应变速率ε的影响指数中,考虑了温度的影响,建立了一种含Nb、Ti等微合金元素建筑用耐火钢应力峰值前的变形抗力模型。     

钢铁企业电力系统能源仿真模型研究

为了缓解钢铁工业能耗占全国能源消耗比例逐渐增高的趋势,以首钢京唐钢铁联合有限责任公司生产历史数据为依据,通过研究生产过程中的物料平衡和能量平衡方程,以及逻辑关系算法,建立钢铁企业电力系统能源仿真模型,包括消耗、回收和转换模型。对比分析不同工况下电力仿真模型的输出反应,获得了理想的结果,可以达到钢铁企业节能降耗的目的。     

A simplified micromethod for fluoride analysis

"VIDAS Stallertest" is a new screening test for breathing allergy. It allows the detection of 10 different lung specific allergens including domestic acarids (D1), pollents (G3, W6, W21, T3 and T9), pets dander (E1 and E2), moulds (M6), cockroach (16). The method is an immunoenzymatic reaction that contains a cartridge and a cone that is cover with the allergen's mixture and is automated on the VIDAS system. The results are compared to various skin tests analyzed by instantaneous reading for 102 patients. "VIDAS Stallertest" shows an excellent agreement (93%) with the allergic patients as well as with those that are not. The specificity of the new screening test is very high (91%). A comparative study between "VIDAS Stallertest" and "Phadiatop" performed on 155 consultants in allergist office shows a correlation of 93%, a sensitivity and a specificity of 91 and 95%, respectively. "VIDAS Stallertest" is a reliable method in first intention for the general practitioner who faces a putative breathing allergy. Moreover, this is an excellent biological check-up for a questionable or negative skin test.     

A simplified technique for radionuclide hysterosalpingography

The nutrient intakes and circulating vitamin levels of 32 patients with rheumatoid arthritis who were treated with methotrexate were evaluated over a 6-month period. Dietary data were obtained and blood was drawn prior to the initiation of and following 12 and 24 weeks of methotrexate therapy. More than 50% of the patients had food intakes providing less than 67% of the recommended dietary allowance for zinc, vitamin E, folic acid, pyridoxine, and magnesium. Patients 51 years or older had better nutrient intakes than patients less than 51 years. Of the patients, 22% consumed vitamin supplements at the time they were recruited for the study. Mean circulating vitamin levels measured over the 6-month period were within normal limits. Our findings agree with previously published reports that patients with rheumatoid arthritis, particularly the subpopulation taking methotrexate, consume diets that are marginal in some nutrients. Additional research needs to be done to identify more sensitive nutrient assays and to establish more definitively the nutrient needs of patients with rheumatoid arthritis taking several therapeutic agents.