Ladle Bottom Research Articles

Exploration and Practice of Nitrogen Addition Process for LF Refining Ladle Bottom Blowing Nitrogen Steel Liquid

Exploration and Practice of Nitrogen Addition Process for LF Refining Ladle Bottom Blowing Nitrogen Steel Liquid

Numerical Analysis of Fluid Flow and Powder Transport Characteristics of RH-Degasser Ladle Bottom Powder Injection (RH-PBI) Process

Numerical Analysis of Fluid Flow and Powder Transport Characteristics of RH-Degasser Ladle Bottom Powder Injection (RH-PBI) Process

Two-Way PBM-Euler Model for Gas and Liquid Flow in the Ladle.

Ladle metallurgy is an important steelmaking technology in high-quality steel production. The blowing of argon at the ladle bottom has been applied in ladle metallurgy for several decades. Until now, the issue of breakage and coalescence among bubbles was still far from being solved. In order to have a deep insight into the complex process of fluid flow in the gas-stirred ladle, the Euler-Euler model and population balance model (PBM) are coupled to investigate the complex fluid flow in the gas-stirred ladle. Here, the Euler-Euler model is applied to predict the two-phase flow, and PBM is applied to predict the bubble and size distribution. The coalescence model, which considers turbulent eddy and bubble wake entrainment, is taken into account to determine the evolution of the bubble size. The numerical results show that if the mathematical model ignores the breakage of bubbles, the mathematical model gives the wrong bubble distribution. For bubble coalescence in the ladle, turbulent eddy coalescence is the main mode, and wake entrainment coalescence is the minor mode. Additionally, the number of the bubble-size group is a key parameter for describing the bubble behavior. The size group number 10 is recommended to predict the bubble-size distribution.

Physical Simulation Study on Flow Field Characteristics of Molten Steel in 70t Ladle Bottom Argon Blowing Process

In the LF refining process, argon blowing at the bottom of ladle can play an important role in unifying the composition and temperature of molten steel and removing inclusions. However, unreasonable bottom argon blowing process can also cause many problems. Slag entrapment and slag surface exposure may occur, affecting the steel quality. Since the working conditions of different enterprises are very different, corresponding optimization is required for specific parameters. There were some problems in 70t ladle of a steel plant, such as unclear control of bottom argon blowing system in different refining periods, unobvious floating removal effect of inclusions in ladle, high total oxygen content and large fluctuation, etc. In this study, a 1:3 physical model was established according to the similarity principle. Then, on this basis, the experimental schemes with different blowing hole positions and argon flow rates were designed for simulation experiments. By means of mixing time measurement, flow field display and oil film measurement, the optimal argon blowing position was double holes 6, 12 (2/3R), and the included angle between them was 135°. The optimal argon flow rate for wire feeding and soft blowing should be 7.6 L/min (corresponding to the actual production of 180 L/min) and 0.6 L/min (corresponding to the actual production of 15 L/min), respectively. According to this scheme, the industrial experiments showed that the contents of total oxygen and nitrogen in the whole process were reduced, the surface density of inclusions in billet was reduced by 11.81% on average, and calcium sulfide and various inclusions containing aluminum were reduced to varying degrees.

Дослідження термічної підготовки ковшів

The purpose of the work is to develop a computer model of ladle heating with an open torch on a drying and high-temperature heating installation to control the thermal preparation process. The task of managing ladle drying and high-temperature heating installations (USVR) is to implement their operating modes, which ensure obtaining the specified temperature profile of the lining layers of steel castings with minimal fuel consumption. The task of controlling by drying and high-temperature heating unit (SHHS) is to implement their operating modes that provide a given temperature profile of steel pouring ladle lining layers with minimal fuel consumption. Since modern technical means of control do not allow obtaining relevant information about the temperature field of the lining of the walls and bottom of the ladle, it is necessary to create a predictive model of its heating by an open torch at the SHHS. A 68-ton rammed steel-pouring ladle KС-68 was chosen as the object of study. According to the research data, the shape and dimensions of the open torch were evaluated at OCC PrJSC “Evraz- Dnipro Metallurgical Plant”. A digital camera recorded the torch at the burner outlet at a natural gas flow rate of 50 m3/h, which corresponds to the standard mode of drying and warming up the ladle. For modeling purposes, the resulting torch shape was approximated by two truncated cones. Determination of the parameters of convective-radiant heat transfer in the “torch – cover – wall – ladle bottom” system was carried out taking into account the temperature of the torch, the thermophysical properties of the lining materials, as well as the irradiance coefficients and the emissivity of the surfaces. The calculation of the temperature field in the lining of the wall and bottom of the ladle was carried out by the finite element method implemented in the ANSYS package. Based on the simulation, a change in the temperature field of the ladle lining was obtained during its heating at the SHHS with an open torch for 6 hours, which corresponds to the current technology. An analysis of the dynamics of the temperature field of the ladle lining obtained as a result of modeling indicates that when it is heated by an open torch at a drying and high-temperature heating unit, thermal stresses do not occur, which are dangerous from the point of view of cracking in the layers of refractory materials. The maximum temperature gradient in the wall is 10 °С/mm, and at the bottom – 6 °С/mm. It has been established that the working surface of the lining warms up sufficiently to avoid thermal shock when steel is poured into the ladle. The results of the research can be useful for optimizing the process of thermal preparing steel pouring ladles.

The Flow Behavior of Molten Steel in an RH Degasser Under Different Ladle Bottom Stirring Processes

The Flow Behavior of Molten Steel in an RH Degasser Under Different Ladle Bottom Stirring Processes

Comparative Study on the In-Ladle Treatment Techniques for Nodulizing the Iron’s Graphite

The objectives of this research is to study and understand the nodulizing of ductile iron using in-ladle treatment process. Among the more common nodulizing agents is magnesium (Mg) which is conventionally added to the cast iron by combining suitable alloys of one or both of these elements with molten cast iron. Depending on the characteristics of each master alloy used as nodulizer, different treatment methods and techniques are used, among these, the most widely used being in-ladle, in-mould, and flow-through, the first being the most used. This research deals with the parameters, that affect the quality of ductile iron produced using in-ladle treatment process. The parameters involved are the percentage of magnesium–ferrosilicon (Fe–Si–Mg) used and the nodulizing technique. In-ladle treatment used consists of a deep pocket into the bottom of ladle, in which magnesium–ferrosilicon is placed into it together with a steel scrap barrier (steel sheets) or calcium carbide. This study, take into account, the degree of assimilation of magnesium, which shows the performance of the chosen process, depending on the nodulizer used and the temperature of the treatment.

Computing Concentration Distribution of Lump Additives in Argon-stirred Melt

To modify easily chemical consistence of molten steel metallurgical plants usually add alloys in a form of lumps through a hopper at ladle`s top. The problem is a large variety of adjusted technological conditions for this process, which leads to iterative discovery of rational ones. The article presents synthesis of a mathematical model for the mentioned process using Navier-Stokes and Euler-Lagrange equations. It is designed for researching of process modes depending on: a horizontal position of addition hopper relatively to argon plug at ladle bottom, an average diameter of spherical addition lumps, a total mass of addition heap, a necessity of the second hopper, a temperature of the melt. It takes into account interconnected three-dimensional fluid and solids dynamics, temperature exchange between melt and lump, also it computes level of concentration homogenization. A numerical experiment shows a significantly better addition homogenization when two hoppers are simultaneously used for a feeding. Adequacy checks are performed using ice balls in air-stirred water.

Effect of Side Blowing on Fluid Flow and Mixing Phenomenon in Gas-Stirred Ladle

To investigate the gas agitation characteristics of side blowing, the fluid flow and mixing phenomenon in a 1:3 scale model ladle of a 150 t industrial gas-stirred ladle with bottom and side plugs were studied by using physical and numerical modelings together. Side blowing enhanced the horizontal flow of water in the model ladle. Compared with bottom blowing, side blowing that is close to the ladle bottom with more than two plugs increases the average velocity of water, which represents the agitation power, improves the uniformity of water velocity distribution, reduces the stagnant region rate, and shortens the mixing time. The mixing time of dual bottom plugs is almost 1.5 times of that of four side plugs at 116 mm under the same flow rate. The mixing time is not only influenced by the agitation power but also by the uniformity of water velocity distribution. Although the agitation power of four side plugs at 450 mm under the flow rate of 1.8 m3/h is about 1.5 times of that at 116 mm with 0.6 m3/h. The mixing time of the 1.8 m3/h flow rate is about 1.2 times of that of the 0.6 m3/h because of the different water velocity distributions.

Numerical Simulation of Melting Kinetics of Metal Particles during Tapping with Argon-Bottom Stirring

Molten steel is alloyed during tapping from the melting furnace to the argon-bottom stirred ladle. The metallic additions thrown to the ladle during the ladle filling time are at room temperature. The melting rates or kinetics of sinking-metals, like nickel, are simulated through a multiphase Euler–Lagrangian mathematical model during this operation. The melting rate of a metallic particle depends on its trajectory within regions of the melt with high or low turbulence levels, delaying or speeding up their melting process. At low steel levels in the ladle, the melting rates are higher on the opposite side of the plume zone induced by the bottom gas stirring. This effect is due to its deviation after the impact of the impinging jet on the ladle bottom. The higher melting kinetics are located on both sides at high steel levels due to the more extensive recirculation flows formed in taller baths. Making the additions above the eye of the argon plume spout increases the melting rate of nickel particles. The increase of the superheat makes the heat flux more significant from the melt to the particle, increasing its melting rate. At higher superheats, the melting kinetics become less dependent on the fluid dynamics of the melt.

Development and Implementation of a Device for the Separation of Metal and Slag During Tundish Filling

Nonmetallic inclusions in steel such as oxides, silicates, aluminates, spinels, etc. substantially reduce the quality of metal. They are mainly introduced by the slag formed on the metal surface of a doublestrand plant. It is proposed to separate the slag from the metal using a special perforated tube installed on the refractory pocket block of the ladle bottom and fixed with gunning mix. The use of this device for continuous slab casting ensures the high quality of hot- and cold-rolled sheets.

An alternative lining of steel ladles: technical and economic aspects

Quality of steel ladles lining to a big extent determine the economic efficiency of steel-making operation. Direct costs on the refractory lining of them can reach 30–50 % of the costs of lining of a steel-making complex. Experience of utilization of refractory materials of different composition considered with the purpose of efficiency increase of refractory materials application in the steel ladles lining under conditions of steel ladle treatment. Considerable abilities shown to make the lining of steel ladle walls and bottom by both carbon-containing and carbon-free refractory materials taking into account the economic aspect. Lining base of steel-making facilities — BOFs, EAFs and steel ladles — is composed by periclase-carbon (MgO–C) refractories. However those refractories have a high heat conductivity, that effects on the heat operation of steel ladles. When using MgO–С materials, vertical fractures can appear in the ladle walls lining as its residual thickness becomes small. Under definite conditions a working lining chipping takes place, problems appear with lining destruction in the pieces angles with cavities formation at the pieces joining. To level the MgO–С drawbacks, periclase-alumo-carbon (MgO–Al2O3–С) and alumo-periclase-carbon (Al2O3–MgO–С) refractory products are used. Al2O3–MgO–C refractories are widely used in most erosion-intensive lining zone — in the combatting place of steel ladle bottom lining. In Russia monolithic lining of steel ladle bottom is successfully displacing the lining by piece products, including alumo-periclase-carbon ones. Such a replace enables to decrease specific refractory consumption and specific costs of them. At present the technology of concrete application to bottom is implemented for ladles of BOF- and steel-making shops. A technology of concrete ladle walls and bottom is intensively implemented for 120–180-ton ladles. The concrete lining of steel ladles has the following advantages: high withstandability against impregnation by metal-slag melt; absence of metal carbonization by the carbon from ladle lining; increase of running duration of safety lining layer by 2–2.5 times; absence of necessity to use nest blocks in both steel outlet unit and for bottom blow-off lance; absence of cracks in lining, wash-outs in seams, angles and edges of pieces; decrease of gaseous hydrocarbon emissions(phenol, formaldehyde, benzapilene) during lining drying, heating-up and operation (only slag belt remains, where pieces have organic binders); saving of materials, working time and manpower while making and maintain the lining; decrease of specific consumption and specific costs for lining per 1t of steel. For lining of steel ladles of big volumes (more 250 t) alumo-periclase (alumo-spinel) products are widely used in China, Europe and Japan. For such a lining the thermo-mechanical tension, arising in monolithic ladle lining, has a less importance, including at its replacing with metal by using crane. It is easier for the products to compensate the ladle geometry change, resulted in metal shall geometry change in time. A positive influence of carbon-free lining, as well as a lining with low content of magnesium oxide, on metal quality noted, first of all for low- and ultralow carbon grades, and pipe low-alloyed steels.

Post-mortem analysis of alumina-magnesia-carbon refractory bricks used in steelmaking ladles

Post-mortem studies in secondary steelmaking ladles are an important way to determine the factors related to Alumina-Magnesia-Carbon (AMC) refractory corrosion. AMC refractory bricks installed in the impact zone of a steelmaking ladle bottom were analyzed after 100 castings. X-ray diffraction, X-ray fluorescence chemical analysis, reflected optical light microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, density and porosity measurements, and mercury porosimetry were used to analyze the chemical and physical characteristics of the slag, the unused refractory and the slag+steel attacked bricks. The corrosion process produced a specific microstructure characterized by: i) a thick discontinuous slag layer composed by secondary spinel+steel+liquid; ii) a thick dense, cracked, and continuous layer consisting of calcium aluminates+steel+liquid at the slag/refractory interface; iii) next to this layer, a wide densified layer with a uniform microstructure in which corundum aggregates and spinel crystals were linked together by elongated CaAl12O19 crystals.The formation of these reaction layers constituted a barrier that effectively suppressed the massive slag penetration and surely reduced the wear rate. Thermodynamic calculations based on simplified and complex condensed phase equilibrium diagrams, were used to further understanding of the corrosion mechanism.

Combustion performance of nozzles with multiple gas orifices in large ladles for temperature uniformity

In order to improve the baking temperature uniformity of the large ladle in steelmaking plants, the flame combustion characteristics of nozzles with different inner structures were numerically simulated with the finite volume method code Fluent. The flow field and premixed combustion reaction inside and outside the nozzle with multiple gas orifices were exhibited. Meanwhile, the influences of the gas injecting angle and the number of gas orifices on temperature, velocity, and pressure fields were studied. The results show that the flame length and width at the rear of flame temperature field reach the maximum values in the nozzle with the gas injecting angle of 20° and 4 gas orifices for the control of premixed combustion inside the nozzle, which could provide better temperature uniformity in ladles. The length of the 1273 K isothermal surface is 4.89 m, and the cross-section area at 4 m away from the outlet of the nozzle is 0.13 m2. The pressure losses of different types of nozzles range from 112.2 to 169.4 Pa and decrease with the decrement in gas injecting angle and the number of gas orifices. The ladle bottom preheating temperature is increased by 320–360 K for the optimized nozzle. The inner surface temperature differences between wall and bottom of the ladle are less than 10%. There is good baking temperature uniformity after the application of optimum structurally designed nozzles.

Mathematical Modeling of the Movement of Moisture in Refractory Concrete and Gunning Bodies During Drying

Amathematical model of the movement of moisture in refractory water-sealed materials of different densities where there is an external temperature field present is constructed. The Fourier thermal conductivity equations, Fick’s diffusion equation, and the method of finite elements are used to solve the problem. The diffusion coefficients of water in the test materials are determined by means of laboratory tests from the loss of mass in the course of drying of the samples. Features typical of the movement of moisture in refractory concrete for the case of deposition on cold and hot surfaces are determined as a result of a subsequent computational experiment, using as examples the casting bottom of a casting ladle and guniting of an intermediate ladle.

Modeling of Gas-Steel-Slag Three-Phase Flow in Ladle Metallurgy: Part I. Physical Modeling

To obtain a better understanding the gas-steel-slag three-phase flow in ladle metallurgy with eccentric gas bubbling, both the single-plug-stirred and dual-plug-stirred water model systems were employed. The plume Froude number derived from the buoyancy of the bubble plume was used to characterize the plume two-phase flow. The elctrical conductivity measurement technique was applied to measure the mixing time. A video technique was used to monitor the slag eye and the open software called ImageJ was taken to quantify the slag eye area. Some experiments were carried out to determine the location of the probe in the ladle where the measured mixing times can be interpreted as the bulk mixing times. The eccentric gas injection in the ladle bottom can improve the mixing efficiency in the ladle. Shorter mixing times can be achieved by injecting gas through two porous plugs, located diametrically opposite at mid-bath radius position (α=180°). A critical gas flow rate is proposed based on the formation of slag eye. The mixing time will decreases sharply at the condition of slag eye formation and collapse alternately. The critical gas flow rate increases with increasing the slag layer thickness and decreasing the porous plug angles. Four fators effect on the slag eye area were investigated: the gas flow rate, slag layer thickness, porous plug locations and angles. A semi-empirical model was developed based on the experimental data of the present work to describe the slag eye area as a function of the heights of the two liquids and the gas flow rate. The present correlation for slag eye area was reviewed against many previous different liquid-liquid systems.

铁水包加废钢再受铁可行性探究

为了降低生产成本，提高生存能力，挖潜增效，永钢通过在2#~5#高炉和1#钢厂实施“铁水包加废钢再受铁”的工业性试验，来间接提高废钢比，并探索废钢预热、加入量、停留时间等对炼钢用铁水的影响。研究结果表明：废钢未预热，铁水包无结底；废钢种类选择了材质较薄的散装电工钢；废钢加入量占铁水包容量的百分比为3%；加废钢的铁水包对铁水停留时间影响不大。综合计算1#钢厂的废钢比由16%提高至18%，效果十分显著，为“铁水加废钢”常态化运行提供了依据。 In order to reduce the production cost and improve survival ability, tapping potential and in-creasing efficiency, Yong Steel indirectly increases the scrap steel rate through the implementation of test ladle with scrap in 2#~5# blast furnace and 1# steel mill, and explores the effect of scrap preheating and residence time on molten iron of steelmaking; the industrial test begins to take effect in Yong Steel. The results show that: without preheating, the hot metal ladle bottom is clean; the bulk electrical steel scrap material is thin and easy to be melted in the high temperature molten iron; each hot metal ladle add some scrap steel, and the amount of steel added to each ladle accounts for 3 percent of the iron ladle; The hot metal ladle packing with scrap steel has little impact on the residence time of the hot metal. The steel scrap ratio of 1# steel mill is increased from 16% to 18%, and the effect is remarkable. Thus it can be seen that it provides a basic research for normalizing operation of “the adding scrap steel into ladle”.

A Mathematical Model for the Reduction Stage of the CAS-OB Process

This paper proposes a novel method for modeling the reduction stage of the CAS-OB process (composition adjustment by sealed argon bubbling–oxygen blowing). Our previous study proposed a model for the heating stage of the CAS-OB process; the purpose of the present study is to extend this work toward a more comprehensive model for the process in question. The CAS-OB process is designed for homogenization and control of the composition and temperature of steel. During the reduction stage, the steel phase is stirred intensely by employing the gas nozzles at the bottom of the ladle, which blow argon gas. It is assumed that the reduction rate of the top slag is dictated by the formation of slag droplets at the steel-slag interface. Slag droplets, which are generated due to turning of the steel flow in the spout, contribute mainly by increasing the interfacial area between the steel and slag phases. This phenomenon has been taken into account based on our previous study, in which the droplet size distribution and generation rate at different steel flow velocities. The reactions considered between the slag and steel phases are assumed to be mass transfer controlled and reversible. We validated the results from the model against the measurements from the real CAS-OB process. The results indicate that the model accurately predicts the end compositions of slag and steel. Moreover, it was discovered that the cooling rate of steel during the gas stirring given by the model is consistent with the results reported in the literature.

Influence of the Addition of a Reducing Mixture Slag and Duration of Treatment on the Desulphurisation and Deoxidation Efficiency

Within the researches made, the establishment of the processing with synthetic slag decreasing possibilities, of the sulphur and oxygen contents, from the steel made in electric arc ovens, of 100 t ladle capacity oven (LF) - (EBT) type, was taken into account. For the formation of the synthetic slag, reducing mixing made of lime, fluorine, bauxite and aluminum slag. The experiments we performed consisted in adding the waste mechanical mixture at the bottom of the ladle, its melting leading to the formation of synthetic slag. The obtained data was processed in the EXCEL program, obtaining correlation equations between the desulphuration, deoxidation and the addition of a reducing mixture, respectively the treatment duration.

Mixing behavior in the RH degasser with bottom gas injection

Shortening the mixing time of melt can enhance the decarburization rate during the Rheinsahl–Heraeus (RH) degassing process. In this study, a numerical method has been employed to investigate and compare the mixing behavior in the RH degasser without and with simultaneous bottom injection of gas (one porous plug, and three porous plugs, respectively). The locations of plug are discussed and optimized to yield the shortest mixing time of melt. Then, industrial trials are preliminarily conducted to study the effect of bottom injection on decarburization rate during the RH degassing. Simulation results show that gas injection through one plug at the ladle bottom, under the up-snorkel, can shorten the melt mixing time remarkably by increasing the melt circulation rate and optimizing the flow pattern in the RH degasser, and the addition of other two plugs at appropriate locations can further reduce the mixing time. Trial results show that a lower [C] content in steel can be obtained in a shorter time for the RH degasser with bottom injection.