Ladle Wall Research Articles

COMPUTER ANALYSIS OF INFLUENCE OF MELT BLOWING MODES ON LADLE LINING MECHANICAL EROSION

In the process of blowing, turbulent melt flows erode the ladle lining and its thickness de-creases due to mechanical erosion. The thickness of the steel ladle lining gradually becomes thinner with each casting. The degree of erosion depends on the tangential melt speed. In steel production, they try to slow down this wear, because each lining repair costs considerable time and resources. Scientists paid attention to this problem in publications, in particular, on mathematical modeling of lining wear. A large number of conditions of this process are subject to research, in particular, the number and location of blowing tuyeres, as well as blowing power. Firstly, it is necessary to quickly mix the impurity in the melt, and secondly, to preserve the lining of the ladle. Computer visualization and analysis of this process involves its course and results in the form of calculated fields, in particular, wear. The result fields are stored in a database. Also they are added and processed through a specially designed website. It allows researchers to register and fill in the experiment form, as well as add literature sources of data. The list of literature is used in almost all experiments to compare results. Simulation of the process at blowout rates of 40, 60 and 90 l/min and the number of blowout plugs (tuyeres) from one to three showed that the greatest scouring is predicted at the bottom, near the blowout plugs, and the transition to each higher blowout rate increases the scouring intensity by about 15%. Turning off the tuyeres after 1 minute of blowing significantly reduces erosion by at least 35%. If we consider the ladle wall, without disconnecting the tuyere, the flow rate of 90 l/min is the most destructive.

Post-mortem analysis of MgO–Al2O3–C bricks containing bauxite used in steel ladle walls

A serious problem with integrated masonry linings ladle was that the ladle wall bricks were difficult to be partially replaced. Thus, the service life of the ladle was determined by the properties of ladle wall bricks. In this study, the new generation of MgO–Al2O3–C bricks with bauxite aggregates was tested in a ladle lining of an integrated steel ladle for 103 cycles, and the corroded microstructure of the used brick was investigated. A multilayered structure of bauxite aggregates could be observed in the used brick, which inhibited the slag penetration along the boundary of the magnesia aggregates and reduced the degree of the aggregates fall off from the used bricks. Besides, during the process of slag penetration, bauxite aggregates could melt into the slag, which increased the viscosity of the slag and weakened the penetration ability of the slag. The MgO–Al2O3–C bricks with bauxite addition could improve the service life of the ladle to a certain extent.

Analysis of fluid flow characteristics of RH reactor with different bottom-blowing arrangements

ABSTRACT A numerical model of RH reactor with bottom-blowing is developed and used to analyse the influence of bottom-blowing position and gas flow rate on the fluid flow of molten steel, shear stress and slag layer. The results show that the flow difference caused by bottom-blowing positions is mainly due to the different movement behaviour of bubbles. When blowing directly below the up-snorkel, the bubble flow is more concentrated. With the increase in the flow rate, the offset of bubbles towards the up-snorkel direction increases, and it is easier to enter the gap between the up-snorkel and the ladle wall to form slag eye, and increase of shear stress on the ladle and the snorkels. When the position is under the up-snorkel which offset towards the centre of the ladle, the wall shear stress is weaker under the same flow rate, and the flow rate allows larger before slag eye forming.

Water modelling on particle dispersion during KR desulphurization process

ABSTRACT In the current study, a 1:7 scaled water model was established to investigate the dispersion of desulphurizer particles during the Kanbara Reactor (KR) desulphurization process. The concentration, movement, and dispersion of the particle in the liquid were visualized and analysed. The influence of the impeller rotation speed, immersion depth, particle density and addition amount, and ladle wall baffle on the particle dispersion were systematically studied. The minimum critical rotation speed at which particles began to disperse into the liquid under different parameters was obtained. A regression equation for the influence of the impeller immersion depth and particle mass proportion on the critical rotation speed was proposed. Particles were easier to be driven into the liquid by the stirring impeller due to the higher particle additions. The area proportion of dispersed particles using the baffle was increased by three times compared with the case without the baffle.

Effect of Build-ups on Ladle Wall on Acoustic Signals in Gas-Stirred Ladles

Effect of Build-ups on Ladle Wall on Acoustic Signals in Gas-Stirred Ladles

Physical Experiment and Numerical Simulation on Thermal Effect of Aerogel Material for Steel Ladle Insulation Layer

The selection of lining material for a steel ladle is important to heat preservation of molten steel. Aerogel insulation materials have very low thermal conductivity, however, they are rarely used in steel ladles. In this paper, the application of a new silica aerogel material on the steel ladle insulation layer is tested, and a new calculation method is designed to study its insulation effect. In other words, the ladle wall temperature is obtained by finite element model (FEM) and experiments, then the heat emission from the ladle wall is calculated by the Boltzmann mathematical model according to the ladle wall temperature, and the temperature loss of molten steel is calculated inversely according to the heat emission of ladle wall. Compared with the original steel ladle (comparison ladle), the application effect is analyzed. Due to the stable heat storage of the ladle wall after refining, the validity of the models are verified in ladle furnace (LF) process. The results show that the new calculation method is feasible, and the relevant parameter settings in the FEM and Boltzmann mathematical model are correct. Finally, after using the new aerogel insulation material, the temperature of molten steel is reduced by 16.67 °C, and the production cost is reduced by CNY 5.15/ton of steel.

Research of bottom blowing and slag layer thickness on bath stirring in a 120t ladle

The relationship between mixing time, ladle kinetic energy and bottom blowing radial position, bottom blowing flow rate, slag layer thickness and a series of operating variables are studied. The mixing time has been measured in a 1:6 scale model, and the method of adding tracers has been improved to obtain more accurate results. In addition, the kinetic energy in the bath is calculated through the VOF+DPM coupling model. The experimental results show that the mixing time in the bath decreases with the increase of the bottom blowing rate or the decrease of the thickness of the oil layer. Compared with the bottom blowing radial position of 0.55R and 0.65R, 0.45R is more conducive to mixing in the bath. As the radial position of the bottom blowing approached the wall, the gas-liquid phase zone began to tilt toward the ladle wall. The kinetic energy in the bath is not necessarily related to the mixing time, but when the bottom blowing flow rate and position are the same, the kinetic energy decreases with the increase of the oil layer thickness. When the thickness of the oil layer is 1 cm, 2 cm and 3 cm, the kinetic energy compared with the thickness of the oil-free layer decreases by 24.07%, 30.56% and 36.30%, respectively.

Perfection of technology and equipment for heating of steel ladles lining at horizontal stands

To change or repair sliding gates, steel ladles are installed in horizontal position, in which they are heated to keep a working temperature of lining. Peculiarities of a steel ladle heating in horizontal position considered. Description of the lining heating process presented, necessity of elaboration a method of its numeral simulation justified. The method should enable to make studies of influence of various methods of burner location on the ladle cover and torch parameters on efficiency of heating for a particular ladle and time available for the heating. A method of mathematical simulation of heat- and mass-exchange processes of lining heating in nonstationary conditions described. Based on examples of various variants of torch power calculation, dynamics of a ladle walls heating was shown. Results of calculation of temperature distribution over a ladle lining presented, as well as the map of gases flow in the ladle volume for various parameters of torch and heating process stages. Taking into consideration, that calculation costs related to simulation of nonstationary ladle heating are very high, a simplified one-dimensional model of calculation of lining heating process was elaborated. In the model correction factors are used, obtained as a result of numeral simulation. The model enables to make calculations in real time conditions and to use them for control at a practical steel ladle heating in horizontal position at a modern automized heating facility.

Numerical and Physical Investigation of the Mixing Process in Gas Stirred Ladle System

Secondary steelmaking or ladle metallurgy is one of the important processes that adjust and homogenize the chemical compositions and the temperature. In this process, argon gas is injected into the melt through porous plugs to accelerate the chemical reaction and the mixing. One of the indicators for the mixing efficiency is “the mixing time”. The purposes of this study were to investigate the effects of gas flow rate and purging system on the mixing time and flow characteristics by using numerical and physical investigation and to predict the velocity magnitude acting on the refractory wall by analyzing the effects of gas flow rate. A 1:5 scaled water model and a full-scale ladle model of Millcon steel PLC were used in the study. The numerical simulation modelling was carried out by using CFD commercial software Flow-3D. The results from the numerical simulation were in consistence with the experiment results. The simulation results showed that with the highest gas flow rate the reduction of the mixing time was around 36% and the velocity magnitude increased to approximately 44% in comparison with the lowest gas flow rate in the full-scale model. The area at the ladle wall near the liquid surface has a higher chance of the damage than other areas. Besides, employing the dual-plugs system led to approximately 33–49% shorter mixing time compared to the single-plug system. The results show that the gas flow rate affects the turbulent kinetic energy directly. However, high turbulent kinetic energy leads to open-eye size which results in re-oxidation and contamination. Therefore, it is important to optimize the flow rate to achieve both productivity and steel cleanliness.

Corrosion Mechanism of A Density-Reduced Steel Ladle Lining Containing Porous Spinel-Calcium Aluminate Aggregates

Refractory monolithics for steel ladle linings are typically products with low porosities and high bulk densities. They achieve high temperature, penetration, and corrosion resistance. Despite the high density of these products, which is due to the low porosity of the aggregates, their matrices still exhibit a high amount of pores. Since calcium magnesium aluminate (CMA) has already proven its resistance to penetration and corrosion as a binder in the matrix, this paper investigated if alumina spinel refractories containing microporous calcium magnesium aluminate aggregates can withstand conditions that occur in a steel ladle wall. The objective was to reduce the castable density with the advantage of a lower material requirement for a ladle lining and reduced heat and energy losses. This was achieved by replacing dense alumina aggregates by up to 38% of porous CMA aggregates (grains with 30 vol% porosity), which resulted in a bulk density reduction from 3.1 g/cm3 for the dense alumina castable to 2.8 g/cm3 for the 38% CMA aggregates containing castable. However, the despite the higher porosity, penetration, and corrosion resistance and thermomechanical properties were not impacted negatively for a model alumina spinel castable. A postmortem investigation was conducted on a newly developed dry-gunning mix that was installed in a steel ladle wall on top of a slag penetrated castable and that achieved a service life of 31 heats versus only 18 heats for the reference mix that contained dense alumina and spinel aggregates. This new repair mix contained the newly designed porous CMA aggregates, which in this case partly replaced the dense alumina and spinel aggregates. These porous aggregates consisted of magnesium aluminate and calcium aluminate micro-crystals. The postmortem study revealed two important phenomena that can explain the improved performance: at the hot face in contact with steel and slag, a thin densified zone was observed that blocked the slag penetration into the porous matrix and the porous aggregates. Iron oxides were almost completely blocked from penetration, and only some manganese oxide was observed in the penetrated zone together with some silica and lime from the slag. Clusters of calcium aluminate (CA6) and magnesium aluminate (MA) spinel build the refractory back-bone on the hot side of the material and gussets filled with mostly glassy calcium aluminum silicates close to the hot face and gehlenite further inside the penetrated zone. Alumina grains had a reaction rim consisting of CA2 or CA6 and a very intimate connection to the surrounding matrix unlike the CMA-free mix that showed micro cracks around the alumina grains. At the colder side, the gunning mix with CMA aggregates showed a very good connection to the substrate, supported by a hercynite formation in the gunning mix resulting from a cross-reaction with remains of iron oxide on the CMA containing repair mix. Furthermore, macroscopic observations of a CMA aggregate containing alumina magnesia castable in the metal zone of a steel ladle revealed that macro cracks developed only very slowly, which resulted in a superior service life.

Vibrations of a laboratory-scale gas-stirred ladle with two eccentric nozzles and multiple sensors

During ladle stirring, a gas is injected into the steel bath to generate a mixing of the liquid steel. The optimal process control requires a reliable measurement of the stirring intensity, for which the induced ladle wall vibrations have proved to be a potential indicator. An experimental cold water ladle with two eccentric nozzles and eight mono-axial accelerometers was thus investigated to measure the vibrations. The effect of the sensors’ positions with respect to the gas plugs on the vibration intensity was analyzed, and experimental data on several points of the ladle were collected for future numerical simulations. It is shown that the vibration root-mean-square values depend not only on process parameters, such as gas flow rate, water, and oil heights, but also on the radial and axial positions of the sensors. The vibration intensity is clearly higher, close to the gas plumes, than in the opposite side. If one of the nozzles is clogged, the vibration intensity close to the clogged nozzle drops drastically (-,36 to -,59%), while the vibrations close to the normal operating nozzle are hardly affected. Based on these results, guidelines are provided for an optimized vibration-based stirring.

Research and Development of Vacuum - Lined Ladle

Due to defect of poor heat preservation property, the common steel ladles can’t pour numbers of boxes by one bag for special steel, such as high manganese steel which is sensitive to casting temperature, casting grain size and mechanical properties. The common steel ladles cooling fast often cause cold ladle and misrun. For better insulation, a vacuum insulation layer was added to the ladle to maintain the temperature of the molten steel, reduce the heat absorption of molten steel by ladle and reduce heat exchange with the outside world. The test results showed that the vacuum-lined steel ladle had a desired insulation performance which was much better than ordinary ladle. It improved the properties of castings and also had distinct energy - saving effect. Its good insulation performance brought a series of advantages, such as heating up fast during preheating of ladle, pouring temperature of molten steel could be further reduced, refining the casting grain size, improving the mechanical properties of the casting and wear resistance. Good insulation performance also could extend pouring time. At the same time, the low temperature ladle wall brought good working environment to foundry workers.

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.

Development perspectives of metal gas-dynamic stirring in a ladle with a side lance application

Blow-off of a liquid metal bath through a lance, located in the bottom part of a ladle wall, is usually considered as one of well-known long time ago variant of steel refining in ladle. However, despite a wide repute and availability of a series of advantages, the technology was not widely spread. An estimation of stirring efficiency and splashes formation at different variants of compressed air supply made. The studies were done at a transparent water model with a color indicator application. It was determined, that upper and bottom lances shifting relating to ladle symmetry axle promotes the stirring intensification and simultaneous decrease of splashes height. The best results were obtained at the simultaneous utilization of asymmetrically located submerged lance and a side lance, oriented in gas-liquid flow direction in the bottom part of the vessel. The side lance is more preferable in maintenance, since for them a ladle fringe is not required as in the case with bottom lances, it is not subjected to falling metal stream action as well as to metal and slag residuals action after tapping finishing. It is possible to provide an improvement of stirring conditions and metal tapping by shifting and inclination of a side lance. Industrial tests showed, that a facility for metal blow off through porous insertions, installed in ladle wall, have a high throughput ability, provide a reliable operation within a course of ladle lining campaign without intermediate repair. It does not require capital outlays and can be recommended for industrial application.

Wall stresses in dual bottom purged steel making ladles

Dual gas purging is often done in a ladle to accelerate the refining operations in steel industries. The purged gas, mainly argon imparts momentum to the molten metal and establishes a turbulent recirculating flow in the melt, which generates shear stresses on the ladle walls. These stresses in-turn leads to the erosion of the refractory lining, which is undesirable. A three dimensional, transient, multi-phase turbulent model has been developed to predict the shear stress distribution along the wall in dual plug, bottom purged ladles. A parametric study has been performed to understand the dependence of wall stresses on various operating parameters like argon flow rate, metal bath depth, slag thickness as well as on the configuration of the gas injectors. A dimensionless correlation is proposed using regression analysis that predicts the maximum wall stress in the form of skin friction coefficient in terms of the above parameters.

A Parametric Study on the Effects of Process Conditions on Dehydrogenation, Wall Shear and Slag Entrainment in the Vacuum Arc Degasser Using Mathematical Modelling

The effect of vacuum pressure and argon flow rate on hydrogen degassing of molten steel in a triple plug, 100 tonne vacuum arc degasser has been examined using a three phase Eulerian CFD-mass transfer coupled model. The model takes into account the interaction between the slag, steel and argon phases over a 20-minute degassing period. Increasing the argon flowrate from 13-29 Nm3hr−1 produces a 10% increase in the hydrogen removal ratio, generating a faster melt velocity and larger slag eye. This also results in the maximum shear stress on the ladle walls increasing by a factor of 2.2 and the shear stress integrated across the wall increasing by a factor of 3.75, thus contributing to enhance refractory erosion. Within the same flowrate range the volume of entrained slag also increases by a factor of 1.4, which may result in increased nitrogen/oxygen pickup. Reducing the vacuum pressure maintains a low equilibrium hydrogen concentration and allows more efficient hydrogen removal, with a 38% reduction in the removal ratio between 102−104 Pa.

Numerical Simulation of Slag Eye Formation and Slag Entrapment in a Bottom-Blown Argon-Stirred Ladle

A transient mathematical model is developed for simulating the bubble-steel-slag-top gas four-phase flow in a bottom-blown argon-stirred ladle with a 70-ton capacity. The Lagrangian discrete phase model (DPM) is used for describing the moving behavior of bubbles in the steel and slag. To observe the formation process of slag eye, the volume of fluid (VOF) model is used to track the interfaces between three incompressible phases: metal/slag, metal/gas, and slag/gas. The complex multiphase turbulent flow induced by bubble-liquid interactions is solved by a large eddy simulation (LES) model. Slag eye area and slag droplet dispersion are investigated under different gas flow rates. The results show that the movement of bubbles, formation and collapse of slag eye, volatility of steel/slag interface and behavior of slag entrapment can be properly predicted in the current model. When the gas flow rate is 300 L/min, the circulation driven by the bubble plume will stir the entire ladle adequately and form a slag eye of the right size. At the same time, it will not cause strong erosion to the ladle wall, and the fluctuation of the interface is of adequate intensity, which will be helpful for improving the desulfurization efficiency; the slag entrapment behavior can also be decreased. Interestingly, with the motion of liquid steel circulation, the collision and coalescence of dispersed slag droplets occur during the floating process in the vicinity of the wall.

Modeling on the Fluid Flow and Mixing Phenomena in a RH Steel Degasser with Oval Down‐Leg Snorkel

The RH vacuum refining process is vitally important for the production of ultra‐low‐carbon steels, due to its effective degassing and homogenizing. A combined physical and mathematical modeling approach is performed in the current study to investigate the multiphase fluid flow and mixing phenomena during the RH vacuum refining process. The numerical simulation coupled VOF and DPM is used to obtain the flow pattern and the interface profile in the RH reactor in the water‐air system. Turbulent characteristics are predicted by a modified k‐ϵ model. A water model is used to validate calculated results. Based on the results of RH water modeling, the 2D‐velocity distribution in the section Y = 0 is captured by particle image velocimetry (PIV) system. To improve the refining efficiency and the service life time of the RH reactor, a new designed RH degasser with an optimized down‐leg snorkel is established. The oval down‐leg snorkel with a larger cross‐sectional area will increase the circulation rate of the fluid by 20% and weaken the impact on the ladle wall compared with the traditional one, which has immense potential in future applications to improve the service life of the ladle.

Numerical modelling of the transport and removal of inclusions in an industrial gas-stirred ladle

ABSTRACTA full-scale, three-dimensional, transient CFD modelling approach capable of predicting the three-phase fluid flow characteristics and the inclusion removal in a gas-stirred ladle was developed. The comparison with experimental data indicates that this model can accurately predict the multiphase fluid flow and slag eye behaviour. The transport and removal of the inclusions in the gas-stirred ladle were predicted by tracing the movement of individual inclusions through computing their particle trajectories and considering a fluctuant top slag layer. The effects of inclusion size, gas flow rates, and injected bubble diameters as well as various removal mechanisms including slag capture, bubble attachment, and ladle wall adhesion on the removal of inclusions were investigated. It is shown that the slag capture is the prevailing mechanism for inclusion removal and the gas flow rate is the most important parameter for enhancing the inclusion removal efficiency.

Study of Low Flow Rate Ladle Bottom Gas Stirring Using Triaxial Vibration Signals

Secondary steelmaking plays a great role in enhancing the quality of the final steel product. The metal quality is a function of metal bath stirring in ladles. The metal bath is often stirred by an inert gas to achieve maximum compositional and thermal uniformity throughout the melt. Ladle operators often observe the top surface phenomena, such as level of meniscus disturbance, to evaluate the status of stirring. However, this type of monitoring has significant limitations in assessing the process accurately especially at low gas flow rate bubbling. The present study investigates stirring phenomena using ladle wall triaxial vibration at a low flow rate on a steel-made laboratory model and plant scale for the case of the vacuum tank degasser. Cold model and plant data were successfully modeled by partial least-squares regression to predict the amount of stirring. In the cold model, it was found that the combined vibration signal could predict the stirring power and recirculation speed effectively in specific frequency ranges. Plant trials also revealed that there is a high structure in each data set and in the same frequency ranges at the water model. In the case of industrial data, the degree of linear relationship was strong for data taken from a single heat.