Lining Of Ladles Research Articles

Durability of Brick Lined Steel Ladles from a Mechanical Point of View

The refractory lining in steel ladles is exposed to chemical and mechanical loads during the heats. Mechanical loads develop from the thermal expansion of the refractories which is confined either by the steel construction or by regions of different temperature within the refractory material. The aim of this work was the investigation of factors influencing the mechanical durability of refractory steel ladle linings and the clarification of failure mechanisms. Especially irreversible strains at the hot face of the working lining caused by compressive stresses induce an opening of joints at the hot face. The irreversible strains reduce the compressive stresses in circumferential direction and increase the probability of tensile failure. A further effect of the irreversible strains is a reduced stability of the working lining. Of special interest in this context is a possible controlled expansion of bricks to counterbalance the irreversible compressive strains.

Ladle Heating Procedure and Its Influence on the MgO–C-Oxidation

The efficiency of ladle heating can be substantially improved by preheating the combustion air using waste gas, oxygen enriching of the air, or changing the air ratio. These actions lead to an increase of the combustion temperature and a decrease of the waste gas volume rate. Hence the knowledge of the flow conditions in the ladle is of decisive importance for further reduction of the waste gas flow rate. The commercial CFD-code (Computational Fluid Dynamic) Fluent 6.3 was used to model the flow conditions in the ladle. The commercial thermodynamic software FactSage 5.3 was used to model the chemical processes such as combustion temperature, chemical composition of the waste gas, and in special the NO x production during natural gas combustion. For the calculation of the temperature distribution in the ladle lining, the flow model was coupled with a FDM (Finite Difference Method)-based thermal ladle model. The change of the combustion temperature and waste gas composition affects significantly the surface of the MgO–C-refractory lining. The oxidation of MgO–C containing 12 wt% carbon was investigated at various temperatures (1500 to 1600°C) in air atmosphere with and without air flow.

Experience of using dry mixes for the working layer of intermediate ladle linings

Results are provided for testing dry torcrete mix grade RANTAL MAG ST for the working layer of intermediate ladle linings under RUP BMZ (Belorussian Metallurgical Plant) and OAO ChMK (Chelyabinsk Metallurgical Combine). Use of dry mixes is markedly simplified due to absence of template heating. The advantages of the proposed method are given in comparison with traditional torcreting.

Development of optimum composition of a batch for periclase-carbon lining of steel-teeming ladles of AFM shops

Results of a study of the effect of antioxidant additives, i.e., metallic aluminum and titanium diboride, on the quality parameters of periclase-carbon ladle refractories are presented. Laboratory studies have shown that the addition of the studied antioxidants into the batch increases the strength and lowers the porosity of the specimens. The size of the decarburized layer due to the addition of metallic aluminum and titanium diboride is virtually the same, but the use of TiB2 adds additional strength to the decarburized and transition layers of the specimens. It is recommended that pilot tests be performed for joint introduction of the additives.

Upgrade of refractory lining of teeming ladles

A gradual upgrade of refractory lining of 160-ton teeming ladles, the disadvantages of the previous lining schemes, and methods for their elimination are described. The implementation of developed techniques has increased the resistance of teeming ladle lining by 60% (from 50 to 80 heats) and the consumption of refractory in the working layer of lining has decreased by 35.7% (from 4.79 to 3.08 kg/t of steel.

Periclase-carbon composite refractories with a new complex binder

We describe the development of the technology of periclase-carbon composite refractories with a new complex binder, which combines the properties of phenolic resins and coal-tar pitch. Theoretical analysis and the results of application in steel teeming ladle lining show that a combination of these thermoreactive and thermoplastic components in the new binder provides a more compact (denser) structure of the coke framework (residue) possessing increased resistance to oxidation. Articles made of the new composite refractory have been successfully tested in the lining of steel teeming ladles. The wear characteristics of new lining materials in steel ladles has been studied.

The possibility of repair of metallurgical ladle lining

Metallurgists have always dreamed of an “eternal ladle”, i.e., the possibility of repairing a metallurgical ladle without removing its old lining. However, the use of thick mixtures for this purpose is problematic, whereas thinner mixtures are prone to cracking under cooling. The author demonstrates that the reason for such cracking is the temperature contraction of the surface layer, which is the first to be cooled, as a consequence, a larger volume becomes enclosed in a shell of a smaller capacity, which leads to its cracking. A method is proposed for cooling the inner volume of lining to remove temperature stresses from the outer layers and prevent their cracking.

Preparation and properties of alumina–magnesia precast block for ladle lining

An alumina–magnesia precast block was prepared by using high-alumina fused corundum as aggregate, and fused magnesia, ultra-fine Al 2O 3 and SiO 2 powders as matrix materials. A small linear expansion for the precast block was achieved through spinel formation from the reaction of MgO with Al 2O 3 in the matrix. The precast block showed a lower apparent porosity, higher modulus of rupture and better slag corrosion resistance compared to the traditional Al 2O 3–MgO–C brick. In addition, the practical application of the precast block to the ladle lining proved it to possess a better thermal insulation which could effectively prevent the temperature drop of molten steel during the refining process. It can be considered that the alumina–magnesia precast block could possibly be applied as a new type of ladle lining material for the production of low-carbon and ultra-low-carbon steel.

State-of-the-art plants for drying and high-temperature heating of ladles

The Stal’proekt Institute has developed state-of-the-art plants for drying and high-temperature heating of steel-teeming ladles. Two new plants for drying tundish ladle lining have been designed for machine No. 6 for continuous billet casting at the Oskol’skii Electrometallurgical Works. Plants for drying and heating 30-ton teeming ladles to a temperature of 800°C and for high-temperature heating of ladle lining (1200°C) have been designed for a currently constructed metallurgical works. All these plants recover flue gas heat and use it for heating air supplied for combustion, thus decreasing the consumption of fuel. The process of drying and heating of lining is analyzed using a mathematical model developed at the institute. The plants are equipped with automatic control systems controlling the temperature schedule of drying and heating the lining. The specified plants ensure cost-effective operation in an automatic mode

A new method for dynamic compaction of bulk mixtures in ramming continuous ladle lining

The defects of the existing methods for producing continuous lining for steel-casting ladles using sand-slinging units are demonstrated and a new solution of the problem is proposed. The proposed device is based on slinging briquettes using compressed air at a speed of 40–80 m/sec and frequency of 3–5 sec−1. The preliminary density of briquettes is 1.56–1.70 g/cm3; they are prepared on the same rotary briquette-slinging unit. The new unit has an original air-distributing control valve. Data are given on the application of a technogenic powder material in experimental studies.

Thermal Stresses Generated in the Lining of a Steel Ladle

Conditions for the thermal regime of 25-ton steel ladles lined with periclase-carbon refractories are analyzed. The input data for numerical analysis are the temperatures at the inner surface of the lining measured experimentally. Temperature profiles over the cross-section of the hot layer of the lining are calculated and then used to determine thermal stresses in the refractory material. A conclusion is drawn that sharp temperature gradients during the heating-up should be avoided. The currently employed heating regimes generate thermal stresses that exceed the strength tolerance limits for refractory materials.

Functional carbonized refractories

Functional carbonized refractories for the lining of steel ladles have been developed. Results of tests carried out on 400-ton steel ladles under industrial conditions are reported. The average durability of the refractory lining was 94.5 heats against rated value of 100 heats.

Steel Cleanliness during Secondary Metallurgy of High-grade Quality Electric Steels

A statistical analysis is carried out of the influence of process parameters on the total oxygen content of high-grade quality electric steels in the ladle furnace station. Furthermore, the micro-inclusions are microscopically investigated. The results show that total oxygen content (O t o t ) and inclusion type are affected by degradation of the magnesite ladle lining and aluminium addition during tapping.

Influence of the Lining on the Thermal Behaviour of a Teeming Ladle

Exact knowledge of the thermal behaviour of the steelmaking ladle is essential for an effective performance of the secondary metallurgical treatment. In order to predict the influence of working parameters, some thermal ladle models have already been developed and presented. The development of new complicated thermal ladle models or the mathematical description of modelling are important. Nevertheless exact model studies of the influencing factors on the thermal state of the ladle are of similar significance. Especially for ladle modernisation concepts, when the lining layer thickness is changed or new refractory materials are used, the question arises if there is an influence of modernisation on the thermal state of the ladle, heat losses or steel melt temperature. The selected refractory materials represent a decisive factor. The thermal properties of the wear‐resistant lining influence the temperature changes and heat losses in the ladle, whereas the properties of the back and insulating lining are accountable for the steel shell temperature of the ladle. The thermal state of the ladle as a function of the real inner ladle lining has already been investigated. The present work is concentrated on the influence of the real back lining and insulating lining.

A Technology for Production of Composite Refractory Materials for the Lining of Steel Ladles

Results of the testing of new refractory materials for the lining of steel ladles are reported. Refractories based on coarsely crystalline periclase (98% MgO) for the slag zone with an endurance of 55 – 60 heats and wear rate of 2.3 mm/heat were tested. For the bottom lining of the steel ladle, alumina-periclase-carbon refractories using fused or sintered alumomagnesian spinels are developed. Performance characteristics of the newly developed refractory materials are discussed.

Monolithic Lining for Steel-Pouring Ladles

The increasing amount of steel being treated outside the furnace and the increase in the quantity of molten metal being transported by rail in ladles are making it necessary to tighten standards on the durability and service life of the ladle linings. Plans developed for a new department at the Chelyabinsk Metallurgical Combine to line steel-pouring ladles will make it possible to replace the traditional brick lining by cast linings composed of refractory concrete. This change will make the lining considerably more durable, decrease accidents, and sharply reduce the amount of manul labor required in the lining operation. This article describes the process and equipment used to make the new monolithic linings.

Impact of slag–refractory lining reactions on the formation of inclusions in steel

The present study was carried out to investigate the impact of slag– refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.

Operating conditions for the lining of a steel ladle in a ladle-furnace unit at the MMP Istil (Ukraine) Joint-Stock Co.

A strategy aimed at improving durability of the refractory lining for steel ladles is considered.

Modelling of high temperature asymmetric creep behavior of ceramics

An extension of the Bingham–Norton's rheological model accounting for high asymmetric tensile-compressive creep behavior is proposed for ceramics subjected to high temperature loadings. Such behavior is observed in heterogeneous ceramics made of grains having a high creep resistance embedded in a softer glassy phase. Two mechanisms of deformation are introduced: namely, under compressive stresses, grain facets are in contact and transmit the load, whereas under tensile stresses the grains are separated and the glassy matrix transmits the load. It leads to a difference in elastic stiffness and strain rate under tensile and compressive stresses. A new three-dimensional constitutive model is developed considering an additive decomposition of the stress tensor into a positive and negative part. Each stress tensor is the driving force of one mechanism of deformation that is characterized in a classical manner. A simplified identification of the model is performed at high temperature on a bauxite-based refractory, which is used in steel ladle linings. It is shown that for this ceramic few material parameters are sufficient to account for major differences of behavior observed in compression tests and three-point bend tests.

Damage of monolithic refractory linings in steel ladles during drying

AbstractSafety linings of steel ladles are made of high content alumina castable. In situ observations confirm that during drying a network of macrocracks appears in the monolithic castable lining, owing to both dehydration of the cement paste and temperature. Crack formation kinetics have been characterised over the life of the lining. To simulate the behaviour of the lining, the thermomechanical behaviour of the castable was characterised in compression and three point bend tests, thermal dilatation tests and TGA analysis in the 20–600°C temperature range. The change in properties is shown to be due mainly to transformation of hydrates in the castable. Numerical simulations of the lining drying process were also performed using a finite element code to verify the causes of cracking. A parametric study was carried out to examine the possibility of reducing the stresses induced by thermal loading. Improved thermal insulation and better control of heating reduce the risk of failure in the lining.