The course of the blast furnace process can be significantly affected by many harmful substances. Some elements may affect the technological parameters of the blast furnace process, others may fundamentally disrupt steelmaking processes following the production of crude iron. Alkaline carbonates also have a negative impact on the quality of blast furnace coke. Zinc and lead contribute to the degradation of the blast furnace lining and thus reduce its service life. For all harmful substances, it is necessary to continuously monitor and reduce their content in feedstocks as well as in crude iron. The elements that reduce the value of the produced metal include phosphorus. This element mainly affects the mechanical properties of the steel produced. The presence of phosphorus at higher concentrations is therefore harmful, except for selected machine steels. For these steels, phosphorus may be added as an alloying element. However, in most steel produced, its content is reduced in secondary metallurgy processes. Within the framework of the research, the content of phosphorus in the input raw materials and the output products of the blast furnace process was monitored. On the basis of the measurements made, the continuous cycle of this element in the blast-furnace process and its influence on the technical indicators of production was analysed. The article aims to evaluate the conclusions of the research conducted to identify phosphorus reduction potential during the blast-furnace process.
Increasing demands on the surface quality of steel slabs together with demands on reduction of water consumption lead to the idea of replacing the secondary cooling zone with water or water-air nozzles by the so-called dry cooling through the supporting rollers. The paper presents the computational study into the dry cooling with the use of the solidification model for continuous steel casting. The simulation is performed for the typical austenitic steel grade S30400. At the moment, the importance of stainless steels grades is increasing again, especially in the automotive industry in design of new types of car bodies as well as in the energetic industry, particularly in case of ultra-critical Rankine cycle. In the paper, a comparison is made for the two cases: a caster with the ordinary secondary cooling zone accommodating water-air nozzles in 13 loops of the secondary cooling zone, and a caster with the dry cooling. In both cases, the radial slab caster casting austenitic steel slabs with the dimensions 1500 × 500 mm is considered.
In investment casting are used ceramic molds. Their quality is critical in the casting process. Ceramic casting molds should be characterized by optimal strength at high temperature and the appropriate porosity, because these features determine the final quality of the casting.
In the article the impact of the base materials quartz and molochite on the thickness and morphology of ceramic molds were studied. For this purpose, wax model sets were produced. In next step they were covered with layers of binder and ceramic compounds, respectively with quartz and a molochite. After preparing the molds and removing wax in the dewaxing autoclave, the ceramic casting molds have been analyzed for wall thickness distribution using a 3D scanner. The study consisted on scanning the model sets and the ceramic molds created on them, and then comparing the obtained scans, resulting thickness of the molds. The morphology, including porosity, was analyzed using computer tomography and a scanning electron microscope. ACKNOWLEDGEMENTS: The work done in the framework of a research project No. PBS3/A5/54/2016 funded by the National Centre for Research and Development.
In the paper the author presented forecasts of steel production size for Poland. The forecasting methodology proposed by the author was two-pronged. Variant I consisted in building separate forecasts of total steel production and steel production in the converter process (BOF) and steel production in the electrical process (EAF). Variant II uses the principle of differences according to which the total steel production minus steel production produced in oxygen converters is the production of steel produced in electric arc furnaces and vice versa the total steel production minus steel production generated in arc furnaces is the steel production in converters (both productions constitute combined production in the steel sector). Variant II consisted of the A version, which built the forecast for steel production in converters (BOF) and estimated forecasts for the production of steel produced in electric arc furnaces (EAF) and version B involving the construction of forecasts for the production of steel produced technology EAF and assessing the prospects for production of steel produced by BOF technology. The forecasting methodology adopted by the author is innovative, and its application enables multi-variant forecasting, while meeting the assumption that the total production is carried out using two key production technologies, the partial outputs of which account for 100%. Forecasts were built using econometric models on the basis of empirical data for time period: 2000-2015. The author made forecasts of steel production by 2020.
Based on the non-stoichiometric Gibbs free enthalpy minimization algorithm (FEM), an equilibrium physicochemical model of the ferrosilicon FeSi75 smelting process has been elaborated, where the influence of process parameters was determined. In above model in the submerged arc furnace the basic parameters are temperatures of the upper and lower reactor, and contribution of the reducer in reaction mixture expressed by the molar ratio C/SiO_2. In addition, considering the carbon content and the content of admixtures in the metallic phase, a small proportion of oxides: Al_2 O_3,CaO,MgO,TiO_2 in the simulation calculations was included: in the reaction mixture. The following temperature ranges were taken in the calculations: upper reactor 1630-1650 ℃ and lower one 1920-2010 ℃. The presented calculation results show good compliance with the observations of the increased quality ferrosilicon FeSi75 (used in the production of special steels) smelting process in industrial conditions. This concerns in particular to the influence of temperature conditions and the contribution of the reducer in the reaction mixture for the silica reduction process efficiency, and the yield of the basic component Si, and the trace elements Al, Ca, Mg, Ti.
Thermo-analytical methods are commonly used for phase transformation temperature identification in a lot of science and industrial applications. Currently, there are most frequently methods based on very small samples analyses like a different scanning calorimetry (DSC) and/or a differential thermal analysis (DTA) realised for various materials mostly in combination with a thermo-gravimetry (DSC/TG; DTA/TG respectively). The aim of such methods of tiny samples is to fit a transformation process without an influence of the sample mass and to get universal like conclusions. On the other hand, older direct thermal analytical method generally done on tens grams and larger samples are not so popular now excluding few applications regarding to cast iron and/or non-ferrous metals and their modifying process monitoring. However, simultaneous utilisation of both mentioned methods during determination of real steel liquidus (TL) and solidus (TS) temperatures leads to suppressing their individual disadvantages and enable to fit the results for such heterogeneous material like steel in the best possible way. The paper is focused on the discussion of TL and TS of 18 continuously cast steels analysed in the frame of No. LO1203 "Regional Materials Science and Technology Centre - Feasibility Program”. The submitted evaluation shows an importance of the parallel utilization of methods, accuracy and reproducibility of the results and also the deviations of the experimentally determined TL and TS and empirically calculated values of the industrial partner and values obtained by thermodynamic calculations.
In the grinding process of steel products, significant amounts of grinding dust contaminated with coolant (oil, oil emulsions) and non-metallic material from abrasive (silicon carbide, aluminum oxide and others) are formed. The grinding sludge created as a result of this mechanism is a valuable source of post-industrial waste containing, in addition to iron, such alloying elements as: cobalt, nickel, chromium, copper, tungsten, molybdenum and vanadium. Taking into account the metallurgical value of post-mill sludge, a method of recovering these elements from it was developed.
The article presents the method of recycling in a three-stage technological process, including deoiling of sludges, sintering and melting in an electric furnace.
The problem of the furnace slag penetration into the ladle is inseparably connected with the process of steel furnaces tap holes closing and opening. We are talking about the so-called slag free tapping. Different closure designs are used just in connection with the so-called slag free tapping. All these devices practically try to minimize the penetration of furnace slag into the ladle during tapping. In practice, however, it is never a complete avoidance of the furnace slag penetration into the ladle. The design and layout of the tap holes vary according to the furnace type. For this reason, the conditions for opening and closing the tap holes (openings) are also changed, consequently the design of the device for the tap holes closing and opening differs. Various ways for closing and opening of metallurgical aggregates tapping holes are used in practice. There may be also some complications during the opening process. There are complications especially with the tap holes, into which a mixture of liquid slag and metal penetrate during the tapping and subsequently, this mixture solidify. The paper presents selected designs of devices for closing and opening tap holes and examples of their use in practice.
Filtration is one of the most efficient methods of removing Al2O3 inclusions from liquid steel. The efficiency of this process depends on the physicochemical parameters of liquid metal, inclusion and properties of the applied filters. The particles attracted during filtration undergo agglomeration, collisions and chemical reactions on the filter surface, with the emphasis on the mechanism of particle collisions and the role of material from which the filter was made. The aluminum oxide inclusions collide with the filter surface and as the growing process continues, the particles also collide with the previously adsorbed inclusions. At the particle and filter interface the mixing of the metal bath is most intense, being a result of a sudden change of flow direction and breaking up the stream of liquid metal which is in a direct contact with material. The efficiency of filtration is defined not only by the behavior of individual particles but of all population. The simulations revealed that only a small fraction of these particles adheres directly to the filter material; most of them stick to the former ones. Attention should be also paid to the fact that some of the inclusions which contacted the filter walls do not form a permanent connection and are then entrained by metal. Authors solved the problem of agglomeration and collisions of Al2O3 inclusions with the ceramic surface of the filter with the PSG method, mainly used for the analysis of agglomeration of inclusions during steel refining in the ladle.
The metallurgical industry is a trade where large amounts of waste are generated, including mill scale and iron-bearing sludge, which in the reduction process can be a valuable raw material for the production of sponge iron. In this publication has been prepared the energy balance for such a process and it has been shown that the electrical energy flow necessary to carry out reduction of mill scale with a CO + H2 gas solution is 17.48% of the total energy stream supplied to the process. The highest value of the supplied energy stream is chemical energy brought with a reducing gas of approx. 71.65%. The largest energy losses occur in gaseous products of reduction and constitute 57.15% of the total energy flux of products. Raising the temperature of the reaction gas from 25°C to 300°C reduces the electricity consumption about 14%. The determined energy losses to the environment are strongly dependent on the final design of the reactor for the reduction of iron-bearing materials.
Based on the equilibrium model with two isothermal reactors, the influence of CaO and MgO oxides on the ferrosilicon process in the submerged arc furnace was determined. It has been determined the influence of addition of CaO and Mgo oxides in the feed mixture on the SiC carbide phase formation, content of Ca and Mg elements in the chemical composition of the FeSi alloy as well as the efficiency of the carbothermal reduction process.
Introduction of argon to the bath is a commonly used secondary metallurgy treatment. The most economical technique of secondary metallurgy is the ladle process at the ladle furnace station. The introduction of inert gas (argon) into the metal bath takes place using porous plugs placed in the bottom of the ladle. Such argon blowing process through the metal bath via a porous plugs proceeds with the intensity necessary to cause the circulation of liquid steel. This movement is necessary to homogenize the temperature and to achieve a state of near chemical homogenization of the liquid steel after introduction of the alloy addition. Another positive effect of gas injection is the adhesion of non-metallic inclusions to the bubbles or their capture by bubbles and removal from the metal bath to the slag.
The work presents the research carried out using the water ladle model in which there is a possibility of simultaneously blowing the bath through one, two or three porous plugs installed in the bottom and additional lance support from above. Different configurations of bath gas introduction (through one, two or three shapes) were analyzed using different flow rate of gas. As a result of the research, visualization of the mixing process of the alloy additive and mixing curves at different process parameters were obtained. These results allowed to analyze the mixing process of the alloy additive.
In this paper, the dependencies of density, surface tension, and average wetting angles on temperature as well as surface tension on time at constant temperature were investigated at three Fe - C - Cr model alloys where chromium content ranged from 0.92 to 4.76 wt. %. All measurements were performed by sessile drop technique in a resistance furnace at temperatures from melting point up to 1600 °C except those at the constant temperature. The effect of chromium, oxygen, and sulfur on the values of the abovementioned quantities was proven. The temperature coefficient of surface tension dσ/dT was positive for all liquid samples due to the influence of oxygen and sulfur. The surface tension and average wetting angles raised with increasing chromium content. Evaluation of time dependencies at a constant temperature showed a decrease of density caused by a higher degree of interaction with the alumina substrate. All results were acquired with satisfactory relative standard deviation.
The article presents the results of research of iron content (II) and iron (III) in mill scale. The total content of iron was marked by the absorptive atomic spectroscopy, however the analysis of Fe content (II) and Fe (III) was carried out with the spectroscopy methods. The gained results indicate between 65-85 % of total content of iron in the analysed samples. It was proved that the content of Fe (II) in the analysed samples amounts to 15-31 % while the content of iron (III) 22-40 %.
Computer-aided image recognition methods are non-invasive, easy to implement and quick to calculate defects detection methods. They seem to be a promising method for investment casting applications - defects can be detected in individual incestment casting processes, reducing the costs caused by defective castings.
As part of the research, defects have been defined and described in wax models, wax model kits, casting molds and castings. For each of the disadvantages, a characteristic signature was created allowing for its later detection in the image. In the next stage pre-processing of models, sets, molds and casts was carried out, including segmentation, denoising and sharpening in order to prepare images for the input form for the algorithm. Next, an algorithm for searching and classifying areas containing separate defects and deviations from correct images was developed. The algorithm uses statistical classification methods and machine learning elements using convolutional neural networks. ACKNOWLEDGEMENTS: The work done in the framework of a research project No. PBS3/A5/54/2016 funded by the National Centre for Research and Development.
The presented paper is focused on the experimental study of the surface properties of selected commercial steels (three alloys based on Fe-C-Cr). The surface tension of given steels and their wetting with alumina substrate in the temperature interval from the melting point to the temperature of 1600 °C were determined using sessile drop technique. The effect of the temperature and the chemical composition on the surface properties of the steels was studied. For an assessment of the influence of the major elements (carbon and chromium), the steels with different carbon and chromium contents, which varied in the range of 0.077 – 0.381 wt. % and 0.049 – 4.990 wt. %, respectively, were chosen. It was shown that higher content of both abovementioned components increased the surface tension of the investigated steels and their contact angle with alumina substrate. The interaction of the steel samples with the alumina substrate was studied using SEM and EDX methods.
Currently, model study is commonly used part of research in field of metallurgical processes. Process of simulation of casting and solidification of steel ingots is no exception. This paper maps possibilities of numerical modelling of casting and solidification of steel ingots, as a part of research of these processes, carried out in Department of Metallurgy an Foundry of Faculty of Metallurgy and Materials Engineering of VSB-TU Ostrava under the conditions of Regional Materials Science and Technology Center. A few programs and software packages applicable to numerical modelling of ingot casting process are available, e.g. QuickCAST and ProCAST. Both programs provide a wide range of potential results, useful for optimization of ingot casting process and resulting quality of ingots, which are presented in this paper.
This paper deals with optimization of ferrite magnet production. The thesis is divided into two parts. The first part introduces general information about magnets and their division. The process of the magnet is described in detail. In the second, experimental part of the input raw material, ferrite metal powder, the basic mechanical and physical parameters were determined, including the angle of internal friction, the particle size distribution, the particle shape and the flow function, serving for a more detailed description of the behaviour of the material throughout the technological line. On the basis of evaluation of measured data, specific steps were proposed to optimize ferrite magnet production and general optimization of weak points of storage and feeding processes.
The article presents research results performed to determine the distribution of non-metallic inclusions on the cross-section of a continuous square-shaped billets, intended for long products. The tests were carried out under industrial conditions during normal production cycle, while casting of carbon steel groups. Samples (as a disc shape) with 20 mm thickness, were taken from ingots. The distribution of inclusions was determined by quantitative analysis, according to a specific scheme.
In modern metallurgical processes, the mixing of a metal bath is a basic operation that allows achieving a state of close chemical and thermal homogenization of liquid steel after the insertion of the alloy addition. Mixing also increases the efficiency of removing non-metallic inclusions. Research into metal bath mixing processes contributes to the optimization of steelmaking processes.
The article presents the calculations made at the conditions prevailing in a ladle furnace with a volume of 145 Mg liquid steel. The effect of mixing power of argon on chemical homogenization bath was determined. The mixing power values for the argon flow rates in the ladle QAr = 100-500 [dm3 / min] were calculated.
Due to the specific requirements for monitoring processes and products in the aircraft industry, non-destructive testing (NDT) is increasingly used in combination with advanced statistical analysis.
The publication presents the results of research aimed at determining the quality of wax models and multi-layered ceramic forms, used for precise casting of critical parts of aircraft engines. Studies on the shape and dimensions of wax models and ceramic moulds were made by 3D scanning using the GOM ATOS CORE 200 scanner. A map of dimensional deviations, created as a result of comparison of scanned wax models with CAD models, was created. The thickness of the moulds was determined by comparing the dimensions obtained by scanning 3D wax models and ceramic forms.
The obtained measurements were then subjected to advanced statistical processing using selected Six Sigma tools. The analysis was carried out in several separate areas of both wax models and forms. The basis of the analysis were the results of measuring 30 points in each of the measurement zones of the blades and moulds models. The consistency of the results with the normal distribution based on the empirical cumulative distributor was verified. The Anderson-Darling test was adopted based on the weighted distance between empirical and theoretical counselor. ACKNOWLEDGEMENTS: The work done in the framework of a research project No. PBS3/A5/54/2016 funded by the National Centre for Research and Development.
Metallurgical processes of steel production are strongly connected with knowledge of the thermo-physical and thermodynamic properties of liquid metal during individual technological steps. Critical factors describing behaviour of steel in the process of its solidification and then important to a correct setting of conditions of steel casting and solidification of steel, which significantly affect the final quality of the as-cast steel, are liquidus (TL) and solidus (TS) temperatures.
Experimental determination of these temperatures (or generally additional phase transformation temperatures) can lead to the refinement of all these phase transformation temperatures as well as to a more precise determination of the interval of solidification of steels. Utilization of this approach, e.g. in the process of optimizing the technology of ingot or continuous casting, could lead to achieve more accurate results moreover in direct connection with numerical simulations, and thus a better knowledge of the impact of optimized technological parameters on the resulting quality of cast steel.
The paper is devoted to the application of method of Design of Experiment (DOE) to analyse and clear quantification of the impact of experimental conditions on the experimental results (measured data) of direct thermal analysis method. First of all, it is a way to find a new approach to quantificate and verificate a statistical significance of experimental effects (influence of experimental conditions) on obtained phase transformation temperatures. The developed method allows to filter relevant data from individual thermo-analytical experiments for final calculation of high temperature phase temperatures more precisely than it was possible ever before. This is crucial for proper liquidus and solidus and liquidus temperatures’ recommendation to real conditions.