High chromium iron castings have been observed to exhibit significantly varying mechanical properties. To establish the origin of inconsistencies in properties, the research was conducted in two phases. First, monitoring to maintain consistency of charge materials and pouring temperature in order to eliminate extraneous operational variables from the causative factors. Second, microstructural variations and consistency in mechanical properties were characterised and compared for different heats with small deviations in chemical compositions within the specification of BS4844:1986 Grade 3D high chromium white cast iron. The investigation revealed that marked homogeneity of microstructure as a result of variation in particularly chemical composition as well as operational parameters such as inconsistencies in pouring temperatures. The solution to this problem lies in narrowing the specification range by raising the lower limits to 2.5% C and 25% Cr, as well as controlling the pouring temperature around 1550oC and reducing solidification time as much as possible.
Three ferrous materials; Hadfield steel, high chromium cast iron and austempered ductile iron (ADI) exhibit a similar phenomenon in which soft stabilised austenite transforms to hard martensite on the worked surface. This property is desirable in applications where toughness is required in the bulk of the component while the surface needs to be hard-wearing. Thus, the microstructure of the component may consist of meta-stable austenite, which is meant to change to martensite by strain-induced transformation as a result of impact or wearing loads applied to the surface. The chemistry of alloys is very different while the metallurgy and transformation mechanisms are closely similar. In this paper, the differences, similarities as well as the most appropriate applications of the materials are discussed.
In the publication were analyzed the most important physicochemical parameters selected a few coals in the context of their use as reductors in the process of smelting ferrosilicon. From the presented in the publication coals useful as reductors, the Wujek coal has been used in the past (exhausted resources), Staszic and Wieczorek coals are currently used, while Bogdanka, Piast and Ziemowit coals are characterized as potentially usable in blends with other coals. At work were compared parameters of coals obtained in: technical and elemental analysis, examination of ash composition, vitrinite reflectance measurement and reactivity of selected coal towards SiO and CO2.
The paper presents few aspects concerning of the new alternative iron making technologies in Romania. A few reasons are analyzed for the apparition and development of such technologies in the world steel market competition. The presence of altenative iron making technologies will be a benefit for metallurgic, economic, social and environmental reasons. The preliminary researches made using wastes from chemical and metallurgical industries are encouraging for developing alternative iron making pilot plants.
The blast furnace process can be negatively affected by a number of harmful elements. These may interfere with the course of the technological process, but can also increase production costs. Harmful elements are contained in the blast furnace charge and they disrupt chemical, physical, but also the thermal processes in the production of iron. Changes in the above processes may produce a range of effects from changes in the flow of gases to the problems with a decrease of the charge or excessive heating or cooling of the hearth. In the ideal proces, we can alocate harmful elements in the slag. But it remains crucial to monitor and reduce the contents of negative elements already in input raw materials. Thus their continuous circulation in the blast furnace is limited. Alkali carbonates represent a large group of polutants. They can re-enter the process and negatively affect the technological as well as economic and operational indicators of blast furnace process. Alkalis may enter the process, for example in the form of silicates or carbonates. This article aims to analyze the content of Na2O compounds entering the blast furnace process and the possibility of reducing their negative consequences. The contents of the compounds and their effects were monitored for a lomg term scale in the context of the research.
This paper deals with the influence of the experimental conditions settings of the chosen DTA method on obtained data. The article is focused on the study of heating rate effect on shifting of liquidus temperature (TL) of Fe-C-Cr based systems (steels). Heating rate belongs to the frequently and easily changing parameter and its influence on the obtained data is substantial. DTA measurements were realised using the SETARAM Setsys 18TM laboratory system. The samples (steels) were analysed at selected controlled heating rates (1, 2, 5, 10 and 20 K/min). It has been found that the value of liquidus temperature shifted with the increasing heating rate towards to the higher values and this dependence was expressed. Application of obtained results can substantially contribute to minimising the influence of the used heating rate mode on the liquidus and enables an extrapolation to the so called "zero" heating rate. It is thus possible to obtain for the investigated systems the liquidus temperatures close to the equilibrium temperatures without necessity of making set of experimental measurements, which is highly time-consuming.
This article describes how to improve the tribological properties of cast iron by local strengthening by ceramic layer, directly in the casting process. The research included manufacturing of the casts with a ceramic layer. Its percentage on the surface was 30%. The research included measurement of thickness and abrasive wear resistance according to ASTM G 65-00. As a result of the research it has been found that the infiltration of the molten metal into the ceramic preform is a main factor which affects the correct production of the cast with local reinforcement. The research results also have proven that the application of a lattice ceramic insert placed in the mould is the most appropriate option, due to the regular distribution of the particles in the cast and obtaining a sound casting.
The paper presents the influence of parameters of ceramic molds on the quality of small-scale castings elements produced by the investment casting. Five types of products of varying dimensions were selected for the study. Seven ceramic coatings were applied to the prepared model sets in various bonding variants. Three types of binder (LUDOX, hydrolysed ethyl silicate, water binder Remasol Plus) and two types of sand (quartz, molochite) were used as ceramic material. Three types of ceramic molds were made.
1.Ceramic Mold with LUDOX/ hydrolysed ethyl silicate + quartz
2.Ceramic Mold with LUDOX/ hydrolysed ethyl silicate + molochite
3.Ceramic Mold with Remasol Premium Plus/ Remasol Plus + quartz
After applying each coating, the ceramic molds were dried under constant humidity and temperature conditions. Finished ceramic molds were casted with high alloy steels. The results were presented in graphs, tables and pictures.
ACKNOWLEDGEMENT: The research was carried out within the framework of the Applied Research Programme of the National Centre for Research and Development no. PBS3/A5/54/2016 titled „The application of three-dimensional, optical digitization, thermovision and tomography in order to assess a technological quality of model wax sets and multilayer ceramic molds in the processes of investment casting of critical parts of aircraft engines.”
This paper presents the results of the effect of Cr in the precipitation of carbides in nodular iron class 100-70-03. In this study was considered the average nominal chemical composition suggested by the ASTM standard and added with content between 0.5 to 3 %Cr. Nodular iron was manufactured in induction furnace using conventional raw materials. "Y" casting blocks were obtained in silicate sand moulds. Thermocouples were placed in Y blocks to obtain the corresponding cooling curves.
"Y" castings were cut to evaluate the fraction and distribution of carbides through the casting as a function of the amount of Cr in the alloy. The cooling curves were analyzed so that on the basis of experimental eutectic temperature with the fraction of carbides precipitated by the presence of Cr. Finally characterization of carbides were done by SEM microanalysis techniques. These nodular iron could be applied to CADI manufacturing components with high hardness and wear resistance.
This paper deals with a recycling and reusing of non-conformity product during the production of magnets. Theoretical part of the paper contains general facts about permanent magnets and theirs productions. Experimental part describes methodology of non-conformity product processing by dry milling to ensure optimal conditions for rebuilding the material to reuse it in production cycle. Granulometry analysis of the milled material showed the formation of clumps and aggregates of size from 20 to 30 microns but an ideal particle size suitable for the production of the magnets is about 1 micron. After evaluation and mutual comparison of results, appropriate measures have been proposed in the recycling technology which has been used.
The behavior of nonmetallic inclusions in liquid steel results from the operation of a set such processes as fluctuation, adhesion and collisions between particles. In the metallurgical processes taking place in the ladle, the agglomeration based on turbulent collisions between oxide particles plays the most important role. Typically, the deoxidization of steel is conducted with the use of aluminum. An oxide having the ability to generate agglomerates is formed. Upon adding yttrium the process of oxides formation also refers to yttrium oxide (Y2O3), which also exhibits a strong grouping tendency. For this reason the collisions between particles will cover both oxides of the same and of different components. For the sake of determining the rate of turbulent collisions of aluminum oxide and yttrium oxide particles through the mixing of a hot metal bath, the Particle Grouping Method and equation of population balance equation were used. The simulations were performed for the assumed mixing energy value ε = 0.001 for 6 exemplary size-groups. The initial number of particles N0, resulting from the deoxidization ability of Al and Y at oxygen content of 10, 50, 100 and 500 ppm and initial radius of the formed oxide, were assumed as variables. The obtained results of simulations are presented in the form of plots illustrating how the number of inclusions in each size-group changed as compared to the initial number (nk/N0) in a function of dimensionless time t*. The analysis of obtained results revealed that at a constant oxygen content, the increase of initial radius shortens the time of fading away of particles in all six size-groups. In the case of large inclusions, their grouping through collisions is faster; it results from the higher probability that particles of large radius will collide. Particles of a very small radius of 1µ were observed to hardly agglomerate, and because of this were hard to remove from liquid steel.
Production of crude steel with the help of oxygen processes will produce, according to forecasts also in the future, large portion of the world-wide steel production. In the connection with this fact the blowing systems are being further developed and improved both in case of oxygen converters, hearth furnaces and in case of electric furnaces or their combinations. These systems, for example, serve both for blowing of refining oxygen on the bath surface or into the melt and for blowing of additional combustion oxygen or blowing of the gas mixture with powdered substances. This paper deals with the main design characteristics of the lances for blowing of refining oxygen on the melt surface. These design characteristics help designers and engineers to design systems that meet the high demands on quality, efficiency and operational reliability.
Steel has never ceased to be the most important structural materials. Steel and cast steel account for more than 92% of total consumption of metals. Unfortunately, this sector generates massive amounts of waste, including iron-bearing types. Substances referred to as waste are subject to rigorous legal regulations the purpose of which is to protect human health and natural environment. Restricting waste generation and utilising the waste already produced are the most fundamental principles of rational use of natural and anthropogenic resources. More and more of metallurgical waste is reclaimed, yet part of it is stored. This paper presents the results of research on waste containing iron (dust, mill scale, sludge) in terms of their environmental impact when stored, the results of the assessment of the quality of water extracts in relation to the legal requirements for the introduction of sewage into waters or to land.
The most important tasks of secondary metallurgy are to accelerate the course of steel production processes and to improve its quality, at the same time limiting the amount of work, energy and sources. The basic and popularly applied treatment of secondary metallurgy is blowing the liquid steel in the ladle by inert gases. The introduction of gas into the liquid steel can be realized by differently constructed porous plugs installed in bottom of the ladle. Because there is aggressive character of the working conditions thus these plugs should be thermally and mechanically resistant, have appropriate permeability, and able to create required amount of gas bubbles and their dispersion in the whole volume of liquid steel. Today in industry three kinds of porous plugs are used differing with construction: plugs with porous segment, crevice type and hybrid plugs.
Article presents the results of modelling research conducted with using the model of ladle with possibilities of blowing the metal bath. Research was carried out for four different types of porous plugs: two plugs crevice types with different crevice placing, plugs with porous segment and hybrid plug (crevices plus porous segment). The results of research was obtained in the form of visualization of gas bubbles creation, mechanism of gas bubbles cone creation (gaseous column) and determination of time and way of mixing the modelling liquid in the dependence on the applied type of plug.
The article presents the results of research of iron content (II) and iron (III) in post-production wastes such as dusts from steel, cast and casting cleaning processes made of iron alloys. 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 40-90 % of total content of iron in the analysed samples. It was proved that the content of Fe (II) in the analysed samples amounts to 2-64 % while the content of iron (III) 5-28 %.
In this work the comparative studies between solvent extraction and transport across polymer inclusion membranes (PIMs) have been carried out for the removal of iron(III) from aqueous chloride solutions. Tricaprylmethylammonium thiosalicylate [A336][TS] and trihexyl(tetradecyl)phosphonium thiosalicylate, [PR4][TS], a thiol-containing task specific ionic liquids (TSIL) were used as extractants/ion carriers in both processes. Effect of different parameters such as hydrogen ions concentration, chloride ions concentration as well as hydrochloric acid concentration in aqueous phase on iron(III) extraction has been investigated. Cellulose triacetate membranes with [PR4][TS] as carrier have been prepared and applied for removal of Fe(III) from HCl and NaCl solutions. Fe(III) ions were effectively removed from the source phase by transport through PIM into 2 M H2SO4 as the receiving phase. Also separation of Fe(III) was carried out from hydrochloric solution containing Ni(II), Co(II), and Mn(II) and the separation coefficients were found. The data generated from the transport of Fe(III) study were compared with that of conventional solvent extraction investigation.
The article presents the way of improving usable properties of cast irons by producing titanate coats in founding process, introducing titanium insert directly before pouring molten metal. It is presented an innovative way to use 3D technology applying SLS method in order to obtain local reinforcement of cast iron. The object of studies was a material consisting of two fundamental parts: bearing part- cast iron, and working part represented by titanic modular insert. The article presents detailed geometry of the insert as well as the micro observation on light and scaning microscope. In addition it was executed micro analyse(linear and point) and mapping of the permanent joints between two materials, and also microhardness and wear resistance were examinated. On the basic of obtained results it was affirmed the presence of titanium carbides on the boundry cast iron- titanium insert. Their dismentios and distribution were irregular in the volume of the material. Moreover, it was observed a local reinforcement of examinated material, as evidence by increase of wear resistance and microhardness compared to basic material.
Our current approach for microstructure images recognition and image-based properties measurement utilized manual iterative image filtering and threshold-binarization process until image areas, corresponding to desired structure elements, were extracted. This approach however, led to information loss and inaccurate results, due to extensive filtering required to remove noise and extract features. Results were very sensitive to scanning method used to obtain images, image quality and coloring. Also, manual binarization process assumes that desired structure features are already known.
In our new proposed approach image is segmented using algorithms based on Watershed [1], Morphological Geodesic Active Contours (MorphGAC), and Morphological Active Contours without Edges (MorphACWE) [2-3] algorithms, providing context-independent image partitioning. After image is segmented, obtained segments are classified and then measurements are taken for desired classes. This approach allows to find more features than binarization approach with higher accuracy, as minimal filtering is required, and MorphGAC/ACWE algorithms tend to be more accurate in edge and contour detection than simple thresholding or linear filters.
Our program and is written in Python, with use of OpenCV and Skimage libraries. It implements mentioned algorithm and provides tools for image filtering, and also analysis and measurements tools including features size and distribution statistics are available. For optimization enhancements, Python C-extensions and OpenCL-based GPU processing will be used if needed.
Future enhancements includes graph theory structure analysis, as image partitioned into segments corresponding to structure elements can be easily represented in graph form. Our goal is also to utilize neural network for microstructure recognition, segmentation and property analysis.
LITERATURE: [1] Serge Beucher, Christian. International Workshop on image processing Real-time Edge and Motion detection/estimation, Rennes, France, September 1979
[2] Luis Álvarez, Luis Baumela, Pablo Márquez-Neila, “Morphological Snakes”, In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition 2010 (CVPR10)
[3] Pablo Márquez-Neila, Luis Baumela, Luis Álvarez, “A morphological approach to curvature-based evolution of curves and surfaces”. In IEEE Transactions on Pattern Analysis and Machine Intelligence (PAMI).
ACKNOWLEDGMENT: The project has been supported by the Polish National Science Centre, Decision number: DEC-2011/03/D/ST8/04041
The surface tension of selected real steel grades and their wetting with alumina substrate in the temperature interval from the melting point to the temperature of 1600 °C were determined using the sessile drop technique. The effect of the major elements (carbon and chromium) on the surface properties of given steels was studied. Carbon and chromium contents were varied in the range of 0.077 - 0.411 wt. % and 0.046 - 12.392 wt. %, respectively. It was shown that with an increasing content of both aforementioned components increased the surface tension of the investigated steels. The temperature dependencies of surface tension exhibit a steeper decrease at higher chromium contents.The contact angle of liquid steels with alumina substrate increased with increasing chromium content in the samples.
The paper presents the results of operating experiments focused on the study of the formation and modification of non-metallic inclusions during treatment of aluminium-killed steels at units of secondary metallurgy. The process melts were focused on analysis of the influence of deoxidizing and slag-making agents and wear of the lining on the steel microcleanness. The experiments were aimed at studying the patterns of formation, origin and conditions of elimination of non-metallic inclusions during treatment of steels on the homogenization station and ladle furnace. The actual evaluation of microcleanness was executed by means of SEM microscope. The results present the number, ratio and analysis of chemical composition of non-metallic inclusions including their plotting in ternary diagrams. The evaluation indicated in the paper represents basic information on the achieved microcleanness, and thus also the produced steel quality.
The article presents results of studies of silicon – molybdenum cast iron crystallization process. This material is use to work in high temperatures. The study included experimental melting (estimated chemical composition was: 4,5% Si; 2,5% Mo; 2,5% C) and analysis of crystallization process. For examination the TDA equipment was used for registration of temperature changes in time and for calculation of derivative curve. The analysis of chemical composition of obtained samples using spectrometer LS500 and Leco analyser was conducted. Metallographic examination of cast alloys was carried out on Phenom Pro-X scanning microscope. In order to determine the phase composition, X-ray diffraction studies of analysed samples were performed. This studies were carried on the Panalytical X'Pert PRO diffraction system, using filtered radiation from the lamp with copper anode and PIXcel 3D detector on the diffracted beam axis. Obtained results allowed to described the crystallization process of ductile silicon – molybdenum cast iron (SiMo) designed to work in high temperatures. It was also possible to identify the elements of microstructure.
During continuous casting of steel, a centerline porosity formation frequently occurs and participates on decrease of internal quality of continuously cast billets. To avoid the centerline porosity formation, a description of casting parameters connection with centerline porosity is necessary. This paper is focused on study of casting speed influence on centerline porosity formation in continuously cast round steel billets through a numerical modelling. Centerline porosity formation is closely related with solidification of billet which can be affected by casting speed change. Usually, in real conditions, the change of casting speed includes a change of cooling conditions both in primary and secondary zone. For determination of influence of technological parameter on observed quantitative parameters of billet, only casting speed was changed during numerical modelling while keeping cooling intensity. With relation of casting speed changes, the attention was paid also on metallurgical length which effects centerline porosity formation. Metallurgical length shortening should lead to reduction of centerline porosity formation. In accordance with literature knowledge, the increasing of fraction solid due to decreasing of casting speed was confirmed. Fraction solid increasing was caused by increase of time which billet spent in cooling zones. Mentioned fact affected positively metallurgical length shortening. Centerline porosity was evaluated by liquid pressure in centerline region of billet. The porosity formation can be assumed at zero liquid pressure in centerline region. It was find out that with decrease of casting speed, the liquid pressure in centerline region increased. Thus, occurrence of centerline porosity decreases with decrease of casting speed.
The paper presents a study of the chemical composition and selected thermal operations on uniformity of the structure and properties of 75 mm thick cast iron (casting mould YIV). The Brinell hardness distribution was investigated on cross-section of the samples. Rp02, Rm, A5 was determined from tensile specimens cut from the center and outer sections of the casting YIV . Samples were taken from two plates cut at intervals of 25 mm from the bottom of the casting. Metallographic microsections were made of the grip sections of the tensile specimens. Using computer image analysis the characteristics of graphite and the structure composition were determined. It was found that the applied heat treatment (ferritizing annealing, normalizing) and the additive alloy (Cu) reduce differences in mechanical properties and structure of matrix in thick-walled castings.
This paper presents actual computational possibilities and experiences from the modelling of qualitative parameters of continuously cast steel billets in ProCAST simulation software achieved during a solving of research projects with industrial partners. The ProCAST simulation programme is a part of the equipment of the “Laboratory of modelling of processes in liquid and solid phases” of the “Regional Materials Science and Technology Centre” at the Faculty of Metallurgy and Materials Engineering at the VŠB – Technical University of Ostrava. In the paper, the list of the required results is reported. Based on the required results for radial continuous casting of steel billets, the most suitable way of the definition of the numerical model and computation are described. The paper describes the pre-processing, processing and post-processing phases of numerical modelling. Also, the problems with determination of the thermodynamic properties of materials and the heat transfer between the individual parts of the casting system, including the definition of the heat losses along the casting strand in the primary and secondary cooling, are discussed.
Directionally solidified sample of Fe-C alloy in a vacuum Bridgman-type furnace was produced under an argon atmosphere. The pulling rate was v = 83.3, 125.0 and 166.7 μm/s (300, 450 and 600 mm/h) with constant temperature gradient G = 33.5 K/mm. The microstructure of the sample was examined on the longitudinal section using an optical microscope and scanning electron microscope. The average interphase spacing λ was measured on longitudinal section of the sample. The relationship between λ and v was determined using linear regression analysis. According to the results, it has been found that interphase spacing λ decreases with an increase of v values. The average interphase spacing λ values were used to verify the λ 2 v- growth law fulfilment.
From manganese smelting history, the focus has always been on the high grade manganese oxide ore as the grade has an influence on number of parameters. This has been largely because of pyrometallurgical advantages that high grade ore offers such as low power consumption and high quality products due to its oxide nature, relatively easy to smelt. However, in the last number of years, industry players have tapped into the use of carbonate sources to supplement the depleting oxide sources, and try meet the steel demands where manganese finds its primary use, hence the importance of further investigations on the use of carbonates that impact the quality of products as well the energy consumption. Following equipments were used: a jones riffle for sample preparation, jaw crusher and zip mill to decrease the size of particles, a graphite crucible and an induction furnace for smelting. Different proportions of oxides and carbonates manganese ores were mixed and smelted at 1550oC under argon atmosphere. The characterization of the ores and products was conducted using XRD, ICP-OES and SEM-EDS. Results showed that it was possible to produce a marketable High Carbon Ferromanganese containing at least 75%Mn with also a slag containing a maximum of 20% MnO for a range of Oxides-Carbonates blends. However, results for Oxides-Carbonates blends with less than 20% oxides have led to alloys that contained only 48% to 68% even though the slag contained ≤20% MnO.
In the paper some aspects of the practical implementation of the simulation systems computer-aided design in investment casting are discussed. Presented hypothesis and methodology are based on original solutions allowing to develop unique tools in the context of designing new technologies. This is closely related to the practical design and implementation of numerical solutions, testing and validation and in the final stage with testing in industrial conditions. An example of such a dedicated system is the DEFFEM package, whose computational capabilities are presented in this paper simultaneously with the directions of further development and implementation work.
The performed tests were focused on the mechanism of reaction of oxide particles of Y2O3 and Al2O3 with the solidification front while casting steel. The presence of oxide inclusions in steel is a consequence of precipitation and segregation processes in the CCS crystallizer. The oxide precipitations in the liquid metal are a result of deoxidization and are generally unfavorable for the future properties of steel; on the other hand, their fine dispersive phase may play the role of nucleation centers of other phases, which in this case is advantageous. Yttrium oxide precipitations are formed when yttrium is used as a modifier and micro additive to steel of definite properties. Unlike Al2O3, the resulting Y2O3 phase may be advantageous because it strengthens steel, which is used in the production of steel having ODS properties or in high-strength construction steel. Owing to considerable differences between the density of aluminum oxide and yttrium oxide, their interaction with the crystallization front will also vary. This will decide about the final distribution of inclusions in the cast ingot. A system of forces connected with the distance, movement of hot metal bath as well as physicochemical parameters of liquid steel and precipitate act on the particle in the vicinity of the solidification front. Authors suggested a numerical solution with the use of own computer program. The calculations were performed in micro scale in reference only to one particle of a given radius, with varying position with respect to the solidification front. On this basis the pathway along which the particle moves as compared to the solidification front was defined, assuming that the front was immobile. The results of calculation were presented in the form of plots illustrating the change of position of the particle of a given radius with respect to its initial position.
Modeling the growth of nonmetallic inclusions can be realized in a number of ways. Authors worked out their own mathematical model for calculating the increase of nonmetallic phase in liquid steel. The spherical shape of the particle and independent increase of inclusions were assumed; the participation of the diffusion of the component dissolved in the liquid phase was ignored. The mixing of metallic bath with the neutral gas of high intensity was assumed as the initial state. The simulations were performed both for the increase of a precipitate composed of two oxides: Al2O3 and Y2O3. Assumption was made that each of the oxides grows in the precipitate area of the precipitate of the same chemical composition. It was assumed that in a metallic bath there are 1,000,000 nuclei, each 5 µm in variant 1, and 10 µm in variant 2. The calculations were performed for the initial oxygen concentration in steel of 0.05% assuming two variants of aluminum and yttrium contents in the metallic bath: 0.05% Al, 0.09% Y – variant 1 and 0.009% Al and 0.06% Y – variant 2. The obtained results were presented in the form of plots of oxides increase in a function of time and change of O, Y and Al content in liquid bath in the precipitation process.