Determination of carburized layer thickness by GDOES method

The aim of this paper is to consider the possibility of using Glow Discharge Optical Emission Spectroscopy (GDOES) for determination of carburized layer thickness. Carburized layer increases the hardness of basic material (low carbon steels with carbon content of 0.2%), thereby it increases its wear and abrasion resistance and it decreases forming of oxidation layer too. The thickness of this layer is usually determined by hardness measuring according to the CSN EN ISO 2639 standard. The results of this standardized method are compared with the results obtained by two methods of GDOES and with pictures of optical microscopy. It has been found that the method of "Bulk" GDOES analysis with gradual grinding is suitable for determining the thickness of carbon enriched layers, while carburized layers which would correspond to standardized hardness 550 HV 1 may be only guessed from the graph of dependence of carbon content on the depth, in which analysis was performed. The pictures from the optical microscope in cross section do not have sufficient predictive value.Web of Science51433

Ocena toplotne upornosti izbranih bentonitnih veziv

Bentonite is one of the most widely used clays associated with various applications. In the case of foundry technology, bentonite is primarily used as a binder for the mold manufacture. The thermal resistance of bentonite binders, also called the thermal stability, is a natural property of clay minerals, depending on the source, the mineralogical and chemical composition of clay and it is also closely connected to the bentonite structure (various interlayer ions, the level of ion substitution of montmorillonite). Generally, there are various methods for evaluating this property. This contribution describes various methods of determining the bentonite thermal stability based on the evaluation of the technological parameters of bentonite molding mixtures and their comparison. These methods were chosen on the basis of a background research and practical experiences. For the experiments the bentonites commonly used in the foundries of the Czech and Slovak region were selected.Web of Science49346946

A low-cost photoactive composite quartz sand/TiO2

The photoactive quartz sand/TiO2 composites were prepared by thermal hydrolysis of the suspension obtained by addition of quartz sand to a titanyl sulfate solution. The required amount of TiO2 in the prepared composites (i.e. 9, 22 and 45 wt.%, respectively) was achieved using a variable titanyl sulfate/quartz ratio. As reference materials, pure TiO2 was prepared using the thermal hydrolysis of the titanyl sulfate solution under the same condition as used during the preparation of composite quartz/TiO2. The composite samples, dried at 105 °C and calcined at temperatures of 500–900 °C, were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy. Structural ordering of TiO2 particles on the quartz surface was studied using atomistic simulations in a Material Studio modeling environment. Photodegradation activity of the composites was evaluated by the discoloration of Acid Orange 7 aqueous solution. The composite containing 22 wt.% of TiO2 and calcined at 800 °C exhibits the highest photoactivity. Higher and lower amounts of TiO2 led to worse results. The quartz/TiO2 composite is a promising material able to replace pure TiO2 in a wide range of building materials.Web of Science22249748

Influence of selected rare earth metals on structural characteristics of 42CrMo4 steel

The influence of rare earth metals (REM) addition on solidification structure of the low-carbon 42CrMo4 steel was investigated. Alloys were prepared by means of a centrifugal casting. The addition of cerium, praseodymium or mischmetal in the steel produced greatly improved solidification structure with a suppressed columnar grain zone, finer grain size in the equiaxed grain zone. The additions occurred in the steel bath in the form of REM oxide and/or oxide-sulphide inclusions and as dissolved REM segregated along with other elements at prior grain boundaries and interdendritic spaces. Microstructure (light microscope), SEM/EDX chemical microanalysis, and TOF-SIMS analysis – mapping of elements in the structure of alloys were obtained.Web of Science55476075

Impact of Ni on the thermophysical and thermodynamic properties of Fe–C–Ni based alloys

Three model alloys based on Fe-C-Ni were studied containing carbon between 0.338 and 0.382 wt. % and nickel between 1.084 and 4.478 wt. %. Phase transition temperatures, heat capacity, enthalpy change, heat of fusion, coefficient of thermal expansion, and density were experimentally and theoretically determined in the high-temperature area from 1000 degrees C to 1595 degrees C. A number of techniques, namely differential thermal analysis (DTA), differential scanning calorimetry (DSC), and dilatometry, were used in this study, and the heat of fusion was determined by two approaches, that is, from the DSC peak area and from the enthalpy change. The experimental data were compared and discussed with the calculation results obtained using SW IDS, JMatPro, and Thermo-Calc operating with the commercially available TCFE8 thermodynamic database. The obtained experimental results show that the liquidus temperature and the coefficient of thermal expansion decrease with increasing nickel content. On the contrary, the density and heat of fusion values derived from the DSC peak increase with increasing nickel content. Furthermore, an ambiguous influence of nickel on the change in solidus temperature, heat capacity, enthalpy change, and heat of fusion obtained from the enthalpy change was observed.Web of Science204332431

Processing of metal waste-sludge from the galvanizing plants

This paper deals with the possibility of obtaining zinc from waste galvanic sludge, which is formed during galvanic plating. The aim of the experimental and practical part was to obtain zinc after the leaching of galvanic sludge. Leaching was performed in sulfuric acid, nitric acid and hydrochloric acid at different temperatures and time intervals with the addition of oxidizing agents as hydrogen peroxide or ozone. A separation of the leach and filtrate using filtration followed. The leach was further processed by a precipitation of iron and other metals using various agents. After a further filtration, the electrolysis was performed in order to obtain pure zinc on the cathode at the electrical voltage of approximately 3.5 V. Leaching using a solution of sodium hydroxide or potassium hydroxide was also performed when the prior dissolving of a major part of zinc into the leach occurred, while iron and non-ferrous metals remained in the leaching residue. After the filtration of the leach, the electrolysis with a high zinc yield of a purity of more than 99% followed. This way seems to be an optimal one for building a semi-industrial line for galvanic sludge recycling. All the partial products, i.e., the leach, the leaching residue, the filtrate, the solid precipitate and the separated metal on the cathode were subjected to chemical analyses. The analyses results are presented in tables and graphs.Web of Science1211art. no. 194

Organická strukturní a typová analýza produktů zpracování uhlí

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta metalurgie a materiálového inženýrství. Katedra (638) automatizace a počítačové techniky v metalurgi

Teplotní charakteristiky letního období na stanici Mošnov =Temperature characteristics of the summer season at the Mošnov station

V tomto příspěvku je ukázán trend zvyšování teploty na příkladu jedné meteorologické stanice v Moravskoslezském kraji (Mošnov), kde jsou k dispozici data od roku 1960. Nárůst teploty je demonstrován na změně maximální denní teploty v jednotlivých letech, na počtu a výskytu letních, tropických a teplých dní, tropických nocí a horkých vln. Zjištěné hodnoty jsou vyhodnoceny a přehledně znázorněny v devíti obrázcích a pěti tabulkách. Dále jsou v článku uvedeny teplotně významné roky, určené na základě uvedených charakteristik. Závěry jsou porovnávány s výsledky českých i zahraničních studií.In this contribution a trend of increasing temperature is shown on the example of one meteorological station in the Moravian-Silesian Region (Mošnov), where complete data are available since 1960. The temperature rise is demonstrated by the change of the maximum daily temperatures in each year, by the number and occurrence of summer, tropical and warm days, tropical nights and heat waves. The obtained values are evaluated and clearly displayed in nine figures and five tables. Furthermore, the temperature significant years determined on the basis of these characteristics, are mentioned in the article. The conclusions are compared with the results of Czech and foreign studies.172

Use of GDOES method for evaluation of the quality and thickness of hot dip galvanised coating

The paper describes an assessment of thickness and quality of hot-dip galvanised coating by means of the glow discharge optical emission spectrometry method (GDOES). For comparison, a metallographic analysis was made using an optical microscope. An important factor influencing thickness and quality of the hot-dip galvanised coating is chemical composition of steel, particularly the amounts of silicon. Structural steels with a low amount of silicon S235JR and S355J2 were chosen for the experiment and high-strength steel S690QL with a high amount of silicon was chosen for comparative purposes. The results of the coating thickness measurement by means of GDOES and optical microscopy show only minimal differences. Steel S690QL shows a thick and uneven zinc coating. In the case of steels S235JR and S355J2 an optimal hot-dip galvanised coating was observed.Web of Science96631831

Utilization of GDOES for the study of friction layers formed on the surface of brake discs during the friction process

The paper deals with the chemical characterization of friction layer, generated on the surface of friction materials during the friction test using the glow discharge optical emission spectrometry (GDOES). Friction layer is formed during the friction process and its character depends on several factors. One of the most important factors is the material composition of brake pads and brake disc. When the brake pressure is released at the end of the braking event, the specific friction layer remains on the surface of both pairs (brake pads and brake disc). Using the GDOES profile analysis, the thicknesses of friction layers were estimated and these results were compared with results obtained by scanning electron microscopy together with X-ray microanalysis.Web of Science7181514150