Solid State Phenomena Vol. 212

Abstract: The study presents results of impedance tests performed for wires made of X10CrNi 18-8 steel after electrochemical polishing and chemical passivation, subject to medical sterilisation with pressurised water steam or ethylene oxide. In order to determine the impact of sterilising agent on electrochemical characteristics of the passive layer, impedance measurements were made. Measurements were made with application of measurement system Auto Lab PGSTAT 302N equipped with FRA2 (Frequency Response Analyser) module. Impedance spectra of the system were determined in the tests and data obtained in the measurement was matched to the equivalent system. It made the ground for determination of numerical values of resistance and capacitance of the analysed systems. Impedance spectra of the tested system are presented in the form of Nyquist diagrams for various values of frequency, and as Bode diagrams. On the ground of performed test it was explicitly proved that application of steam sterilisation and sterilisation with ethylene oxide of wires made of X10CrNi 18-8 steel after chemical passivation used for urological guide wires has a favourable impact on their electrochemical characteristics.

Abstract: In the paper the results of tests on obtaining zinc coatings on chains produced of the 23MnNiCrMo5-2 steel of grades C and PW9 have been presented. The growth kinetics of coatings obtained in the traditional galvanizing process at the temperature of 450°C has been established. The structure of coatings obtained on chains of various grades has been developed. The chemical composition of structural components of the coating has be established. It has been determined that the obtained coatings are continuous and they are quite thick. No significant impact of the chain grade upon the structure of coating has been established, however, it has been observed that the thickness of coating slightly decreases as the grade increases.

Abstract: The effect of corrosion in an "acid rain" (pH = 3.5) environment on the structure of the surface layer of the ZnAl22Cu3 alloy are presented in this study. Base alloy, alloy with silicon and alloy with silicon and rare earth elements were tested. The scope of the examination included potentiostatic tests in acid rain and studies of structure of surface layer of samples after corrosion tests. The studies have shown, that corrosion processes initially run quickly which leads to reduction of zinc in the surface layer and enriching in aluminum and copper so that the corrosion rate decreases. The presence of the silicon precipitates does not decrease the corrosion resistance of the ZnAl22Cu3 alloy in acid rain environment. The addition of rare earth elements improves the corrosion resistance of the ZnAl22Cu3 alloy in acid rain environment.

Abstract: Studies were conducted on the kinetics and mechanism of oxidation of chromium-manganese steel under partial oxygen pressure p_O2 from 10^-11 to 10^-2 Pa at a temperature of 1173 K. The low oxygen partial pressure was produced in a gas mixture of CO-CO₂ and helium containing 0.2 ppm of oxygen. The kinetics of oxidation was examined by thermogravimetry using a thermobalance made by Setaram Company. Scale growth mechanism was determined with the use of markers. The oxidation products were analyzed by scanning electron microscopy (SEM, EDS). It was found that at low partial pressure of oxygen, MnO oxide was forming on the steel surface. From an analysis of the curves of the steel weight growth per unit surface in function of time it followed that the oxidation assumed a parabolic course. A relationship has been determined between the coefficient of self-diffusion of manganese in MnO and the oxygen partial pressure.

Abstract: The influence of surface modification and steam sterilisation process on the corrosion characteristics of wires made of X10CrNi18-8 steel used for production of guide wires in endourological treatment was analysed in the study. Corrosion tests were made in artificial urine solution with application of electrochemical testing system VoltaLab PGP201. Resistance to pitting corrosion was evaluated on the ground of registered anodic polarisation curves by means of potentiodynamic method. The tests comprised wires with surface that was ground, electrochemically polished and chemically passivated. Steam sterilisation was performed in autoclave Basic Plus by Mocom. The tests proved that surface modification improved corrosion characteristics of the wire to a great extent. The best corrosion resistance in artificial urine was observed in wire whose surface was successively ground, polished and chemically passivated. It was also proved that chemical passivation process has a favourable impact on corrosion resistance improvement under sterilisation conditions.

Abstract: In the paper the authors present the results of corrosion resistance tests on coatings obtained in zinc-aluminium baths with the addition of Mg by use of the batch hot dip method. The content of Al in the bath was 31%, while the content of magnesium was 3 and 6%. In order to define corrosion resistance, two standard corrosion tests were performed in neutral salt spray and inmoist atmosphere containing sulphur dioxide. Corrosion resistance of tested pieces was compared with the corrosion resistance of a traditional zinc coating. It was established that Zn-31AlMg coatings have very good corrosion resistance in the tested environments, better than that of zinc coatings.

Abstract: The topic of this publication is classification and assessment of environmental aspects in metallurgical enterprise on an example of steel plant. The analysis included aspects which have negative influence on the environment. Taking into account the structure of the proceedings of the process of melting steel in converter and electric furnaces there were key aspects established which are treated as priority in investment programs and current activities within environmental protection process in order to limit their negative influence on the environment. The publication proposes a method of acting in the assessment of environmental aspects for each type of steel plant. The publication can be useful for the engineers and technologies from staff and to services taking care of environmental protection in metallurgical enterprises.

Abstract: Based on archival temperature measurement data regarding a blast furnace (capacity of 3200 m³) hearth and bottom refractory lining, empirical isotherms T = 300°C, for various periods of the first five years of the furnace campaign were determined. This resulted in an attempt to assess the hearth and bottom refractory lining in the third month and subsequently, in the next years of the blast furnace operation. The empirical isotherms, determined after the first three months, were compared to the isotherms determined using the method of mathematical modelling. These empirical isotherms were compared to each other, respectively in one-year intervals. The most distinctive changes of the hearth and bottom refractory lining were observed during the first three months of the furnace campaign. In the further period of five years, the changes were insignificant. During the early stage of furnace operation, observed deterioration of the refractory lining was associated with partial damage of the bottom ceramic layer and elephants foot-shaped defects of the refractory lining in the lower, thickened parts of the hearth walls. Early, elephants foot-shaped wear of the refractory lining is related to the mechanism of its wash-out by liquid products of the process during tapping, which results from certain maladjustment of the hearth and bottom inner geometry in modern furnaces to the hydrodynamic conditions of metal and slag flow.

Abstract: Based on the Minimum Gibbs Free Enthalpy algorithm (FEM) and a model of reaction zones located around electrode tips in the submerged arc furnace, an analysis of the raw material chemical composition influence on the ferrosilicon smelting process was carried out. A model of the ferrosilicon process in the submerged arc furnace is a system of two closed isothermal reactors: an upper one with a lower temperature T₁, and a lower one with a higher temperature T₂. Between the reactors and the environment as well as between the reactors inside the system, a periodical exchange of mass occurs at the moments when the equilibrium state is reached. Based on the model, sets of calculations were performed: for a Fe-Si-O-C system and, subsequently, for a more complex Fe-Si-O-C-Al-Ca-Mg-Ti system. For both systems, the energy and mass balance values were calculated and the effects of raw material contaminants on the efficiency of the ferrosilicon melting process were determined.

Abstract: The publication presents changes occurring in technological processes of producing steel after transformation of economic system in Poland after year 1989 and conducted repair programs within restructuring of metallurgical industry of iron and steel. Changes were based on withdrawals of economically unprofitable technologies, including open hearth furnaces through expansion of electrical and converter technologies of steel manufacturing up to activities which were connected with changing the profile of manufactured assortment.