Papers by Author: J. Siwka

Abstract: The values of nitrogen solubility in the liquid Fe-N-Cr alloy and in liquid chromium were determined experimentally. The alloy of a chromium content of 8; 13; 18; 25; 35; and 69, respectively, and chromium of purity of 99.7 wt % were subjected to experiment. The original data on nitrogen solubility in liquid iron and the data on nitrogen solubility in liquid chromium (the authors' own studies) were converted in relation to the new standard state that is represented by pure nitrogen. The energy parameter, h Fe-Cr, was determined based on literature data. Using the coefficient values for the Fe-Cr alloy, calculated on the basis of our own investigation results, the values of the energy parameter h were determined. The determined energy parameter h in the form of a temperature function relationship will enable the determination of the numerical values of the for the Fe-Cr alloy of any arbitrary composition.

Abstract: The recycling of aluminium packagings is the complex process in due to of the variety of applied varnishes. The compounds of these varnishes in the raised temperature are decomposed and the reactions products may be: gas and/or carbon and in some cases mineral compounds from pigments and the filling materials. Removing the layer organic from aluminium packagings be holds mainly on the thermal processes. In the paper are described the results of removing the varnish coats from surface of the aluminium cans for drinks. The investigations were carried out in the rotary furnace (Linn High Therm) in the temperatures 620 oC in air atmosphere. The surface of sheet after thermal process was submitted the chemical microanalysis on the scanning microscopes Inspect F. It was found that it is possible to obtain practically no oxidizing surface of aluminum sheet. On the surface were the solid residues from mineral pigments and filling materials e.g. oxides Ti, Ba and Si.

Abstract: The structural and phase transformations and the strengthening of nitrogen-containing steels resulting from alloying and thermomechanical treatment have been investigated using X-ray diffraction analysis, optical microscopy, hardness measurements and tensile testing. For the modeling of thermomechanical treatment processes, a DIL 805A/D dilatometer with a deformation capability and a Gleeble 3800 simulator were used. Rational nitrogen or nitrogen plus carbon concentrations are determined by basic composition of an alloy. They are limited by the processes of precipitation of excess phases during crystallization and their dissolution during heating stage of the thermal or thermomechanical treatment. Combined alloying by carbon and nitrogen leads to significant complication of phase and structural transformations in steels, including hot deformation that manifests itself in changes of strain-stress diagram parameters. Effectiveness of increasing of a hot deformation resistance under alloying by nitrogen and carbon depends on a basic composition of steel, C/N ratio and temperature-strain rate deformation conditions.

Abstract: Investigation into the effect of carbon and nitrogen contents of steels with an addition of chromium, nickel and manganese on their structure and properties after thermoplastic treatment has been carried out within the present study. For the physical modeling of thermoplastic treatment processes, a DIL 805A/D dilatometer with a deformation capability and a Gleeble 3800 simulator were used. The effect of carbon and nitrogen contents and the sum of these elements (C+N) on the hardening of the material during hot plastic working. The softening of the material depends on the C/N element ratio. The influence of the constituents under analysis on the dynamics of removal of cold work effects is different; C speeds up, while N slows down this process. The influence of the sum of the elements C and N depends on the type of nonmetallic phase precipitates. The structure and properties of such steels are determined by quenching and tempering cycles.