Aleš Nagode

Core-Loss Prediction for Non-Oriented Electrical Steels Based on the Steinmetz Equation Using Fixed Coefficients With a Wide Frequency Range of Validity

An accurate prediction of the core losses is crucial for the optimal design and selection of the electrical steels used in electrical devices. The measured specific core losses are divided into three main parts, i.e., the eddy-current loss, the hysteresis loss, and the excess loss. In this paper, a simplified, predictive model for the core loss in a non-oriented electrical steel using fixed coefficients is proposed. The coefficients for a wide frequency spectrum up to 10 000 Hz of validity for the prediction of the eddy current, the hysteresis, and the excess components were calculated with respect to a sinusoidal voltage using the modified Steinmetz equation and a polynomial regression analysis.

The effect of sol–gel boehmite coatings on the corrosion and decarburization of C45 steel

AbstractSol–gel boehmite coatings were produced on the polished surfaces of hypo-eutectoid C45carbon steel by dip coating. After the deposition the coatings were heat treated by drying at RT, 150 and 200 °C. It was found that for crack-free coatings, the drying temperature needs to be ≥150 °C. Properly heat-treated boehmite coatings then improve the corrosion resistance of steel, while proposed alumina coatings derived from the boehmite coatings during annealing of the steel affect the decarburization. The coated steel samples were annealed at temperatures that are typical for the heat-treatment and thermomechanical process of C45 steel, i.e., AC3 (austenitization, thermomechanical process). The sol–gel alumina coating decreased the decarburization rate of the quenched steel during the tempering (≤600 °C), which meant that the hardness reduction on the steel surface was smaller. Alumina coatings have a smaller effect on the decarburization at higher temperatures; however, the metallographic analyses indicate that the coatings can retard the oxidation rate in comparison to the decarburization rate and thus, somewhat increase the visual level of the decarburization. Under annealing conditions (T = 950 °C, t = 0.5–2 h) at which the oxidation rate is higher than the decarburization rate the decarburization process is not important since the decarburized layer is peeled off the steel surface together with the scale. No visual decarburization is then observed.

The superplasticity of friction stir processed Al-5Mg alloy with additions of scandium and zirconium

Abstract The paper describes the effect of minor additions of scandium and zirconium on the superplastic behaviour of friction stir processed Al-5Mg based alloy. The measurements included the flow curves and tensile elongations of (in wt.%) Al-5Mg-0.1Zr, Al-5Mg-0.2Sc, and Al-5Mg-0.2Sc-0.15Zr alloys at initial strain rates ranging from 1 × 10−3 to 1 × 10−1 s−1, and at forming temperatures from 350 to 500°C. The inclusion of friction stir processing at tool rotation rates of 95 and 475 rpm considerably enhanced the superplastic behaviour of the Al-5Mg-0.2Sc-0.15Zr alloy, which was reflected in elongations without failure of over 1900%. Other friction stir processed alloys, treated at lower tool rotation rates, did not achieve superplasticity due to abnormal grain growth. The results yielded by the friction stir processed alloys are compared with the superplastic behaviour of the same alloys produced conventionally by cold rolling.

Cantata Ode to Soča and the Recluse Trapped in the Ruins of His World

Article is a reflection upon f. Hugolin Sattner’s cantata “Ode to Soca”, which was created in the time of First World War and great battles of Isonzo. It outlines composer’s ideological, political and aesthetic outlook as a basis for his creativity thus applying methods of history of mentalities.

Improved Model Based on the Modified Steinmetz Equation for Predicting the Magnetic Losses in Non-Oriented Electrical Steels That is Valid for Elevated Temperatures and Frequencies

In this paper, four different grades of fully finished, non-oriented (NO) electrical steels, i.e., M530-50A, M400-50A, M350-50A, and M290-50A, were selected. Their measured magnetic properties were the basis for the derived and validated magnetic-loss prediction model. Based on the experimental data and the modified Steinmetz equation, a simplified predictive model valid at temperatures up to 230 °C, in the frequency range 30–2000 Hz, and magnetic flux densities up to 1.0 T, is proposed. The model’s prediction coefficients are proposed for the eddy current, hysteresis, and excess loss components. An empirical equation for predicting the magnetic losses, valid up to 1.0 T, highlighting the changes in the magnetic losses with temperature is derived. The equation leads to excellent agreement between the measured and predicted magnetic losses for four grades of NO electrical steel.

The mechanics behind formation of secondary ledeburite during tool steel welding

In this article we describe the microstructural changes in the heat affected zone (HAZ) of the tool steel W. Nr. 1.2379, which was surfaced or welded by the submerged arc welding technique (SAW) with different welding parameters. Microstructure of the welds and of the surfacing welds was analysed by optical and scanning electron microscope. In this research, we particularly studied microstructural changes in the area of primary chromium carbides in the HAZ and their effect on the weld crystalization. We came to the conclusion that the temperature in the HAZ is high enough during the welding process that it caused primary carbides to dissolve and concentration of the carbide-forming elements and carbon increased in the surrounding austenite matrix area to eutectic composition, which remelts and solidified as secondary eutectic (ledeburite).

Tungsten heavy alloy as a filler metal for repair welding of dies for high pressure die casting

Abstract This paper presents the preliminary test of tungsten heavy alloy as a filler metal for repair welding of high pressure die casting dies. H13 grade hot work tool steel was used as a base material. Multipass gas tungsten arc welding was used to fill a single-V butt joint with tungsten heavy alloy in the form of a welding rod. The microstructure of the weld was examined using scanning electron microscopy and optical microscopy. It was found that tungsten grains are not dissolved completely during welding and areas of fine eutectic were formed during solidification of the weld. The hardness of the weld was measured in three courses across the weld and increased in the heat affected zone while the weld hardness was below 380 HV0.3. Charpy V-notched samples were prepared from the weld. The high content of tungsten grains distributed in the nickel–iron weld matrix resulted in low impact toughness of 5.1 J. Face bend testing of the weld was conducted in order to study weld ductility.