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A developed methodology for determining the physical properties of mineral fibers prepared from different input mixtures under the same spinning wheel conditions is described and discussed. Energy dispersive X-ray fluorescence spectroscopy was combined with simultaneous thermal analysis and thermogravimetry to study the mineralogical composition and typical melting and crystallization temperatures. The mechanical properties measured with nanoindentation were related to the mineralogical properties and the results obtained are in agreement with the literature. The developed methodology shows reliable performance and demonstrates the ability to study the mechanical properties of mineral fibers, their mineralogical composition, and thermal properties. The presented experimental methodology opens up the possibility of researching the mechanical properties of mineral fibers for the purpose of defining production recipes in the field of mineral thermal insulation materials.

Toma` Lazar1, Primo` Mrvar2, Martin Lamut3, Peter Fajfar2 1National Museum of Slovenia, Pre{ernova cesta 20, 1000 Ljubljana, Slovenia 2University of Ljubljana, Faculty of Natural Sciences and Engineering, Department of Material Science and Metallurgy, A{ker~eva cesta 12, 1000 Ljubljana, Slovenia 3Slovenian centre of excellence for space sciences and technologies, A{ker~eva cesta 12, 1000 Ljubljana, Slovenia peter.fajfar@omm.ntf.uni-lj.si

The present work describes the formation of amorphous alloys in the (Al1−xCex)62Cu25Fe13 quaternary system (0 ≤ x ≤ 1). When the amount of Ce falls in the range 0.67 ≤ x ≤ 0.83, the alloys obtained exhibit a completely amorphous structure confirmed by powder X-ray diffraction. Otherwise, at compositions x = 0.5, 0.58, 0.92 and 1, a primary crystalline phase forms together with an amorphous matrix. The crystallisation temperature (Tx) decreases with increasing Ce content, varying from 593 K for x = 0.5–383 K for x = 1. Composition x = 0.75 is considered as the best glass former, exhibiting a large supercooled liquid region of 40 K width that precedes crystallisation. In order to form bulk amorphous alloys, ribbons with this later composition were consolidated into few millimetre thick discs using pulsed electric current sintering at different temperatures, yet preserving the amorphous structure. Meanwhile, increasing temperature above 483 K triggers crystallisation of a primary phase isostructural ...

In Štore Steel steelworks steel is casted on a three strand continuous casting machine. Lining of tundish is mainly made from a magnesia based material. Tundish cover powder is based on alumina and silica. It also contains aluminum and carbon. During casting, the composition of cover slag is constantly changing. When steel in casted in sequences the change in cover slag composition depends on the amount of CaO rich ladle slag. The composition of tundish cover slag at the end of the casting sequence lies in the area of gehlenite (2CaO·Al2O3·SiO2) in ternary phase diagram CaO·Al2O3·SiO2. The result of the reaction between melted steel, refractory material and tundish cover slag are enstatite (MgO·SiO2) and monticellite (CaO·MgO·SiO2). Merwinite (3CaO·MgO·SiO2) is formed in the end of the casting sequence because of high basicity of the gehlenite based tundish cover slag. Clogging on the inner side of submerged entry nozzles (SEN) are made of calcium aluminates (CaO·2Al2O3) and spinel (MgO, MnO)·Al2O3. Only when steel is casted in sequence composition changes in tundish cover slag and clogging occurs.

Štore Steel produces steel grades for spring, forging and engineering industry applications. Steelmaking technology consists of scrap melting in Electric Arc Furnace (EAF), secondary metallurgy in Ladle Furnace (LF) and continuous casting of billets (CC). Hydrogen content during steelmaking of various steel grades and steelmaking technologies was measured. Samples of steel melt from EAF, LF and CC were collected and investigated. Sampling from Electric Arc Furnace and Ladle Furnace was carried out using vacuum pin tubes. Regular measurements of hydrogen content in steel melt were made using Hydris device. Hydrogen content results measured in tundish by Hydris device were compared with results from pin tube samples. Based on the measurement results it was established that hydrogen content during steelmaking increases. The highest values were determined in tundish during casting. Factors that influence the hydrogen content in liquid steel the most were steelmaking technology and alloying elements.

The objective of the research that has been presented was to model the effect of differences in chemical composition within one steel grade on hardenability, with a very broad and heterogeneous database used for studying hardness predictions. This article presents the second part of research conducted with neural networks. In the previous article [1] the most influential parameters were defined along with their weights and on the basis of these results, an improved model for predicting hardenability was developed. These developed neural networks were applied to model predictions of hardenability for three steel grades VCNMO150, CT270 and 42CrMoS4. The results proved that the correlation between the chemical composition differences within a chosen steel grade and the hardness changes can be modeled. If the database is big enough, predictions would be accurate and of high quality. But for a less comprehensive database, the differences in hardness predictions for various chemical compositions of the steel grade concernedwere observable.

The origin of stains on the surface of anodized aluminium profile was investigated. Stains were visible on the surface under the specific angle of observation. Anodized surface and layer were investigated by scanning electron microscopy, metallography of cross section of the layer was performed and EDS analyses were done. Presented are results of investigation. No difference was observed by scanning microscope between the surface with and without stain. The metallography of cross section of anodized layer revealed prevailing compact layer, only in the region with the stain a small pores were observed below the surface. The pores were not connected to the surface. The EDS analyses detected in the pores the presence of oxygen, sulphur, fluorine and nickel. Sulphur confirmed the sulphuric acid was used as electrolyte at anodizing process, but fluorine and nickel are evidence that pores were cold sealed in solution containing NiF2. Investigations confirmed that apparent stains were an optical effect, a consequence of different refraction of the light due pores in the layer. The main reason for the rests of pores in anodized layer was not optimised anodizing process.

A die was investigated for the pressure die-casting of Mg-alloy. The die was made of martensitic chromium hot-work steel grade and the surface was gas nitrided. Due to damaged surface the die was removed from the production line after 20.000 shots. Light microscopy and electron microscopy studies were performed. Mechanical properties as well as fracture toughness of the basic material were determined. The results of the investigations are presented. It was established that the base material properties correspond to declared properties. The corrosion phenomena in the form of pits were observed on all surfaces of the die. Metallography revealed that the nitrided layer consisted only of diffusion layer, without a γ′ compound layer. The depth of the pits was limited to the thickness of nitrided layer and in the pits the presence of Ca, Cl and S was detected. No cracks were observed in nitrided layer and all the edges of pits were rounded. The damages were caused by a combined mechanism of corrosion–erosion. The main reasons for the damages were not optimised nitride layer properties.

The corrosion resistance of AISI 321 stainless steel depends on the formation of thin and compact Cr2O3 oxide layer that protects the steel surface. But sometimes anomalies appear, that enable formation of the protective layer and the steel becomes sensitive to oxidation at elevated temperatures. In such a case, the oxide layer is not compact enough and the oxide fall off the surface. Presented are investigations of flakes on the surface of stainless steel heaters for household application. The flakes appeared during the first short time heating test of the heater. Analyses revealed that the flakes on the heaters originated from the hot rolling process. The rolled in hot cracks enabled the formation of the flakes on the surface of the heater.

Protective surface layers on AISI 321 stainless steel were prepared by thermal treatments at two different temperatures in air and two controlled atmospheres. Different oxide and/or nitride layers were formed. Surface morphology of the layers was investigated by scanning electron microscopy (SEM). Auger electron spectroscopy (AES) depth profiling of the samples was performed. Since depth profiling suggested layer thicknesses of the order of hundreds of nanometres, an attempt was made to obtain some fast, averaged information about the layer compositions using wavelength dispersive spectroscopy (WDS) at two different beam energies to obtain probing depths best suited to the layer thickness. X-ray photoelectron spectroscopy (XPS) profiling of one layer was also performed to obtain information about the chemical states of the elements inside the layer. The analysed samples showed considerable differences with respect to their surface morphology, oxide/nitride layer thicknesses, compositions and layer-metal interface thickness.

Castings made of Al-alloy were after mechanical machining cleaned, wrapped with plastic envelope and stored for two months. During that period, a local corrosion appeared in the form of darker spots on the surface of the castings. Results of XPS investigation of spots on Al-castings are presented. On the surface and in the corrosion products the rests of washing media were present. The main reason for the spots was condensed-water corrosion inside the plastic envelope. The rests of detergent together with the presence of condensed humidity enabled corrosion process to occur during the storing period.

Hot tests of foaming behaviour of steelmaking slags were conducted on a laboratory scale up to 1760 °C using a Tammann furnace. The foaming behaviour of the slags was quantified on the basis of a new measuring method. The volume increase and the progress of the foaming process can be continuously observed and calculated by means of picture analysis. The gas content of foaming slags was compared with the results of the measurements performed in steel plants. The influence of the magnesia content on the foaming behaviour is investigated. The chemical composition of the slag is beside the CO evolution the decisive factor influencing slag foaming behaviour. The highest volume increase values observed lie in the region of 2500 % in relation to the initial volume.

Experiments into the swelling and foaming of synthetic iron oxide gangue melts prove that two basic prerequisites have to be met for the occurrence of these phenomena. Firstly there must be present within the specimens relatively large volume fractions of a liquid FeO-containing phase which come into contact with carbon. This leads to heavy gas formation. Secondly, slags of this type must exhibit a certain gas retention capability. In this respect, a precipitated iron support skeleton can be helpful. Medium-basic slags swell very well and over a relatively long period. Highly basic slag melts, following a brief period of swelling, are quickly resolidified by 2CaO.SiO 2 precipitation. In the case of acidic specimens, only a small or no volume increase is observed. Pure iron oxide melts undergo virtually no swelling whatsoever

Tests to use metallized pellets of pyrite residue were carried out in a 40-(metric)-tonne electric-arc furnace of 12,000-kVA power.The pellets were added in quantities of 15 to 45 per cent of the total charge, which was loaded with baskets.It can be stated that, despite the lesser degree of metallization and the lower FeMet content in the metallized pellets of pyrite residue, the production of the steel proceeded without any difficulties, conversion and carbon boil were normal, and the yield of the steel produced was satisfactory.The mechanical properties (strength, ductility, expansion. contraction) of these steels made from pellets were found to be the same as or superior to those of steels made from scrap alone. Resume Des essais utilisant des boulettes metallisees de residus de pyrites ont ete realises dans un four a arc electrique de 40 tonnes (metriques) et d'une puissance de 12000 kva.Les boulettes ont ete ajouees dans des proportions allant de 15 a 45 pour cent de la charge totale, cette ...