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Hofors, Sweden

Riyahimalayeri K.,Ovako Hofors AB | Olund P.,Ovako Hofors AB | Selleby M.,KTH Royal Institute of Technology
Steel Research International | Year: 2013

This study sets out to find some model/s that could calculate the closest oxygen activity of molten steel to the measured oxygen activity in an ASEA-SKF ladle furnace. Ten steel heats grade SAE 52100 were chosen, the oxygen activities of the molten steel after vacuum degassing process were measured, then by means of two different equations and one computer programs the theoretical oxygen activities were calculated and compared to the measured results. In order to calculate the activities of Al2O3 in the top slag four different models and two different constants were applied. Both Wagner and Turkdogan's equations were found to be useful. It was seen that increasing the wt% Al from 0 up to 0.05 in molten steel, increasing CaO/Al 2O3 ratio in top slag, and reducing equilibrium temperature of slag-steel could contribute to reduction of oxygen activity of molten steel. The scanning electron microscope observations revealed that the main types of observed non-metallic inclusions in these samples were spinels and calcium aluminates and by increasing the CaO content of the inclusions their equivalent circle diameters grew. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Kasimagwa I.,Ovako Hofors AB | Brabie V.,Dalarna University | Jonsson P.G.,KTH Royal Institute of Technology
Ironmaking and Steelmaking | Year: 2014

Studies of the reactions between the MgO-C refractory and a CaO-Al 2O3-SiO2-MgO slag system have been carried out through thermodynamic simulations, laboratory experiments and microscopy studies of the microstructure of the refractory samples after the experimental procedures. Corrosion experiments were conducted using the rotating immersion method of the MgO-C refractory rods in a liquid slag: in the temperature range of 1773-1923 K, revolution speed of 200 rev min-1, with varying slag compositions and times (2700-8100 s). Laboratory experiments have shown that the time during which the ladle lining is exposed to a liquid slag with high stirring and slag composition are two important parameters which have large effect on the kinetics of the refractory wear. The rate constants calculated in the present work are in the range of 4 × 10-7 to 1 × 10-6 m s-1. The estimated activation energy from the experimental results is 26 kJ mol-1. © 2014 Institute of Materials, Minerals and Mining. Source

Grosse A.,Badische Stahl Engineering GmbH | Libera K.,Badische Stahl Engineering GmbH | Eriksson R.,Ovako Hofors AB
AISTech - Iron and Steel Technology Conference Proceedings | Year: 2012

The installation of a combined burner system in a stainless EAF was successfully accomplished. The results with respect to reduction of electrical energy consumptions and P-ON times are promising. Furthermore this installation is one of the first, which is used for oxygen injection in the steel bath apart from the burner mode. Due to the correct slag chemistry and temperature the oxygen penetration in the steel bath works successfully. The usage of the combined burner system in a special steel EAF with the use of heavy oil as fuel showed a tremendous decrease of electrical energy consumption and P-ON times. Additionally an increase of the metallic yield was achieved. The previous skull formation inside the furnace was prevented. The optimization of a shaft furnace was conducted by an improved arrangement of burners underneath of the shaft and by modification of the operational profile. Furthermore the more efficient usage of post combustion has improved the overall performance of the shaft furnace, particularly with respect to oil and energy consumptions. Also an improvement of the metallic yield could be observed. Source

Recknagel S.,BAM Federal Institute of Materials Research and Testing | Richter S.,BAM Federal Institute of Materials Research and Testing | Reinholdsson F.,Ovako Hofors AB | Pettersson J.,Uppsala University | Gustavsson I.,Gustavsson Consulting
Steel Research International | Year: 2012

In an intercomparison study three low alloy steel materials were analyzed on their content of the trace element Mg, and five different analytical techniques were used, namely spark-OES, inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma time of flight mass spectrometry (ICP-TOFMS), inductively coupled plasma quadrupole mass spectrometry (ICP-QMS), and glow discharge mass spectrometry (GD-MS). Solid steel discs were used for analysis with spark-OES and GD-MS. For the analyses with ICP-OES, ICP-TOFMS, and ICP-QMS steel chips were wet-digested in aqua regia, and the wet-digestion was performed either in polypropylene tubes placed in a heating block or in Teflon pressure vessels using a microwave assisted system. The Mg concentrations obtained for the three steel materials were: 2.0, 2.8, and 10.3μgg-1, respectively, and the spread in results was acceptable, giving RSD values in the range of 20-30%. The robust analytical method spark-OES can be used for determination of the element magnesium in low alloy steel at trace element concentrations, 2-10μgg-1, which was confirmed by comparison with the results obtained by the four sensitive analytical methods: ICP-OES, ICP-TOFMS, ICP-QMS, and GDMS. The results agreed well. Copyright © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Davydenko A.,KTH Royal Institute of Technology | Mostafaee S.,KTH Royal Institute of Technology | Mostafaee S.,Ovako Hofors AB | Karasev A.,KTH Royal Institute of Technology | Jonsson P.,KTH Royal Institute of Technology
Steel Research International | Year: 2015

The modern sustainable stainless steel making industry is characterized by different factors such as an efficient utilization of energy in the Electric Arc Furnace (EAF) by a slag foaming practice and an utilization of waste products from its own production facilities. In this study, the foaming briquettes applied for a combined slag foaming and waste product reduction in the EAF are characterized. The recipes of the briquettes were made based on a literature review and previous experience. Afterwards, the composition and density of briquettes were estimated and compared to calculated data. Moreover, weight reduction experiments were made on a laboratory scale at temperatures up to 1500-°C in an argon atmosphere in order to characterize the products (metal, slag, and gas). Based on these results, the calculations were compared with experimental data. The following main results were found: (i) the density of briquettes can be successfully verified, (ii) briquettes have different mechanical properties depending on the materials used for production of briquettes, and (iii) the briquettes yield in different amounts of metal and gas. Moreover, it was found that light briquettes (without FeCr) produced almost double the amount of gas in comparison with heavy briquettes (containing FeCr); valuable metals can be recovered from briquettes, and recipes of briquettes can be optimized based on the amount of metal droplets in briquettes and the total utilization of carbon. This study is focused on a characterization of briquettes, which are used for slag foaming and waste product reduction in the Electric Arc Furnace (EAF) during the stainless steel production. The experimental data is compared with calculations according to the obtained results. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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