Interaction Between MgO-Based Refractory And Fe-Al Alloy

The development of steel properties has been attention in steelmaking.The weight reduction in automotive industries is an important issue due to high cost of manganese alloys and the reduction of CO2 exhaust.For this aim,the make of high Al steel is demands for industry and environment.Inclusions have a crucial role in determining properties and quality of steel.The purpose of this study is to investigate interactions between MgO-based refractory and Fe-Al alloy in order to understand the mechanism of inclusions formation in melts containing high aluminium.Interactions between molten Fe-Al alloy containing 5.1%and 2.1%dissolved aluminium and MgO-based refractory material containing 27%SiO2 were investigated.The high-frequency induction furnace was used to investigate the reaction between Fe-Al alloy and refractory samples at 1550 ? at different holding times from 1 min to 60 min.The phases at the interface and inclusions in the Fe-Al alloy were investigated by scanning electron microscope.The reactions between alloy and refractory produced an interface layer,which its thickness increased with increasing Als content in alloy and reaction time.Forsterite phase in refractory was transformed to MgO·Al2O3 spinel,owing to the reduction of iron oxide and silica in forsterite by Als in the Fe-Al alloy at the interface.The interface layer separated locally from the refractory material and formed cluster and single particles in the Fe-Al alloy.In view on the reaction rate,the disintegration of the refractory material increased the reaction area but interfered with increasing thickness of the spinel layer.The dissolution rate of silica into the molten alloy decreased with increasing the reaction time because of the slowed down transport of aluminium diffusing through increasing spinel layer became the rate controlling step.FactSageTM 7.0 calculated results indicated that the content of silicon in the alloy was higher than magnesium,as the result of transformation of forsterite phase to MgO·Al2O3 spinel at the interfaceInteractions between Fe-2%Al and Fe-5%Al alloys and different tundish refractories,and a spinel generation in the Fe-Al alloys were investigated in laboratory experiments at 1550 ? in an alumina crucible using a high-frequency induction furnace.The results indicated that the formation of a spinel layer at the interface was owing to both the oxidation-reduction reactions and the phase transformation at the interface according to initial phases in refractories.The thickness of the interface layer increased with increasing the content of the Als in Fe-A1 alloys,the SiO2 content in the refractory and the immersion time,however,the Als content was a dominant factor.Both experimental results and thermodynamic calculations concluded that MgO-Al2O3 spinel inclusions along with a small amount of CaO-MgO-Al2O3 were the main inclusions in Fe-Al alloys.MgO-Al2O3 inclusions were mainly formed at the interface by alloy/refractory interactions and then mechanically transferred into molten alloys.