Reactive Filters for Steel Melt Filtration

Abstract

There exists an increasing pressure on the metal-making and metal-using industry to remove solid and liquid inclusions such as deoxidation products (oxides), sulfides, nitrides carbides, etc. and thereby improve metal cleanliness. It is well known that size, type, and distribution of non-metallic inclusions in metal decrease dramatically the mechanical properties and especially the fracture toughness, the tensile strength, the ductility as well as the fatigue of the cast products resulting to excessive casting repairs or rejected castings. [1] In case of the oxide inclusions in steel melts, Wasai et al. [2] assigned the dendritic, maple-like and polygonal inclusions to the group of the primary inclusions generated directly after adding aluminum in the metal melt. In contrast, the network-like, coral-like, and spherical inclusions, which are composed of alumina, hercynite, and wü stite, are classified as secondary inclusions. The secondary inclusions are formed due to the lower solubility of oxygen in the melt as a function of the temperature above the liquidus temperature of the melt. In case of the secondary inclusions, the a-, g-, and d-alumina modification are more frequently detected in steel melts. Below the liquidus temperature tertiary and quartenary inclusions are generated that present the highest impact on fractures toughness of steel casts according to Ovtchinnikov. [3]

Formation of Corundum, Magnesium Titanate, and Titanium(III) Oxide at the Interface between Rutile and Molten Al or AlSi7Mg0.6 Alloy

“…[23] In ref., [23] both phenomena were attributed to a specific wetting behavior during the filtration. The formation of oxide layers, in particular MgTiO 3 and Al 2 O 3 , also supports the hypothesis that rutile interacts "reactively" with the AlSi7Mg0.6 or Al melt, [4] which means that rutile coatings can be used to reduce the oxygen content of the molten metal in combination with the active filtration of inclusions as supposed in ref. [23] …”

“…Rutile (TiO 2 ) coatings deposited on corundum (a-Al 2 O 3 ) substrates are supposed to actively filter magnesium aluminate spinel (MgAl 2 O 4 ) and alumina, which are known as major types of inclusions present in the aluminum alloy melts. [2,3] The filtration efficiency of the functionalized metal melt filters is often enhanced, if the same phases are already present at the interface between the filter surface and the melt, [4] for example, as a product of the chemical reaction between the metallic melt and the functional coating.…”

Impact of Nanoengineered Surfaces of Carbon‐Bonded Alumina Filters on Steel Cleanliness

“…The used apparatus has been presented in detail by Aneziris et al [19] Before melting, the casting simulator was evacuated to a pressure of 2 mbar and filled with Ar 4.6 (purity ¼ 99.996 %). The whole procedure was performed twice.…”

Interactions between Exogenous Magnesia Inclusions with Endogenous Inclusions in a High Alloyed Steel Melt

“…[11,12] Additionally, this may reduce very small tertiary and quaternary inclusions. [13] MgO-based inclusions, for example, are formed in steel as a result of the erosion of vessel lining refractory or as a chemical reaction product. Furthermore, MgO-containing solid or liquid inclusions, such as magnesia (MgO), spinel (MgO Á Al 2 O 3 ), forsterite (2MgO Á SiO 2 ), and (3CaO Á Al 2 O 3 )-MgO clusters are formed during steelmaking processes, for example, deoxidation treatment or by reactions with MgOrich alkaline slags.…”