Filter Coatings Based on Combination of Nanomaterials for Steel Melt Filtration

Abstract

Carbon‐bonded alumina foam filters are coated using special slurries based on graphene oxide (GO), carbon nanotubes (CNTs), and alumina nanosheets. The aim of such filters is to reduce the concentration of nonmetallic inclusions in the steel melt prior to casting into the molds. To assess the purification efficiency of the coated filters, a steel casting simulator is used. After immersion for a short time into steel melts with artificially generated alumina impurities, the filters are analyzed by optical microscopy and scanning electron microscopy. In addition, the population of remaining inclusions in the treated steel is investigated by the means of a special scanning electron microscope. The results show that, compared with a reference melt where no filter is used, the nanocoated filters cause inclusion growth and the formation of new silicate inclusions. The best purification efficiency, regarding only alumina inclusions, is given by the GO–C sample, whereas the combination of GO with alumina nanosheets or CNTs deliver worse performance.

Carbon Nanotube‐Reinforced Aluminum Matrix Composites

“…The elementary steps involved in the fabrication of CNT/Al composites by this process are 1) homogeneous dispersion of CNTs in a porous structure, 2) filling the porous structure by infiltrating Al matrix, and 3) solidification until a dense composite is obtained. The external pressure is applied to overcome the friction resistance of the molten metal during infiltration procedure . Also, the need for coating of reinforcements to reduce the contact angle and increasing the wettability is greatly decreased by this method.…”

“…The external pressure is applied to overcome the friction resistance of the molten metal during infiltration procedure. [39] Also, the need for coating of reinforcements to reduce the contact angle and increasing the wettability is greatly decreased by this method. Very few researchers followed this route due to the potential damage of CNTs at elevated temperature.…”

Tailoring Nonmetallic Inclusions in 42CrMo4 as a Preparative Tool for Active and Reactive Steel Melt Filtration

“…[6] Therefore, metal melt filtration by ceramic foam filters offers promising results for reducing the content of NMIs. [5,[7][8][9] Ceramic foam filters are applied either for reactive filtration offering functional coatings which chemically react with the steel melt or for active filtration intercepting inclusions by filter coatings similar to the inclusions' chemistry. [10] Recent studies show the effect of reactive filtration with different functional coatings tested in a so-called metal casting simulator under a fully controlled Ar atmosphere.…”

“…[10] Recent studies show the effect of reactive filtration with different functional coatings tested in a so-called metal casting simulator under a fully controlled Ar atmosphere. [5,8,9] Depending on the individual coating and the time, the carbon-bonded alumina filters are in contact with molten steel, a reduction of Al 2 O 3 inclusions by a maximum of 95% is observed by immersion tests. The functional coatings are found to remove endogenous inclusions by 1) formation of secondary alumina at the filter/metal interface, 2) physical adsorption of the formed inclusions on the filter, and 3) CO bubbles created due to interface reactions delivering inclusions to the slag layer.…”

“…[8] However, apart from the high filtration efficiency for Al 2 O 3 particles, immersion tests suffer from formation of other oxides, inclusion growth, and a reduced amount of Al and other elements. [5,8,9] The latter effect of Al loss in the steel below a certain level due to immersion tests might first sound beneficial but can cause the formation of a few but large plate-like Al 2 O 3 particles and would, therefore, explain an inclusion growth. [11,12] Such Al 2 O 3 particles in the range of more than 50 μm in diameter with plate-like shape were reported by Seleznev et This study investigates the effect of different temperatures during deoxidation of 42CrMo4 on nonmetallic inclusions (NMI).…”