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Low Carbon MgO-C Refractories for Clean Steel Making in Steel Ladles(1)

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Low Carbon MgO-C Refractories for Clean Steel Making in Steel Ladles

In recent years, with the demand for high-quality steelmaking, constant efforts have been made to diminish the impurities during steelmaking to produce high-grade and clean steel products to meet the stringent requirement of end-users; particularly for some critical grades and applications. For this purpose, many researchers have studied on diminishing or controlling the impurities in the steel by using advanced refining technology. A higher amount of flake graphite addition in MgO-C refractory in steel ladle gives better non-wettability to the molten metal and slag to provide better corrosion resistance. However, the presence of a higher amount of carbon increases the thermal conductivity of the refractory leading to an increase in heat loss, steel ladle shell deformation, and high carbon pickup to the molten steel. As a result, the refractory manufacturers have faced serious challenges of stringent quality requirements from the market and to develop smart and innovative refractory materials. The present paper discusses the use of nano-carbon in MgO-C refractories for steel ladle application to reduce the carbon pickup from the refractories in the ladle to produce clean steel. In this work, varying amounts of flake graphite with magnesia aggregate in MgO-C refractories were studied along with two types of nano-carbon introduced in the matrix part of the refractories. These two types of nano-carbon have the same DBP absorption number but differ in iodine absorption number and surface area. Refractory samples were fabricated using industrial friction screw press and the samples were coked in 1000°C/4 hrs. in reducing the atmosphere. The effect of types and amount of nano-carbon on the properties of MgO-C refractories have been examined. Apparent porosity, bulk density, cold crushing strength, spalling resistance, and oxidation resistance have been evaluated. The corrosion resistance test was conducted at at1650°C/4 hrs. to measure the extent of slag penetration and corrosion. The hot modulus of rupture (HMOR) was measured and the effect of nano-carbon on HMOR values has been evaluated. The effect of different amounts of nano-carbon varying from 0.5 to 1.5% on the physical, chemical, mechanical, thermo-mechanical and corrosion resistance properties of MgO C refractory has also been studied in detail。[/vc_column_text][ult_buttons btn_title=”Introduction” btn_align=”ubtn-center” btn_size=”ubtn-large” btn_title_color=”#ffffff” btn_bg_color=”#dd9933″ icon_size=”32″ btn_icon_pos=”ubtn-sep-icon-at-left” btn_font_style=”font-weight:bold;” btn_font_size=”desktop:20px;”][vc_column_text]Carbon bonded MgO-C refractories present unique Thermo-mechanical and chemical properties. Therefore, they have established high duty refractory products in steel making applications, particularly for converters, EAF and steel treatment ladles. However, this kind of refractory suffers two main drawbacks of poor oxidation resistance and low mechanical strength due to the presence of carbon(graphite, carbon black, and pyrolytic carbon from the resins or pitches). An approach to overcoming these problems has been usually made by incorporating the additives (antioxidants) [1-3] and surface modification or improving the graphite properties [4-6].In the last decade, the composition of MgO-Crefractories has been improved under ecological and economical aspects, especially in terms of binders [7]and additives used for reinforced oxidation resistance and better thermo-mechanical properties. The presence of a higher amount of graphite in the brick gives better-wettability to the molten metal and slag to give rise to better corrosion resistance. But high carbon content increases the thermal conductivity of the brick leading to an increase in heat loss of the process. At the same time, high carbon content increases carbon pickup to the molten steel, which deteriorates the property of the steel. The release of carbon dioxide during tempering and preheating during lining causes environmental pollution and an increase of Carbon FootPrint.The reduction of carbon content in MgO-C brick decreases the thermal conductivity and affects the thermal spalling resistance as well as corrosion resistance. So the reduction of fixed carbon content in MgO-C brick without hampering the property itself is a great challenge. This can be achieved by using high surface area carbon source to the matrix part of the brick since a small amount of carbon addition inMgO-C refractory cover the whole matrix of the brick.[/vc_column_text][vc_text_separator title=”Nanoparticles in refractories” border_width=”5″][vc_column_text]The refractory industry is highly matured and in order to counteract stiff competition from the foreign markets, the only way is to develop new technologies. Thus, the use of nanoparticles has brought about a revolution in the refractories field by exhibiting remarkable performance [8-10] by altering structural, microstructural, chemical, and mechanical properties at high temperatures due to its high surface to volume ratio [8] and higher reactivity with the matrix. Refractory manufacturers are actively engaged and lots of work have undertaken in the research front application of different types of the lower amount of nano-particle addition in various refractories without sacrificing much of the key performance determining properties [11-16]. Researchers are actively engaged to look into the whole aspects including the use of different nanoparticles to lower down the amount as well as to ensure uniform distribution of minor additives throughout the matrix.[/vc_column_text][vc_text_separator title=”Use of carbon” border_width=”5″][vc_column_text]Traditionally, MgO-C bricks contain 10-20% carbon depending upon their application requirement in various steelmaking furnaces and vessels because of their excellent corrosion and thermal shock resistance. MgO-C brick faces various problems long term applications due to its graphite content. Higher graphite content in the brick increases the carbon pickup by steel, which is not desirable for good quality steel because it requires carbon content as low as possible. Another problem is heat loss, because of its high thermal conductivity, which leads to a reduction in molten metal temperature. If the carbon content is reduced in the bricks the thermal and thermo-mechanical properties such as thermal spalling resistance, corrosion resistance at high temperatures are decreased which are related to the properties (aspect ratio and surface area) of carbon. Hence, a high surface area containing MgO-carbon MgO-C bricks with desired properties is required. The particle size of the carbon material added to the brick has a great impact on the properties and performance of the brick. A small number of nanomaterials can be used in place of micron-sized materials due to their high surface area and mono-modal particle size distribution. The oxidation behavior of nano-carbon is very similar to that of fine graphite with average particle size of 5
μm. Nano-carbons with higher graphitic ability showed better oxidation resistance than those with low graphitic ability. The service life of MgO-C brick depends upon the carbon oxidation. The oxidation resistance could be enhanced by optimizing the typesof carbon source and antioxidants.[/vc_column_text][vc_text_separator title=”Use of antioxidants” border_width=”5″][vc_column_text]Nano-carbon addition requires some special kind of antioxidant in order to improve the oxidation resistance but also reinforce the strength-based ceramic bonding since the rate of oxidation for nano-carbon is higher than that of graphite. Metal carbide along with metal powder addition can be a suitable antioxidant for nano-carbon added MgO-C bricks. In the present investigation, two types of nanocarbon were used along with flake graphite, in order to develop a new generation low carbon MgO-C brick with superior properties.[/vc_column_text][ult_buttons btn_title=”Experimental” btn_align=”ubtn-center” btn_size=”ubtn-large” btn_title_color=”#ffffff” btn_bg_color=”#dd9933″ icon_size=”32″ btn_icon_pos=”ubtn-sep-icon-at-left” btn_font_style=”font-weight:bold;” btn_font_size=”desktop:20px;”][vc_text_separator title=”Raw materials and refractories fabrication” border_width=”5″][vc_column_text]Commercially available high purity fused magnesia with a large crystal size of 500–1500 μm(bulk density of 3.54 g/cm³, 97.5% MgO) having different sizes: coarser, medium, and fines were taken. Different size fraction has been taken in order to maintain the granulometry of the mixture. Natural flake graphite containing 94% fixed carbon, antioxidants, two types of nano-carbons (NC-1 and NC-2), and liquid resin with a viscosity of 9000 cps as a binder and other additives were taken as base raw materials for fabrication of MgO-C refractories. All the raw materials were mixed by using a high intensive mixer machine at room temperature by following the standard commercial mixing practice. After mixing, bricks were pressed with a specific pressure of 2 T/cm2 with the help of the hydraulic press. The pressed bricks were tempered at 200-220°C. After tempering, the bricks were subjected to furtherproperty characterization.[/vc_column_text][ult_buttons btn_title=”General Characterization” btn_align=”ubtn-center” btn_size=”ubtn-large” btn_title_color=”#ffffff” btn_bg_color=”#dd9933″ icon_size=”32″ btn_icon_pos=”ubtn-sep-icon-at-left” btn_font_style=”font-weight:bold;” btn_font_size=”desktop:20px;”][vc_text_separator title=”Particle size analysis and surface area” border_width=”5″][vc_column_text]The particle size and its distribution of flake graphite and nano-carbons was measured by laser scattering technique in a computer-controlled particle size analyzer (Malvern, Mastersizer 2000, UK).In order to determine the surface area of the same, Brunauer-Emmett-Teller (BET) analysis has been done on a Quantachrome (USA) machine. For BETanalysis, liquid nitrogen has been used to cover the surface area of the particles.[/vc_column_text][vc_text_separator title=”AP, BD and CCS” border_width=”5″][vc_column_text]After pressing, the pressed brick samples were tempered by following the standard temperature-time curve up to 220°C in a tempering kiln. Coking was carried out at 1000°C for 4 hrs to study the materials refractory properties under a reducing atmosphere(carbon bed). Since the cured samples pass through heat treatment, which results in a thermally stable refractory and crystallization. The test samples were cut from the tempered brick as per the standard. Apparent porosity (AP), Bulk density (BD), and cold crushing strength (CCS) were measured as per the standard of IS: 1528, Part-12 (1974) for AP and BD, and IS: 1528, Part-4 (1974) for CCS tested for both tempered and coked samples. Each value of AP, BDand CCS is of an average of five parallel samples.[/vc_column_text][vc_text_separator title=”HMOR” border_width=”5″][vc_column_text]Hot modulus of rupture (HMOR) is determined by theconventional three-point bending test conforming to ASTM C133-97, using HMOR testing apparatus(Netzsch 422, Germany). All the specimens forHMOR testing are dried at 110°C after wet cutting,without pre-firing in air atmosphere. The heating ratefor HMOR testing is 5°C/min till the final firingtemperature of 1400°C in air atmosphere with asoaking time of 30 min.[/vc_column_text][vc_text_separator title=”Oxidation resistance” border_width=”5″][vc_column_text]For the oxidation resistance test, cylindrical samples(diameter 50 mm, height 50 mm) were cut from the tempered bricks and placed in an electrically heated furnace under a normal atmosphere at 1400°C for 3 with a heating rate of 5°C/min. After natural cooling, the samples were horizontally cut into two pieces. After the oxidation test, the black surface remaining was measured at eight different locations and the average value was noted down.[/vc_column_text][vc_text_separator title=”Spalling resistance” border_width=”5″][vc_column_text]

Spalling resistance test was conducted by the use of the standard test method, IS 1528 (Part 3) –1983. The test was performed from 1400°C to air quenching. Soaking and cooling for each cycle were maintained for 15 min throughout the cycle. The cut piece samples of all the trials were chosen for the determination of the spalling resistance test.

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For conducting a slag corrosion test, a high-frequency induction furnace was used in which a sample size of115 x 60 x 40 mm3 was cut from the bricks to form a cylindrical space of 360 mm dia. Initially, ~6.5 kg of metal was placed into the central hole of the crucible after the metal is getting melted, and reaching the desired temperature of 1650°C, then 80 gm of ladle slag sample was placed into the molten metal. Slag removal and addition of fresh slag of about 60 gemstones in every 30 minutes interval. After completion of eight cycles of slag addition and removal, the hot-metal was discharged from the crucible. Table 1shows the chemical analysis and basicity of ladle slag used in the slag corrosion test.
Table 1: Chemical composition (%) and basicity of the slag chemistry of ladle slag
Chemical composition (%) and basicity ofthe slag chemistry of ladle slag

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For pore size distribution (PSD) analysis, cubic samples of 10 X 10 X 10 mm3 were cut from the tempered bricks. The test samples were dried at110°C for 4 hours and cooled in desiccator before performing the test.

[/vc_column_text][vc_text_separator title=”Microstructure analysis” border_width=”5″][vc_column_text]Microstructure analysis was done for the slag corrosion tested samples by using optical microscopy analysis.[/vc_column_text][ult_buttons btn_title=”Results and Discussion” btn_align=”ubtn-center” btn_size=”ubtn-large” btn_title_color=”#ffffff” btn_bg_color=”#dd9933″ icon_size=”32″ btn_icon_pos=”ubtn-sep-icon-at-left” btn_font_style=”font-weight:bold;” btn_font_size=”desktop:20px;”][vc_column_text]Several formulations have been made by using various types (flake graphite and nano-carbon ofNC-1 and NC-2) and amounts of carbon, and additives (metal powders) in MgO-C refractories. The variation of apparent porosity with varying amounts of graphite and nano-carbons percentage has been studied in the MgO-C refractory. The optimum apparent porosity has been achieved in refractory containing a particular amount of flake graphite and two types of nano-carbon were reported here (Table 2). The apparent porosity of NC-2 showed a slightly low value in comparison to NC-1 and flake graphite added MgO-C refractory for every composition. The specific surface area of NC-2 was higher than-1, therefore NC-2 nano carbon caused more efficient filling of the pores between the aggregates of the magnesia. Overall, the effect of nanocarbon addition was successful in reducing the apparent porosity while there was a decrease in graphite content. However, a few test results which have given desired properties are shown in Table 2. For comparison purposes, the conventional graphite added MgO-C bricks used in steel ladle are also reported.

Table 2: Properties of developed MgO-C bricks

Properties of developed MgO-C bricks[/vc_column_text][vc_text_separator title=”Particle size distribution and surface area” border_width=”5″][vc_column_text]

Figure 1 shows the particle size distribution of flake graphite, NC-1 and NC-2 nano-carbon materials used for making MgO-C refractories. All the raw materials showed a monomodal size distribution. The average particle size of NC-1 is 203 nm, NC-2 is 185 whereas the average particle size of graphite is 50 µm. The BET surface area of flake graphite is 6.38 m2 /whereas NC-1 is 107 m2/g and NC-2 is 142 m2/g. High surface areas of nano-carbon possess higher reactivity and expected to play a vital role in the performance. However, the extent of uniform distribution in the mixer is important prior to the press. Table 3 shows the chemical composition and some characteristics of NC-1 and NC-2 nano-carbons.

Figure 1: Particle size distribution of (a) FlakeGraphite, (b) NC-1 and (c) NC-2 powder samples.

Figure 1: Particle size distribution of (a) FlakeGraphite, (b) NC-1 and (c) NC-2 powder samples. Figure 1: Particle size distribution of (a) FlakeGraphite, (b) NC-1 and (c) NC-2 powder samples.

 

 

 

 

 

 

 

 

Figure 1: Particle size distribution of (a) FlakeGraphite, (b) NC-1 and (c) NC-2 powder samples.
 

[/vc_column_text][vc_column_text]Table 3: Chemical composition and somecharacteristics of NC-1 and NC-2 nano-carbons

 

 

 

 

 

 

 

Table 3: Chemical composition and somecharacteristics of NC-1 and NC-2 nano-carbons[/vc_column_text][vc_text_separator title=”Pore size distribution” border_width=”5″][vc_column_text]

Figure 2 shows the pore size distribution analysis of tempered samples. Nano-sized carbon present in the matrix occupies the pores and voids thereby decreases the total pore area. In general, the larger pore sizes of 10 and above are prone to slag penetration. Since the slag comes in contact with the brick, the oxidation of surface carbon takes place followed by penetration of slag in the exposed pores leading to the dissolution of MgO grains and finally corroding away the bricklayer. The larger amount of offline pores (<10) provides better thermal spalling resistance. Because it acts as a good thermal conductor and easily dissipate the heat from the refractory system and can accommodate the generated stress during thermal fluctuation there improve the spalling resistance. Pore size distribution is an important factor when evaluating the corrosion resistance. The finer pores and the smaller in size creates dense matrix structure and able to keep the grains embedded. The quality of t
he matrix and the total amount of pores is also important for the slag corrosion resistance.
Figure 2: Pore size analysis of (a) Conventional,(b) NC-1 and (c) NC-2 added MgO-C bricks
Figure 2: Pore size analysis of (a) Conventional,(b) NC-1 and (c) NC-2 added MgO-C bricks

[/vc_column_text][vc_text_separator title=”AP, BD and CCS of tempered bricks” border_width=”5″][vc_column_text]There is a marginal increase in BD and decrease in AP with respect to a certain amount of nano-carbon addition in the tempered bricks as compared to conventional MgO-C bricks as mentioned in Table 2.This is mainly due to the nano-carbon along with graphite added in MgO-C refractory had effectively filled the pores and voids and were in correct proportion to cover the pores in magnesia matrix. When the MgO-C refractory contains lower than the specified amount of graphite along with nanocarbon, high apparent porosity had been attained again. It could be due to the fact that graphite along with nanocarbon was not sufficient to cover the pores in the magnesia matrix. Therefore, nano carbon was not able to fill up the pores of the matrix, and hence apparent porosity expected to increase. Thus, the optimum apparent porosity has been achieved refractory containing a certain amount of graphite and nano carbons. Moreover, apparent porosity of NC-2showed slightly low value in comparison to NC-1 for every composition. As the particle size of NC-2 was higher than NC-1, therefore NC-2 nano carbon caused more efficient filling of the pores between the aggregates of the magnesia. Overall, the effect of a no carbon addition was successful in reducing the apparent porosity while there was decrease graphite content.No significant change in BD value for two types of nanocarbon added MgO-C refractory. The increase in BD values as compared to conventional one may be due to two reasons: First there was an increase in the percentage of magnesia in the matrix. Secondly,nano-carbon effectively fill up the pores and voids,hence increase in the BD values. Higher CCS value was observed for the samples with the addition of nano-carbon is mainly due to the low amount of graphite. The CCS values of NC-2were greater than that of samples containing graphite and NC-1. This may be due to the densification of the matrix by effective packing thus the strength is more prominent as supported by Griffith’s rule. MgO-C Refractories

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[/vc_column_text][vc_text_separator title=”AP, BD and CCS after coking” border_width=”5″][vc_column_text]The effect of nano-carbon addition on AP, BD andCCS in MgO-C refractories after coking is given inTable 2. Coked CCS of samples containing nano-carbon is more in comparison to that of conventional graphite containing bricks. The fine particle size of nano-carbon occupies the pores and voids in the brick matrix thereby densify the matrix, whereas, flake graphite containing bricks releases the stress during coking. Due to this, the strength after coking is decreased. MgO-C Refractories[/vc_column_text][vc_text_separator title=”HMOR” border_width=”5″][vc_column_text]Highest HMOR value was observed in the qualityhaving nano-carbon. This is mainly due to thedensification of the matrix and less oxidation ofcarbon. In case of conventional MgO-C refractories,presence of more amount of flake graphite restrict thecontact between the aggregate and matrix part ofmagnesia grains thereby the bond strength is gettingreduced as compared to lower amount ofnano-carbon added MgO-C bricks.[/vc_column_text][vc_text_separator title=”Oxidation resistance and strength” border_width=”5″][vc_column_text]

Table 2 and Figure 3 show the percentage of the black surface remaining of all the formulations after the oxidation test was conducted at 1400°C for 3 hrs. It was observed that the nano-carbon added bricks with a little number of antioxidants have better oxidation resistance than that of the flake graphite added one. The oxidation resistance depends on the selection of antioxidants and its amount for the nano-carbon, graphite, and combination of both [17]. When the atmospheric oxygen comes into contact with nanocarbon, it reacts with oxygen and forms CO and CO2. These gases got entrapped inside the pores, hence increasing the gas pressure inside the pores. These enhancements of gas pressure inside the pores can effectively suppress the diffusion of oxygen into the refractories. As a result, oxygen would be expected to diffuse only a short distance and the oxidation rate was decreased significantly. Thus, the refractory containing nano-carbon addition had shown enhanced oxidation resistance as compared to flake graphite added one. The cut surface of the samples showed that with nano-carbon addition, a dense structure is achieved. Strength after oxidation is also higher in the case of nano-carbon added quality as compared to the conventional bricks.
Figure 3: Oxidation resistance of MgO-C brick fired at1400°C for 3 hrs: (a) Conventional, (b) NC-1 and (c)NC-2 added MgO-C refractory.

[/vc_column_text][vc_text_separator title=”Spalling resistance test” border_width=”5″][vc_column_text]In general, it is expected to have low thermal shock resistance for the bricks containing a lower amount of carbon than the higher amount of conventional flake graphite added one. However, no remarkable change in thermal shock value was observed irrespective of varying amounts of carbon in the brick.This is mainly due to the presence of lower residual fracture energy in nano-carbon added based bricks as compared to the conventional flake graphite added one, which in turn helps to improve the spalling resistance. This can be correlated with the gap between the aggregates: Both nano carbons had a high value of Dibutyl phthalate (DBP) absorption.DBP is the ability of the material to form the gap between the aggregate. Increase the gap between the aggregate did not mean to increase in apparent porosity. The increased distance of separation between aggregates was already filled up by nano-carbon, therefore it could not affect the apparent porosity. High DBP means it has a high tendency to form a gap between the aggregates. This space between the aggregate may help to decrease the elasticity of the refractory material. It could be due to the reason that NC-2 had lesser particle diameter than NC-1 and as the particle diameter became small. The gaps between the aggregates were able to accommodate more carbon nanoparticles without increasing porosity resulting in lower modulus of elasticity. As the modulus of elasticity of the MgO-Crefractory decreased then the thermal spalling resistance has been expected to improve. Therefore the improvement in the stress relaxation of refractory can be observed. The thermal stress in the refractory was less which in turn expected to improve the thermal shock resistance of MgO-C refractories with the inclusion of nano-carbon. MgO-C Refractories[/vc_column_text][vc_text_separator title=”Slag corrosion test” border_width=”5″][vc_column_text]

Ladle slag is used for the corrosion test in the induction furnace. MgO-C bricks with the addition of nano-carbon have better slag corrosion resistance than normal graphite (Figure 4). The slag corrosion resistance of NC-2 is better than NC-1, it could be correlated with the iodine absorption number. Nano-carbon is specified on the basis of the Iodine absorption number, this is tendency of nano-carbon to absorb iodine. More the iodine absorption number and more will be the specific surface area of the nanoparticle. The iodine adsorption number of NC-2 (160 m2
/gm), which had a higher iodine absorption number as compared to NC-1 (121 m2/gm), which means that the NC-2 had a high specific surface area as compared to NC-1. The presence of DBP in the high specific surface area helps the nano-carbon to remain in the deflocculated state during mixing, thereby, helping the nano-carbon to cover the grain boundary of magnesia and increase the non-wettability character of the magnesia-graphite matrix.
Figure 4: Photograph of MgO-C samples after slagcorrosion tests (a) Conventional, (b) NC-1 and(c) NC-2.
Figure 4: Photograph of MgO-C samples after slagcorrosion tests (a) Conventional, (b) NC-1 and(c) NC-2.

[/vc_column_text][vc_column_text]Therefore, it prevented the attack of slag and they did not allow it to penetrate into the MgO-C refractory and prevent the corrosion of magnesia. Thus, the slag resistance properties of NC-2 are higher than the NC-1. Moreover, with a decrease in the percentage of graphite and inclusion of nano-carbon in carbon-containing refractory was better than the flake graphite added one. The nano-carbon fills up the pores and did not allow the slag to penetrate. Hence there was increasing in slag corrosion resistance.[/vc_column_text][vc_text_separator title=”Microstructure analysis of corroded samples” border_width=”5″][vc_column_text]The microscopic observation of the corrosion tested sample of Figure 4(c) was given in Figure 5 (a-f). Figure 5(a) shows the microstructure away from the hot face of the brick (middle part) after the slag corrosion test. The matrix part of the brick showing graphite flakes and fused magnesia (M) grains. Figure 5 (b and c) shows the slag and brick interface near the working face. The slag has penetrated the refractory material into the open pores (P) by capillary forces and the iron present in the slag diffuses through the grain boundaries [18].

Figure 5 (a-f): Microstructural observations of MgO-Csamples after slag corrosion test
Figure 5 (a-f): Microstructural observations of MgO-Csamples after slag corrosion test

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Reaction rims (Figure 5 (d and e) are formed around the periclase crystals when the slag comes and contact with brick, which has a higher reflectivity than the original periclase at the core. This indicates that there is a compositional variation at the periphery and the core of the periclase crystals. The higher reflectivity at the periphery is due to the formation of the magnesia-wustite (MW) phase. The Fe2+in FeOcontaining slag diffused into the periclase crystal by replacing Mg2+and forming a new phase at the periphery of magnesia grains. The peripheral zone after converting to magnesio-wustite shattered into finer grains (Figure 5c). This phenomenon leads to fracture and disintegration of MgO grains near the brick and slag interface due to the thermo-mechanical stress [18]. Some of the unreactedpericlase grains are floating on the slag containing magnesia-wustite (Figure 5f). The corrosion of oxides often occurs not only by dissolution or evaporation of oxide but also by the penetration of slag into the pores of the brick. MgO-C Refractories

[/vc_column_text][vc_text_separator title=”Probable wear mechanism:” border_width=”5″][vc_column_text]

The slag contains mostly of CaO and FeO. The matrix part decarburized (oxidation of graphite) due to the reaction of FeO in the slag with the graphite to form metallic Fe and CO gas as per the following equations, and the Fe2+diffused into the periclaseforming reaction rim which contains mostly of magnesia Wustite
FeO C = CO + Fe
Fe + MgO = (Mg,Fe)O 
Due to the density variation between the core and the reaction rim leads to thermal expansion mismatch causing shattering the reaction rim to finer Magnesia-with grains and going along with the slag. Due to deficient in Fe in slag, the viscosity of slag might have increased resulting in hindrances of slag infiltration further and making anchored type texture(Figure 5d) of high slag adherence with the brick. Due to this the slag coating was intact in the brick

[/vc_column_text][vc_text_separator title=”Conclusions” border_width=”5″][vc_column_text]MgO-C bricks containing graphite and nano-carbon incombination with small amount of metal additives areequivalent and in some cases better than that ofconventional graphite content (12%) bricks toproduce clean steel. Presence of sub micron pores inthe matrix part of MgO-C refractories improves theproperties like corrosion, spalling and oxidationresistance. MgO-C Refractories[/vc_column_text][ult_buttons btn_title=”One stop service for steel industy” btn_align=”ubtn-center” btn_size=”ubtn-small” btn_title_color=”#ffffff” btn_bg_color=”#dd9933″ icon_size=”32″ btn_icon_pos=”ubtn-sep-icon-at-left” btn_font_style=”font-weight:bold;” btn_font_size=”desktop:15px;”][vc_row_inner][vc_column_inner width=”1/2″][ult_buttons btn_title=”Get more information on the steel industry” btn_link=”url:https%3A%2F%2Fwww.lmmgroupcn.com%2Fsteel-industry-technology%2F||target:%20_blank|” btn_align=”ubtn-center” btn_size=”ubtn-small” btn_title_color=”#ffffff” btn_bg_color=”#dd9933″ icon_size=”32″ btn_icon_pos=”ubtn-sep-icon-at-left” btn_font_style=”font-weight:bold;” btn_font_size=”desktop:15px;”][/vc_column_inner][vc_column_inner width=”1/2″][ult_buttons btn_title=”This article is reproduced, the original link” btn_link=”url:https%3A%2F%2Fwww.academia.edu%2F16504363%2FLow_Carbon_MgO-C_Refractories_for_Clean_Steel_Making_in_Steel_Ladles||target:%20_blank|” btn_align=”ubtn-center” btn_size=”ubtn-small” btn_title_color=”#ffffff” btn_bg_color=”#dd9933″ icon_size=”32″ btn_icon_pos=”ubtn-sep-icon-at-left” btn_font_style=”font-weight:bold;” btn_font_size=”desktop:15px;”][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row]

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