3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes and contains the nature of this invention ai manner in which is to be performed.
4. DESCRIPTION
STATEMENT OF INVENTION:
This present invention relates to the use of different anti-oxidants for making low carbon containing MgO-C refractory. Different anti-oxidants used are boron carbide, aluminium (Al), silicon (Si) and magnesium (Mg) metal powders and their combinations. This invention is useful in slag line steel ladles, BOF (Basic oxygen furnace) / LD (Linz-Donawitz) converters, and Electric arc furnaces (EAF) where it can show greater resistance against chemical attack from basic slag as well as low vulnerability to attack by iron oxide and alkalis with much reduced heat loss from the process.
BACKGROUND OF INVENTION:
MgO-C refractory is a mixture of suitably graded sintered / fused magnesia refractory aggregates, fines, bond materials and some anti-oxidants. Magnesia is the most accepted basic refractory raw material with high melting point, very good chemical stability and excellent corrosion resistance against high basic slag and iron oxide and alkalis. Carbon in the form of graphite is used in magnesia-carbon refractories which offer many advantages in refractory applications such as lower wettability by metal and slag due to the non-wetting nature resulting in improved corrosion resistance. Graphite has also a low thermal expansion, low modulus of elasticity with high thermal conductivity that result in a higher thermal shock resistance in the MgO-C refractory system. Due to such advantages, refractory manufacturers were trying incorporate more amount of graphite in to the MgO-C bricks but with the progress in technology and knowledge it has become clear that higher carbon content in the brick imparts several drawbacks which are listed below,
1. Higher energy loss due to increased conductivity of refractory, causing higher energy consumption per unit of steel produced.

2. Chances of carbon pick-up from refractory become high, whereas steel making is basically a decarburization process and user industries are very stringent about the purity of steel.
3. Releases more amount of the carbon dioxide or carbon monoxide gases to the atmosphere.
4. The most important is the oxidation of carbon at higher temperature.
Carbon-containing refractory materials have received great attention over the last few years due to their importance in the steelmaking process. The oxidation of carbon present in the refractory compositions at temperatures above 500°C results in a porous structure causing decrease in mechanical strength and chemical resistance. In order to improve the oxidation resistance of oxide-carbon refractories, the refractory manufacturers use chemicals, known as antioxidants. Generally metal powders and their alloys are added that get oxidized and prevents carbon from oxidations, thus improves oxidation resistance and mechanical properties of these refractories. Antioxidant materials easily react with oxygen and carbon, forming respective oxides and carbides and reducing the pores volume and mitigating carbon oxidation also by the formation of liquid phases The appropriate selection of the antioxidant to be used (type and amount) in a given application will depend on several parameters, including the refractory composition, heat treatment conditions (atmosphere and target temperature), slag chemical composition, and thermo mechanical stresses that develop during the process.
A few literatures were found where aluminum metal powder, boron carbide or combination of these two was incorporated to nano caron containing MgO-C to prevent the oxidation of carbon. Reference may be drawn to the work of Z.X. Yang, N.R. Ha and K.H. Hwang (UNITECR 2009, in Salvador Brazil, October 13-16), where 2-6 wt.% metal aluminum powder, boron barbide (B4C) were added to nano carbon (particle size 33nm) containing MgO-C refractory. 6 wt % boron carbide results a better oxidation resistance comparable to the aluminum metal powder addition due to impermeable dense Mg3B2O6 layer on the mortar surface. Taking another reference of Li Lin, Tang Guangsheng, He Zhiyong, Liu Kaiqi, Peng Xiaoyan (UNITECR 2009, in Salvador Brazil, October 13-16), where 2.9 wt % of mixture of aluminum metal powder and boron carbide anti-oxidant was incorporated to nano carbon (20-25nm) containing MgO-C

refractory where graphite and nano carbon black varies from 0 wt %-l wt% and 0 wt%- 0.6wt% respectively. They found out that when the amount of carbon black reached up to 15 mass%, the values of MOR, HMOR and CCS of specimens increased up to 40%, 39% and 45% respectively compared with the samples without the addition of nanometer carbon black. In another reference, Journal of Iron and Steel Research, International, 2010, 17(10), 75-78, where carbon black were added to MgO-C refractory with a mixture 3 wt% of aluminum metal powder and boron carbide anti-oxidant. The CCS, MOR before and after coking at 1500 °C was better than the 16wt % graphite content conventional refractory. In other references of Mousom Bag, Sukumar Adak, Ritwik Sarkar [Ceramics International 38 (2012) 4909-4914 and Ceramics International 38 (2012) 2339-2346] where it mentioned that 3 wt% graphite with 0.9 wt% nano carbon black combined with 2 wt% aluminum metal powder and boron carbide showing improved or similar mechanical, thermo mechanical properties compared to conventional 10wt% graphite containing refractory.
It is also known as set forth in U. S. Pat. No. 4,431,745 that adding amounts of metal less than 0.5 wt.% does not produce the desired effects of increasing wear resistance and oxidation resistance. Also, as is shown in this patent the use of high levels of metal addition results in decreasing corrosion resistance. It is also known that metal addition can have other negative effects such as the fluxing action caused by oxidized aluminum, increased porosity and porous textures caused by volatilized magnesium, and the loss of carbon from the brick due to the reduction of silica formed from oxidized silicon in the presence of carbon. With reference to US.S Patent No. 4,306,030, the metals used in magnesite carbon brick were aluminum, silicon, and magnesium. The metals increased oxidation resistance by lowering the permeability of the brick and by consuming oxygen that would otherwise have oxidized carbon.
The improvement of mechanical properties of the low-carbon MgO-C samples containing carbon black (CB) is expected to suppress the damage generation in the matrix during heating, therefore, the transfer of oxygen in samples is suppressed in some extent. Oxidation resistance and thermal shock resistance of the low-carbon MgO-C composites are improved with the addition of CB, especially the addition of nanometer CB. According to the report by Torigoe A, Inoue K, Hoshiyama Y. [Taikubustu, 2004, 56(6): 278] the dispersion of CB particles in the

matrix can lower its elastic modulus and improve its thermal shock resistance, therefore, excessive sintering of MgO in the matrix is suppressed. Moreover, inorganic nano-particles can block the expansion of the cracks and contributes to crack energy transfer effect, as per the study by Y. Xuejun, Q. Zheming, H. Liang-quan. [Aerospace Mater Technol, 2003, 33(4): 34].
In another reference, [Ceramic International 40[3] 4333-4340 (2014)] Tianbin Zhu, Yawei Li, Shaobai Sang, Shengli, Yuanbing Li, Lei Zhao, Xiong Liang, reported that 2 wt% silicon metal powder anti-oxidant with 1 wt% Al metal powder were incorporated in MgO-graphene, MgO-nanotube and MgO-carbon black refractory. Nano structured carbon was reported to react with anti-oxidants at lower temperature resulting in different in-situ ceramic phase which helped to increase in the mechanical strength as well as thermal shock resistance of the MgO-C refractory. In literature, it is cited that partial incorporation of nano carbon in MgO-C refractory along with Al-metal powder is showing a similar refractory properties as like as in conventional refractory. To improve the oxidation resistance, peoples have developed MgO-C refractory with low carbon content having carbon level 5-7% by introducing nano carbon black. Being finer, nano carbon gets oxidized at the temperature range between 400°C -700°C comparable to flaky graphite which has the temperature range 800 -950°C. So now days it's a major challenge to the refractory researcher to improve the oxidation resistance for nano carbon containing compositions.
OBJECTIVE OF THE INVENTION:
The main objective of the present invention is to provide synergistic composition for low carbon containing magnesia carbon refractory and its anti-oxidants combination, where partial replacement of graphite is done by addition of nano carbon, which obviates the draw backs as described above.
Yet another objective of the present invention is to provide a synergistic composition for the production of low carbon containing MgO-C refractory which has higher oxidation resistance and higher strength at higher temperature due to the formation of in-situ ceramic phase because of higher surface area and higher reactivity of nano carbon.

Another objective of the present invention is to provide a synergistic composition for the production of low carbon containing MgO-C refractories which have the greater corrosion resistance against the penetration of slag.
In the present invention a synergistic composition has been developed for the production of low carbon containing MgO-C refractory using fused magnesia aggregates of different fraction (4-6mm, l-3mm, 0-lmm and fines >75μ), additives such as Carborose P, carbon source as graphite, nano carbon black and anti-oxidant such as boron carbide, Al metal powder, Si metal powder, Mg metal powder. In literature, it is evident that, formation of the in situ ceramic phases like aluminum carbide, aluminum nitride, magnesium aluminum spinel were found when aluminum metal powder anti-oxidant were introduced in graphite containing conventional MgO-C refractories. Similarly formation of silicon carbide, silicon nitride and fdrsterite phases were found in silicon containing conventional MgO-C refractory.
SUMMARY OF INVENTION:
Advantageous effects of invention.
In the present invention, a synergistic composition has been developed for the production of low carbon MgO-C refractory using fused magnesia as refractory aggregates, nano carbon black and graphite as a source of carbon, boron carbide and metal powders as anti-oxidants, carbarose P as additives and liquid and powder resin as binder. The total carbon content in the compositions has been reduced to half or one third level of the conventional MgO-G refractories.
Metal powder anti-oxidants containing low carbon magnesia carbon refractory of the present disclosure has many advantages since, the boron carbide and metallic anti-oxidants i.e. silicon, aluminium, magnesium and the refractory aggregates are materials with high purity, the advantage is increase in high temperature structural strength, oxidation resistance and high refractory properties as there is formation of in situ ceramic phase.
Furthermore the presence of nano carbon and finer metallic anti-oxidants facilitated greater formation of in situ ceramic phase at higher temperature hence a superior oxidation resistance and strength is obtained at higher temperature. Additionally nano carbon were used which

results a compact structure due to its finesse and possibility of formation of in situ ceramic phase due to its higher surface area and higher reactivity.
The novelty of the present invention resides in optimum use of nano carbon and combination of anti-oxidants to obtain high oxidation resistance and high hot strength in nano carbon containing low carbon magnesia carbon refractory. Oxidation resistance and other refractory properties were remarkably high even at higher temperatures compared to that of the conventional magnesia carbon refractories.
The inventive steps lie in the preparation of low carbon magnesia carbon refractory using magnesia aggregates and fines and optimum use of nano carbon and graphite as carbon source. Selection and optimum use of anti-oxidants helps to get the optimum benefit of the carbon sources. Mixing process of nano carbon to the composition plays the critical role for improved properties even in low carbon refractories.
STATEMENT OF INVENTION:
The present invention provides a synergistic composition for the production of low carbon containing magnesia carbon refractory with high oxidation resistance and high hot strength which comprises: mixing intimately 70 to 95wt % fused magnesia, 1 to 5 wt % metallic anti oxidants, 0.5 to 2 wt. % boron carbide, 2 to 20 wt. % carbon containing both graphite and nano carbon, 0.5 to 2 wt % carbarose P as additives, 0 to 2 wt% powder resin and 2 to 4 wt% of liquid resin as binder.
In another embodiment of the present invention, the chemical constituent of the fused magnesia used may be in the range of MgO (95 to 97.5 wt %), AI2O3 (0.05 to 0.2 wt %), CaO (1 to 2 wt %), SiO2 (0.2 to 0.5 wt %), Fe2O3 (0.1 to 0.4 wt %) and Na2O (0.1 to 0.4 wt %).
In yet another embodiment of the present invention, the chemical constituent of the flaky graphite used may be in the range of carbon (92 to 95 wt %), volatile matter (0.5 to 1.2 wt. %), ash (4 to 8 wt. %) and surface area 2 to 10 m2g-1.

In yet another embodiment of the present invention, the chemical constituent of the nano carbon black used may be in the range of carbon (97 to 99 wt %), volatile matter (1 to 2 wt. %), ash (0.1 to 0.4 wt. %) and surface area 80 to 150 m2gl.
In still another embodiment of the present invention, the chemical constituent of the metals powders used are chemical grade ones with purity level above 97 wt%.
In still another embodiment of the present invention, the chemical constituent of the boron carbide use d may be min 80% pure.
DETAILED DESCRIPTION:
The present invention provides a synergistic composition for the production of low carbon containing magnesia carbon refractory with high oxidation resistance and high hot strength using 70 to 95wt % fused magnesia, 1 to 5 wt % metallic anti-oxidants, 0.5 to 2 wt. % boron carbide, 2 to 20wt% carbon containing both graphite and nano carbon, 0.5 to 2 wt % carbarose P as additives, 0 to 2 wt% powder resin and 2 to 4 wt% of liquid resin as binder.
The raw materials mentioned above are used in the preparation of low carbon magnesia carbon refractory. Fused magnesia grains of different size fractions are first mixed with nano carbon black properly for 10 to 20 min in a mixer with heating facility, where temperature varied between 30 to 65°C. The liquid resin separately heated in the temperature range of 40 to 80°C is then added to the batch composition and thoroughly and mixed for 5 to 15 mins. Then all the fine fractions of magnesia and other fine batch materials, namely, antioxidant powders, carbarose P, powder resin, graphite, etc are added to the batch composition and whole mixture is further mixed for 15 to 45 min. The purpose of mixing the raw materials is to make a refractory batch and transform all the solid components and the liquid additions into a macro homogeneous mixture that can be subsequently molded or shaped by one of the numerous fabrication methods employed by modern refractory manufacturers. The mixed batch composition is then allowed to be aged for 0 to 6 h in the temperature range of 15 to 35°C and then pressed using a hydraulic press with a specific pressure in the range of 1 to 2 ton/cm2. Pressed shapes were again allowed

for ambient curing for 0 to 6 h and then oven curing in the temperature range to 140 to 250°C for 6 to 24 h to complete the polymerization of the resin and strength development. Coking of the cured samples is done in the range of 900 to 1200°C for 2 to 6 h in reducing environment.
The present invention utilizes raw materials like commercial fused magnesia with a purity in the range of 95 to 97.5 wt%; metals powders as antioxidants with purity level above 97 wt%; nano carbon black with purity 97 to 99 wt%, volatile matter in the range of 1 to 2 wt. %, ash content 0.1 to 0.4 wt. %, surface area 80 to 150 m2g-1; and flaky graphite with 92 to 95 wt % carbon content, volatile matter in the range of 0.5 to 1.2 wt.%, ash in the range of 4 to 12 wt. % and surface area between 2 to 10 m2g-1.
Final products are then characterized by various refractory related property measurements. Density and cold crushing strength (CCS) of cured and coked samples were characterized as per the standard IS: 1528, Part-12 (2002) and IS: 1528, Part-4 (2002) respectively. Hot modulus of rupture (HMOR) was determined by three-point bending test at 1400°C in air with a soaking time of 30 min, as per ASTM CI33-7 standards, using 125 mm x25 mm x25 mm sized samples in a HMOR furnace apparatus (Bysakh, India make). For oxidation resistance, cylindrical samples (50 mm height and 50 mm diameter) were fired at 1400°C (heating rate 5°C/min) with 2 h soaking time in air atmosphere. Fired samples were cut horizontally into two pieces, and oxidation was measured diametrically by measurement using a Vernier calipers. Coking was done by placing the shapes in a reducing atmosphere at 1000°C for 2 hours. Slag corrosion test by static crucible method was done at 1600 °C for 2 h using a 50 mm cube sample with a drilled hole of dimension 20 mm diameter and 25 mm height. Steel converter slag was used for corrosion resistance test. Corroded samples were cut along the vertical axis into two pieces, and the sections were examined for slag corrosions and penetration by dimensional measurement.
The invention is described with the help of following experiments and examples for understanding the importance of composition in external practice. However the examples, which are given here by way of illustration, should not be construed to limit the scope of the present invention.

Example 1
Fused magnesia with purity 97% with different grain size having 4-6mm (500g), l-3mm(2000g) and 0-1 mm (1250g) were mixed with nano carbon (50g) properly so that most of the magnesia grains were coated with carbon layer. Then liquid resol resin was mixed with the bulky magnesia carbon mix. After that all fines [graphite (150g) + aluminium metal powder (l00g) + carborose P (50g) + B4C (50 gram) + powder resin (50gram)] and magnesia fines (850g) were mixed for 30 minutes and then pressed at 1.5 ton/cm2. Pressed samples were cured at 220°C for 12 hours and cured samples were characterized for density and CCS, fired at 1000°C for coking and 1200°C with soaking time 2 hours for oxidation resistance test. Corrosion resistance and Hot MOR were carried at 1600°C and 1400°C respectively.
Example 2
Fused magnesia with variation of grain size from <75 Micron to 6 mm were used for the batch preparation. 50 gram nano carbon black were mixed with magnesia [4-6mm(500g), l-3mm (2000g) and 0-1 mm (1250g)] by a mechanical mixture so that the carbon particles were coated the magnesia grains properly. Then liquid resol resin was mixed with bulky magnesia-carbon mix for 10 minutes. Anti-oxidant, silicon metal powder 100 gram mixed with 850 gram magnesia fines (<75Micron), 150 gram of graphite, 50gram carborose P, 50gram of B4C and 50gram powder resin properly. Then the mix fines powder were mixed with bulky magnesia -nano carbon mix and mixed it for 30 minutes then pressed at 1.8 ton/cm2. Cured at 200°C for 14 hours and cured samples were characterized for density and CCS, fired at 1050°C for coking and 1200°C with soaking time 2 hours for oxidation resistance. Corrosion resistance and Hot MOR were carried at 1600°C and 1400°C respectively.
Example 3
Fused magnesia varying from <75 Micron to 6 mm were used for the preparation of 5 kg batch. 500 grams of 4-6mm. 2000grams of l-3mm, 1250 grams of 0-lmm magnesia grain were mixed with 50 gram carbon black properly so that magnesia grains were coated with carbon black particles properly. Then the liquid resol resin was mixed with the magnesia carbon mix for 10 minutes. In another one pot 850 gram magnesia fines (<75Micron), 150 gram of graphite, 50 gram carborose P, 50gram of B4C and 50gram powder resin were mixed with 100 gram of

magnesium metal powder. Then the fine mixes were added to the magnesia carbon mixture for 30 minutes. After that the mixture were pressed at 1.6 ton/cm2 in a hydraulic pressure. Pressed samples were cured at 190°C for 16 hours and cured samples were characterized for density and CCS, fired at 1000°C for coking and 1200°C with soaking time 2 hours for oxidation resistance. Corrosion resistance and Hot MOR were carried at 1600°C and 1400°C respectively.
Example 4
Fused magnesia with different fraction of grains was used for the preparation of conventional MgO-C refractory. 500 gram of 4-6mm. 2000gram of l-3mm, 1250 gram of 0-lmm magnesia grain was used for the preparation of 5kg batch. Then the liquid resol resin was added to the magnesia and stirred it for 10 minutes. In another pot 100 gram of aluminum metal powder was added to the mixture of 250 grams of magnesia fines (<75Micron), 800 gram graphite, 50gram of B4C, 50 gram of carborose P, 50gram powder resin and mixed it 30 minutes. After that the mixture was pressed at 1.7 ton/cm2 in a hydraulic pressure. Pressed samples were cured at 210°C for 12 hours and cured samples were characterized for density and CCS, fired at 1000°C for coking and 1200°C with soaking time 2 hours for oxidation resistance test. Corrosion resistance and Hot MOR were carried at 1600°C and 1400°C respectively for the evaluation of hot refractory properties.
Example 5
500 grams of 4-6mm magnesia, 2000grams of l-3mm magnesia, and 1250 grams of 0-1 mm magnesia grain were mixed with 50 gram of nano carbon black in a mechanical mixture. Then the liquid resol resin was added and was mix for 10 minutes. 100 gram of aluminum metal powder was mixed with 750 grams of magnesia fines (<75Micron), 250 gram graphite, 50 gram of B4C, 50 gram of carborose P and 50 gram powder resin in another pot. The fines mixture was added to the magnesia- nano carbon mix for 30 minutes and pressed at 1500 kg/cm2 in a hydraulic pressure. Pressed samples were cured at 220°C for 12 hours and cured samples were characterized for density and CCS, fired at 1000°C for coking and 1200°C with soaking time 2 hours for oxidation resistance test. Corrosion resistance and Hot MOR were carried at 1600°C and 1400°C respectively for the evaluation of hot refractory properties.

Example 6
In a 5 kg batch, 500 gram of magnesia with a grain size 4-6mm, 2000 gram of magnesia with a grain size l-3mm, 1250 gram of magnesia with a grain size 0-lmm were mixed with liquid resol resin. Then the mixture of 100 gram of aluminum metal powder, 800 grams of magnesia fines (<75Micron), 250 gram of graphite, 50 gram of B4C, 50 gram of carborose P and 50 gram powder resin was added to the bulky magnesia-resin mix in a mechanical mixture for 30 minutes. The prepared composites were pressed at 1.6 ton/cm2 in a hydraulic pressure. Pressed samples were cured at 220°C for 12 hours and cured samples were characterized for density and CCS, fired at 1050°C for coking and 1200°C with soaking time 2 hours for oxidation resistance. Corrosion resistance and Hot MOR were carried at 1600°C and 1400°C respectively for the evaluation of hot refractory properties.
Example 7
500 gram, 2000 gram, 1250 gram of magnesia having grain size 4-6mm, l-3mm, 0-lmm respectively was added to liquid resol resin and mixed it for 10 minutes. Then the mixture of 900 gram of magnesia fines (<75Micron), 100 gram aluminum metal powder, 150 gram of graphite, 50 gram of B4C, 50 gram of carborose P and 50 gram powder resin was added to the magnesia-resin mix about 30 minutes in a mechanical mixture. Then the samples were pressed at 1500 kg/cm2 in a hydraulic pressure. Pressed samples were cured at 220°C for 12 hours and cured samples were characterized for density and CCS, fired at 1010°C for coking and 1200°C with soaking time 2 hours for oxidation resistance. Corrosion resistance and Hot MOR were carried at 1600°C and 1400°C respectively for the evaluation of hot refractory properties.


The main advantages of the present invention are:
The present synergistic composition utilizes different metallic powder as anti-oxidants with different amounts of graphite and nano carbon and having much lower total carbon content in the composition. Purity and high reactivity of nano carbon resulted in improved properties even at much reduced carbon content.
The combination of antioxidants is important as two different forms of carbons are used with
different characteristics. Mixing of nano carbon, proper selection of graphite and nano carbon
content and right combination of antioxidants are important. ,
The present synergistic composition where nano carbon black were used which gives a compact structure with high strength due to the formation of in situ ceramic phase as nano carbon has high surface area which gives a higher reactivity at higher temperature.
The present synergistic compositions have high hot strength and high oxidation resistance due to the formation of in situ ceramic phase.
The present synergistic composition enhances the refractory properties of the product.

5. CLAIMS We Claim
1. A synergistic composition for the production of low carbon containing magnesia carbon refractory with high oxidation resistance and high hot strength using 70 to 95wt % fused magnesia, 1 to 5 wt % metallic anti-oxidants, 0.5 to 2 wt. % boron carbide, 2 to 20wt% carbon containing both graphite and nano carbon, 0.5 to 2 wt % carbarose P as additives, 0 to 2 wt% powder resin and 2 to 4 wt% of liquid resin as binder.
2. A process as claimed in claim 1, wherein fused magnesia grains of different size fractions are first mixed with nano carbon black for 10 to 20 min in a mixer with heating facility in the temperature range between 30 and 65°C.
3. A process as claimed in claim 1 and 2, wherein liquid resin is separately heated in the temperature range of 40 to 80°C and added to the batch composition and thoroughly and mixed for a time period of 5 to 15 mins.
4. A process as claimed in claim 1 to 3, wherein all the fine fractions containing magnesia and other fine batch materials, namely, antioxidant powders, carbarose P, powder resin, graphite, etc are added to the batch composition and whole mixture is further mixed for 15 to 45 min.
5. A process as claimed in claim 1 to 4, wherein the mixed batch composition is allowed to be aged for 0 to 6 h in the temperature range of 15 to 35°C and then pressed using a hydraulic press with a specific pressure in the range of 1 to 2 ton/cm2.
6. A process as claimed in claim 1 to 5, wherein the pressed shapes were again allowed for ambient curing for 0 to 6 h and then oven curing in the temperature range to 140 to 250°C for 6 to 24 h.

7. A process as claimed in claim 1 to 6, wherein raw materials like commercial fused magnesia with a purity in the range of 95 to 97.5 wt%; metals powders as antioxidants with purity level above 97 wt%; nano carbon black with purity 97 to 99 wt%, volatile matter in the range of 1 to 2 wt. %, ash content 0.1 to 0.4 wt. %, surface area 80 to 150 m2g-1; and flaky graphite with 92 to 95 wt % carbon content, volatile matter in the range of 0.5 to 1.2 wt.%, ash in the range of 4 to 12 wt. % and surface area between 2 to 10 m2g-1; are utilized.
8. A complete process for the manufacture of a low carbon containing magnesia carbon refractory containing fused magnesia, graphite, nano carbon, a combination of antioxidants with reference to examples.