High Cold Crush Strength Resistant Sintered Magnesia Carbon Bricks for Steel Casting

 The application experience of magnesia-carbon brick in converter, electric furnace and ladle shows that it is very suitable for steel smelting because of its superior high temperature resistance, slag erosion resistance and good thermal shock stability.Magnesia-carbon brick is applied to the slag line and the steel outlet with serious erosion because of its high fire resistance, high slag resistance and solubility, and high temperature creep rate of magnesia which is difficult to be wetting by slag and molten steel.So far, huge economic benefits have been created due to the extensive use of magnesia-carbon bricks in the steelmaking process and improved iron and steel smelting technology.At present, magnesia-carbon brick has some shortcomings, such as high price graphite consumption, increasing heat consumption, and continuous carburization into molten steel, which pollutes molten steel. In order to reduce the cost of raw materials and pure molten steel, the low carbonization of magnesia-carbon brick can solve these problems well. 

The characteristics of magnesia-carbon brick are mainly reflected in the following aspects:
1. Tissue compactness of magnesia-carbon brick
The structure compactness of magnesia-carbon brick depends on the type and amount of binder and antioxidant, the type of magnesia, the particle size and amount of graphite, etc. In addition, molding equipment, brick pressing technology and heat treatment conditions all have certain effects.In order to ensure that the apparent porosity is below 3.0%, the forming pressure is 2t/cm2, and the bulk density of the matrix part can be enhanced to improve the corrosion resistance, magnesia-carbon bricks with particle size less than 1mm are used in the air eye brick and the steel outlet brick.Different binder also has certain influence on the compactness of magnesia-carbon brick. The volume density of magnesia-carbon brick is higher when the binder with higher carbon residue rate is selected.Add different antioxidant effect on the density of magnesia carbon brick are obviously different, and in 800 degrees, show porosity increases with the oxidation of antioxidants, after more than 800 degrees, do not contain metallic magnesium carbon brick show porosity does not change, but its containing metal show porosity decreased obviously, 1450 degrees to 800 degrees only half, add metal show the lowest porosity of aluminum magnesium carbon brick.
The heating rate of magnesia-carbon brick will also affect the change of its apparent porosity. Therefore, when magnesia-carbon brick is used for the first time, the temperature should be increased at a low speed as far as possible to make the binder decompose completely at a lower temperature. During the use of magnesia-carbon brick, the influence of temperature difference on porosity is also obvious, the greater the temperature difference, the faster the porosity increases.
2. High temperature performance of magnesia-carbon brick
2.1 High temperature mechanical properties Different additives have different effects on improving the high temperature strength of magnesia-carbon bricks. The research shows that for the high temperature bending strength above 1200℃, there is no additive.Calcium boride & lt;Aluminum & lt;Aluminum magnesium & lt;Aluminum + calcium boride <Aluminum magnesium + calcium boride, where aluminum magnesium + boron carbide between aluminum magnesium and aluminum magnesium + calcium boride.
2.2 Thermal Expansion Property The participation expansion value of magnesia-carbon bricks without metal addition is far lower than that with metal addition, and the participation expansion value increases with the increase of metal addition.
2.3 The thermal expansion and high temperature flexural strength of magnesia-carbon bricks are different in different directions under various anisotropy, which is mainly caused by the orientation of flake graphite. The principle and method of bricklaying with working lining are determined.Magnesia-carbon brick in vertical direction has higher high temperature strength and lower thermal expansion.

Because of the different working conditions of converter lining, the effect of magnesia-carbon brick is also different. 

Lining furnace opening position is constantly impacted by cold state and hot state liquid steel, so the refractory material used in the furnace opening must be resistant to the scouring of high temperature slag and high temperature exhaust gas, and is not easy to hang steel and easy to clean up in time.The furnace cap part is not only subjected to serious slag erosion, but also to the temperature change of rapid cooling and rapid heating, as well as the comprehensive effect of high-temperature air flow of carbon oxidation and dust and high-temperature exhaust gas scouring, so the magnesia-carbon brick with strong slag erosion resistance and anti-spalling property is used.Lateral loading requirements magnesia carbon brick in addition to high slag erosion resistance, but also has the very high temperature is strong and has the quite good spalling resistance, so often used to join metal antioxidant high strength magnesium carbon brick, studies have shown that join aluminum magnesium carbon brick in low temperature when the high temperature strength of the composite to add metal aluminum and silicon metal samples is low, and at high temperature, the high temperature strength has increased.The slag line is the three-phase junction of furnace lining refractory material, high-temperature molten slag and furnace gas, which is the most severely corroded part by slag. Therefore, magnesia-carbon bricks with excellent slag corrosion resistance are needed to be laid, and magnesia-carbon bricks with high carbon content are needed in the slag line part.

2. The use of magnesia-carbon brick on electric furnace
At present, the wall of electric furnace is almost all constructed by magnesia-carbon brick, so the service life of electric furnace is determined by the life of magnesia-carbon brick. The main factors that determine the quality of magnesia-carbon brick include the purity of magnesia, the type of impurities, the grain binding state and grain size of magnesia-carbon brick from MgO.The purity, degree of crystallization and scale size of the flake graphite as the source of carbon introduction;Usually, thermosetting phenolic resin is used as binder. The main influencing factors are the amount of addition and carbon residue.Now have shown that adding antioxidants magnesia carbon brick can change and improve its matrix structure, but when used under normal operating conditions of the furnace, antioxidants are not magnesia carbon brick of the necessary raw materials, and only used for high FeOn arc furnace slag, such as the use of direct reduced iron or have irregular parts and electric furnace hot parts of the oxidation, add various kinds of metal antioxidants can become an important part of magnesia carbon brick.
The corrosion behavior of magnesia-carbon brick at slag line shows the formation of obvious reaction dense layer and decarburized loose layer.The reaction dense zone also becomes the slag invasion zone, which is the erosion zone where the high temperature liquid slag infiltrates into the interior of the magnesia-carbon brick after a large number of pores are formed after decarburization.In this region, FeOn in the slag is reduced to metallic iron, and even the desorption phase and intergranular Fe2O3 in solid MgO are reduced to metallic iron.The penetration depth of the slag into the brick is mainly determined by the thickness of the decarburized loose layer and usually terminates at the place where the graphite remains.Under normal conditions, the decarburization layer in magnesia-carbon brick is relatively thin due to the presence of graphite.
There are two ways of steel outlet of electric furnace: tilting steel outlet of trough and steel outlet of bottom of furnace.When using the discharging tank to tilting the steel, magnesia-carbon brick is basically not used, and Al2O3 or ZrO2 quality is selected, and C, SiC and Si3N4 and other non-oxygen substances are added.When the bottom of the furnace is used, the outlet is composed of an external sleeve brick and an internal tube brick.At the bottom of the furnace, the steel outlet is made of magnesia-carbon brick pipe brick. The pore size of the pipe brick is determined by the furnace capacity and the time of steel drawing, and the inner warp is generally 140 ~ 260mm.
The middle block and low block magnesia-carbon brick were used in the outlet of an electric furnace in a steel mill, and the sintered magnesia-carbon brick was replaced by the sintered magnesia-carbon brick on both sides of the copper outlet, and the furnace life was increased from about 60 to more than one time.The magnesia-carbon brick at the slag line after use is kept intact and does not stick slag.The slag line does not need refilling furnace, which reduces the labor intensity and improves the purity and productivity of molten steel.
3, aluminum magnesium carbon brick in the use of ladle
When MGO-C brick is used in refining ladle furnace and ladle, it is mainly used in clearance and slag line.According to the operating conditions, the refractory materials used in these parts must have high temperature resistance, heat shock resistance, resistance to slag erosion caused by mechanical erosion.So in the past, magnesia-chrome refractories were used for these parts, but because of the pollution of chromium to the environment, the amount has been reduced, and now magnesia-carbon bricks are used.

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Our company has thirty years producing experience in refractory products. Our manager will supervise on a various refractorys production materials, process control, quality supervision and package delivery, and ensure the products are 100% qualified. 
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Our company has passed ISO9001 quality management system certification and SGS certification. And the annual supply of shaped and unshaped refractory product is 28, 800-35, 000 tons. 
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Now we have gained a global sales network reaching Taiwan, Russia,  Korea, Vietnam, Pakistan, Bulgaria, French, India, Egypt,Congo, Angola, South Africa, and so on.
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5. Testing equipment: 
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High Temperature RUL Tester
Bulk Density Tester
The Pressure Tester
Refractoriness Tester 

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