Magnesium carbon brick is a composite material composed of magnesium sand, graphite, phenolic resin binding agent and anti-oxidant; In order to make the magnesium carbon brick to play its maximum performance, its design needs to take into account the structural matching and refractory raw material properties and so on.
The main principles followed in terms of structure are:
1.Design of particle ratios in accordance with the principle of closest packing in order to make magnesium-carbon bricks denser.
2.Graphite in addition to the surface of the magnesium sand particles, but also partially in the matrix, which can attenuate the slag along the grain boundaries of the magnesite erosion and penetration in the matrix, reducing the destruction of magnesium-carbon bricks.
3.Relief of expansion stresses in magnesium sand aggregates by means of graphite etc. coating on the surface of magnesium sand aggregates.
4.The distribution of the antioxidant should be matched as closely as possible to the distribution of the graphite and phenolic resin.
For low carbon magnesium carbon bricks (total carbon mass fraction of not more than 8%) or ultra-low carbon magnesium carbon bricks (total carbon mass fraction of not more than 3%), due to the low carbon content, is not enough to form a continuous carbon network, at this time, magnesium carbon bricks of the organisational structure of the design of the fire brick is particularly important; for the mass fraction of 10% to 20% of the traditional magnesium carbon bricks, the structural design is relatively simple.
Magnesium sand used for magnesium carbon bricks mainly has electrofused magnesium sand and sintered magnesium sand. Ordinary fused magnesia magnesite crystalline grain size is generally greater than 80μm, large crystalline magnesia magnesia crystalline grain size is generally in the range of 2000 ~ 15000μm, and sintered magnesia magnesia crystalline grain size is relatively small, generally greater than 40 ~ 60μm. due to the slag invasion of magnesia magnesium sand is generally carried out along the grain boundaries, so in the requirement of better resistance to slag erosion of magnesium-carbon bricks, magnesia magnesium sand try to select the crystalline grain size is larger, less grain boundary Fused magnesium sand, or even large crystalline fused magnesium sand. Scalar graphite is generally selected -197, -196, etc., that is, the particle size is larger than 100 mesh, purity is higher than 97% or 96% (mass fraction). The bonding agent is hot-hardening phenolic resin, which builds the mechanical interlocking force between magnesium sand particles and graphite, etc., through the mesh structure formed by the cross-linking reaction of its own chain segments during the curing process.
In order to prevent the graphite and resin carbon oxidation and lead to the destruction of the structure of magnesium carbon bricks, in the magnesium carbon bricks to be added to the oxygen affinity of some of the components, so that in graphite or resin carbon oxidation before the oxidation of the first and oxygen combination, so as to prevent the oxidation of graphite, this component is called anti-oxidant, like metal Al, Si, Al-Mg alloys, and so on, as well as B4C, ZrB, and so on. Antioxidant is very important, which is also the most researched direction in magnesium carbon bricks.
More details about Magnesium carbon brick
What are mag carbon bricks used for?
Magnesia Carbon Brick
This material has good performance in thermal resistance, corrosion resistance, and spalling resistance. These bricks are widely used in converters, EAFs, ladles, and refining furnaces.
What are the properties of MgO-C bricks?
MgO-C bricks are composed of magnesia clinker, flake graphite, antioxidants, resin components, etc., and have high resistance to corrosion, spalling, and slag penetration thanks to the characteristics of their constituents.
What is the temperature of magnesia carbon bricks?
Magnesia carbon bricks is a high melting point of basic oxide oxide (melting point 2800 ℃) and difficult to be slag invasion of high melting point carbon material as raw material, add a variety of non-oxide additives.