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The Role of Medium-grade Magnesia as Refractories

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The Role of Medium-grade Magnesia as Refractories

Date:2017-05-10 author: click:

The Role of Medium-grade Magnesia as Refractories



The steelmaking system includes converters, electric furnaces, out-of-furnace refining furnaces, ladles and tundishes. In electric furnaces, dry vibrating materials, prefabricated or cast-in-situ furnace covers or use of furnace covers: triangular areas and other parts, have achieved better refractory effect; in converters and electric furnaces, refractory spraying coatings are generally used to repair the damage, such as manual repair, wet, dry or flame spraying and slag splashing protection. In converters, the traditional slag splashing technology is widely used, and the furnace life can reach more than 10,000 times. There are many kinds of refining furnaces outside the furnace. The RH and DH degassing devices are inserted into the corresponding pipe linings. Generally, high aluminium refractory castables are poured into the whole in a large area, and the service life is about 20-80 times. Ladle and tundish are important subsidiary Industrial Equipment of steelmaking furnace, and also the most thermal equipment consuming refractories.



Iron systems include sintering, coking and blast furnaces and their accessories. The service life of the ignition furnace of belt sintering machine is 3 to 6 years when it is made in situ with refractory plastics and clay combined refractory castables or hoisted with phosphoric acid refractory castables. When the linear ignition device is used, the top pressure of the furnace is much lower and the working conditions of the furnace are better. The light high strength refractory castables or refractory fibers and their products can be used as lining, which also achieves better results.



Plastic Phase Forming: The lattice of metal will slip under the action of stress, which has plastic characteristics. It is introduced into refractories. Compared with the hard inorganic material particles, it will play a plastic forming feature in the forming process, making the green density prepared under the same forming pressure higher than that without adding metal samples.



Promoting sintering: The effect of metals on the sintering of refractories can be attributed to two factors: first, the introduction of plastic phase formed by metals can improve the density of green bodies, shorten the distance between particles and reduce the energy required for mass transfer during sintering; second, the melting point of metals is generally lower than that of refractory raw materials, which can generate liquid phase at lower temperatures, and liquid phase formation. The capillary force and its viscous flow speed up the atom migration rate and the green body shrinkage, and promote the densification process of sintering.



Improving toughness: Metals can improve the toughness of composites by means of crack bridging, crack deflection and crack barrier. Crack bridging is the most effective toughening mechanism. When cracks extend to the interface between metal materials and matrix materials, cracks lengthen their stress due to the ductility of metal particles, which will impose a bridge stress on the upper and lower surfaces of cracks. On the one hand, crack bridging is the most effective toughening mechanism. It can prevent the crack opening and reduce the intensity factor of the crack tip. In addition, it can also produce plastic deformation with the crack opening, which consumes the energy of the crack tip and plays a toughening role.

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