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Introduction of magnesia carbon brick for converter

2020-10-14 08:22:29

1. The main composition of magnesia-carbon bricks: magnesia-carbon bricks are refractory products made of magnesia and graphite as the main raw materials, plus an appropriate amount of binder, through high-pressure molding and low-temperature heat treatment. Magnesia-carbon bricks started in Japan and were a new type of refractory product developed in the early 1970s. Mainly used for converters for steelmaking, working linings for electric furnaces, and working linings for refining ladle outside furnaces. Magnesium oxide powder manufacturers


2. Introduction of the main raw materials used in the production of magnesia carbon bricks in our factory:


1. Fused magnesia: It is an alkaline refractory material made by melting natural magnesite ore, light burned magnesia or sintered magnesia through an electric arc furnace. The main crystalline phase of fused magnesia is periclase, the melting point is 2800℃, it starts to sublime in vacuum at 1600℃, and it starts to sublime in reducing atmosphere above 2000℃, the density is greater than 3.40g/cm3, and the porosity is 0%-10 %, Mohs hardness 5.5, strong corrosion resistance to alkaline slag, stable chemical properties, no reaction or weak reaction with various refractory materials except silica bricks at a high temperature of 1500℃. The appearance should be more obvious after complete melting and crystallization, and other magnesia or impurities are not allowed to be mixed.

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2. Graphite: It is a natural mineral with carbon as the main component. It has the properties of heat conduction, electrical conductivity, lubrication, plasticity and corrosion resistance. It is the main raw material for carbon-containing refractories. Graphite for refractory materials is mostly flake graphite, which is divided into high purity, high carbon, medium carbon, and low carbon graphite according to the fixed carbon content. The color is iron black and steel gray. Density is 2.09-2.23g/cm3, melting point is 3700℃±100℃ (in vacuum), high thermal conductivity, small expansion coefficient, small elastic modulus, good lubricity, good electrical conductivity, stable chemical properties, and acid at room temperature , Alkali and organic solvents do not react, hard to wet with molten steel, and have good corrosion resistance.


3. Phenolic resin: a non-aqueous organic binder for refractory materials. It is made by polycondensation of a mixture of phenol (or cresol, xylenol, or resorcinol) and formaldehyde (or sugar aldehyde) under the action of a catalyst. The main advantages are (1) high carbonization rate (52%); (2) good adhesion and high strength of the formed body; (3) high bonding strength after firing; (4) hardening speed can be controlled at room temperature; ( 5) Less harmful substances, which can improve the working environment. According to heating properties or structural forms, there are thermosetting phenolic resins and thermoplastic phenolic resins. According to product forms, there are liquid phenolic resins and solid phenolic resins (granular and powder). They are classified by curing temperature, and there are high-temperature curing types 130℃-150 ℃; There are medium temperature curing type 105℃-110℃; there is normal temperature curing type 20℃-30℃.


Thermosetting phenolic resin binders generally require that the moisture in the aldehyde resin should be less than 1.8%. Its viscosity changes with temperature. The viscosity decreases with the increase of temperature. It is a suitable viscosity. The use temperature should be controlled between 40-45℃. At the same time, there is the phenomenon that the viscosity changes with the storage time. The storage time is prolonged and the viscosity changes greatly. If the storage period is too long, it will solidify and become unusable. Generally, the storage time is 30 days (in the warehouse) at high temperatures in summer and longer in winter. The relative storage time of thermoplastic phenolic resin will be longer, and the trapping time of magnesia-carbon bricks for converters with this combination can reach 30 days without affecting the molding viscosity, but a curing agent (Urotropine) must be added for dry strength.


3. Technical regulations for the production process of magnesia-carbon bricks for converters. Magnesium-carbon bricks are generally unfired products. The production process mainly includes raw material processing preparation, batching, mixing, molding, and heat treatment. (See the following for the magnesia-carbon brick process flow chart) A. Batching process: It is an important process 1. It should be measured strictly according to the requirements of formula granularity and ratio. This is the requirement. As a batching personnel, you can first identify the raw materials and use measurement tools correctly and skillfully; during work, you should pay attention to whether the raw materials have changes in color, particle size, odor, concentration, feel, etc. Any abnormality should be reported immediately. The granular materials and powder materials used should not be damp or agglomerated. Pay attention to rain and moisture. Fine powders below 1-0 should be packaged in double plastic moisture-proof packaging. B. Mixing process: It is also an important process, because the forming performance of the mixed mud directly affects the quality of the bricks. General requirements for the feeding sequence: coarse magnesia particles, medium particles (3-6, 1-3, 1-0) --- phenolic resin --- graphite --- fine magnesia powder, additives. After the pellets are added, the binder is mixed for a period of time at low speed to make the liquid resin adhere evenly on the pellets, and then graphite is added, and the graphite is added to make it stick to the liquid film of the magnesia particles through kneading and extrusion. The graphite on the shell of the magnesia particles is pressed onto the particles and part of the excess resin is removed. Only then can high-speed mixing be carried out, otherwise it will cause graphite to float on the material and make a good mud material. Because graphite has good thermal conductivity and small heat capacity, while the heat capacity of coarse magnesia particles is large, the friction heat generated during high-speed mixing is beneficial to wetting graphite. Only after the above series of operations are completed, can the fine magnesia powder and additives be added to continue mixing. When the graphite, magnesia particles, fine powder and additives have been wetted, and the excess binder on the particles has basically come out At the same time, when the graphite wrapped around the magnesia particles is densely pressed onto the particles, the mixing can be completed.


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Yingkou Dingfeng Metallurgical Technology Co., Ltd.

18041722333

Contact: Mr. Zhang

Telephone: 18041722333

Mail box: 810678900@qq.com

Address: Liangjunzhai Village, Yong'an Town, Dashiqiao City, Yingkou City, Liaoning Province

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