Due to the different working environment of each part of the lining material of the converter, the uneven corrosion of each part of the lining of the converter is caused. Although the slag splashing technology can make the lining by splashing slag, it is difficult to form a uniform slag hanging layer on the surface of the lining, and it is difficult to repair the parts with serious local corrosion damage. Therefore, the repair of the lining of the converter is a powerful measure to extend the life of the lining, balance the damage of the lining and reduce the production cost. Due to the unstable factors of converter operation, when some parts of the lining are damaged prematurely, the repair of the lining should start, and this repair should be maintained until the life of the lining is terminated. To the later stage of the use of the lining, the amount of repair will continue to increase, and the time used for repair will continue to extend, which has affected the stable operation of the converter, and the life of the lining should be suspended. There are two kinds of repair materials used in the converter: jet repair material and hot flow repair material.

Hot flow repair material for converter

The hot flow repair material is mainly used for the repair of the steel face and the steel side of the converter, also known as the large surface repair material, referred to as the large fabric. When in use, the repair material is put into the furnace from the mouth, and the furnace body is shaken. Under the action of residual heat in the furnace, the repair material flows and spreads on the corroded part of the furnace lining. The hot flow repair material should have the following properties:

(1) The free flow material has good spreading and fluidity at the residual heat temperature of the converter lining (800~1200℃).

(2) The artesian material solidifies soon after spreading.

(3) The solid artesian material has good bonding property with the original lining material.

(4) The free flow material itself should have good erosion resistance, which can prevent the repair material layer from being eroded away in the next smelting.

The artesian material takes magnesia and magnesia dolomite sand as the basic raw materials, and the process performance mainly depends on the binder. Commonly used binders are asphalt, resin, or a mixture of both. The traditional large surface feed of the converter is heavy burnt magnesia mixed with medium temperature asphalt, that is, the so-called burnt feed. General repair a carbonization time to 40 ~ 60min, the service life is about 10 times; On the basis of asphalt magnesia, the grade of raw materials is improved, some modified resins and additives are used, which can significantly improve the service life of large surface feeding materials, and shorten the curing time to 30~40min.

Another material is the water-containing magnesium artesian large surface repair material. This material is essentially magnesium free-flowing castable, it contains a lot of silica fume, the water added is generally 5% to 7%, basically the same as magnesium free-flowing castable. Because the flowing medium is water, the sintering time is short and environmentally friendly. Moreover, it is a castable, adding little water, so its bulk density is higher and strength is higher, so the erosion resistance and erosion performance is better, that is, it has a good service life, and the service life is generally 25 to 35 furnace times. Since the magnesium material will soon harden and lose fluidity after adding water, a blender should be placed on the construction site, and after mixing with water, it will be immediately put into the furnace.

Since magnesia carbon brick is more suitable for converter than magnesia brick, it should be a development direction to repair the large surface of converter with magnesia carbon free-flowing material, which is worth further development and application. At the same time, in the future, under the goal of reducing unit consumption and cost, the binder of large fabrics should also be a future research and development direction.

Spray feed for converter

Where the lining of the converter is partially damaged during the furnace service and it is not suitable to be repaired with supplementing material, such as the trunnion and slag line, spraying supplementing technology can be used. The refractory material is sprayed to the badly damaged part of the furnace, so that it can be sintered as one with the furnace lining brick, and the furnace lining can be repaired. The main raw materials of the Bessemer are magnesia, binder, plasticizer and a little water. The commonly used spraying methods include dry spraying, semi-dry spraying and flame spraying. The specific requirement for the lining of the converter is to have sufficient refractoriness; Can withstand the role of high temperature in the furnace; The spray filler can be attached to the furnace lining to be sprayed; Less material shedding; The adhesive layer can be sintered well with the red hot furnace lining surface (800 ~ 1000℃) to be sprayed and fused together with sufficient strength. The adhesive layer can withstand the erosion of high temperature slag, molten steel, furnace gas and metal oxide vapor. The spray feed can flow smoothly in the spray pipe.

The spraying machine which implements the semi-dry spraying operation includes a storage tank, a compressed air conveying mechanism and a nozzle; The spray feed in the storage tank is sent to the nozzle by compressed air, mixed with an appropriate amount of water (10%~18%), and sprayed to the working surface of the furnace lining at a certain speed under air pressure. After bonding curing. The process factors that affect the effect of semi-dry spraying are:

(1) The furnace lining spray is carried out in a hot state, so the residual degree of the working surface has a significant impact on the spray effect, and it is generally believed that 800~1000℃ is better;

(2) The particle composition, binder, amount of water added, air pressure and so on have a serious impact on the adhesion rate of the spray filler. The basic raw materials of the spray filler are magnesia and magnesia dolomite sand, and the binder is mainly powdered sodium silicate, sodium phosphate, phosphate of calcium and potassium, chromate and so on. One of the functions of the binder is to make the spray filler adhesive, which can be effectively attached to the working surface of the furnace lining; Another function is to form a high temperature mineral phase at high temperature, so that the spray supplement can not only firmly burn with the furnace lining working surface as a whole, but also make itself have good erosion resistance. It is often required to contain a certain amount of CaO in the component of the spray supplement, which can improve the high temperature performance and adhesion of the spray supplement. The effectiveness of the spray supplement is measured by the adhesion rate and the number of uses, the general adhesion rate is greater than 85%, and the number of uses is 3 to 5 times.

Flame spray repair is a new technology which is difficult to apply to the repair of coke oven and then extend to the lining of converter. Semi-dry spraying is a simple and convenient method for the converter lining, but it has a fatal weakness, that is, adding water in the spraying process, which will produce a large amount of water vapor and accumulate a certain steam pressure when it comes into contact with the repairing face due to the action of residual heat, leaving hidden dangers for the bonding of the spraying and working face and the use of the spraying. However, the flame spray does not add water, but with flammable materials, flammable gas and oxygen, the spray feed burns and heats in the spray process, a part of the material into a molten state, and when it comes into contact with a fairly high temperature working face, it will immediately melt and burn into a whole. The combustible materials and combustible gases included coke powder, coal powder, propane, methane, oxygen, etc. The flame spray repair is mostly carried out in the working gap after the converter steel output, the spray repair time is very short, the furnace liner residual degree is relatively high, the adhesion effect is good, the service life is relatively long, and the general spray repair can be used 10 to 20 times.

In order to improve the quality of the spray supplement, it should be developed in the direction of magnesia and magnesia carbon spray supplement. The spraying method should be developed from semi-dry spraying to flame spraying. In recent years, a kind of dry process magnesium carbon spray supplement (w(MgO)> 85%, C: 7%~ 10%) is a dry material, dry spray to hot furnace lining, containing heating agent combustion, resulting in melting of the binder, the spray supplement sprayed on the furnace lining is welded on the furnace lining. This adhesion rate reaches more than 90%, this spray supplement is also similar to flame spray supplement, coupled with magnesium carbon, so the use effect is very good, and the service life is increased to more than 30 times.

After reading the performance and composition of the two materials respectively, I believe that you can make a judgment on your own, and choose the appropriate repair material according to different furnace conditions and different parts.

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