What are the requirements for the tapping hole when the converter is tapped?
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What are the requirements for the tapping hole when the converter is tapped?

Views:5     Author:Site Editor     Publish Time: 2021-03-19      Origin:Site

The tapping port should always maintain a certain diameter, length and reasonable angle to maintain an appropriate tapping time and ensure that there is no residual molten steel in the converter. If the tapping hole is deformed, it will cause the molten steel to flow easily during tapping, a large amount of steel slag will flow into the ladle, and the tapping time will be prolonged. This will not only cause the phosphorus content of molten steel to increase, but also reduce the alloy absorption rate . The tapping time is too short, the added alloy is not fully melted, and the dispersion is not uniform, which affects the alloy absorption rate. Long tapping time will aggravate the secondary oxidation of molten steel, increase the burden of deoxidation, and have large thermal vibration fluctuations, and also affect the turnover rate of the converter.

 

      The tapping hole should be changed on schedule, and the method of overall change can be adopted, or the method of making the steel hole again can be used. In actual operation, it is necessary to maintain the correct maintenance of the tapping port to extend the service life of the tapping port. On the one hand, the material of the tapping port must be optimized, and on the other hand, it is necessary to create sticky slag and increase slag without affecting the quality. Protection of the tapping hole. In addition, the use of slag tapping methods can also extend the service life of the tapping port.


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Magnesia carbon bricks are widely used in metallurgical processes, but due to their harsh working conditions, the service life of magnesia carbon bricks is still a big problem, especially the damage of magnesia carbon bricks at the slag line of the ladle is particularly serious.        In the ladle, especially at the slag line of the ladle, the chemical composition of the slag is complex and changeable, and the temperature changes drastically and frequently. Therefore, magnesia carbon bricks with better performance are often used in the slag line. The corrosion mechanism in the slag in the ladle has been deeply studied at home and abroad, and the detailed summary is summarized as follows.  

 

(1) Corrosion of magnesia carbon brick by slag:        

In the ladle, the lining of the slag line is most vulnerable to damage due to the complex physical and chemical environment at the slag line. The chemical attack of slag on magnesia-carbon bricks is mainly through the dissolution of magnesia and the oxidation of carbon in the matrix of magnesia-carbon bricks. Under the combined action of the following factors, the magnesia-carbon bricks are damaged:  

1. The effect of alkalinity: the lower the alkalinity of the slag, the more serious the erosion of the magnesia carbon brick. If the alkalinity of the slag increases, the activity of SiO2 in the slag will decrease, which can reduce the oxidation of carbon. With the increase of the temperature, the FeO activity in the slag decreases, which relatively slows down the corrosion behavior of the slag on the magnesia carbon brick.  

2. The influence of MgO: When analyzing the composition of the LF slag line, it is found that the MgO content in the slag layer is as high as 30%. We believe that the higher the MgO content in the slag, the slower the erosion of the magnesia carbon brick, the alkalinity of the slag The stronger the slag, the slower the erosion of the magnesia carbon brick.  

3. The influence of Al2O3: Al2O3 in the slag will reduce the melting point and viscosity of the slag, increase the wettability of the slag and refractory materials, make the slag easier to penetrate from the magnesia grain boundary, and make the periclase separate from the magnesia carbon brick matrix .  

4. The influence of FeO: First, the FeO in the slag can easily react with the graphite in the magnesia carbon brick at high temperature, and produce bright white iron beads to form a decarburized layer. Secondly, the periclase in the magnesia carbon brick will also be the same. The FeO in the slag reacts to produce low melting point products.  

In the process of repeated heating and cooling of the ladle, due to the inconsistency of the thermal expansion rate between the formed mafic composite low melting point product and the mafic ore, the magnesium oxide on the surface of the refractory material is broken, which in turn leads to the dissolution of the brick body. Foreign scholars also believe that increased iron content in steel slag is detrimental to the life of magnesia-carbon bricks. First, iron FeO accelerates the oxidation of carbon on the surface of magnesia-carbon bricks, and secondly, FeO will react with MgO to loosen the structure of the magnesia-carbon brick working surface. The joint action of the magnesia carbon bricks accelerates the erosion.  

 

(2) Oxidation of carbon in magnesia carbon brick:        

When the magnesia carbon brick is in contact with the molten slag, the carbon will decarburize with FeO and other oxides in the molten slag, forming a decarburized layer under certain conditions, resulting in a loose structure of the magnesia carbon brick working surface, which is the damage of the magnesia carbon brick main reason. Carbon reacts with CO2, O2, SiO2 and other oxides and is continuously oxidized by iron oxides in the slag; secondly, the loose structure formed by the decarburization layer produces larger cracks and pores under the action of thermal expansion and scouring of the slag, which makes the slag easy to penetrate. It forms a low-melting phase with MgO. At the same time, under the action of violent mechanical agitation in the molten pool and violent scouring of steel slag, the surface layer structure of the magnesia carbon brick is changed, and it is gradually damaged from the outside to the inside, resulting in serious damage to the magnesia carbon brick. After the temperature exceeds a certain value, the brick structure will be destroyed and rapidly corroded. This is due to the consumable reaction of MgO and graphite at high temperatures. Electric furnace magnesia carbon brick  

 

(3) The effect of stomata:        

Due to the presence of micro-pores inside and on the surface of the magnesia carbon brick, the erosion of the magnesia carbon brick is more likely to occur. During the use of magnesia-carbon bricks, the pores play an accelerating role in the formation of the decarburized layer, which in turn causes the slag to corrode the magnesia-carbon brick refractories more seriously. When the outside air enters the pores in the magnesia-carbon bricks for cooling, the oxygen in the air reacts with the surrounding carbon to generate CO gas and is discharged through the micro pores. The continuous occurrence of the two processes makes the porosity and pore size gradually increase. The most important factor that produces pores is the selection of the binder in the magnesia carbon brick. Generally, phenolic resin is used as the binder. If a small amount of phenolic resin is added to the magnesia carbon brick, the porosity will not be too high about 3% in the cold state, but the phenolic resin will decompose to produce water, hydrogen, methane, carbon monoxide, carbon dioxide and other gases after heating. The formation of pores under the flow of these gases increases the porosity. Therefore, the magnesia carbon brick is corroded by the slag passing through the pores, which makes the oxidation of carbon and the dissolution of MgO more intense, thereby causing damage to the magnesia carbon brick. Due to the repetitive nature of the gas generation process, the damage of magnesia carbon bricks is increasing.



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