Technical measures for smelting clean steel

Smelting clean steel should be based on the variety and application requirements. The operations of hot metal pretreatment-steelmaking-refining-continuous casting should be under strict control. The main technical countermeasures are as Neutral Ramming Mass

follows:
(1) Hot metal pretreatment. The sulfur content of molten iron in the molten iron desulfurization or triple desulfurization process should be less than 0.005% or even less than 0.002%.
(2) End-point control of converter compound blowing and steelmaking. Improve dephosphorization conditions, increase the final hit rate of the end point composition and temperature, reduce the dissolved oxygen content of the steel grade, Tundish Nozzle

and reduce the number of non-metallic inclusions in the steel.
(3) Slag blocking and tapping. The slag blocking is adopted for tapping, and the thickness of the slag layer in the ladle is controlled below 50mm. Can avoid phosphorus back and improve the yield of the alloy, reduce oxide inclusions.
(4) Ladle slag modification. In the tapping process, slag modifier is added to the steel stream. Reduce iron oxide and adjust ladle slag composition.
(5) Refining outside the furnace. According to the quality requirements of steel grades, one or more refining combinations are selected to complete the refining task of molten steel, to achieve dehydrogenation, extremely low carbonation, High Alumina Brick

extremely low sulfidation, denitrification, reduce inclusions and form control of inclusions, etc.
(6) Protection pouring. The use of protective pouring technology in the pouring process is particularly important for the production of clean steel. The ladle-tundish-crystallizer adopts long nozzle argon seal protection pouring, the

tundish adopts double-layer protective slag, and the crystallizer adopts protective slag. It has the function of adsorbing inclusions and reducing secondary oxidation.
(7) Tundish metallurgy. Organize reasonable molten steel flow and reasonable molten steel residence time in the tundish to promote the floating of inclusions.
(8) Crystallizer operation technology. Choose protective slag with proper performance; immersion nozzle centering and proper insertion depth; pulling speed and liquid level stability; applying crystallizer electromagnetic stirring

technology; controlling the flow of molten steel, which is beneficial to the upward discharge of gas and inclusions and improves the quality of the slab .
(9) Internal quality control of the slab. Use electromagnetic stirring and light pressure technology to reduce center looseness, center segregation and shrinkage. Increase the density of the slab.
(10) Use straight crystallizer arc continuous casting machine and vertical curved continuous casting machine to facilitate the floating of inclusions.

Article source:
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Nozzle filling compound treatment method

In view of the impact of the nozzle filling compound on the quality of the molten steel in the tundish, part or most of the nozzle filling compound, which is very polluted by molten steel, is taken away manually, which greatly reduces the pollution to the molten steel and reduces the impact on the tundish. Corrosion of refractory materials. The specific operation method is as follows:
(1) Raise the ladle to a high position under the action of the hydraulic cylinder of the ladle turntable.
(2) Put on the ladle shroud, the lower port of the ladle shroud leaves the liquid surface and slag surface of the impact zone.Silica Ramming Mass
(3) Place the container for collecting nozzle filling compound under the ladle shroud port.
(4) Open the slide mechanism to the maximum position, that is, the upper and lower slide holes are aligned.High Alumina Brick
(5) Collect the nozzle filling compound.
(6) Approximately 1/2 to 2/3 of the nozzle filling compound will be collected, and the steel will be casted immediately.
(7) Lower the ladle and insert the ladle shroud into the molten steel in the impact zone.

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Refractory materials for cement kilns

refractory brick

1,cement kiln working environment and the requirements of refractory
The new dry cement kiln is a large system. From raw materials preheating, decomposition, to high temperature calcination to produce clinker, until the cooling out of the material, before and after the total length of several hundred meters. And this is only the main system, there are a large auxiliary system, such as ventilation systems, waste heat power generation systems, are at high temperatures, need to protect the refractory material. However, such a large main and auxiliary system in addition to the work in a serious chemical erosive atmosphere, the other conditions are different, the temperature is not only different levels, there are varying degrees of variation and frequency. Force situation is different, have been washed by the air, there are raw clinker wear, there are mechanical stress. The air erosion strength, wear and mechanical stress and the size of the different, the situation is very complex. Therefore, the performance requirements for refractory materials is also very complex. It is not possible to use only one material to meet all requirements. Must use a series of refractory materials. In view of the above situation, cement kiln refractory use environment although vary widely, but in general there are a few common, that is: a serious chemical erosive atmosphere; greater mechanical stress and wear, strong thermal stress. The difference is mainly due to the difference in temperature. The main requirements for refractory materials are: resistance to chemical attack, high strength, wear resistance, thermal shock resistance, different parts of the refractoriness are quite different. If combined with the actual cement company repair work, it is best to early hardening easy early sintering high strength, it would be better.
2,several commonly used refractory performance comparison
Cement kiln refractory castables are the following: Alkaline castables, high-silicon castables, high-alumina castables.
Alkaline castable refers to the magnesium, magnesium aluminum spinel material based on a class of castables. This material is particularly alkaline resistance, the inadequacies of the thermal expansion coefficient is greater, less thermal shock resistance, such as to solve the thermal shock problem, the application effect in the cement kiln is also good.
High siliceous material refers to the alumina content of less than 30% of the aluminum siliceous material, such materials at a certain temperature and kiln materials and kiln gas in the alkali compounds in the surface of the material quickly formed a closed dense protective glaze Layer, to prevent the continued infiltration of alkali, so as to protect the material inside the alkali is no longer continue to attack, the formation of good resistance to alkaline. However, the weakness of such materials is that the soft temperature is low, low strength, poor wear resistance.
Performance of Alkaline Castables for Kiln Kiln
High alumina refractory brick refers to the formation of a class of alumina-based materials. Mainly including a variety of corundum mullite and so on. The common characteristics of these materials are high hardness, high wear resistance, the inadequacies are not alkali, because the alumina and (K, Na) 2O reaction can form β-alumina, resulting in volume expansion, destruction of material structure, when there is Silica material in the presence of nepheline can form, not only volume expansion, and the lower melting point, the use of a significant decline in performance.
3,Analysis of Damage Mechanism of Refractories for Cement Kiln
1: Alkaline peeling
2: Thermal shock cracks and mechanical stress damage
3: wear air erosion material wear
4: damage caused by non-material properties
Construction defects: construction caused by poor performance of the material caused by defects, poor mobility, material segregation, construction cracks, etc.
Maintenance did not meet the process requirements: baking, no sintering strength low auxiliary equipment: mixing machine, tire mold, vibration anchor welding, bandage, structure, set the size of each location
4, high strength and high wear resistance castable performance analysis
1: high strength and high wear resistance analysis: performance from the nature of the material itself. The cast material is made of high-alumina corundum material, corundum we all know that high hardness and high strength of the material, wear resistance is yes. But in the castable only grain wear is useless, but also must be binding agent and the same part of the matrix wear-resistant Caixing. In the matrix is ??added with corundum homogeneous material @ -AL2O3 powder, so the castable overall wear resistance is very good.
2: thermal shock resistance analysis: pure corundum material wear resistance is good, but the thermal shock is poor, but also part of the sio2, to produce part of the mullite, mullite thermal expansion coefficient of only magnesia three One by one, corundum half, coupled with the thermal expansion coefficient of corundum caused by the micro-cracks toughening effect, which improves the thermal shock resistance of the material.
3: alkali-resistant problem solving: If the corundum is also barely alkaline resistance in the past, mullite in alkaline conditions is very unstable. So ordinary high-alumina materials used in the cement kiln is certainly not work. But the high strength and high wear-resistant castable due to the formation of anti-alkaline protective film can be formed on the material, the corundum mullite from the protective effect, so the corundum mullite to maintain its excellent characteristics, but also have a very good Alkali resistance. Therefore, the full satisfaction of the cement kiln on the requirements of refractories.


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