Influence of smelting process on service life of furnace lining

 Continuous smelting and batch smelting have a great influence on the service life of the furnace lining. During continuous smelting, the furnace lining is always in a hot state and is less affected by temperature changes. During intermittent operation, the lining of the furnace will change from low temperature to high temperature to low temperature, which is periodically quenched and heated. The result of this rapid cooling and rapid heating changes will cause cracks in the furnace lining, thereby reducing the service life of the furnace lining.

Except for magnesia-aluminum spinel linings, magnesia and quartz linings have poor resistance to rapid cooling and rapid heating. Among them, the quartz lining is particularly significant. During the heating and cooling process of the lining, the linear expansion or contraction rate of the sintered layer of the lining is 0.9%. That is to say, for every batch of smelting furnace, the volume of the furnace lining will expand and contract once. This rate of change is the largest below 800 °C. If the furnace lining is continuously smelted, the temperature of the furnace lining wall will not be lower than 800 °C, so the rate of change of the volume of the furnace lining is very small, and the time of crack generation will be delayed. The life of the furnace lining is increased. Therefore, in order to prolong the life of the furnace lining, the temperature of the crucible must be kept above 800°C when the large industrial frequency furnace for smelting cast iron is shut down.

During the smelting process, the solution will penetrate into the interior of the refractory matrix through the capillary channels in the refractory matrix to erode the furnace lining. The components infiltrated into the refractory matrix include: CaO, SiO2, FeO in the slag; Fe, Si, Ai, Mn, C in the molten steel, and even metal vapor, CO gas, etc. These infiltrating components are deposited in the refractory capillary channels, resulting in the discontinuity between the physical and chemical properties of the refractory working surface and the original refractory matrix. Under the rapid change of operating temperature, cracks, spalling and structural looseness will appear. Strictly speaking, this damage process Much more serious than the dissolution damage process.

Taking the basic furnace lining as an example, increasing the content and viscosity of magnesium oxide is beneficial to reduce the erosion of the furnace lining and improve the slag collection effect.

1. The influence of melting temperature on the service life of furnace lining

During the smelting process, the temperature of the molten steel is too high, which will cause the temperature of the slag to rise, and the erosion of the furnace lining will intensify, causing the lining to be damaged prematurely along the slag line. In addition, high temperature will also accelerate the fluidity of molten steel and accelerate the penetration of cracks into the furnace lining, which intensifies the chemical erosion of the molten metal on the furnace lining. While controlling the smelting temperature as much as possible, there should be no long-term high temperature or heat preservation waiting for casting. Excessive temperature will not only easily burn the alloy, but also increase the energy consumption. In short, the higher the melting temperature, the lower the service life of the furnace lining.

2. The influence of smelting steel grade on the service life of furnace lining

When melting high carbon and high manganese steel with low melting point and good fluidity, the penetration effect of molten steel on the furnace lining is intensified, which will reduce the service life of the furnace lining.

When smelting low-carbon, high-nickel-chromium steels with poor fluidity, the furnace lining has a relatively long service life.

Materials with high melting point require higher temperature, and prolonged high temperature will also reduce the service life of the furnace lining.

Therefore, high carbon steel and high manganese steel should be smelted in the later stage of the furnace lining when smelting steel grades.

In addition, when smelting different materials, attention should be paid to the properties of metal materials. For example, when smelting metals with high sulfur content in the previous furnace, the furnace wall is easily eroded when smelting high-manganese steel in the next furnace. Therefore, when smelting steel grades, high carbon steel and high manganese steel should be smelted in the later stage of the furnace lining.

3. The influence of slag on the service life of furnace lining

The pH of the slag should be compatible with the material of the furnace lining. The appropriate slag should be selected according to the material of the furnace lining. Alkaline slag is suitable for magnesia lining, but can be corroded by high-CaO slag and SiO2 slag. Excessive CaF2 will also corrode basic lining and cause premature erosion in the slag line area. Acidic slag is suitable for quartz lining, and magnesia-aluminum lining is only suitable for weak alkaline or neutral slag. Alumina lining will show typical amphoteric in different pH at high temperature, and it can adapt to slag with different pH, which is slightly worse than acidic furnace lining and basic furnace lining.

4. Influence of smelting operation on the service life of furnace lining

Whether the metal charge can be smoothly melted during the melting period has a great influence. The tightness of the charge is directly related to the melting speed of the charge. In order to heat and melt quickly, the charging should be as tight as possible, but the bridging phenomenon should be avoided during the melting process, which will overheat the molten metal in the lower part, make the molten metal absorb and increase the burning loss of alloying elements, prolong the melting Time, high temperature and violent eddy current will seriously erode the furnace wall, resulting in great damage to the furnace wall by bridging and handling. When the metal liquid level is too low, special attention should be paid to feeding. If large blocks are added and high power is input to the electric furnace, the bottom will be severely overheated and the erosion will be exacerbated. serious. After the molten metal reaches the appropriate temperature and quality requirements, the power should be cut off, which is not only safe and reduces energy consumption, but also protects the lower half of the furnace lining from being damaged by the scouring of the superheated molten metal. The smelting time should be shortened as much as possible to reduce the power consumption of molten steel smelting.

The air burning and the lower part of the furnace body are under the condition of local electromagnetic stirring. Will severely and accelerate the erosion of the furnace lining.

We Changxing Refractory Material Co.,LTD is professional manufacturer and supplier of refractory materials for more than 30 years. Our high quality refractory products are good sold to many countries say South Africa, Bangladesh, Indonesia, Malaysia, etc.

Article Source:smelting process on service life of furnace lining
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Refractory Products for Steel Making

The process of firing refractory bricks includes three process

 The process of firing refractory bricks includes three processes

1. Kiln installation

The so-called kiln loading refers to the operation process of reasonably arranging and stacking bricks that meet the technical conditions of semi-finished products in the kiln according to the structural characteristics of the kiln and the requirements of the thermal system when the products are fired. For the tunnel kiln, it is also called loading (kiln) car.

1) Determine the kiln installation height and kiln installation method according to different brick types. Usually, the kiln height of magnesia bricks and first-class high-alumina bricks is 1-1.1m; that of silica bricks is 1-1.7m; and that of clay bricks is between the two. Most of the bricks are installed flat, the silica bricks are installed vertically and the clay bricks are installed sideways.

2) According to different brick types, determine the kiln loading ratio of ordinary bricks and special-shaped bricks. Generally, the ratio of special-shaped bricks and ordinary bricks on the same kiln car is about 4:6. At the same time, it is necessary to determine the kiln installation positions of different varieties according to different brick types. Generally, the standard and ordinary bricks are installed in the lower part, and the special-shaped bricks are installed in the upper part, and some special-shaped bricks or adobes that are easy to crack when fired are packaged (bricks wrapped in bricks).

3) On the premise of ensuring the quality of firing, increase the density of bricks (that is, the amount of bricks per unit kiln car) to increase production and reduce fuel consumption.

Making a reasonable kiln installation plan is the premise to ensure the quality of the kiln installation, but if the kiln installation operation is improper, the qualified rate of the appearance of the fired product will be reduced. Therefore, in the production of refractory materials, the basic requirements for the quality of the kiln are to ensure that the brick stack is flat, stable and straight, to avoid bonding between the bricks due to high temperature firing, and to reduce the distortion of the fired products. In order to meet the above requirements, a layer of sand filling with a particle size of 0.5-3mm is usually evenly sprinkled between each layer of bricks when the kiln is installed. Products with different properties have different requirements for kiln filling sand. Usually, clay bricks and high alumina bricks use silica sand, bauxite chips, rice husk or rice husk ash; silica bricks use waste silica brick sand or silica sand; Magnesia bricks use magnesia or chrome ore.

2. Firing

The adobe undergoes a series of physical-chemical reactions during the firing process, making the adobe compact, increasing its strength, stabilizing its volume, and ensuring accurate dimensions. The whole firing process can be divided into three stages:

(1) The heating stage, that is, from the time when the product enters the kiln or is ignited to the time when the product reaches the highest temperature for firing. As the temperature increases, the liquid phase formation temperature and the phase synthesis temperature are reached. Due to the diffusion, flow, dissolution, precipitation, and mass transfer process of the liquid phase, the particles are further approached by the surface tension of the liquid phase to promote the densification of the green body. The strength is increased, the volume is reduced, the porosity is reduced, and the green body is sintered.

(2) The heat preservation stage at the highest firing temperature. Various reactions in the green body tend to be complete and sufficient, the amount of liquid phase increases, the crystalline phase grows further, and the brick body reaches densification. In the firing process of the product, not only the surface must reach the firing temperature, but also the interior of the product must also reach the firing temperature. This temperature homogenization process is achieved by heat transfer, which requires a certain amount of time. It can be seen that the larger the product and the higher the kiln density, the longer this time will be. In addition, due to the uneven temperature of various parts in the kiln, a certain holding time is also required.

(3) The cooling stage refers to the period from the highest firing temperature to the kiln exit temperature. During this stage, the structural and chemical changes that the article undergoes at high temperatures are essentially fixed. At the beginning of this stage, some physical-chemical changes are still going on in the product, such as the crystallization of the physical phase, the crystal transformation of some crystals, the solidification of the glass phase, and the generation of microcracks. The cooling system will affect the physical properties of the product such as strength and thermal shock resistance.

In order to reasonably fire various refractory products, the firing system of each product should be determined in advance, including: the maximum temperature of firing; the heating rate at each stage; the holding time at the highest temperature; product cooling The lower cooling rate; the nature of the atmosphere in the kiln in the above stages. The firing process of refractory products can be completed by two heating methods, that is, the products are fired at a lower temperature for a longer time, or at a higher temperature for a shorter time. But in fact, due to the slow heat transfer in the kiln and the uneven heating of the products in the kiln, there is a limit to the use of fast firing refractory products.

The firing system of refractory products is not only related to the variety, shape and size of refractory products, but also closely related to the type of firing equipment. For example, a large downdraft kiln requires a slower heating rate and a longer holding time to ensure the uniformity of the brick temperature. An unsuitable firing system will increase the reject rate and reduce the quality of the product. The proper firing system is based on theoretical guidance and practical experience.

3. Out of the kiln

Kiln exit is the operation process of taking out the burnt products from the kiln after cooling, or unloading them from the kiln car. The quality of the kiln operation has a direct impact on the appearance quality of the finished product. In the production of refractory materials, the following points should be paid attention to in the kiln operation:

(1) When taking and placing bricks, handle them with care to avoid appearance defects of the product due to careless operation out of the kiln.

(2) Products of different brick numbers should be stacked strictly separately, that is to say, products of different brick numbers cannot be placed on the same brick board when they leave the kiln, otherwise, it is easy to cause confusion when checking and selecting finished products. Because the appearance of some products with different brick numbers can be exactly the same, but there is little difference in a certain size (several mm or more than a dozen mm), if they are mixed on a brick board, it is easy to distinguish them when checking. The product of one of the brick numbers is mistaken as a waste product, which will not only cause waste, but also affect the use.

(3) Tool bricks (frame bricks, drawn bricks, etc.) should be arranged and stacked for continued use during kiln installation.

(4) Pay attention to safe operation and labor protection when leaving the kiln and transporting bricks.

We Changxing Refractory Material Co.,LTD is professional manufacturer and supplier of refractory materials for more than 30 years. Our high quality refractory products are good sold to many countries say South Africa, Bangladesh, Indonesia, Malaysia, etc.  

Article Source:The process of firing refractory bricks includes three process
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High Alumina Bricks & Magnesia Bricks

What are the measures to improve the purity of continuous casting steel

 Purity refers to the quantity, shape and distribution of non-metallic inclusions in steel. The inclusion in steel shall be reduced to the required level according to the steel grade and product quality,

We should start from the following five aspects:

① Reduce [O] content in steel as much as possible.  

② Prevent the molten steel from interacting with air.

③ Reduce the interaction between molten steel and refractory materials.  

④ Reduce slag entrainment in molten steel.  

⑤ The improved flow promotes the floating of inclusions in molten steel.

In terms of process operation, the following measures shall be taken:

(1) Slag free tapping: slag retaining balls are adopted for the converter and eccentric bottom tapping is adopted for the electric furnace to prevent a large amount of slag from falling into the ladle.  

(2) Ladle refining: select the appropriate refining method according to the steel grade, to uniform the temperature, fine tune the composition, reduce the oxygen content, remove gas inclusions, etc.  

(3) Non oxidation casting: after the molten steel is treated by ladle, the total oxygen content in the steel can be reduced from 130ppm to below 20ppm. If the injection flow from ladle to tundish is not protected or poorly protected, the total oxygen content in tundish steel will rise to the range of 60-100ppm, which will return to the level before external refining, and the effect of external refining will be wasted.  

(4) Tundish metallurgy: the tundish adopts large capacity, and the addition of retaining walls and dams is an effective measure to promote the floating of inclusions. For example, for 6T tundish, the scrap rate of slab inclusion is 12%, and the inclusion is 0.82 pieces / m2; 12t tundish + retaining wall, 0 scrap inclusion in slab, 0.04 inclusions / m2.

(5) Submerged nozzle + casting mold powder: the mold powder shall be able to fully absorb inclusions. The submerged entry nozzle material, nozzle shape and insertion depth shall be favorable for the floating and separation of inclusions.

We Changxing Refractory Material Co.,LTD is professional manufacturer and supplier of refractory materials for more than 30 years. Our high quality casting powder are good sold to many countries say South Africa, Bangladesh, Indonesia, Malaysia, etc.  

Article Source:  improve the purity of continuous casting steel
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What are the prominent problems in the tundish

 

At present, there are many problems in the tundish used in China, especially in the tundish used for billet caster. 

The specific performance is as follows:

(1) The shape of tundish cavity is unreasonable. Due to the unreasonable shape of the inner cavity, the flow of molten steel in the tundish is unreasonable and the residence time is short, which can not purify the molten steel. The distance from the drop point of the large ladle injection into the tundish to the tundish nozzle is short, or the distance from each nozzle is too different; The volume at the drop point of the ladle is too small, resulting in serious steel slag mixing and lining scouring, affecting the service life of the tundish and polluting the molten steel.

(2) The capacity of tundish is small and the depth of molten pool is shallow, so it is not suitable for high-speed caster. The molten steel stays in the tundish for a short time, which makes it difficult to purify the molten steel and remove inclusions; It is difficult to maintain constant casting speed when changing the package; During pouring, the steel slag in the tundish is agitated seriously, which makes it difficult to float the inclusions and easy to enter the mold, especially when changing the tundish.

(3) The position of tundish nozzle clogging is not properly designed, especially the nozzle on both sides is too close to the two sides, which is easy to cause unsmooth pouring of the two side nozzles.

(4) The tundish nozzle control device is too thin and unreliable, which makes it difficult to accurately control the flow of molten steel, making it difficult to stabilize the liquid level of the mold and often causing out of control accidents.

(5) The large deformation of tundish and the problems of design and manufacturing accuracy result in insufficient centering accuracy of multiple water outlets.

(6) The lifting device of tundish is ineffective, and most of them can not be lifted, which brings difficulties to the continuous casting process and causes many defects of the slab.

(7) The distance from the bottom of tundish to the upper mouth of crystallizer is improperly selected. Most of the distance is too high, which makes it difficult to align the nozzle, and also makes the nozzle too long, which increases the refractory consumption per ton of steel nozzle.

(8) Insufficient attention has been paid to the quick change technology of submerged entry nozzle.

The above tundish can only be used at low casting speed, which is not suitable for the requirements of high casting speed. Modern tundish should not only adapt to the conditions of constant speed casting at high drawing speed, high steel throughput and strength, and intense agitation in the tundish, but also play the role of purifying molten steel and removing inclusions.

 The specific measures adopted include:

(1) Optimize the shape of the inner cavity of the tundish, make the liquid steel flow reasonably in the tundish, expand the volume of the large ladle at the drop point of the tundish and optimize the distance from the drop point of the large ladle to each water inlet under the condition of adapting to the high pulling speed; 

(2) Tundish with large capacity deep melting bath; 

(3) Prevent deformation of tundish shell; 

(4) Adopt firm and reliable tundish nozzle control device; 

(5) Adopt reliable tundish lifting device under load; 

(6) Optimize the distance from the tundish to the upper mouth of the crystallizer.

Article Source: What are the prominent problems in the tundish
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Brief introduction of gunning material

 The EAF gunning material bears the same high temperature and harsh working environment as the repaired furnace lining during the smelting process. Therefore, in addition to high refractoriness, erosion resistance, erosion resistance, spalling resistance, etc., the EAF gunning mix must also be compatible with the repaired furnace lining. The lining has good adhesion.

The gunning materials for electric furnaces include magnesia, magnesia-dolomite, magnesia-chromite, magnesia-carbon, magnesia-dolomite-carbon, etc., and some highly active seawater magnesia are used in the aggregate. To promote sintering and improve the density and strength of the gunning layer. In order to make the gunning material solidify quickly during the gunning operation and attach to the furnace lining at the same time, a small amount of additives are often added to the aggregate.

The advantages of add additives

1.When adding Al, Mg and other low melting point metal powders for gunning, the oxidation heat of metal powder helps to increase the temperature, and harmless oxides are formed in the EAF gunning material to improve the adhesion between the gunning layer and the furnace lining.

2.Add spinel Cr2O3, SiC, B4C, etc. to improve the oxidation resistance and corrosion resistance of the material.

3.Add a small amount of organic fibers with a length of 1~5mm, and melt at low temperature to form air passages, which is conducive to the evaporation and discharge of water in the binder and prevents bursting.

4.Add 0.1~2mm and 10~40mm long metal fibers for tapping and other parts to improve the corrosion resistance of the gunning layer.

5.Add part of the slag of the metallurgical furnace to improve the adhesion and corrosion resistance of the EAF gunning mix.

We Changxing Refractory Material Co.,LTD is professional manufacturer and supplier of refractory materials for more than 30 years. Our high quality EAF gunning material are good sold to many countries say South Africa, Bangladesh, Indonesia, Malaysia, etc. Shall any interests, welcome to contact us. Our team would make best to be your reliable partner!

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EAF gunning material for sale

Measures to increase the life of tundish

 

1. The working layer of tundish adopts dry material

Under the condition that the technological conditions and the material and masonry form of tundish refractory are fixed, the life of tundish mainly depends on the chemical erosion, high temperature melting loss and mechanical erosion of the molten steel in the working layer of tundish. The tundish dry material has strong erosion resistance and erosion resistance, which can meet the requirements of long continuous pouring time.

2. The lining is made of magnesia refractory

Magnesium refractory adsorb the inclusion in steel is very strong, and good erosion resistance, erosion resistance, can meet the requirements of high number of continuous casting furnace, but also improve the quality of molten steel. After use, it is observed that the lining slag line of the middle bag is the thinnest, and other parts are 30 ~ 40mm. After a pouring time is completed, it is easy to disassemble the middle bag.

3. Use a current stabilizer

Because the steel flow directly impacts the tundish from the large tundish, the erosion of tundish is very serious, which is likely to cause the penetration of tundish. For this reason, it is decided to use the current stabilizer. The material of the current stabilizer is magnesium carbon, and the structure of the current stabilizer is a container structure with hollow cavity. The bottom of the inner cavity of the current stabilizer is large, and the mouth is small. The continuous casting tundish current stabilizer with this structure can prevent liquid steel from slagging obviously and stably, the tundish steel water quality is high, and the tundish refractory material consumption is low.

4. Raise the water level of the intermediate steel envelope

The original minimum liquid level requirement for tundish pouring was 600mm, but now it must be greater than 700mm. After the liquid level of molten steel is raised, the stagnation time of molten steel in tundish is prolonged. In a deep molten pool, the resistance between molten steel from ladle to flow stabilizer is large, and the flow velocity of the contact surface of flow stabilizer is small, thus the impact on the flow stabilizer is small, and the continuous pouring time of flow stabilizer is improved. The tundish life is also improved.

5. Improve slag overflow operation

The original slag overflow mouth close to the pouring point, slag overflow is difficult. With the increase of the number of continuous casting furnace, slag quantity is large and can not be discharged in time, slag line erosion on the lining is serious, and affect the quality of molten steel. For this reason, the position and shape of the slag overflow mouth is changed, and the assessment system is formulated. The slag thickness should not exceed 30mm, and the slag thickness should be controlled below 30mm in time when the rhythm is appropriate, so as to prevent serious erosion of the slag line of the wall and the occurrence of the wall through the steel. At the same time, the large contractor should strengthen the operation, and avoid a large amount of slag into the tunbale, which will cause serious erosion of the slag line of the bale wall.

6. Improve the service life of tundish water outlet

Improve the level of production scheduling, reduce the choke flow caused by equal steel and other reasons, stabilize the temperature of molten steel stage, reduce the secondary pouring caused by operation problems, so as to improve the service life of tundish water outlet, and then improve the life of tundish.

7. Improve the deoxidation process of molten steel

In order to improve the deoxidation effect, the amount of deoxidizer is increased, and the ladle is fed with silicon calcium wire for inclusion denaturation of molten steel. The process not only improves the deoxidation effect of the converter steel, reduces the oxide inclusion in the steel, but also improves the pouring ability of the steel and eliminates the flow of the tundish nozzle caused by the poor fluidity of the steel. At the same time, the free oxygen content in the molten steel is reduced, which reduces the erosion to the water mouth of the tundish and prolonging the life of the tundish.

8. Reasonable temperature regime

In order to ensure the normal pouring ability of molten steel, the water superheat of intermediate clad steel is strictly controlled within 10 ~ 25℃. In order to improve the success rate of the first furnace, the steel output temperature of the converter is 30 ~ 40℃ higher than the normal pouring temperature. According to the lower limit control the water temperature of the intermediate steel envelope, the qualified rate increased from 80% to 95%.

9. Make sure you bake

When baking tundish, the burner in the middle of the oven should be directly facing the center of the current stabilizer to ensure the baking effect of the current stabilizer. Specific requirements for baking tundish: medium fire baking shall be no less than 30min, and large fire baking shall be no less than 1h. Medium fire baking means that the flame reaches the bottom of the bag but does not launch, and large fire baking means that the gas valve is fully or basically open, the flame reaches the bottom of the bag and rebounds, the air volume is suitable, and the flame temperature reaches the highest. Once the fire starts, the dry lining tundish shall not cease fire or reduce the flame in the middle to ensure that the temperature of the middle bag wall reaches more than 1000℃.

10. Improve the production organization model

Make reasonable use of production organization mode, arrange the use of tundish in a planned way, avoid the waste of tundish, make reasonable use of tundish according to the order of masonry in normal circumstances, and give full play to the service life of tundish.

11. Reasonable production system

The connection of molten steel between converter and continuous casting is a necessary condition to ensure the normal production of continuous casting. The molten steel for continuous casting is required to be on time, the information transmission of production scheduling is increased, and the production organization is reasonable to ensure the stability of the water level of tundish steel, and at the same time, the liquid level of tundish is guaranteed within the required range, so as to ensure the service life of tundish.long water mouth) in order to avoid the oxidation of molten steel.

Article Source: Measures to increase the life of tundish
Company name: Henan Changxing Refractory Materials Co.,Ltd
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Technical measures for smelting clean steel

 The smelting of clean steel should be based on the variety and application requirements, and the operations of hot metal pretreatment-steelmaking-refining-continuous casting should be under strict control. The main control technical countermeasures are as follows:

(1) Hot metal pretreatment. For hot metal desulfurization or three desulfurization process, the sulfur content of molten iron should be less than 0.005% or even less than 0.002%.

(2) Converter compound blowing and steelmaking end point control. Improve dephosphorization conditions, increase the end-point composition and temperature one-time hit rate, reduce the dissolved oxygen content of steel grades, and reduce the number of non-metallic inclusions in steel.

(3) Block slag and tap steel. The slag blocking method is used to tap the steel, and the thickness of the slag layer in the ladle is controlled below 50mm. It can avoid phosphorus reversion, increase the yield of alloy, and reduce oxide inclusions.

(4) Ladle slag modification. During the tapping process, a slag modifier is added to the steel stream. Reduce iron oxide and adjust ladle slag composition.

(5) Refining outside the furnace. According to the steel quality requirements, select one or more refining combinations to complete the task of molten steel refining, to achieve dehydrogenation, extremely low carbonization, extremely low vulcanization, denitrification, reduction of inclusions and inclusion shape control, etc.

(6) Protection pouring. The use of protective pouring techniques during pouring is particularly important for the production of clean steel. The ladle-tundish-crystallizer is poured with shroud argon seal protection, the tundish uses double-layer mold slag, and the crystallizer uses mold slag, etc. It has the functions of adsorbing inclusions and reducing secondary oxidation.

(7) Tundish metallurgy. Organize reasonable molten steel flow in the tundish, reasonable residence time of molten steel, and promote the floating of inclusions, etc.

(8) Crystallizer operation technology. Select the casting mold powder with suitable performance; The submerged nozzle is centered and the insertion depth is suitable; the casting speed and the liquid level are stable; The electromagnetic stirring technology of the crystallizer is used; The flow of molten steel is controlled to facilitate the floating and discharge of gas and inclusions, and improve the quality of the slab .

(9) Internal quality control of billets. Use electromagnetic stirring and light pressure technology to reduce center porosity, center segregation and shrinkage cavity. Increase the density of the slab.

(10) Straight crystallizer arc continuous casting machine and vertical curved continuous casting machine are used to facilitate the floating of inclusions.

We Changxing Refractory Material Co.,LTD is professional manufacturer and supplier of refractory materials for more than 30 years. Our high quality refractory products are good sold to many countries say South Africa, Bangladesh, Indonesia, Malaysia, etc.  

Article Source:Technical measures for smelting clean steel
Company name: Henan Changxing Refractory Materials Co.,Ltd
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Technical description of the AOD furnace process

 AOD furnace method (argon-oxygen decarbonization method) is a more advanced technology for refining stainless steel. AOD furnace method has the advantages of simple equipment, convenient operation, strong adaptability, less investment and low production cost, and is widely used.

The molten alloy of the blast furnace and the intermediate frequency furnace is injected into the AOD furnace through the ladle, and O2, Ar or N2 mixed gas is blown during smelting to decarbonize the molten steel. At the same time, reducing agent, desulfurizer, ferroalloy or coolant are added to the feeding system to adjust the composition and temperature of the molten steel, and smelting qualified stainless steel water for continuous casting machine.

The delivery and regulation of mixed gas during refining is one of the main systems of argon oxygen furnace. The gas produced by the oxygen workshop is transported into the gas storage tank near the workshop through the pipeline, and after metering, decompression, adjustment and mixing, the mixed gas is sent into the furnace through the side gun according to the flow rate and ratio required by the process.

At the beginning of smelting, oxygen is decarbonized through a double-layer water cooling oxygen blowing pipe and blown into the metal melting tank at the top furnace mouth. For refining, use the mixed gas to send into the side gun into the furnace (installed on the side of the side wall near the bottom of the furnace). When loading and discharging the steel, the furnace body leans forward at a certain Angle, and the (side) tuyere is above the steel liquid level. When blowing normally, the tuyere sinks into the deep part of the dissolution tank. The central tube of the tuyere blows into the mixed gas of oxygen and argon or nitrogen, and adjusting the ratio of oxygen and argon can reduce the partial pressure of carbon monoxide to achieve the purpose of decarbonizing and preserving chromium. The type of AOD furnace tuyere is unique, it is a gas cooled consumption tuyere. The tuyere adopts a double casing structure, the outer pipe only through argon or nitrogen to cool the tuyere, the inner tube through oxygen and nitrogen, or argon mixed gas. Both the flow rate of the central pipe and the air mask ring can be controlled in the main control room.

Using the three-way side-gun technology. It can enhance the oxygen supply strength and improve the metal material yield, and this technology can shorten the AOD smelting time. Stable and reliable control system can reduce the consumption of gas and various refractory raw materials in smelting, and obtain stable product quality.

Article Source:https://www.cxrefractories.com/en-refractory-news?article_id=1248
Company name: Henan Changxing Refractory Materials Co.,Ltd
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