Summary of tundish construction

 (1) The tundish dry material composition and distribution operation have an impact on the density and uniformity of the working layer of the tundish; the standard distribution operation can reduce the looseness and segregation of the dry material in the tundish.

(2) Optimize the process, reduce the vibration time of the tundish from 15 minutes to 8 minutes, and extend the baking time from the original 2 hours to 3.5 hours, which improves the strength of the magnesium dry material during use.

(3) Through the design of the special nozzle foam plug for repairing the tundish, the use effect of the upper nozzle of the tundish is guaranteed, and the problems such as steel slag blocking the eye caused by the irregular shape of the nozzle are solved.

Wanhao is a manufacturer who is specialized in designing various kinds of furnace and making refractory products for electric furnace, ladle, tundish, blast furnace, AOD furnace, IF furnace, etc.

Article Source:Summary of tundish construction

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Measures of changing magnesium dry material tundish in continuous casting workshop

 

1. The situation before switching

Due to the history and production status and other reasons, the tundish working layer used in the production of Tanggang No. 2 Steel mill is mostly silicon plate, only one continuous casting machine uses part of magnesium coating, the average life of the tundish is only 6 ~ 7h, the operation rate of the continuous casting machine is only about 70%. Because the life of tundish is too low, and the amount of head and tail billet and tundish is too large, the consumption of steel material is too high, the average consumption of steel material is about 12kg. Moreover, due to the poor sintering effect and sintering strength of the silicon plate, the pollution of the silicon plate to the molten steel is too large, which can not meet the requirements of casting purity.

2. Use specific measures and effects

(1) Improve and optimize the materials of the intermediate working layer

Tundish working layer is the key point of tundish. When molten steel flows from large tundish to tundish, tundish working layer is directly in contact with molten steel, which is not only scour by molten steel but also eroded by molten steel and slag. Tundish plays the role of purification, uniform composition, temperature, shunt and heat preservation for molten steel. At present, the tundish working layer commonly used in steel works mainly includes silicon plate, magnesium plate, magnesium paste and tundish magnesium dry material, among which the best use effect is magnesium paste. The original continuous casting machine used magnesium coating material and silicon plate, not only short life and simplification effect on the molten steel is not obvious, and even pollution to the molten steel, in order to meet the needs of production, the introduction of magnesium dry material.

(2) Improve the intermediate package dry material package tire

Due to the original use of tunic working layer silica plate and magnesium coating on the impact sensitive area and slag line area is less considered, the current use of tunic roasters are triangular distribution of three fire nozzle, so the size of dry material coated tire is only calculated according to the permanent layer coated tire size minus the thickness of the working layer, no adjustment to the different parts; Baking is also the use of in-use roaster, resulting in dry baking uneven, not only a waste of gas, but also affect the use of the working layer. In order to solve the above problems, the technical personnel on the continuous casting machine tundish flow of molten steel and molten steel, steel slag on the scouring and erosion of the working layer as well as the baking capacity and heat transfer of the roaster for on-site analysis, calculation and verification of the calculation results, through many times of analysis and calculation, the development of our factory intermediate bag and the improvement of the roaster. Through the improvement of the shape of the middle bag tire, basically eliminate the erosion of the permanent layer and even the tundie leakage accidents caused by the uneven erosion of molten steel slag; At the same time, by improving the distribution of the burner, the phenomenon of reducing the life of the tundish or even directly scrapping the tundish caused by the falling off of the working layer magnesium material due to uneven baking is prevented.

(3) Improve the service life of the upper water outlet and the slider

An important reason why the pouring life of the tundish used in the original continuous casting machine is only about 20h is that the erosion resistance of the upper water mouth is relatively weak. When the pouring life reaches more than 24h, the zirconium core of the upper water mouth has basically been eroded, and the service life of the slider is only about 4h. Through the detailed analysis of the composition of molten steel and the situation of site pouring with the manufacturer, it is concluded that the main factors affecting the life of the upper water outlet and slider are as follows: the internal control and fillet design of the upper water outlet and slider are not suitable for the flow of molten steel in continuous casting machine, resulting in excessive scouring force of molten steel on the inner wall of the upper water outlet and slider; The zirconia content of the upper inlet and sliding block is low, resulting in the erosion resistance of the upper inlet and sliding block is reduced. After reaching the above conclusion, the internal chamfer of the top nozzle and slider was improved, and the zirconia content in the zirconium core was increased by 4.2%.

(4) The impact plate at the bottom of tundish and the impact surface are thickened

The tundish impact plate at the bottom of the tunduct and the impact surface of the tunduct are the weakest link in the tunduct. These two positions are affected by the dual effects of gravity impact and high temperature molten steel erosion at the same time, and the breakdown of the working layer is the most likely, and sometimes even the leakage accident occurs. On the basis of sufficient demonstration, we thickened the bottom plate of the tunduct by 50mm and processed it into a dent at the position of the large surface of the tunduct The large surface of tundish is thickened 40mm, which effectively prevents the occurrence of tundish leakage accident.

(5) Establish and improve the baking system, optimize the baking temperature curve of tundish, so as to achieve the best sintering effect of tundish lining.

Due to unreasonable temperature rise in the baking process of tundish in production, the lining collapse phenomenon occurs from time to time, which seriously affects the improvement of the life of tundish. Therefore, we re-optimize and revise the baking curve of tundish.
Wanhao is a manufacturer who is specialized in designing various kinds of furnace and making refractory products for electric furnace, ladle, tundish, blast furnace, AOD furnace, IF furnace, etc.

Article Source:Measures of changing magnesium dry material tundish in continuous casting workshop

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Factors affecting the quality of tundish repair

 

1. Loose Wall

The looseness of the tundish wall is mainly reflected in the contact position between the tundish wall and the bottom of the tundish. The looseness of the wall is manifested in two forms: one is that it extends longitudinally from the position of the wall to form an irregular surface; The other is that the elongated powder falls down to form a "slit shape". There are two reasons for the looseness: one is that the binder volatilizes, resulting in a decrease in the overall bonding strength, especially the outermost one; the other is that the fine powder containing resin does not wrap the particles, which eventually causes slag to fall off easily. The low-temperature baking strength and medium-temperature strength of the dry-type material can be better improved by mixing boron glass powder and phenolic resin in the magnesium dry-type material.

Based on the site conditions, it was found that the reasons for the low quality of the tundish repair were as follows:

(1) The tundish fabric was unreasonable. The ratio of the binder in the current tundish is relatively low, and there is a phenomenon of piled up and concentrated distribution during the construction of the masonry, which leads to the segregation of large-grained magnesia in the dry material.

(2) The vibration time of the wrapped tire is long. At present, 4 motors are used for tire wrapping in the tundish. In order to increase the compactness at the position of the slag line, the vibration time is 15 minutes. Although the bulk density of the tundish dry material is increased, the lower dry material aggregate and powder are prone to separation, and the phenomenon of "bridging" between the dry material is prone to occur, causing the bag wall to loosen.

(3) The lower baking temperature of the tundish is low. The flame of the burner cannot reach the bottom, the temperature of the upper part of the tire is high, and the temperature of the lower part is relatively low, resulting in insufficient reaction temperature and low strength of the dry material that is about to harden. But still relatively loose.

2. Cracks in cladding wall

Horizontal stripes appear on the bag wall at the head of the middle bag. The dry material thickness at this position is 110 mm, and the crack depth is 40 mm. The main reason is that the current release agent is applied once, the thickness is only 0.1-0.2 mm, and the application is uneven, causing the tundish dry material to stick to the tire, and cracks to the dry material after the tire is started. Stress concentrations were created during lifting of the tire mold, which in turn caused surface cracks.

3. The shape of the upper nozzle does not meet the requirements

The current operating procedures for repairing packages only require that no sundries should be mixed in the nozzle. During operation, workers only use waste woven bags to plug in the nozzle, there is no uniform standard, and there is no reasonable mold, resulting in debris often remaining in the nozzle, and the shape of the tundish upper nozzle is irregular.

Wanhao is a manufacturer who is specialized in designing various kinds of furnace and making refractory products for electric furnace, ladle, tundish, blast furnace, AOD furnace, IF furnace, etc.

Article Source:Factors affecting the quality of tundish repair

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