Measures of magnesium dry material 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.