Development On Longevity And High Efficient Thermal Insulation Technique Of Ladle With Thin Layer And Its Application

Ladle is indispensable during the process of steelmaking, and whose life-span and thermal insulation property have an important influence on steelmaking process and product quality.In 2006, the new blast furnace 1350m3 of ChongSteel was put into use, which results in the yield of steel increasing up to 3.30 million tons per year. Under the condition that the production place and amount of ladles are limited, it is difficult to come true. Based on investigation, in order to realize the scale, the yield of oxygen convertor must attain about 80 tons. When permanent layer decreases 30mm, there is a 600mm free space in ladle, and the aim of 80 tons production can come true. At the same time, in order to accomplish the production scale of 3.30 million tons per year, it is necessary to improve the life-span and the turnover rate of ladle further .Because the thickness of permanent layer reduces, the thermal insulation property may decrease. Therefore, aiming at the requirement of the production scale of 3.30 million tons, focus of this study is how to implement high efficient and improve thermal insulation property of ladle when whose thickness of permanent layer is reduced.By studying on the construction way and material of brick of ladle, refining technique and slag system, the requirement of prolonging the life of the ladle with thin layer was realized firstly. The life-span of ladle has increased from 65～70 times to more than 120 times, which has enhanced about 80% than traditional ladle of ChongSteel. Through improving slide mechanism, the prepared time of ladle has decreased 5～6minutes, the turnover rate of ladle increased, and the prepared time on line from more than 12 minutes to less than 10 minutes. Thus the production scale of 330 million tons per year is realized.Through thermal analysis and simulation calculation of ladle, the idea that the heat is reduced via ladle wall is proposed. Whereas the material and thickness of insulating layer are the main factors affecting heat-loss. Because the conduction coefficient of work layer and permanent layer are high, material property has less influence on heat-loss than thermal insulating layer. The covering agent plays an important role in decreasing heat-loss of slag layer, but the ratio is only 4.41% of total heat-loss of ladle.By investigating the thermal insulation property of insulation layer and permanent layer, compressive strength, the thermal insulation property of covering agent and industrial trials, the system of 20mm HeBei hard fibreboard and 90mm 3# mixed permanent layer and 1# complex grain covering agent was adopted, which has not only alleviated temperature reduction in molten steel transport before becoming thin, but also thermal insulating effect been better than original ladle with thick wall, and the temperature at tapping, Ar station or out-ladle furnace decreased 5℃.By investigating the variation of temperature of baking process of ladle, the better system of the completely repaired ladle with changing permanent layer, completely repaired ladle without changing permanent layer and the dig repair ladle was obtained to ensure the temperature stability of molten steel in transport. Based on the application of research results above, the qualified rate of temperature of tundish has increased more than 87%.