Research On Numerical Simulation Of Temperature Field And Crack Analysis Based On The On-line Data In Continuous Casting Slab

In this paper, the physical model of continuous casting crystallizer was established based on the production line of 1# continuous casting machine. The research object was the temperature fields of crystallizer and slab when Q345 steel slab with specifications of 2900 × 150 mm was taken shape in continuous casting crystallizer. Firstly, numerical simulation was taken on the typical working conditions of the slab( the speed of cooling water flow was 6 m/s, the temperature of cooling water was 305 K(32 ?), the casting speed was 1 m/min, and the degree of superheat was 20 K). The inner surface temperature field of crystallizer and the temperature field of slab under the typical working conditions were analyzed, in order to ensure the accuracy of research model. Then, the cooling water flow rate, the cooling water temperature and the casting speed were changed to explore situation changes in the inner surface temperature field of crystallizer and the temperature field of slab. The results showed that:(1)When the cooling water flow rate was increased, when the cooling water temperature was decreased, or when the casting speed was decreased, the indicators such as the inner surface temperature of crystallizer, the inner surface average temperature of crystallizer, the wall temperature when slab was out of crystallizer, the temperature difference of cooling water between import and export, were all showed decreasing trend. To be specific, as the speed of cooling water flow was increased from 5 m/s to 6 m/s then 7 m/s, the inner surface temperature of crystallizer export were decreased by 20? and 14?; the inner surface average temperature of crystallizer were decreased by 37? and 27?; the wall temperature when slab was out of crystallizer were decreased by 18? and 13?; and the temperature difference of cooling water between import and export were 1.3? and 0.91? respectively under the three speeds of cooling water flow.(2)The cooling water flow rate, the cooling water temperature and the casting speed all have obvious influence on the slag layer. In fact, uneven distribution of the slag layer will result in the uneven temperature gradient of slab, thereby affecting the quality of the slab.Simultaneously, the crack diagnostic database was established based on the production data of 1# Continuous casting machine. Data Mining was used to classify and extract the crack diagnostic database to form the defect database and no defect database. Since the data was time-series data in both databases, every slab could be tracked by the characteristics of time-series data. Through comparative analysis on production data of the slabs with and without defect, the primary causes to the formation of the surface longitudinal cracks were inferred and the appropriate improving suggestion were provided. The results showed that cracks were greatly affected by the wave amplitude of crystallizer liquid surface, the cooling water temperature of crystallizer and that of the secondary cooling area. These improvement measures were:(1) when the other operating conditions were at constant, inlet temperature of the crystallizer cooling water for S355-J2 steel should be maintained at 34.5 ?-37.5 ?, and that for X70-1 steel should be maintained at 31 ?-32 ?;(2)The wave amplitude of liquid surface should be controlled in 4 mm or less;(3)the control of cold water temperature should be strengthened as far as possible not less than 30 ?.