Research On Coordinate Optimization Of Secondary Cooling And Radiation Zone Of Large Round Bloom Continuous Casting

With the rapid development of the market of large-section alloy-steel round bloom in China.Continuous casting has gradually become the first method for casting large section blooms.Unreasonable cooling condition after mold will also cause serious temperature fluctuation,which will affect the inner quality of the bloom.Nowadays,improving the quality of blooms has become the key point of optimizing continuous casting process.The Heat Preservation Cover(HPC)is adding from the outlet of secondary cooling zone to the final solidification,which is different from the cover that ensures smooth bending and straightening process.The multiple short and enclosed segment is used to reduce “stack effect” of HPC,the heat will be recycled at he same time.HPC provides slow cooling for bloom,and the liquid core is longer,and the solidification process is longer,too.The feeding time is extended and the stress distribution of bloom is homogenized.The HPC is not only decrease the degree of center shrinkage cavity and crack defects,but also affect the segregation distribution of blooms.The slice moving boundary model and large-section alloy-steel round blooms have been selected in this paper.The mathematical model of mold,secondary cooling and radiation cooling has been established and optimized,the nucleation parameters have been determined,too.The influence of temperature,solidification structure,shrinkage cavity and macro segregation on different secondary cooling and radiation zone cooling condition have been researched.The coordination between HPC and secondary cooling zone has been also discussed.Results show that,the water flow in second segment of secondary cooling zone is more influence on the bloom temperature.The temperature rebound of previous zone will be decreased by increasing water flow in secondary cooling zone or decreasing the blackness of the HPC materials.However,the temperature rebound will increase and the degree will higher.The results also show that the strong secondary cooling.The results also show that strong secondary cooling can influence the radius of shrinkage cavity and segregation probability.For the coordinate control cooling between secondary cooling zone and the HPC.By determined the changes among columnar crystal strength,length and width of Columnar to Equiaxed Transition(CET),total shrinkage porosity and surface temperature rebound,a 60 L/min secondary cooling water coordinate with HPC with blackness of 0.8 was selected.The surface temperature rebound decreased 8.14 ?,the average content of C decreased from 0.357% to 0.352%,carbon segregation in diameter direction is under control.The columnar crystal length increased by17.93 mm,the total shrinkage porosity fell by 14.71%,the shrinkage porosity has been controlled.