Numerical Simulation And Process Optimization Of Electromagnetic Stirring At Secondary Cooling Zone Of Slab Continuous Casting Machine

In the paper,the improvement of central segregation and negative segregation is the main subject.The solidification structure is improved by electromagnetic force,the columnar crystal is broken,and the equiaxed crystal region in the center of the slab is expanded,thereby,reducing the central segregation and negative segregation of the white band.Secondary cooling zone electromagnetic stirring is located at the region of strong growth in columnar crystals.So,it is significant to study the influence of the secondary cooling zone electromagnetic stirring on the quality of slab.Based on the process conditions of 250 mm× 1800 mm slab continuous casting machine with secondary cooling zone electromagnetic stirring,the solidification model,electromagnetic field model and flow field mode were established by using ANSYS software and the distribution laws of magnetic field,magnetic field and flow field were obtained.At the same time,the impacts of electromagnetic parameters and casting process parameters were investigated through numerical simulation and industrial experiment.It is indicated:(1)The white band is composed of dense secondary dendrites growing in the stirring zone and dendritic clusters clustered in the dendrites after primary dendrites break.White band in the C element content was low and white,forming a negative segregation area,that is,white band.While the outer region is enriched C element area,forming positive segregation area,and black.Usually the white band produced by electromagnetic stirring is a one-layer structure or a two-layer structure;(2)With the casting speed increasing from 0.80 m/min to 0.90 m/min,the disappearance of liquidus line and solidus line postponed 1.6 m and 2.9 m respectively,and the temperature between the electromagnetic stirring rollers rises from 1526.3? to 1530.4?.With the superheat growing from 20? to 30?,the disappearance of liquidus line and solidus line postponed 0.5 m and 0.4 m respectively,and the temperature between the electromagnetic stirring rollers rises from 1523.8? to 1527.9?;(3)The magnetic flux density showed parabolic distribution along the axial line in the secondary cooling zone electromagnetic stirring.It reached its maximum value in the centre of stirrer and decreased along the axial line.And the distribution of electromagnetic force is same.With the current intensity raising for each additional 100 A,the electromagnetic force increased by about 1135 N/m3.when the current frequency was 5 Hz.As the current frequency growing from 5 Hz to 8 Hz,the electromagnetic force increased from 2611 N/m3 to 4155 N/m3 with the current density fixed in 300A;(4)With electromagnetic stirring,the stirring velocity increase with the current intensity and frequency.As the second-zone electromagnetic stirring current was fixed in 5 Hz,the maximum stirring velocity raised from 41.7 cm/s to 74.7 cm/s.with the increase of current intensity from 300A to 400 A.Similarly,the maximum stirring velocity raised 2.7 cm/s with increasing frequency of 1 Hz;(5)The actual tests showed that the optimal frequency and current intensity for S-EMS were 5 Hz and 360 A.When the continuous casting speed was 0.80 m/min and with electromagnetic stirring of secondary cooling zone parameters.And central carbon segregation index in slab can be controlled below 1.15,the carbon segregation index of white band in the slab can be controlled below 0.84.