Numerical Simulation Study On Thermal/Mechanical Behavior Of Thin Slab Continuous Casting During Liquid Core Reduction

Thin slab continuous casting and rolling process has the characteristics of compact structure,high production efficiency and rolling directly and is widely used in the world.The CSP is a representative of thin slab continuous casting and rolling process,the actual production of micro-alloyed steel in the process of hot-rolled coil frequently brings bad rotten edge defects.Studies have shown that bad rotten edge defects are usually caused by slab corner crack defects of micro-alloy steel.Strong cooling new technology on slab corner can effectively solve the crack defects of the micro-alloy steel,but the CSP in the actual continuous casting,the slab's strong cooling control in the high temperature zone after out the mold will result in corner's deformed resistance increased significantly in the liquid core reduction process,thereby affecting the production.Therefore,in this paper,the production process of QSTE380TM micro-alloyed steel thin slab which produced by a domestic steel mill is taken as the research object.The directly coupled method is used to establish the thermo-mechanical coupling 3D model of the CSP continuous casting solidification process.Simulating traditional and new technology's the evolution law of the 3D temperature field along the casting flow direction and studying the deformation and stress behavior of slab on liquid core reduction process of segment 1.Finally,the following conclusions are obtained.(1)In traditional thin slab continuous casting process,the wide face and corner temperature of slab after out the mold were about 930? and 870? respectively.The corner of the slab gradually return to the temperature from the segment 1 to the maximum of 998? in the segment 2.At the end of each segment of second cooling,the corner temperature of the slab is 970?,980?,960? and 940? respectively.At the same time,due to the non-uniform cooling effect on the surface of the slab,the center in the wide surface of the slab grows rapidly,while it grows slowly at 1/4 of width and presents heterogeneity.The solidification end point of the slab is 8.8 m away from the meniscus.(2)The displacement along the thickness of the original and new technology is roughly the same in the position of slab center and narrow center.The strong squeezing effect of the hydraulic roller makes the whole surface of the slab synchronously move to the direction of the liquid core reduction(the direction of decreasing the thickness).When the slab is away from the liquid core reduction roller and gets into the gap between the two rollers at the position,the surface of slab presents tortuous phenomenon.The maximum displacement of the corner of the original and new technology castings were 14.1 mm and 14.6 mm respectively.(3)The surface stress of the slab has reciprocating periodic variation law in a large amplitude due to contact extrusion and release of roll.Temperature returning effect on the segment 1 causes the equivalent stress in the original and new technology to stable in 54 MPa and 60 MPa,respectively,and the equivalent stress at each position of the wide surface remains about 44 MPa.The maximum equivalent stress values in the slab corner of the original and new technology is 55.6 MPa and 78.5 MPa,respectively.(4)In the liquid core reduction process,the equivalent strain at each position of the slab shows an upward trend in the form of a staircase,and the distribution is corner>wide face>narrow face in general.With the closer to the corner of slab,the equivalent strain becomes greater,and the narrow center's strain is smallest.At the end of liquid core reduction process,the maximum equivalent strain of the traditional and new technology is 0.24 and 0.30,respectively.