Numerical Simulation For Soft Reduction Of Slab Continuous Casting

Continuous casting has been the main method of molten steel fashioned. The innerdefect of continuous casting blank are mainly center segregation and center porosity,which will influence the quality of casting blank seriously. Current main ways to solvethem are dynamic soft reduction, which has a good effect to solve the problem of innerqualities, so it is widely used around the world.To reach the effect of soft reduction, effective parameters including reductionposition, rate, and rolling reduction should be confirmed. The distribution of stress andstrain of casting blanks in process of soft reduction under different technologicalparameters should be got and researched in order to reach the demand of parameters ofsoft reduction.So, basic heat transfer functions, stress and strain functions, heat physical properties,mechanic parameters, boundary conditions were confirmed according to technologyconditions of the continuous casting machine in LIANYUAN steel, and followingresearch work were done:1) Solidification model of casting slab was built by method of finite difference, thesolidification end positions under different working conditions were calculated, and therelationship between productive technology conditions and the positions ofsolidification end was analysed.2) The model of soft reduction of slab was built by method of finite elements, stressand strain distribution under different working conditions were calculated, thedeformation characteristics of slab in process of reduction were analysed, and so werethe regularity of distribution of equivalent stress and equivalent plastic strain. In addition, experiments of measuring temperatures and shooting nails were doneon the continuous casting machine in LIANYUAN steel so that surface temperaturesand thickness of solidification shell of the casting blank were got to contrast to the fielddata.Researches above showed that the position of the end of solidification was relatedlinearly with drawing speed, degree of superheat and water ratio. Stress on the forwardedge of the end of solidification was all less than critical stress with the rollingreduction of2cm and2.5cm, so inner flaws are not easily produced. Stress on castingblanks would increased with rolling reduction increased and drawing speed decreased.In width direction, change of rolling reduction would largely changed the stress oncasting blanks,while a little in thickness direction.In process of soft reduction, strain on casting blanks was mainly little, liquid corebored the major strain while blank shell only a little. Strain along the width directionwas almost uniformity, while more different along the thickness direction. Meanwhile,in process of soft reduction, speeds of strain increasing along the corner, wide face,narrow face of casting blanks were different, the fastest in the corner, and slower in thewide and narrow face. For Q235B steel, suitable area for soft reduction was wheresurface temperature were900℃~1000℃.