| The biggest problem in grade transition process is that the composition of intermixing slab is different from the former steel and the after steel. These intermixing slab need to downgrade only even as scrap steel processing, and must carry on the specialized management. So accurately predict transition starting position and length of the intermixing slab is a problem worthy of studying.Taking Mei Steel two flow slab continuous casting machine as the research object, on the basis of hydraulics physical simulation experiment and numerical simulation, using the method of mathematical regression, interpolation and critical dimensionless concentration determination method, set up prediction model of intermixing slab location and length in continuous casting grade transition process. When the tundish’s inside flow control device has been set, physical simulation and numerical simulation were used to study intermixing slab location and length in continuous casting grade transition process. The following results are obtained:(1) For flow rate into tundish, if the request is not high on the dimensionless concentration(below 90%), increasing flow rate into tundish can also reduce the intermixing slab length. However, too much steel quantities into tundish can cause the dimensionless concentration fluctuation and mutation. It is difficult to grasp its change law and is not conducive to the establishment of the model.(2) Increasing pouring steel quantities out tundish can significantly reduce the mixing time of old and new steel, that mean reduce the intermixing slab length. In physical simulation experiments, when residual molten steel is 15 t and dimensionless concentration is 95%, slab width increased from 1000 mm to 1800 mm per 100 mm the mixing time will reduce about 18 s.(3) Decreasing residual molten steel significantly reduce the mixing time of old and new steel, that mean reduce the intermixing slab length. In physical simulation experiments, when slab width is 1600 mm and dimensionless concentration is 95%, the mixing time of residual molten steel 10t、15t、20t is 279s、322s、388s respectively.(4) In physical simulation experiment, we studied the influence of different flow rate of the two flow on the length of intermixing slab produced by the two flow. the conclusion show: change flow rate of the first flow, the length of intermixing slab produced by the second flow have little impact.(5) Under the same casting process conditions, the results of numerical simulation and physical simulation experiments are in high agreement. The conclusions of mathematical model to simulate the different amount of pouring steel quantities out tundish and residual molten steel are completely consistent with physical simulation experiment. Through numerical simulation to obtain the mixing process information of old and new steel that physical simulation experiment cannot get. So, numerical simulation is carried out to verify and supplement the physical simulation. |
