Research And Application Of Dynamic Soft Reduction Process Parameters For Wide And Thick Slab Continuous Casting

Dynamic soft reduction technology has become one of the best methods to improve center segregation and shrinkage in continuous casting products, and it is also an important sign of modern caster. Taking a domestic wide and thick slab caster as research object, research of the soft reduction key process parameters was carried out in the paper. The main content and conclusion in the research are as follows:(1) The study of cooling characteristics of the secondary cooling nozzles in continuous casting. The parameters of the flow characteristics, water flow density distribution and spraying angle of the nozzles were obtained from the study. At the same time, the rationality of secondary cooling system of the caster was analyzed and evaluated.(2) Determination of the high temperature mechanical properties of the slab. The determination lays a foundation of the process parameters of second cooling water and provides accurate physical parameters of the offline soft reduction simulation model. The high temperature mechanical properties include thermal expansion and contraction coefficient, zero strength temperature, zero ductility temperature, tensile strength and reduction of area at high temperature.(3) The study of the temperature distribution and the thermal shrinkage of the wide and thick slab. Based on the temperature distribution of the slab and the high temperature mechanical properties determined, the shrinkage value of the slab was calculated in the continuous casting process, to provide important process parameters of online soft reduction control model. The results show that the casting speed plays a great influence on the slab shrinkage, and with the increase of the casting speed the thermal shrinkage value decrease.(4) The simulation study of the wide and thick slab reduction rate and reduction ratio. The model of the reduction theory was analyzed. Using the high temperature mechanical properties and the production process, a finite element simulation calculation was made for modeling the process of the slab soft reduction to obtain slab reduction rate and reduction ratio in different casting speed and steel grades. The results show that the reduction rate and reduction ratio decrease approximately linearly along the casting direction of the strand, that the reduction rate does not change with the change of casting speed and that the steel grade has little effect on reduction rate and reduction ratio.(5) The simulation of the slab reduction efficiency. The theory model of reduction efficiency was analyzed. Combined with the high temperature mechanical properties and the production process, a three-dimensional finite element simulation calculation was made for the process of the slab soft reduction to obtain reduction efficiency in different reduction amount and different solid fraction. The result shows that in2080mm×260mm section the reduction efficiency increases with the reduction amount when it is less than4.5mm,and that when the reduction amount is bigger than4.5mm, the reduction efficiency remain basically unchanged. In2080mm×300mm section, the reduction efficiency increases with the reduction amount when it is less than5.5mm,and that when the reduction amount is bigger than5.5mm, the reduction efficiency remain basically unchanged.(6) The application of process parameters of soft reduction model. Combined with slab production process, the online model is optimized, including reduction zone and reduction amount. The ratio of class C of1.0for center segregation is95%for Q345B and AH36.