Soft Reduction Model For Slab Continuous Casting Machine With Dynamic Soft Reduction

Dynamic soft reduction technology for conticaster has become one of the best methods to eliminate center segregation and shrinkage cavity of as-cast semi-products, and it is an important indication of modern conticaster. Based on the domestic VAI slab continuous casting machine, research of the soft reduction model was carried out in the paper. The main research and results are as follows:1. Determination of the high-temperature physical parameters of the slab. The high-temperature physical parameters of trial steel which are the base for the secondary cooling water and the off-line reduction simulation were measured. The high-temperature physical parameters include high-temperature thermal expansion contraction coefficient, high-tem-perature thermoplastic curve, TzsT and T ZDT.2. The test of the cold state characteristics of the secondary cooling nozzles.The parameters of the flux characteristics, water flow density and spraying angle were achieved from the test. Meanwhile, the layout of the nozzle had been put forward by analyzing the existing secondary cooling system and the result of the test.3. The simulation of the slab natural shrinkage. The shrinking volume of the casting slab is an important parameter for the reduction on-line control model. Based on the high-tem-perature physical parameters tested and the real-time temperature field of the slab, the shrinking volume of slab was calculated during the whole CC process. The result shows that the casting speed has a great effect on the slab shrinkage, and the as the shrinking volume becomes smaller as the casting speed is high.4. The simulation of the slab reduction rate. The theory model of the reduction rate was analyzed. Combined with the high-temperature physical parameters and the conditions of practice, a finite element numerical calculation was performed for the process of the slab soft reduction. And the range and laws of the reduction rate were obtained under various casting speeds and steel grades. The result shows that the reduction rate and gradient decrease approximately linearly along the casting direction of the strand. The range of reduction gradient does not change with casting speed. But the steel grade has little effect on reduction rate and gradient.5. The simulation of the slab reduction efficiency. The theory model of reduction efficiency was analyzed. Combined with the high-temperature physical parameters and the conditions in practice, a three-dimensional finite element numerical calculation was made for the process of the slab soft reduction. The range and laws of reduction efficiency were obtained under various casting speed, steel grade, reduction amount and solidification rate. The result shows that the reduction efficiency of Q345E increases with the reduction amount when it is less than2.1mm. When the reduction amount is bigger than2.1mm, the reduction efficiency is independent with the reduction amount. The reduction efficiency of AH36,45#and A36-1B increases with the reduction amount when it is less than3.5mm. When the reduction amount is bigger than3.5mm, the reduction efficiency of AH36,45#and A36-1B is independent with it.