Simulation Of Solidification Structure In Continuous Casting Billet

With the development of the continuous casting technology, how to improve the billet quality is one of the main problems that are studied on continuous casting technology. The formation of solidification structure has important influence on the processing performance and mechanical properties of steel. Therefore, it is very meaningful to have a simulation of solidification structure of continuous casting billet.Based on150mm×150mm billet continuous casting machine in a steelworks, this paper establishes macro-temperature field model with the finite difference method and solidification structure formation model using cellular automaton method. Simulating software was made by using a popular developing tool Visual Basic6.0. Windows of software is devised to be simple and flexible, and the post-processing program makes the simulation results be visual, and gives people intuitive visual effects. The temperature data is processed by the Origin and the Tecplot software, and the effect is good.This paper modifies the physical parameters and nucleation parameters according to some literature. The software can obtain clear picture of solidification structure. The dendrite ratio obtained by calculating is22%which is similar to the dendrite ratio of actual billet (The dendrite ratio of actual billet is20%). The billet is corroded after polishing, and then is observed and taken photos by using the optical microscope. The grain size of actual billet is similar to that calculated by the software. Therefore, through two aspects verification, we think that the model can get comparatively accurate dendrite ratio and grain. This model also reproduces the process of columnar to dendrite transition. When the growth fronts of columnar crystal are hampered by new nuclei, the columnar crystal stop growing and a large number of dendrite appear at the same time.After changing average nucleation undercooling and maximum nucleation density and analyzing the result calculated by the model, we can draw a conclusion that grain size will increase with average nucleation undercooling increasing and decrease with the maximum nucleation density increasing. Through analyzing the results simulated, we can draw a conclusion that dendrite ratio will decrease with average nucleation undercooling increasing and increase with the maximum nucleation density increasing.After changing process parameters of continues casting, and analyzing the result, we can draw a conclusion that grain size will increase with the pouring temperature increasing and the cooling intensity increasing. The dendrite ratio will decrease with the pouring temperature increasing and the cooling intensity increasing. Influence on the solidification from the casting speed can be explained through the cooling intensity. When casting speed increase, the cooling intensity will increase at the same time, and dendrite ratio will decrease. We can get the positive factors that make the dendrite ratio:lower pouring temperature, weaker cooling intensity, and slower casting speed.