Numerical Simulation And Experimental Research On Flow Field During The Twin-roll Strip Casting Process

Twin-roll casting is a proven technology for economical production of thin strip direc tly from the melt. The advantages of this casting technique are numerous—reduced capital costs, energy consumption, operating costs and scrap rate compared with a conventional casting route. In recent years, many researchers and companies have paid great attention to the thin-roll strip casting.Despite its large potential,twin-roll strip casting is a complex issue of highly coupled, and has many problems(molten pool’s serious level fluctuation, instable flow field and temperature field,nonuniform solidification structure,poor process stability) to be solved.The quality of the strip depends on the structure size of the metal delivery systerm and the selection of the strip casting process parameters. In this paper, it will optimize the structure size of the metal delivery systerm to make the high temperature metal liquid uniform in the pool.On this basis,to provide theoretical guidance and basis for the production,further studies of strip casting process parameters influencing on the flow field and temperature field would be done.Based on the ?160mm ?170mm vertical twin-roll strip casting of Yanshan university, a three-dimensional numerical model coupled with heat transfer,fluid flow, solidification and oscillation has been developed. And then, applying the commercial program FLUENT,a transient algorithm has been used for simulating the twin-roll Al Si9Cu3 aluminum alloy strip casting process and discussed the distribution of flow field and temperature field of the inner pool in detail.In this study, the main researches are as follows:Using the orthogonal test design,the difference of pool’s outlet temperature and the difference of the pool’s surface turbulent kinetic energy as test targets,five factors having effect on both test targets were researched. The five factors are:A(splitter length),B(splitter diameter),C(splitter height),D(nozzle width) and E(nozzle angle).For the former test target,the degree of influence sequence is C>A>B>E>D.And for the latter,the sequence is B>A>C>E>D.In this paper,the best solutions of the five factors are 25 mm,10mm,16 mm, 4mm and 30°.Considering casting roll rotation on the flow field and making the temperature field and flow field coupled in the physical simulation, the hot-water model was used to verify the influence of casting process parameters on the pool’s flow field and temperature field for the first time.Using the three-dimensional mathematical model established in this paper,this paper studied the effect of casting speed, pool’s contact angle, pouring temperature and roll’s gap width for the distribution of pool’s outlet temperature, pool’s surface temperature, pool’s flow field and pool’s level turbulent kinetic energy. And the best process parameters are 0.10m/s、 45? 、878.3K、2mm.Numerical simulation and hot-water model experiment both proved that:the whirlpool’s speed of the metal liquid in the pool increases with the casting speed increasing. In the lower of the pool, with the increase of casting speed, the lowest point of the swirl would approach to the gap line of the roll because of the Kiss point moving down.The area of the swirl became larger when the whirl-pool’s speed increased.