Numerical Investigation On Fluid-thermal Field Of Nozzle Cavity During The Continuous Cast-rolling Of Wide Aluminum Alloy Strip

Due to its short process,low energy consumption and low cost,twin roll continuous casting and rolling is widely used in the production of aluminum sheet and foil.The nozzle system is an important part of achieving stable,efficient and high-quality casting and rolling production.With the development of casting and rolling technology in the direction of ultra-wide and ultra-fast,the nozzle structure has developed from the initial 3C type to the Hunter type that is now widely used,and the structure type has also been developed from the first-level shunt to the third-level shunt.However,in engineering practice,most enterprises rely on experience and analogy to design the distribution structure of the nozzle and the casting and rolling process,resulting in unstable quality of the cast and rolled strip.Therefore,this paper uses numerical simulation methods to investigate the effect of the nozzle structure and the casting and rolling parameters on the melt flow heat field in the cavity of the wide Hunter nozzle,to solve the current structure of the double-roller casting and rolling wide-width aluminum slab nozzle The common problem of design provides a method for the design of the nozzle of double-roll casting and rolling,and provides ideas and directions for optimizing the casting and rolling process and improving the quality of the cast and rolled billet.This study is based on the Hunter-type nozzle structure used in the wide-width 1030 aluminum alloy casting and rolling production line with a specification of 1610 mm 6.2mm.The structure of the nozzle(structure parameters,structure type)and the method of experimental testing and numerical simulation were used The influence of casting-rolling process parameters on the thermal field of aluminum alloy melt flow in the nozzle cavity.The research results obtained are as follows:(1)The physical parameters of the 1030 aluminum alloy melt were collected by referring to the literature,and the mathematical model of the melt viscosity and temperature was established using the Arrehenius formula;the thermal conductivity of the nozzle material was experimentally determined and combined with the time of casting and rolling The experimental results of temperature measurement have constructed a mathematical model of heat transfer on the wall of the nozzle.(2)Using the low Reynolds number k-? turbulence model,a three-dimensional mathematical model of the thermal field of the 1030 aluminum alloy melt flow in the nozzle cavity was established,and the model was solved using Fluent finite element analysis software.Finally,according to the results of numerical simulation and the vertical plate The verification of the stage proves that the overall distribution of the melt flow heat field in the wide Hunter nozzle cavity is not uniform,the molten aluminum flow and temperature at the edge of the nozzle are higher than the middle and ribs,and the melt at the nozzle outlet The temperature and flow rate of the body generally decrease from the side to the middle.(3)The numerical simulation method was used to study the influence of the structural parameters and structure type of the wide Hunter nozzle on the melt flow thermal field.The results show that the cross-channel spacing is the macro-influencing factor of the melt flow thermal field,and its size setting It is more reasonable at 50 ~ 60mm;the shape of the shunt block and the gap size of the shunt block are local influencing factors of the thermal field of the melt flow.The shunt spacing affects the distribution of the melt flow between the gaps of different shunt blocks.The shape not only affects the distribution of melt flow but also the direction of melt flow;when a nozzle with a multi-stage split structure is used to distribute aluminum liquid,the resulting melt flow thermal field is more uniform,and the aluminum liquid is in the nozzle The temperature drop is smaller,but the structure of the multi-stage split nozzle nozzle is complicated,which requires high performance of the nozzle material and the purification and impurity removal process of the melt,which increases the cost of casting and rolling production and restricts its production in casting and rolling.Applications.(4)The melt flow heat field in the nozzle cavity is affected by the combined effect of the two process parameters of casting speed and casting temperature.The casting speed mainly changes the distribution of the melt flow thermal field,and the casting temperature generally adjusts the melt flow.temperature.When the casting-rolling speed is adjusted from 0.8m / min to 1.6m / min,as the casting-rolling speed increases,the temperature drop of the melt decreases,and the unevenness of the flow field increases.When the casting-rolling speed is 1.2m / min,The distribution of the flow and heat field is the most reasonable.While ensuring the uniformity of the flow field,it also reduces the temperature drop of the melt;when the casting temperature is 685 ?,the minimum temperature of the melt in the nozzle is close to the freezing point,casting and rolling production When the casting nozzle cavity is clogged with dross,the minimum temperature of the melt in the casting nozzle cavity is higher than the freezing point when the casting temperature is 695 ? and 705 ?,but considering that reducing the casting temperature can play a role in refining the slab Because of the role of grains,it is most reasonable to choose a casting temperature of 695 ° C.In summary,the optimal combination of casting and rolling parameters is: casting temperature 695 ?,casting and rolling speed 1.2m / min.In this paper,for the best combination of casting and rolling process parameters,two parameter control groups are set up to verify the production of casting and rolling.The verification results show that the numerical simulation results are basically consistent with the actual production conditions.When using this set of casting and rolling parameters for production The distribution of the heat field of the melt flow in the nozzle is reasonable,and the quality of the strip produced is high,indicating that the calculation accuracy of the model is high,and the results obtained have high reliability,which can play a guiding role in production.