| Due to the advantages of resource recycling,energy saving and emission reduction,low raw material costs and short production cycle,scrap aluminum recycling is widely concerned by the aluminum alloy casting industry.Therefore,it will be of great economic and social values to research and develop the scrap aluminum recycling technology and equipment,and to further improve the energy utilization rate and casting quality of the scrap aluminum recycling process.In this paper,the relationships between process parameters and energy efficiency,process parameters and casting quality,respectively,were mainly studied in scrap aluminum melting regeneration.The energy-efficiency analysis model of aluminum alloy casting was established and a high energy-efficient scrap aluminum recycling process was established.The method of quality control and forecast of aluminum alloy was put forward to promote the green production and quality upgrading of scrap aluminum recycling industry.Because of lacking a unified indicator to evaluate energy efficiency in current aluminum alloy casting industry,a more scientific concept of energy efficiency,defined as qualified product quality by unit energy consumption,was proposed,in which the energy flow and material flow were both considered.In order to solve the complexity of the whole casting process,the process was divided into four main steps:melting,alloying,refining and metamorphism,and the efficiency calculation models of these four steps were respectively established.The energy consumption events in each step could be composed of material melting endothermic,uniform energy consumption,furnace radiating,flue gas radiating,furnace door radiating,furnace tools endothermic,slag energy consumption and gas dissolved heat.Through the analysis of energy consumption events in each step,the main energy consumption items followed by flue gas radiating,material melting endothermic and furnace door radiating,the total of three steps more than 90%of total energy consumption in the whole process.Define the sensitivity of energy efficiency and use it to measure the impact of the energy efficiency of each process on the overall process energy efficiency.The results showed that the melting step and the alloying step had more significant impact on the overall process energy efficiency,and their energy efficiency sensitivity reached 83.58%and 12.09%respectively.The effect of the process parameters of each step on the step energy efficiency were studied by the combination method of theory and experiment.The results showed that the influence of the process parameters on the energy consumption in descending order was the gas temperature,the melting temperature,the opening time of the furnace and the melting time,and their influence laws on the energy efficiency of the melting step could be regarded as the linears.The influence laws of species,quality and burning rate of alloying material on the energy efficiency of the alloying step was analyzed and the alloying principle was obtained,that is,"Try not to dilute the feed,try not to fill silicon".Finally,a new casting process was developed,which could improve the energy efficiency of about 40%and handle large quantities of scrap aluminum using a new double-chamber furnace.The new process has the advanced features of precise ingredients by the starting ingredients and converter ingredients,continuous dissolution of melting,on-line detection of solid raw materials,zero adjustment of chemical composition,synchronous detection of chemical composition and slag content,etc.,significantly shortening the smelting time and improving energy efficiency.In order to achieve precise control of chemical composition,the chemical composition of the aluminum alloy was digitally characterized and four grades of excellent,good,qualified and poor were set according to the characteristics of the chemical composition requirements.And the combining principle of "non-zero item of poor grade membership degree" and "maximum membership degree" was formulated to evaluate the chemical composition grade of aluminum alloy.Then,the optimized control scheme of the chemical composition of the molten alloy was established by using the modified fuzzy control model and the on-line detection of the scrap raw materials.The experimental results showed that this scheme has a good effect on controlling the chemical composition of the molten alloy.The variation of typical chemical elements during the A356 aluminum alloys melting process with scrap aluminum as raw material was studied experimentally.When the melting temperature was constant,the Mg content decreased linearly and the Fe content increased linearly with the holding time.The content of Sr and Ca showed a gradual decrease of Exp3P2 laws with the holding time,respectively.Based on these experimental rules,the content prediction models of alloying elements with high content and trace elements were established,and the error of prediction was less than 10%via production verification.The relationship between microstructure and process parameters of A356 aluminum alloy regenerated with scrap aluminum was studied.The results showed that the average grain size of ?-Al decreased with the holding time In the early stage,and the grain refining rate increased with increasing smelting temperature.When the holding time exceeded 3h,the average grain size of a-Al at 640 ? kept decreasing,while the average grain size of ?-Al in other smelting temperature showed an upward trend.The higher the smelting temperature,the more serious the grain coarsening.When melting at low temperature,the secondary dendritic arm spacing of ?-Al dendrites had no significant change with the holding time,but decreased gradually with the holding time at high temperature.The morphology of eutectic silicon showed a modification effect deterioration trend from thin fiber to lamellar with the extension of holding time,and the higher the melting temperature,the shorter the holding time of deterioration.The eutectic silicon size firstly decreased and then increased at 720 ? and its evolution mechanism could be explained by the theory of the eutectic silicon dissolution and cluster decomposition and chemical elements' influence on eutectic silicon nucleation.Using the GUI function in Matlab language,the above research results were programmed,and the software of energy efficiency analysis and quality forecasting were compiled in aluminum alloy casting process.This software has two major functions of energy efficiency analysis and quality forecasting in aluminum casting process.It is applicable to the energy efficiency analysis of smelting aluminum alloy in Natural gas regenerative furnace and the contents prediction of four elements of magnesium,iron,strontium and calcium in hypoeutectic Al-Si alloy.And program interface for any elemental content prediction and microstructure prediction of the other aluminum alloy has been set,which is used to the development of quality forecasting function. |
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