基于分布参数模型的变厚度盘坯气淬过程控制策略研究

发布时间：2018-07-03 21:26

本文选题：空气淬火 + 数值模拟　；参考：《哈尔滨工业大学》2016年硕士论文

【摘要】：淬火工艺的提升可以提高金属材料的机械、化学等性能,目前工业中使用的淬火方式根据淬火介质划分可以分为水冷淬火、油冷淬火、气冷淬火等,相比于水冷淬火、油冷淬火等淬火方式,气冷淬火具有材料内部组织应力小、淬火速度快等优点。本文基于一种新型的空气淬火装置,研究了该装置对变厚度盘坯的淬火效果。针对具有多种形状特征的盘坯,通过控制空气淬火装置中气体的流速,得到了使盘坯内部温降均匀,适合内部材料晶相组织生成的淬火工艺参数。本文对盘坯的气体淬火过程进行了数值模拟研究,简化了淬火过程中的湍流控制方程,分析了淬火过程中盘坯表面的换热情况。通过计算盘坯表面第一层网格无量纲距离验证了仿真湍流模型的准确性,分析了盘坯不同区域表面Nu数的分布特点,盘坯表面平均Nu数与Re数的关系。盘坯为了达到淬火过程理想温降需要相应喷嘴中气体流速随时间进行变化,针对这一根据温度逆求解流速的问题,设计了FLUENT/Simulink协同仿真闭环控制系统,使用这一控制系统得到了喷嘴气体流速在淬火过程中随时间变化曲线。这种协同控制方法可以准确控制基于分布参数模型的盘坯内部区域各点的温度下降曲线。根据盘坯淬火过程具有大时滞、惯性、耦合的特点,在建立闭环控制系统的控制模型时,改进了传统的模糊控制等控制策略,最终得到了盘坯理想淬火过程对应的淬火结构中喷嘴气体的流速变化数据。使用本文提出的控制方法,改善了传统的淬火工艺,能够提高盘坯淬火后各项力学性能。使用该淬火结构对盘坯进行了淬火实验,提取了盘坯内部某些监测点温度下降数据,分析了这些监测点的温度下降规律,比较了这些监测点实验值与仿真值的下降趋势及误差,并给出了相应的误差分析。
[Abstract]:The upgrading of quenching technology can improve the mechanical and chemical properties of metal materials. The quenching methods used in industry at present can be divided into water cooling quenching, oil cold quenching, air cooling quenching, etc., compared with water cooling quenching, the quenching methods used in industry at present can be divided into water cooling quenching, oil cold quenching, air cooling quenching and so on. Gas-cooled quenching has the advantages of low microstructure stress and fast quenching speed. Based on a new type of air quenching device, the quenching effect of the device on variable thickness disc billet is studied in this paper. By controlling the flow rate of the gas in the air quenching device, the quenching process parameters which make the internal temperature drop uniform and fit for the formation of the crystal phase structure of the inner material are obtained for the disc with various shape characteristics. In this paper, the numerical simulation of the gas quenching process of the slab is carried out, which simplifies the turbulent governing equation during the quenching process and analyzes the heat transfer on the surface of the disc during the quenching process. The accuracy of the simulation turbulence model is verified by calculating the dimensionless distance of the first layer grid on the slab surface. The distribution characteristics of the Nu number on the surface of the slab in different regions and the relationship between the average Nu number and re number on the slab surface are analyzed. In order to achieve the ideal temperature drop in the quenching process, the gas velocity in the nozzle needs to change with time. In order to solve the flow rate inverse according to the temperature, a fluent / Simulink collaborative simulation closed-loop control system is designed. By using this control system, the curve of nozzle gas velocity varying with time during quenching is obtained. The cooperative control method can accurately control the temperature drop curve of each point in the inner region of the slab based on the distributed parameter model. According to the characteristics of large time delay, inertia and coupling in the process of disc quenching, the traditional fuzzy control strategy is improved when the control model of the closed-loop control system is established. Finally, the flow velocity data of nozzle gas in the quenching structure corresponding to the ideal quenching process of disc billet are obtained. By using the control method proposed in this paper, the traditional quenching process is improved, and the mechanical properties of the disc after quenching can be improved. The quenching experiment was carried out on the disc billet with the quenched structure, and the temperature drop data of some monitoring points in the slab were extracted, the law of temperature drop at these monitoring points was analyzed, and the decreasing trend and error between the experimental value and the simulation value of these monitoring points were compared. The error analysis is given.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG156.3

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