Influence of die casting process parameters on castability and properties of thin walled aluminium housings

Abstract

The objective of this study is to clarify effects of high pressure die casting process parameters for castability and mechanical properties. So the optimal die casting conditions for producing for thin walled Al component was conducted computational solidification simulation and actual die casting with three different venting systems, four straight, checker and full checker vent. Furthermore, the die casting process parameters, such as die controller temperature, high injection speed and die open time, were experimentally evaluated. The results of computational solidification simulation were found that the control of process parameters could lead to soundness of surface and no defect and improvement of mechanical properties. As increasing the high injection speed from 2˙0 to 4˙0 m s^?1 and die temperature, the castability was increased. The full checker venting system had best castability with good surface quality among the three cast specimens.     

Conference Reports

Abstract

The outcome of a long-term programme on the computer-aided design of castings, carried out at Sharif University of Technology, has been the development of computer simulation software known as SUTCAST. This is currently employed in 16 local foundries. The program is based on a numerical method involving a classical approach to an explicit three-dimensional heat-transfer finite difference method. The software has been designed for the solidification simulation of pure metals, and eutectic and long-freezing-range alloys. It has been written for IBM personal computers and compatibles in the Turbo C version 2.01 programming language.

This paper discusses the computer solidification simulation of an Al—12%Si casting poured in a sand mould and the heat- transfer coefficient at the metal—mould interface. A mathematical model for the estimation of the gap width at the metal—mould interface during solidification based on the plane strain thermoelasticity equations is suggested.

The solidification process for Al—12%Si contained with a sand mould was monitored by measuring temperature at different locations within the casting and the sand mould. An experimental procedure was employed to measure the displacement of the metal and mould walls during solidification. The width of the gap was measured as the difference between the location of the casting and the inner surfaces of the mould, which varies with time.

The computer results are compared with the experimental data and are shown to be in good agreement as regards to cooling curves, solidification time and gap size.     

用Cellular Automaton方法模拟压铸镁合金AM50的微观组织

基于Cellular Automaton(CA)方法的基本原理,建立了压铸镁合金AM50形核和等轴晶粒生长的二维数学物理模型,能够对任意晶向的等轴晶晶粒生长进行模拟。模型耦合了宏观传热与微观组织模拟计算,镁合金AM50阶梯块压铸件的温度场通过热传导反算法计算求得。对阶梯块压铸件不同阶梯表面的微观组织进行了模拟,并与金相试验结果进行了对比,它们在晶粒尺寸上吻合较好。     

大型铸钢件凝固过程数值模拟

铸钢件凝固收缩大,铸造工艺复杂,进行凝固过程计算机模拟十分必要.本文基于有限差分法建立铸钢件凝固过程传热计算的数学模型,开发铸钢件凝固过程三维温度场数值模拟分析软件.利用该软件计算了大齿轮毛坯铸钢件凝固过程的温度场,结果与实际情况吻合较好.     

铝合金石膏型精密铸件凝固过程数值模拟与实验验证

应用自行开发的铸件充型及凝固模拟系统,对铝合金石膏型精密铸件的凝固过程进行了数值模拟。采用自行设计制备的多通道自动测温装置,对所模拟的铸件进行现场测温。为了提高模拟精度,对铸件铸型热物性参数进行了实测,并采用最小二乘法进行拟合。通过计算机模拟预测了铸件的缩孔区,分析了铸件缺陷产生的原因,提出了合理的工艺方案,消除了铸件内缩孔的发生。实验验证的结果表明,数值模拟结果与测试值拟合较好     

基于数值模拟技术镁合金压铸模浇注系统优化设计

设计3种类型的浇注系统,运用铸造专用模拟软件JSCAST对3种浇注系统进行压铸数值模拟试验,分析液态金属充型及凝固过程中的速度场和温度场的分布,根据凝固规律有效预测铸件中可能存在缩孔及气孔缺陷的分布,从而选取T型浇注系统作为缸盖罩的最佳浇注系统并对其进行优化。试验结果验证了优化设计的可行性以及压铸过程数值模拟的可靠性,对压铸生产具有一定的指导意义。     

板坯连铸二冷计算机仿真的研究和应用

连铸二冷计算机仿真是准确、迅速预测和分析工艺参数对浇注过程的影响规律以及优化连铸操作工艺参数的重要手段。基于沿拉坯方向上移动的有限薄片层思想,建立板坯连铸凝固传热数学模型,应用面向对象的编程语言Visual Basic 6.0开发了板坯连铸二冷计算机仿真软件,并针对国内某板坯连铸机应用仿真软件对其进行凝固过程模拟、对其二冷凝固过程进行工艺优化。应用红外线测温仪对板坯表面温度进行测试,测试温度与仿真结果吻合较好,说明连铸计算机仿真软件的计算是可靠的。     

低碳合金钢铸件消失模铸造技术研究与应用

运用计算机辅助三维设计、计算机辅助凝固过程数值模拟和计算机辅助数控编程制造CAD/CAE/CAM一体化技术手段,通过优化设计产品模型结构、铸造工艺参数、产品模具工装结构、浇冒口工艺系统以及模具型腔数控加工的刀具定位源文件,研究开发了货运列车低碳合金钢零部件转8A型承载鞍消失模铸件产品.与普通砂型铸造相比,其铸件单体重量减轻了3kg,铸件重量精度达到MT7级,铸件尺寸精度达到CT8级,铸造工艺出品率达到65%;本文也对大批量产生过程中容易出现的铸造缺陷进行了分析并提出了解决的办法.     

Heat transfer and solidification analysis in the mould region of a horizontal copper alloy billet continuous caster

Abstract

Mathematical modelling has been widely used as a powerful tool for process design and optimisation of the continuous casting process. A three-dimensional heat transfer model was developed to simulate heat transfer and solidification in a horizontal billet continuous casting system. In this model, the air gap formation and its effect on heat extraction from the billet was also modelled and considered. The developed model was run to simulate the heat transfer and solidification for an industrial billet casting machine. The predicted temperature distribution within the mould and billet was compared with those measured on an industrial caster and good agreement was obtained. Parametric studies were carried out to evaluate the effects of different parameters on the temperature distribution and solidification profile within the cast brass billet. Finally, the secondary dendrite arm spacing (SDAS) was determined experimentally and a semi-empirical correlation between measured SDAS and corresponding calculated cooling rate was proposed for continuously cast brass billet.     

铝合金压铸工艺数值模拟分析

采用压铸工艺成形铝合金薄壁长轴类零件。首先根据压铸模具浇注系统的设计原则,对铝合金件压铸模的浇注系统进行了设计计算;其次运用procast软件对铝合金压铸成形工艺进行数值模拟,根据压铸过程中的温度场云图,进行了压铸模具的热平衡分析和压铸件的充型凝固分析;最后针对模拟的结果进行了压铸模具的设计。     

CAE模拟分析在前盖压铸模设计中的应用

应用Anycasting软件对铸件的填充过程、凝固过程和模具温度场进行模拟分析,利用模拟结果优化模具结构,尽量避免模具设计对铸件质量产生的不利影响,降低铸件缺陷产生的概率,缩短产品开发周期。     

数值模拟技术在汽车齿轮室模具温度场分析中的应用

以汽车齿轮室压铸件为例,对铸件凝固过程进行分析,使用模拟软件Flow-3D得到了压铸镁、铝合金模具温度场的分布特征,研究了镁、铝合金压铸件及压铸模具温度场随浇注温度、模具预热温度变化的情况。数值模拟结果可为汽车齿轮室模具优化设计提供参考。     

局部加压铝合金的凝固变化及其数值模拟

局部加压方法是压铸中用于消除铸件厚壁处缩孔缺陷的一种新工艺.该研究通过试验模型测量局部加压过程中金属型、铸件和加压杆的温度变化曲线,分析了传热与凝固现象.结果表明,局部加压使铸件的凝固时间大为缩短,加压杆前端的温度大幅上升,而金属型的温度则无明显变化.利用变网格技术,根据加压深度通过适时修改网格文件、初始条件和边界条件的方法,模拟了铝合金在局部加压过程中的凝固变化,并与试验结果进行了对比和讨论.     

轴承支架半固态压铸过程数值模拟

采用数值模拟方法分析了半固态铝合金的表观粘度及浇注温度对轴承支架铸件压铸充型和凝固过程的影响。结果表明,半固态铝合金的充型速度随其表观粘度的增加而显著下降,而浇注温度对充型速度的影响与液态压铸时的一致。铸件同一部位的凝固温度随半固态铝合金浆料充型时的表观粘度增加而提高。凝固后铸件内未出现铸造缺陷。     

Multi-objective optimization of process parameters during low-pressure die casting of AZ91D magnesium alloy wheel castings

Multi-objective optimization has been increasingly applied in engineering where optimal decisions need to be made in the presence of trade-offs between two or more objectives. Minimizing the volume of shrinkage porosity, while reducing the secondary dendritic arm spacing of a wheel casting during low-pressure die casting(LPDC) process, was taken as an example of such problem. A commercial simulation software Pro CASTTM was applied to simulate the filling and solidification processes. Additionally, a program for integrating the optimization algorithm with numerical simulation was developed based on SiPESC. By setting pouring temperature and filling pressure as design variables, shrinkage porosity and secondary dendritic arm spacing as objective variables, the multi-objective optimization of minimum volume of shrinkage porosity and secondary dendritic arm spacing was achieved. The optimal combination of AZ91 D wheel casting was: pouring temperature 689 °C and filling pressure 6.5 kPa. The predicted values decreased from 4.1% to 2.1% for shrinkage porosity, and 88.5 μm to 81.2 μm for the secondary dendritic arm spacing. The optimal results proved the feasibility of the developed program in multi-objective optimization.     

Water analogue validation of numerical model for fluid flow during slow shot phase in die casting process

Abstract

Air that becomes entrapped in the molten metal during the die casting process has a major effect on the formation of porosity in horizontal cold chamber die castings. In this study, a three-dimensional computational fluid dynamics model was developed to study the flow patterns of liquid metal in the injection chamber, in which the moving boundary conditions of the plunger movement was considered in detail. According to the principle of die casting machines, a water analogue system was designed and built to investigate the slow shot process. A colour high speed camera was used to record the fluid flow patterns under different plunger movement profiles. The numerical simulation results agreed well with the water analogue experimental results, which validated the numerical model of shot processing in the cold chamber of the die casting process.     

铸造模拟在大型复杂铸铁件上的实用研究

使用计算机进行铸造模拟有助于复杂铸铁件的铸造工艺设计,流动和凝固解析的结果可以作为日常确定方案时的重要参考.利用凝固解析功能确立了独特的使用方法,可以预测和优化大型铸铁件的打箱时机,预测铸件热处理时的铸件温度分布,以及采用简易模型进行铸件内部应力的估算.这些方法对铸铁件生产是行之有效的.     

结晶器喂钢带连铸坯凝固过程的数学模拟

利用旅行薄片微元体能量守恒原理,引入喂钢带相对速度参量,发展了连铸凝固旅行薄片数学模型.采用有限体积法,用Visual Basic语言独立编制源码模拟程序,并对一典型喂钢带的连铸工艺进行模拟分析,得到了连铸坯温度分布和喂进钢带凝固状态的曲线.结果证明,喂进钢带改变了结晶器内温度场的分布和传统的由表及里凝固方式,钢带在结晶器内先凝固后熔化,降低了钢水过热度和铸坯断面温度梯度,使得温度分布更有利于等轴晶结晶过程的进行,有利于铸坯断面形核率的提高.同时该模型也给出了钢带尺寸、拉速和过热度等参数对连铸坯凝固过程的影响.