金属型铸造凝固过程温度场数学模型及定解条件的确定

一、概述 金属型铸造时生产量一般都很大，对铸件的质量要求很高，而且要求铸件是稳定的，也就是说同一副金属型中铸造出来的铸件质量应该是一样的。金属液的凝固过程对铸件质量影响很大，因此模拟凝固过程温度场的分布，对优化铸造工艺、预测与控制铸件质量和各种铸造缺陷，以及提高生产效率都非常重要。具体讲，凝固过程温度场模拟可实现如下目的。     

基于数值模拟改善下环类铸件椭圆度工艺研究

本文利用计算机数值模拟技术，预测大型下环类铸钢件生产中经常出现的变形及尺寸偏差等铸造缺陷，进而优化工艺，降低铸造成本。通过对水轮机下环的铸造工艺进行计算机数值模拟，掌握在铸件凝固过程中的应力变化，并验证应力数值模拟的准确性。通过对典型铸件工艺的数值模拟和验证研究，实现了数值模拟技术在生产中的实际应用，避免了工艺设计的盲目性，缩短了新工艺的设计周期和设计成本。 对铸件凝固过程进行应力数值分析，可以更好地了解铸件凝固过程中应力和变形的动态变化，在此基础上进行尺寸精度控制，为实际生产提供科学指导。     

柱塞泵盖铸造工艺及数值模拟应用

通过对柱塞泵盖液压铸件结构分析,预先设计方案模拟比较确定铸造工艺方案,运用数值模拟进行充型模拟和凝固模拟,预测铸造过程中的铸造缺陷。通过对充型及凝固过程的可视化分析,进行工艺优化,根据优化工艺实际制作模具浇注铸件验证。通过使用数值模拟为薄厚不均匀液压球墨铸铁铸件的开发提供理论依据和实践指导,缩短新产品开发周期、降低开发成本。     

铁型及覆砂层厚度对铸件凝固的影响

为解决球墨铸铁铸件冷却凝固的影响因素问题,将数值模拟技术应用到铸造过程分析中,讨论了铁型覆砂铸造工艺中40 mm、20 mm两种不同铁型,6 mm、8 mm、10 mm、13 mm四种覆砂层厚度对球墨铸铁铸件冷却凝固的影响,建立了铸造过程中铁型厚度、覆砂层厚度、铸件厚度三者之间的关系。进一步测量了实际球墨铸铁铸件的冷却凝固曲线,验证了模拟数据,得出了铁型覆砂工艺适合球墨铸铁铸件的工艺参数。研究结果表明,该研究对球墨铸铁铸造实际应用具有较为可靠的工艺参考价值。     

阀体不锈钢件铸造过程的计算机辅助设计

利用Pro/E三维造型软件,运用MAGMAsoft铸造数值模拟软件对阀体铸钢件充型凝固过程进行了模拟分析。通过对铸件铸造全过程的CAD/CAE研究,准确地反映了铸件充型凝固过程的实际状况,预测了可能产生的铸造缺陷及产生缺陷的部位。研究结果表明,在靠近阀体铸件热节部位放置冒口以及在法兰底部添加冷铁,可使之顺序凝固,能有效地改善热节状态,达到消除和控制缺陷的目的,使铸件能够达到质量要求。     

大型铝合金综合传动箱铸造工艺模拟

利用北京北方恒利科技发展有限公司开发的铸造模拟软件CAStsoft对大型铝合金综合传动箱铸件的凝固过程和充型过程进行模拟。通过对凝固过程的温度场和铸造缺陷的分析，依据分析结果对工艺进行改进，最后设计出合理的铸造工艺。铸造过程计算机模拟可以减少或取消新产品的工艺实验，能够有效地避免可能出现的铸造缺陷，保证工艺的可靠性，缩短新产品的试制周期。     

铸造CAD／CAE系统研究及应用

以Pro／E生成铸件三维模型（包含铸造工艺信息），基于MAGMAsoft进行凝固过程数值模拟，以便校核和优化工艺设计。根据模拟结果，找出了铸件铸造缺陷产生的原因，并通过修改工艺参数对工艺进行了改进和优化，制定出了合理的工艺方案。     

凝固过程应力场模拟技术在大型铸钢件中的应用

基于FDM／FEM方法，对某水轮机下环铸件的整个铸造过程中的热应力进行了模拟计算。模拟中采用接触单元法处理铸件与砂芯之间力的作用，改进了传统的铸件／铸型边界条件处理方法。根据应力场模拟结果，分别采用不同的判据，对铸件整个凝固、冷却过程中的热裂和冷裂倾向性进行了预测。揭示了铸件从凝固到冷却至室温的变形规律，为控制铸件收缩尺寸提供了参考。实际生产结果与预测结果相吻合。     

铁路货车转向架用摇枕铸造凝固模拟及工艺优化

铸造凝固模拟软件作为一种有效的铸造工艺设计和优化工具在全球的铸造行业中得到了广泛的应用。本文利用ProCAST软件对铁路货车转向架用摇枕的凝固过程进行了数值模拟,并根据模拟结果,对摇枕原有铸造工艺提出了进一步的改进措施,使铸件的补缩和凝固更加合理。     

铝合金汽车轮毂铸件凝固过程缺陷CAE分析

用对比定量的方法研究了浇注温度、模具预热温度对模具温度场的影响,探讨了冷却方式、浇注速度及模具结构对铸件缺陷的影响.运用某铸造模拟软件对其模具及铸件进行了压铸过程温度场分析和轮毂低压铸造充型及凝固过程做了模拟分析,介绍了铸件缺陷-缩松,缩孔的成因,利用CAE技术分析了铝合金汽车轮毂在凝固过程中浇注速度、冷却方式对缩松,缩孔的影响。     

金属铸造界面传热系数的试验研究及其确定

金属铸造凝固过程中,在接触界面间会产生热阻.热阻的大小随空间和时间变化,常常主导着热传导的过程,通常将热阻的影响表示为界面传热系数,在温度场数值模拟中,铸件与铸型间的界面传热系数是关键的参数.利用有限元分析软件ANSYS结合试验数据,模拟了铸造凝固过程的温度场,分别考虑了不同界面传热系数对模拟结果的影响,并将模拟数据与试验结果进行了比较,发现了金属型铸造界面传热系数随时间变化的规律,以及铸件与铸型的接触位置对界面传热系数的影响.     

基于CASTSoft_CAE软件的铸件缺陷预测

以金属凝固理论为基础,I-DEAS和CASTSoft_CAE软件为平台,建立法兰盘凝固过程的三维模型。对法兰盘凝固过程的温度场和凝固过程进行数值模拟,温度最大值出现在法兰盘中心部位,最小值出现在法兰盘边缘。应用新山判据预测铸件可能出现缩孔、缩松等铸造缺陷的位置,发现在法兰盘中心处出现缺陷。     

低压铸造薄壁板件的流动与传热耦合数值模拟

采用 VOF法处理自由表面 ,达西源项法处理固 -液两相区流动 ,开发了铸造过程流动与传热耦合数值模拟软件。通过对流场及温度场分别采用不同的计算域和时间步长 ,大大提高了计算效率。利用该软件模拟了一薄壁板件的低压铸造过程 ,并进行了实验验证。数值模拟结果表明 ,对薄壁件而言 ,充型过程的流动对铸件初始温度分布影响较大 ,但充满后的残余流动对温度分布影响较小     

ZL104铝合金刀盘体的铸造工艺优化

公司生产的ZL104铝合金刀盘体铸件厚壁处常出现缩松缩孔缺陷。使用芸峰CAE软件对此盘体原有的铸造工艺进行凝固过程模拟仿真,预测缩松缩孔缺陷位置与实际生产相吻合。优化工艺后,再次用CAE软件进行模拟仿真,得到合理的方案后,在实际生产中应用,毛坯加工后该区域的缩松缩孔完全消除,获得了合格零件。     

Novel technologies for the lost foam casting process

Lost foam casting (LFC) is a green precision casting process categorized as a near net forming technology. Yet, despite its popularity, it still suffers from some technological problems, such as poor filling ability of the castings, coarse and non-dense microstructure, low mechanical properties for the Al and Mg LFC processes, and defective carburization for the low carbon steel LFC process. These drawbacks restrict the development and widespread application of the LFC process. To solve these problems, the present study developed several novel LFC technologies, namely, LFC technologies under vacuum and low pressure, vibration solidification, and pressure solidification conditions; expendable shell casting technology; and preparation technology of bimetallic castings based on the LFC process. The results showed that the LFC under vacuum and low pressure evidently improved the filling ability and solved the oxidization problem of the alloys, which is suitable for producing complex and thinwall castings. The vibration and pressure solidifications increased the compactness of the castings and refined the microstructure, significantly improving the mechanical properties of the castings. The expendable shell casting technology could solve the pore, carburization, and inclusion defects of the traditional LFC method, obtaining castings with acceptable surface quality. Moreover, the Al/Mg and Al/Al bimetallic castings with acceptable metallurgical bonding were successfully fabricated using the LFC process. These proposed novel LFC technologies can solve the current technological issues and promote the technological progress of the LFC process.     

铸铁激光表面重熔处理的数值模拟

本文采用变热物性参数建立了较合理的数学模型,计算了激光表面处理过程中温度分布明亮变化,对熔化深度和相变总深度进行了预测,同时与试验结果比较,发现两者相吻合。并首次用彩色图象显示过程中温度分布及变化。从而为凝固过程提供了分析基础,为工艺参数优化提供了理论依据。     

On the nature of the thermal response behaviour of metallic moulds-characterisation of the transient temperature field

The thermal response behaviour of the metallic mould is of fundamental and paramount importance in controlling the rate of solidification of castings as well as their mechanical and technological properties. This problem is, therefore, addressed in the present paper in order to gain an insight into the mechanism of heat transfer through the mould wall and to provide the designer with some basic information. In order to reveal the nature of the time variation of the temperature field within the mould wall, the analysis is confined to the case of undimensional heat flow under transient condition. This has been accomplished by applying the finite element method in a dimensionless form. Conclusions regarding the individual and combined effects of various governing variables on the thermal process have been drawn. Depending on the combination of the principal variables, the results indicated that there are four fundamental patterns for the transient temperature field. Experimental data regarding the time variation of the temperature at the mould inner surface is presented in some analytical form. Using this data, the application of Duhamel's integral to predict the temperature field under transient boundary condition is demonstrated.     

Prediction of solidification time during solidification of aluminum base alloy castings cast in CO2-sand mold

Solidification of molten metals during various casting methods poses many practical problems associated with phase transformation and heat transfer processes. Evaluation of solidification time is one of the very important parameters used for assessing the properties of the material. In the present study, experimental investigation was carried out to measure the solidification time in a cylindrical hollow casting cast in CO₂-Sand molds and the same has been compared with the results obtained through computed by using an implicit alternating direction (IAD) method, including the treatment of interfacial nodes between metal and mold, and boundary nodes at the mold surface. Aluminum-4.5% copper alloy has been used. Computed cooling curves at various locations and temperature distributions in core-metal-mold were presented. The results shows that the solidification time obtained by experimental study compares well with the one predicted by the analysis made through IAD modeling. A successful comparison with reported experimental results shows that the technique is appropriate for simulation of solidification process of aluminum castings.     

铸钢件工艺CAD通用软件的研制与应用

叙述铸钢件工艺ＣＡＤ的基本方法，在工艺校核方法上成功引入铸件凝固三维数值模拟技术，得到设计结果与实际情况相符的效果。