基于数值模拟缸体浇注系统的设计与优化

针对镁合金发动机缸体的结构特点设计了浇注系统,并用铸造分析软件对其充型和凝固过程进行了模拟。通过观察分析模拟结果,预测了充型时间、凝固时间以及铸件中可能存在的缩孔缩松缺陷的分布与尺寸,并设计了优化浇注系统。     

复杂结构ADC12铝合金汽车支架挤压铸造工艺参数优化

目的 解决ADC12铝合金汽车发动机支架在挤压铸造成形工艺下的缺陷问题。方法 利用ProCAST模拟软件对该汽车发动机支架的挤压铸造充型和凝固过程进行模拟,对挤压铸造工艺参数进行正交试验设计并模拟得到最佳工艺参数,对铸件浇注远端厚壁部位采取局部加压优化措施,并对厚壁部位进行X-Ray探伤,观察铸件的缺陷情况。结果 对挤压铸造的工艺参数进行正交试验极差分析后,发现各工艺参数按对铸件凝固后质量的影响程度从大到小的顺序依次为挤压比压、浇注温度、模具温度。通过正交试验得到优化后的工艺参数为浇注温度730 ℃、模具温度300 ℃、挤压比压150 MPa。局部加压时挤压销的最佳激活时间为4 s,此时可以完全消除铸件内部的缩孔缩松缺陷。选择优化后的工艺参数生产该汽车发动机支架,产品外观完整,没有出现表面裂纹等缺陷。在X-Ray探伤下无明显缺陷,内部质量良好。结论 选择合理的浇注温度、模具温度和挤压比压可以有效减少铸件内部的缩孔缩松缺陷,采用局部加压并合理控制挤压销的激活时间可以完全消除缩孔缩松缺陷。     

差压铸造薄壁铝硅合金铸件的位置效应

采用差压铸造工艺,研究垂直缝隙式浇注系统浇注的铝合金硅铸件不同位置的组织和力学性能变化.采用石英砂型、SiC砂型和冷铁,浇口处铸件的晶粒最细小,致密度高、力学性能最好;铸件冷端的组织和性能次之;位于两者之间的铸件的组织和性能最差.分析表明对于具有垂直缝隙式浇注系统,差压铸造凝固压力对金属的凝固作用具有位置效应,浇口处液态金属温度高,凝固时间长,凝固压力对浇口处金属的凝固作用显著;铸件冷端金属凝固时间短,凝固压力对该处金属的凝固作用不显著,铸型的冷却速度对铸件组织和性能的影响起显著作用.浇口处与冷端之间的金属液体的凝固受压力和冷却速度的影响小,铸件的晶粒尺寸最大、密度最小、性能最低.冷却速度提高,铸件的任意位置的组织和性能都相应得到提高.     

上倾倒框铸铝件铸造工艺设计及模拟优化

目的 消除ZL114A铝合金上倾倒框铸件的铸造缺陷,获得优质铸件,对该铸件的铸造工艺进行优化设计。方法 使用Unigraphics NX软件进行三维建模,利用ADSTEFAN软件对铸造过程进行模拟。对模拟的充型过程、凝固过程及相关缺陷进行分析。结果 将铸件倒放不利于实现铸件顺序凝固,4个顶冒口的补缩效果不理想,故调整了浇注系统的位置及比例、冒口的位置及大小。最终选取了正放底注式的浇注系统,双侧冒口与单个顶冒口的补缩系统,可获得理想的充型及凝固顺序,有望基本消除铸造缺陷。结论 所采用的计算机模拟方法可以为铸造工艺设计及优化提供指导,为尽可能减少铸造缺陷,保证铸件质量和工艺性奠定了良好的技术基础。     

低压铸铝件缩孔缺陷数值模拟与工艺改进

目的 为了避免铝合金盖板低压铸造过程产生的缩孔缺陷,对盖板结构进行分析。方法 采用数值分析技术,对盖板低压铸造过程进行数值模拟,将模拟结果与实际铸件缺陷进行对比,分析缩孔缺陷的产生原因。为消除铸件缩孔缺陷,在模具内增设冷却水道,并对该工艺进行模拟分析。结果 铸件凝固过程中,当合金固相率达到75%时,铸件特征位置处的补缩通道开始陆续关闭,形成了孤立液相区,导致凝固结束时形成缩孔缺陷。当模具内增设冷却水道后,铸件的缩孔体积分数由3.5%下降到0.8%。结论 通过在模具内增设合理的冷却水道,能加快铸件厚大部位的凝固速度,有利于实现顺序凝固,从而避免缩孔缺陷,提高铸件质量。     

铸造Al-Cu合金凝固缺陷研究现状

铸造Al-Cu合金的凝固缺陷严重影响了铸件的性能,控制或消除凝固缺陷对提高铸件成品率有重大意义。综述了铸造Al-Cu合金在工程中出现的常见凝固缺陷,如偏析、热裂、显微疏松、缩孔等。重点分析了各类缺陷的形成机理与特点,从合金化、熔铸工艺、热处理工艺、数值模拟等角度提出了减少铸造Al-Cu合金凝固缺陷的方法。     

基于数值模拟的K418B高温合金精密铸件组织与性能研究

目的 探究高温合金调压铸造的充型凝固过程,研究调压铸造工艺对铸件组织缺陷和力学性能的影响规律,并验证数值模拟对实际生产指导的可靠性。方法 以某精密构件为研究对象,借助ProCAST数值模拟软件模拟了铸件的调压铸造充型凝固过程并对组织缺陷的形成进行了预测。对成形铸件的特征关键部位进行了取样,通过金相显微镜和扫描电子显微镜对铸态试样的微观组织进行了观察,借助准静态万能拉伸试验机测试了特征试样的室温和高温(750 ℃)拉伸性能,并对断口形貌进行了观察和分析。结果 数值模拟结果表明,金属液充型平稳,凝固过程基本符合自上而下的顺序凝固,铸件缺陷较少,缩孔体积分数仅为0.22%。实验结果表明,铸件的铸态组织为典型的树枝晶组织,晶粒尺寸细小均匀;二次枝晶间距较小,组织致密,缩松缩孔缺陷较少,这与数值模拟的结果吻合较好;铸件的平均抗拉强度超过900 MPa,最大伸长率为15%,该铸件具备较好的综合力学性能。结论 通过数值模拟方法指导铸造生产具有一定的可靠性,同时,通过调压铸造工艺可以生产出具有较好组织和力学性能的高温合金薄壁铸件。     

ProCAST软件在铸造凝固模拟中的应用

为研究铸造工艺对铸件质量的影响,利用计算机进行了铸件的凝固模拟.介绍了有限元软件Pro-CAST的组成模块、功能以及应用,在应用实例中利用ProCAST软件模拟预测了铸件砂铸工艺中产生的宏观缩孔缺陷.研究表明:铸件中存在模拟预测的宏观缩孔缺陷;对浇注系统和冒口设置参数进行了优化,优化后的工艺提高了铸件产量,降低了成本;模拟结果表明,铸造模拟软件ProCAST能够准确地预测铸件在充型凝固过程中可能产生的缺陷.     

发动机活塞裙铸造过程模拟及工艺优化

目的优化发动机活塞裙铸件铸造工艺。方法采用UG等软件设计活塞裙铸件浇注系统以及采用MAGMA铸造仿真软件对铸造工艺进行仿真预测,分析铸件凝固温度场,预测缩孔、疏松等铸造缺陷,进一步优化铸造工艺。结果铸件整体上实现了自下而上的顺序凝固,虽然通过冒口获得了一定程度的补缩,但凝固温度梯度不明显,冒口疏松缺陷依然延伸至铸件上端面。通过合理设置冷铁,增加冒口和内浇口数量,从而实现铸件顺序凝固,使补缩效果更为明显,可有效降低缩孔、疏松缺陷。结论采用MAGMA铸造仿真软件分析凝固过程并预测缺陷,通过改进和优化工艺,可以有效预防活塞裙铸件缺陷的产生,提高铸件合格率。     

基于ProCAST的制动铸件精确成形数值模拟与工艺提升

目的 针对排气制动阀铸造工艺控制不当会产生缺陷这一问题,结合模拟分析,提出合理的铸造工艺方案,以减少铸件缺陷。方法 基于ProCAST软件对蝶阀阀体铸造工艺进行模拟,研究阀体铸件在充型、凝固过程中的速度场、温度场、固相率分布和缺陷分布,并根据模拟结果对工艺进行优化。结果 添加侧冒口和冷铁后,阀体的缩松缩孔缺陷得到了有效控制,缺陷体积减少了95%以上,获得了完整铸件。结论 通过铸造模拟有效指导了排气制动用蝶阀的生产实践,优化了生产工艺,节约了生产成本。     

Studies on squeeze casting of Al 2124 alloy and 2124-10% SiCp metal matrix composite

Aluminium 2124 alloy and its composite with 10% SiC particles of average particle size of 23 μm were squeeze cast at different pressures. The effect of squeeze pressure during solidification was evaluated with respect to microstructural characteristics using optical microscopy and image analysis and mechanical properties by tensile testing. The microstructural refinement, elimination of casting defects such as shrinkage and gas porosities and improved distribution of SiC particles in the case of the composite were resulted when pressure is applied during solidification. A pressure level of 100 MPa was found to be sufficient to get the microstructural refinement and very low porosity level in both the alloy and the composite. The improved mechanical properties observed in the squeeze cast alloy and the composite could be attributed to the refinement of microstructure within the material.     

ProCAST软件在熔模铸造工艺优化中的应用

为解决企业生产中某精铸件存在的缺陷问题,利用数值模拟软件ProCAST对其充型过程和凝固过程进行模拟,并预测缩孔和缩松的存在情况.根据数值模拟的结果对该铸件工艺方案进行相应的改进,显著降低了缩孔和缩松缺陷,并提高了产品的合格率.应用表明:铸造模拟软件能够准确地预测充型凝固过程中可能产生的缺陷,从而辅助工艺人员进行工艺优化.     

Interfacial Thermal Resistance and the Solidification Behavior of the Al/SiCp Composites

The objective of this investigation is to study the effects of applied pressure on the solidification time and interfacial thermal resistance of A356/10% SiC_p during squeeze casting. Samples were prepared for various but constant squeeze pressures up to 130 MPa while maintaining the melt and mold temperatures at 800°C and 400°C, respectively. It was observed that the solidification time was 60 s when no squeeze pressure was applied but it decreased to 42 s when the squeeze pressure was maintained at 130 MPa. The results also showed that the cooling rate increased with squeeze pressure. The solidification time calculated from one-dimensional heat flow theory was found to be close to that obtained from the experimental cooling curves. The interfacial thermal resistance between the mold and the casting was calculated and it decreases when the squeeze pressure increases.     

The effect of die geometry on the microstructure of indirect squeeze cast and gravity die cast 7050 (Al-6.2Zn-2.3Cu-2.3Mg) wrought Al alloy

The indirect squeeze casting process has been used to cast a 7050 (Al-6.2Zn-2.3Cu-2.3Mg) wrought Al alloy to near-net shape with excellent die replication. Defects which occur with gravity casting, in particular (1) shrinkage pipe, (2) macro-porosity and (3) hot-tearing, are largely removed by squeeze casting, although regions of macro-porosity can re-appear when thick sections are fed through substantially thinner sections. Squeeze casting results in a considerable refinement of microstructure compared to gravity casting due to a marked decrease in solidification time. The decrease in solidification time is caused by intimate contact between the pressurised melt and the die, which leads to an increase in the heat transfer coefficient. Decreasing the section thickness also results in a refinement of the microstructure due to a reduction in solidification time. This revised version was published online in September 2006 with corrections to the Cover Date.     

基于UG 与CAE 的压力机底座铸造工艺设计与数值模拟

目的通过对压力机底座的充型凝固过程进行数值模拟,预测其浇铸质量同时基于模拟结果提出相应的工艺改进措施。方法使用UG与CAE软件对压力机底座铸造工艺进行三维建模和数值模拟分析。通过研究零件的结构特点,确定选取砂型手工铸造方法,并使用三箱造型,选取合适的分型面与浇铸位置。采用UG软件做出锻压机底座的三维模型和浇注系统设计,然后利用Anycasting软件进行充型模拟。对充型与凝固过程进行了整体的缺陷分析。结果利用Anycasting模拟浇铸过程发现,在整个充型过程中,充型平稳,无卷气、夹渣、缩孔、缩松等缺陷的出现。结论通过模拟结果确定了浇注系统和补缩系统设计合理,相应工艺设计合理,可以铸造出符合要求的压力机底座。     

Microstructure characterization and tensile properties of direct squeeze cast and gravity die cast 2017A wrought Al alloy

Squeeze casting is a pressurized solidification process wherein finished components can be produced in a single process from molten metal to solid utilizing re-useable die tools. This one activates different physical processes which have metallurgical repercussions on the cast material structure. Desirable features of both casting and forging are combined in this hybrid method. 2017A aluminium alloy, conventionally used for wrought products, has been successfully cast using direct squeeze casting. Squeeze casting with an applied pressure removes the defects observed in gravity die cast samples. Tensile properties and microstructures are investigated. The results show that the finer microstructure was achieved through the squeeze casting. Furthermore, higher pressures improved the fracture properties and decreased the percentage of porosity of the cast alloy. The ultimate tensile strength, the yield strength and the elongation of the squeezed cast samples improved when the squeeze pressure increased.     

Ti-3Al-2.5V钛合金精密铸造浇注系统优化研究

利用数值模拟方法,研究了重力场和立式离心场下,不同浇注系统（顶-底、螺旋、径向和树形系统）Ti-3Al-2.5V钛合金铸件的充型和凝固过程及缩孔缺陷分布规律,并通过实际铸造实验,对铸件的机械性能及缩孔缺陷进行了检测。结果表明,重力场下的顶-底浇注系统氧含量波动范围大,不同浇注系统对合金力学性能影响不大,缩孔的模拟结果与实际铸造情况都吻合较好。相比而言,重力场下由于金属液的紊流更容易形成夹杂、钛豆、缩孔等缺陷,而离心场下由于离心力的作用,形成缩孔等缺陷的数量相对较少。     

两种铸造模拟软件在钛合金铸件研制中的应用对比

目的 研究分析两种铸造模拟软件在钛合金铸件模拟方面的差异及准确性。方法 利用华铸CAE和ProCast软件对某钛合金铸件的温度场、流场和缩孔缺陷进行数值模拟。为了验证模拟结果的准确性,进行实际浇注验证实验,并通过X射线探伤,检测缩孔缺陷的位置。结果 华铸CAE网格剖分简单、计算时间快,但是模型边界拟合较差,ProCast软件网格划分复杂、计算时间较长,但是网格可以较好地反映模型形状,模型边界拟合较高。结论 两种软件对温度场的模拟差异不大,凝固顺序基本一致,两种模拟软件的缩孔预测结果和实际缩孔位置吻合性都较好,说明两种数值模拟软件可以很好地预测钛合金铸件内缩孔分布。     

Study on squeeze casting of an in situ 5 vol.-% TiB2/2014 Al composite

Abstract

An in situ 5 vol.-% TiB₂/2014 composite was prepared by an exothermic reaction of K₂TiF₆, KBF₄ and Al melts. The effect of introduction of in situ formed TiB₂ particles on the squeeze-casting formability of the composite was discussed. The microstructural evolution and changes in the mechanical properties of the composite at different squeeze pressures were investigated. The results showed that a pouring temperature of 710°C, a die temperature of 200°C and a squeeze pressure of 90 MPa were found to be sufficient to get the qualified squeeze cast and maximum mechanical properties for an Al 2014 alloy. However, the pouring temperature, die temperature and squeeze pressure need to be increased to 780°C, 250°C and 120 MPa for the composite to get the qualified squeeze cast and maximum mechanical properties as a result of the effect of introduction of in situ formed TiB₂ particles on the solidification process, plasticity and fluidity of the composite. The microstructural refinement, elimination of casting defects such as shrinkage porosities and gas porosities and improved distribution of TiB₂ particles in the case of the composite result when pressure was applied during solidification. Compared with the gravity-cast composite, the tensile strength, yield strength and elongation of the squeeze-cast composite at 120 MPa increased by 21%, 16% and 200%.