大型异形铝铸件的铸造工艺研究

大型异形铝铸件,铸造工艺难度较大,常需依赖于丰富的生产经验辅之以计算机凝固模拟分析技术。针对不同的形状,制定相应的铸造工艺。对管体、轮毂、支腿垫块、螺旋桨等典型产品较为成熟的生产工艺进行介绍。通过对这些典型铸件的工艺案例进行分析,探讨大型异型铝铸件的铸造工艺设计方法。     

Numerical simulation and process optimization for producing large-sized castings

3-D velocity and temperature fields of mold filling and solidification processes of large-sized castings were calculated, and the efficiency and accuracy of numerical calculation were studied. The mold filling and solidification processes of large-sized stainless steel, iron and aluminum alloy castings were simulated by using of new scheme; their casting processes were optimized, and then applied to produce castings.     

铝合金压铸件充型和凝固过程的数值模拟

分析了压力铸造的工艺特点以及对压铸过程数值模拟软件系统的要求,利用基于有限元算法的铸造过程数值模拟软件对铝合金压铸件的充型和凝固过程的物理场进行了数值模拟,模拟结果对实际铸件的生产具有重要指导意义。     

Computer simulation for centrifugal mold filling of precision titanium castings

Computer simulation codes were developed based on a proposed mathematical model for centrifugal mold filling processes and previous computer software for 3D mold filling and solidification of castings (CASM-3D for Windows). Sample simulations were implemented for mold filling processes of precision titanium castings under gravity and different centrifugal casting techniques. The computation results show that the alloy melt has a much stronger mold filling ability for thin section castings under a centrifugal force field than that only under the gravity. A "return back" mold filling manner is showed to be a reasonable technique for centrifugal casting processes, especially for thin section precision castings.     

反重力铸造对高强度铝合金凝固组织影响的研究

采用反重力铸造方法生产高强度铝合金铸件已成为航空、航天领域内获得优质构件的重要途径。研究了反重力铸造对高强度铝合金ZL114A和ZL205A铸件凝固组织的影响。结果表明,合金的凝固组织存在着不同的位置效应,对于ZL114A合金铸件,冷端晶粒尺寸最小,靠近浇口处晶粒尺寸粗大。对于ZL205A合金铸件,随距浇口处距离的减少,枝晶间分布的网格状θ（Al2Cu）相逐渐由粗变细,α（Al）枝晶内分布的黑色点状T（Al12CuMn2）相逐渐减少。分析表明,在反重力铸造补缩压力相同的情况下,合金的凝固温度范围不同是造成凝固组织不同位置效应的主要原因。     

钛合金离心精密铸造充型过程计算机模拟

建立了离心力场下铸造充型流动的数学模型 ,在自行研制的三维铸件充型 /凝固模拟软件 (CASM 3DforWin dows)基础上 ,研制开发了相应的离心力场铸造充型的计算机模拟软件。对钛合金薄壁铸件在重力场下及不同离心精密铸造工艺条件下的充型过程进行了实例模拟计算。计算结果表明 :在离心力场下金属液的薄壁充型能力比重力浇注强得多 ,而“拐头反充”式离心浇注方式是一种合理的离心力场下的铸造工艺方案     

基于CAE分析的汽车齿轮室浇注系统的优化

利用铸造模拟软件对汽车齿轮室充型和凝固过程进行了数值模拟，预测了零件在铸造过程中可能出现缺陷的位置。以模拟结果为依据，对其浇注系统进行反复的修改和优化。在铸件最后凝固的地方大量增设溢流槽，满足铸型内气体的排放要求，同时增设多个内浇道，使得液态合金更加平稳向型腔内推进，以减少卷气对铸件质量的影响。模拟结果表明：改进后的方案中液态合金充型平稳，且零件的铸造缺陷明显减少，从而提高了铝合金压铸件的整体质量。     

钢液导热系数对大型钢锭凝固过程的影响

数值模拟是提高大型钢锭质量、优化浇铸工艺、降低实验费用和帮助缺陷诊断分析的重要手段之一.模拟结果是否可靠很大程度上取决于数学模型假设是否合理,合金热物性参数和边界条件的设置是否准确等因素.利用ProCAST铸造模拟软件,分析了钢液导热系数对钢锭充型和凝固过程中的温度分布、凝固时间和缩孔、疏松的影响规律.结果表明,导热系数的提高显著缩短钢锭整体凝固时间,增加钢锭中心产生缺陷的可能性,因此有必要在模拟计算之前准确测量该物性参数.另外,对于在同一模具中浇铸具有不同物性参数的各类合金,该结果为了解其凝固规律提供了参考.     

铸件充型凝固过程数值模拟发展现状

铸件内在质量很大程度上取决于铸件的充型和凝固过程。将计算流体力学、计算传热传质学和计算机可视化技术应用于铸造工艺设计 ,可以使铸造技术人员更清楚地了解铸件形成过程 ,快捷地确定较为合理的铸造工艺参数。本文对铸件充型和凝固过程的数学模型、计算方法及商品化软件方面的发展现状进行了综合评述 ,并展望了该领域的发展前景。     

铸件模数Mc对A357合金二次枝晶臂间距及致密度的影响

研究试样直径和铸件模数Mc与铸件二次枝晶臂间(SDAS)的关系，通过测试A357合金不同凝固条件下铸件不同部位的SDAS，得出砂型铸造凝固条件下SDAS与铸件模数M之间的关系式。研究了铸件模数等对铸件致密度的影响，确定了获得高致密度铸件的合理的凝固条件。     

铝合金铸件凝固过程效应力数值模拟

通过铝硅合金准固态力学行为和流变性能的测试，获得了该合金铸件凝固过程应力应变本构方程。并在此基础上开发了考虑材料高温力学性能，分析三维轴对称铸件凝固过程热粘弹塑性问题的热应力模拟程序，对带热节铝硅合金铸件的计算表明，计算结果与实验结果吻合较好。     

运用均衡凝固理论解决英国铸件的缩孔问题

用实例给出运用均衡凝固理论,特别是薄、宽、短矩型冒口颈解决英国铸造厂球墨铸铁件的缩孔问题.表明均衡凝固理论作为工艺设计的理论和方法对生产高品质铸件有普遍意义.对计算机凝固模拟进行了讨论.计算机凝固模拟软件可以帮助设计人员改进工艺设计,提高铸件品质.但是认为购置和应用了计算机凝固模拟软件就能产生立竿见影的效果是对计算机凝固模拟软件的误解.在未来很长时期内,计算机凝固模拟作为一个有力的工具,仍然需要有实际铸造工艺设计经验的专家使用才能发挥其作用与潜力,才能达到预期效果.计算机凝固模拟软件与铸造工艺设计的专家系统软件和人工智能软件相结合将能够更好地解决铸造工艺设计问题.     

压力场对ZL101铝合金消失模铸造性能的影响

采用自行研制的压力凝固试验装置,研究了ZL101铝合金消失模铸造过程中,不同的压力和加压速率对铸件性能的影响.试验结果表明,随着外加压力的增加.铸件的密度和力学性能逐步提高,孔隙率显著降低,当外加压力达到0.5MPa以上时,ZL101消失模铸件的力学性能提高趋缓;加压时,不同的加压速率对消失模铸件的密度及性能影响很大,当加压速率为0.003～0.030 MPa/s时,铝合金消失模铸件性能较好;由于在压力下凝固,ZL101铝合金消失模铸件针孔等缺陷减少、密度提高,铸件耐腐蚀性进一步提高.     

Modeling characteristics for solidification in single-crystal,investment-cast superalloys

Macroscopic traits of solidification such as thermal gradient, solidification rate, and other criteria functions were extracted from computer modeling data of a single-crystal, investment-cast superalloy. The thermal histories were used to predict the presence or absence of grain defects in the shaped castings. Freckle defects were found on castings with various processing parameters, even though the traditional microstructural defect map predicted no freckles and a consistent microstructure. The findings suggest that the traditional defect map criteria are insufficient to accurately describe the formation of these and other single-crystal grain defects. Hence, additional criteria for porosity formation and other phenomena were investigated and found to be sensitive to changes in solidification conditions and grain defect formation. The additional functions were found to be necessary to fully capture the total energy of all solidification phenomena. When these functions are used in conjunction with the traits of the microstructural defect map, the prediction of defects in single-crystal castings can more accurately describe solidification under the stringent requirements of single-crystal turbine components.     

采用温度回升法对任意结晶区间的铸件凝固结晶潜热的数值计算

铸件凝固结晶潜热的释放行为与凝固传热、溶质传输及铸造合金种类与成分等诸多因素有关，合金凝固过程中其温度、固相体积分数与液相成分(T-fs—CL)三者之间一般存在着非线性强耦合关系．采用合金凝固传输统一模型及温度回升(补偿)法提出的处理任意结晶温度区间(包括零结晶区间)凝固潜热释放问题的数值迭代计算方法，对不同合金成分与不同固相反扩散效应的二维Al—Cu合金铸件定向凝固传输过程进行了数值计算，表明该方法对于从纯金属到共晶成分的不同成分合金及从Scheil模型到Lever-Rule模型之间的任意凝固模式均是有效的．将该方法推广应用于叶片铸件三维凝固传输过程的T-fs—CL耦合数值模拟仍显示出高的计算效率．通过对计算结果进行的三维图像数据处理，展示了铸件几何形状对凝固传输行为的重要影响．     

日本铜合金金属型生产铸铁件状况

铸铁件金属型铸造技术已在工业发达国家得到应用，铜合金金属型生产铸铁件在日本得到很快发展。本文介绍了铜合金金属型的特点及其对所生产的球墨铸铁件、灰铸铁件性能的影响；比较详细地介绍了日本铜合金金属型生产铸铁件的状况。     

横向翻转浇注工艺铸造耐压外壳铝合金铸件

从铸造工艺、工装设计上进行改进创新,采用横向翻转浇注工艺铸造耐压外壳铸件。铸件在凝固过程中能从冒口不断地得到液态金属的补充,实现定向凝固。减少铝液二次氧化带来的夹渣,使铝液充型过程平稳,不易发生紊流。解决了铸件法兰密封面弥散性针孔和铸件轴密封处及凸台因壁厚不均产生缩松造成气密性差的问题。在实际铸造过程中通过对模具预热温度、合金浇注温度、翻转速度进行控制,提高了铸件整体质量。通过几年批量生产验证,一次检漏合格率达到99．8％。     

铝镁合金消失模铸造技术研究及应用新进展

阐述了铝镁合金消失模铸造技术的现状,重点介绍了铝镁合金消失模铸造在浇注充型、振动凝固、压力凝固、壳型铸造等技术研究方面的新进展。作者认为,消失模铸造铝镁合金,必须重点解决针孔、缩松等缺陷,提高液态合金的充型能力和铸件的力学性能。     

A study of thermal parameters and interdendritic feeding in lost foam casting

Thermal parameter-based criterion functions are of great practical importance to predict dispersed microporosity in castings. Using an experimental approach, the present study is a pioneering application of the thermal parameter-based criterion functions to predict the microporosity formation in lost foam casting (LFC) of A356 alloy. A series of plate castings with controlled hydrogen content were made with various thermal conditions by varying the dimensions of feeders and in gate design. Extensive analysis of the thermal parameters shows that changing the gate and feeder design modifies the distribution of the thermal parameters; furthermore, it influences the distribution of microporosity along the central line of the plate castings. The thermal parameters and criterion functions based on Darcy’s law show consistency, thus supporting the interdendritic feeding mechanism of microporosity formation. The criterion functions such as Niyama, LCC, and KCL can be used to predict microporosity formation during solidification of LFC, depending on the hydrogen content in the casting. The limitation of the interdendritic feeding mechanism and the effect of hydrogen on the gas pore formation are also discussed.     

Inference of optimal speed for sound centrifugal casting of Al-12Si alloys

True centrifugal casting is a standard casting technique for the manufacture of hollow, intricate and sound castings without the use of cores. The molten metal or alloy poured into the rotating mold forms a hollow casting as the centrifugal forces lift the liquid along the mold inner surface. When a mold is rotated at low and very high speeds defects are found in the final castings. Obtaining the critical speed for sound castings should not be a matter of guess or based on experience. The defects in the casting are mainly due to the behavior of the molten metal during the teeming and solidification process. Motion of molten metal at various speeds and its effect during casting are addressed in this paper. Eutectic Al-12Si alloy is taken as an experiment fluid and its performance during various rotational speeds is discussed.