Forming Mechanism of Gaseous Defect in Ti-48Al-2Cr-2Nb Exhaust Valves Formed with Permanent Mold Centrifugal Casting Method

A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48A1-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance. The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.

Analysis of deformation characteristic in multi-way loading forming process of aluminum alloy cross valve based on finite element model

The deformation characteristic in the forming process of aluminum alloy 7075 cross valve under multi-way loading was investigated by numerical simulation method. The results indicate that there exist 4 deformation patterns in the multi-way loading forming process of cross valve, such as forward extrusion, backward extrusion, forward-lateral extrusion and backward-lateral extrusion; one or several patterns occur at different forming stages depending on loading path. In general, the main deformation pattern is forward extrusion or backward extrusion at the initial stage; the main deformation pattern is backward extrusion at the intermediate stage, and the backward extrusion and forward-lateral extrusion occur at the final stage. In order to improve the cavity fill and reduce the forming defects, the lateral extrusion deformation should be increased at the initial and intermediate stages, and the forward extrusion deformation at the final forging stage should be reduced or avoided.

Finite element simulation of aluminum alloy cross valve forming by multi-way loading

Deformation behavior,temperature evolution and coupled effects have a significant influence on forming process and quality of component formed,which are very complex in forming process of aluminum alloy 7075 cross valve under multi-way loading due to the complexity of loading path and the multiplicity of associated processing parameters.A model of the process was developed under DFEORM-3D environment based on the coupled thermo-mechanical finite element method.The comparison between two process models,the conventional isothermal process model and the non-isothermal process model developed in this study,was carried out,and the results indicate that the thermal events play an important role in the aluminum alloy forming process under multi-way loading.The distributions and evolutions of the temperature field and strain filed are obtained by non-isothermal process simulation.The plastic zone and its extension in forming process of cross valve were analyzed.The results may provide guidelines for the determination of multi-way loading forming scheme and loading conditions of the forming cross valve components.

基于Anycasting的汽轮机阀体浇注系统优化模拟

分析了生产中铸造质量要求较高的汽轮机阀体的浇注系统,并对其进行改进。运用铸造模拟仿真软件Anycasting对原浇注系统及改进后浇注系统进行模拟仿真。实验结果表明,改进后的浇注系统能获得优良的铸件,并节约了大量钢材。研究结论对大型铸件工艺设计以及实际生产具有指导意义。

Design and Verification of an Auxiliary System for High Vacuum Die Casting

Vacuum die casting is the optimal method to produce high quality aluminum alloy components.At present,there are still very few systematic studies on vacuum die casting theory and equipment design.On the basis of the existing theories of the vacuum die casting pumping and venting systems,a simplified model is established in this research.The model has an aggregate unit consisted of ＂vacuum pump ＋ buffer tank＂ and a cylindrical container（including the shot sleeve,cavity and exhaust channel）.The theoretical analysis is carried out between the cavity pressure and the pumping time under different volume models.An auxiliary system for high vacuum die casting is designed based on the above analysis.This system is composed of a vacuum control machine and a new vacuum stop valve.The machine has a human-computer control mode with ＂programmable logic controller（PLC） ＋ touch screen＂ and a real-time monitoring function of vacuum degree for buffer tank and die cavity.The vacuum stop valve with the ＂compressed gas ＋ piston rod ＋ labyrinth groove＂ structure can realize the function of whole-process vacuum venting.The new system shows great advantages on vacuuming the cavity with a much faster speed by making tests on an existing die casting mold and a 250 t die casting machine.A die cavity pressure less than 10 kPa can be reached within 0.8 s in the experiment and the porosity of castings can be greatly decreased.The systematic studies on vacuum die casting theory and equipment have a great guiding significance for high vacuum die casting,and can also be applied to other high vacuum forming in related theoretical and practical research.

基于ProCAST的铜合金通海阀铸造工艺优化

目的结合ZCuAl7-7-4-2合金的铸造特性,研究复杂薄壁铸件通海阀的铸造成形工艺,探究初始浇注方案下的充型、凝固规律,优化工艺并提出合理的铸造工艺方案。方法根据通海阀的结构特点,设计出底注雨淋式浇注系统,并利用流体力学理论和截面积比值法确定浇注系统的具体参数,使用ProCAST软件研究不同工艺参数、冒口尺寸对铸件质量的影响,以得到最优的浇注方案。结果在底注雨淋式浇注系统的充型过程中,金属液温度分布均匀、流速平稳,凝固顺序合理,所得铸件缺陷较少,其中疏松缩孔体积为0.63 mm3,且集中分布在阀盖处。优化浇注温度和浇注速度能够有效减少铸造缺陷,优化出的最佳浇注工艺参数组合如下:浇注温度为1180℃,浇注速度为3.5 kg/s。结合该模拟结果改进冒口尺寸后,彻底消除了铸件的铸造缺陷。结论优化工艺参数和浇注系统设计能够有效提高铸件的生产质量,便于铸件的一次成形,对实际生产提供指导。

基于Experto-ViewCast的高压阀壳熔模铸造工艺研究

运用Experto-ViewCast软件对某304不锈钢阀壳的熔模铸造工艺方案进行了设计。通过对凝固过程的模拟计算,确定该铸件容易出现缺陷的部位;针对缺陷所在的位置设计铸造工艺,并通过凝固模拟确定设计的铸造工艺能有效的消除铸件中的收缩缺陷;对铸件应力场与应变场进行模拟计算,检验设计的方案会不会造成铸件的裂纹缺陷,完善铸造工艺的设计。经某生产企业生产实践,证明按照该设计方案生产的阀壳没有缩松、缩孔、裂纹等缺陷,经水压试验未发现渗漏现象,能获得理想的铸件。

基于ProCAST的汽车挂车阀压铸工艺优化

某汽车挂车阀由压力铸造工艺制造生产,铸件的合格率较低。通过对阀体结构进行充分剖析,并利用专业模拟分析软件ProCAST,对其压铸充型过程和凝固过程进行仿真模拟。根据模拟结果,对铸件模具工艺进行优化和生产验证。结果表明,优化后的压铸工艺能够改善产品的缺陷,提高产品的合格率。

基于ProCAST的超临界阀体铸造工艺优化

超临界阀体作为超临界发电机组的重要部件,严格控制产品的内部质量是关键。本文以阀体为研究对象,确定了阀体的铸造工艺,用Pro-E三维设计软件完成了阀体的三维模型设计,对其铸造工艺进行了数值模拟,成功预测了铸件缩孔、疏松缺陷,并有针对性的提出了工艺改进意见,优化了铸造工艺,成功完成了产品的生产制作。

基于ProCAST吸阀壳体铸铝件铸造工艺设计

以吸阀壳体铸件为研究对象,通过对铸件材质、形状、大小及结构特点进行详细分析,提出合理的铸造工艺设计方案。运用ProCAST数值模拟软件进行铸造工艺数值模拟,对模拟结果的充型过程、缺陷分布以及工艺改进性等方面进行分析。结果表明,采用平做立浇工艺、开放式底注式浇注系统,再添加冒口及冷铁,使铸件形成一个自下而上的顺序凝固,可消除铸件存在的缩松、缩孔缺陷,确保得到符合使用条件的合格铸件。

Modeling of Filling and Solidification Process for TiAl Exhaust Valves During Suction Casting

Investment and suction casting （ISC） represents an economic and promising process route to fabricate auto-motive exhaust valves of γ-TiAI based alloys, but information available on the metal flow and the temperature changeseduring mould filling and solidification process for the ISC process is meager. A sequentially coupled mathematical flow-thermal model, based on the commercial finite-volume/finite-difference code FLOW-3D and the finite-element code PROCAST, has been developed to investigate the ISC process. In term of calcu-lating the flow and temperature fields during the filling and solidification stages, potential defects including the gas bubbles and the surface air entrainment occurred in the mould filling process and the shrinkage porosities formed in the solidification process are predicted and the reasons for the formation of these defects are also analyzed. The effects of filling pressure difference control methods and moulds on gas bubble and surface air entrainment behavior are presented. It is found that by changing the filling pressure difference control methods from general suction casting to ＂air leakage＂ suction casting and reducing air leakage flow rates, the gas bubbles are eliminated effectively, and the surface air entrainment attenuate dramatically. With resort to a mould with a tetragonal runner, the surface air entrainment decrease to the lowest level. Finally, the water analogue and suction casting experiments of exhaust valves are implemented for further validation of the simulation results.

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。

Application of Numerical Simulation Technique to Casting Process of Valve Block

The numerical simulation technique was applied to the casting process of a valve-type part. The mold-filling and solidification stages of the casting were numerically analyzed. The filling behavior, solidification sequence, and thermal stress distribution were reproduced and the possible defects, such as cold shut and shrinkage, were predicted. Based on the simulation result, the double-gating system was replaced by a single-gating system. Meanwhile, the chills were used to regulate the solidification sequence of casting. To eliminate the cracks in the casting, the sand core was converted into a canulate one. By modifying the original process, the defects were eliminated and the casting with good quality was obtained.

基于数值模拟的通海阀铜合金铸件工艺优化

针对某船舶通海阀在铸造过程中易产生缩孔、缩松等缺陷问题,以Cu-7Ni-7Al-4Fe-2Mn合金通海阀铸件为研究对象,使用三维制图软件UG构建了铸件3D模型,并结合通海阀铸件的结构特性,设计了底注式浇注系统。利用数值模拟软件模拟了铸件的砂型铸造过程,分析了可能出现缩孔、缩松缺陷的位置,优化了通海阀铸件的浇注系统。研究了浇注温度、浇注时间、铸型预热温度等参数对铸件缩孔、缩松率的影响规律,结合正交试验方法优化出匹配的铸造工艺参数。研究结果表明,工艺参数对通海阀铸件缩孔率的影响程度从大到小依次是浇注时间、铸型预热温度、浇注温度。优化后的工艺参数分别为浇注温度1 200℃,浇注时间30 s,铸型预热温度35℃。通过在铸造缺陷较多的部位增大冒口尺寸,有效减少了缩孔、缩松铸造缺陷的产生。

蠕墨铸铁抗高温冲击磨损性能的研究

蠕墨铸铁是高功率密度柴油机燃烧室气缸盖的主要制作材料,随着转速、爆压、功率密度的不断升高,气门与蠕铁气门座之间的频繁碰撞冲击导致冲击磨损加剧。利用自制冲击磨损试验机进行了不同环境温度(室温、300、400、500℃)和不同冲击频率(10、12、14 Hz)下的冲击磨损试验。结果发现,蠕墨铸铁的磨损量随着冲击次数的增加先快速增大随后趋于缓慢;随着冲击频率、工况温度的升高,磨损量先缓慢增大随后快速增大。材料冲击表面具有凹坑、犁沟、材料堆积的现象,且随着冲击次数、冲击频率、环境温度的升高,磨损面出现大量片状剥落层以及塑性变形。磨损机制主要以磨粒磨损和接触疲劳磨损为主,同时伴有轻微的黏着磨损和冲蚀磨损。

火力发电厂蒸汽管道ZG15Cr1Mo1V铸造水压堵阀裂纹缺陷成因分析

铸造水压堵阀裂纹缺陷已是火电金属监督检验典型问题之一,为探究裂纹缺陷成因,指导现场检验和缺陷处理,本文以ZG15Cr1Mo1V主汽和再热热段堵阀大规模裂纹缺陷为研究对象,从材料特性、水压堵阀结构特征、制造工艺、服役特点等方面展开分析。结果表明:堵阀制造阶段已存在微小原始缺陷,运行服役后扩展形成裂纹缺陷;材料特性和制造工艺决定其存在原始缺陷的倾向较大;分型铸造方式导致阀体两侧缺陷差异明显;水压试验时堵阀仅前侧受力的状况造成阀体前后侧裂纹缺陷差异;相贯线过渡区域、口环连接区域易形成缩松、微裂纹等缺陷,且过渡区域多为应力集中区,导致裂纹缺陷易在此富集与扩展;制造热处理和运行服役阶段温度、压力的作用,促使裂纹缺陷的生成与扩展。

袖阀管应用于灌注桩后注浆的现场试验

针对传统的灌注桩后注浆技术存在的不能多次压浆的问题,将袖阀管注浆技术与灌注桩后注浆技术结合,研究探讨将袖阀管应用于灌注桩后注浆施工。在雄安新区某工点通过开展现场试验,发现袖阀管注浆容易出现注浆管连接耗时长、注浆器与射浆孔匹配难度大、袖阀管堵塞等问题,采用相关技术措施后,袖阀管注浆施工顺利完成,验证袖阀管注浆应用于灌注桩侧、桩端加强的可行性。

一种304不锈钢圆球阀的熔模铸造工艺优化

在304不锈钢圆球阀传统的熔模铸造生产过程中,采用经验确定的工艺参数往往无法完全消除缺陷,在阀体与法兰转角处存在一些缩孔,严重影响产品质量。利用ProCAST软件对不锈钢圆球阀铸件的成形进行了仿真和缺陷分析,发现传统工艺方法在阀体与法兰转角处存在较多大而集中的缩松。重新设计浇注系统结构、调整工艺参数,设计了正交试验方案。结果显示,在浇注温度1550℃、浇注速度1.0 kg/s、型壳预热温度1150℃工艺参数下,阀体与法兰转角处的缩孔消失。

阀壳类铸钢件防漂芯研究及应用

通过对阀壳类铸钢件典型缺陷的分析,找到造型下芯不稳定、芯骨刚度不足导致砂芯变形或浇注过程砂芯上浮的根本原因,提供一种新型双排芯骨的设计方法,通过砂芯的芯头固定、合箱验箱、反变形量多种措施的结合,解决了阀壳类铸钢件的漂芯问题,从而提高了产品的质量。

45钢阀体挤压铸造模具设计

45钢阀体挤压铸造模具设计为组合式模具。模具的模芯和冲头采用性能较高的H13钢，模套及定位结构部分采用45钢或40Cr钢。成形设备采用专用的挤压铸造液压机，最大挤压力为1500kN，最大锁模力为2000kN。上、下冲头取2。的起模斜度，侧冲头取了0．5。的起模斜度，冲头速度为0．30～0．35m／s。顶出方式采用下冲头上行直接顶出，冲头与模具之间的单边配合间隙取0．16～0．2mm。采用管道式冷却和插管式冷却相结合，对模具受到较大热应力的部分进行冷却。为了保证制件高度方向的精度，在分型面十字方位上开设有4个溢流槽。为了提高模具的抗熔焊能力，采用自制的硅藻土类绝热涂料，喷涂厚度为0．2～0．5mm。