压铸条件和淬火时效对GD—AlSi9Cu3合金力学性能的影响

通过改变压铸工艺参数和淬火时效，测定在静态载荷和动态循环载荷下ＧＤＡｌＳｉ９Ｃｕ３合金的力学性能和断裂力学性能，试验所获得的数据可用来估算压铸件的失效风险率     

Distortion Behavior of a Heavy Hydro Turbine Blade Casting During Forced Air Cooling in Normalizing Treatment Process

Distortion behavior of blade castings in heat treatment process determines their geometrical accuracy, and improper control of it may result in additional repair, shape righting, or even rejection. This article presents a novel approach for discovering the distortion behavior of heavy blade castings during heat treatment process in production. Real-time measurements of distortion and temperature field of a heavy hydro turbine blade casting weighted 17?ton during forced air cooling in normalizing treatment process were carried out by using deformation measurement instruments and an infrared thermal imaging camera. The distortion processes of the typical locations of blade and the temperature field of the blade were obtained. One corner on the blade outlet edge side exhibits variation of distortion with two peaks and a valley. The range reaches 97?mm and the final distortion value is 76?mm. The maximum temperature difference on blade surface reaches 460?°C after 80?min of cooling. Influences of thermal stress and phase transformation stress on the distortion of the blade were elucidated and discussed. The results are of great significance for the understanding and control of the distortion behavior of hydro turbine blades in heat treatment.     

压铸件包紧力的动态分析

铝合金压铸件包紧力从模具内的冷却开始到顶出铸件的过程中,始终是动态变化的。模具与合金随温度变化对应有不同的热膨胀系数,模具设计时应根据不同压铸合金选择不同的收缩率。压铸生产中因为温度变化造成的顶出铸件故障可以通过调整温度来解决。     

Influence of technical parameters on strength and ductility of AlSi9Cu3 alloys in squeeze casting

An orthogonal test was conducted to investigate the influence of technical parameters of squeeze casting on the strength and ductility of AlSi9Cu3 alloys. The experimental results showed that when the forming pressure was higher than 65 MPa, the strength (σ_b) of AlSi9Cu3 alloys decreased with the forming pressure and pouring temperature increasing, whereas σ_b increased with the increase of filling velocity and mould preheating temperature. The ductility (δ) by alloy was improved by increasing the forming pressure and filling velocity, but decreased with pouring temperature increasing. When the mould preheating temperature increased, the ductility increased first, and then decreased. Under the optimized parameters of pouring temperature 730 °C, forming pressure 75 MPa, filling velocity 0.50 m/s, and mould preheating temperature 220 °C, the tensile strength, elongation, and hardness of AlSi9Cu3 alloys obtained in squeeze casting were improved by 16.7%, 9.1%, and 10.1%, respectively, as compared with those of sand castings.     

铝合金变速箱外壳压铸模设计及工艺分析

针对铝合金铸件在压铸充填过程中常伴有气孔、缩孔、冷隔等缺陷的现象,以汽车铝合金变速箱外壳为例,分析变速箱外壳的结构特征,对其浇注系统、冷却系统、抽芯结构进行设计,确定最佳工艺参数,经过试验与分析,最终经过实际压铸生产验证,确定了工艺方案的合理性。结果表明:当定模温度为200℃、动模为220℃、铝液浇注温度为670℃、慢压射速度为0.18 m/s、快压射速度为4.5 m/s、内浇道的压射速度为48 m/s、留模时间为30 s时,铸件成形品质较好。合理压铸工艺设计不仅能提高生产效率以及产品的合格率,还能简化模具设计制造流程,减少模具开发成本。     

镁合金压铸件的生产

叙述了镁合金的特性,并讨论了镁合金贮存、熔炼、精炼以及压铸模具等对生产优质镁压铸件的影响。     

镁合金方向盘骨架压铸过程的数值模拟

采用铸造模拟软件AnyCasting对镁合金方向盘的低压铸造工艺进行模拟。结果表明,调整好上下模的初始温度及浇注温度,增设冷却水道,可以得到铸造质量良好的铸件。当浇注温度为680℃,上下模初始温度分别为200℃和350℃开启冷却水道时铸件缺陷较少,质量较好。     

汽车轻量化先进铸造技术

全面评述了用于汽车轻量化的铸造铝和镁合金及铸造工艺的发展.已开发的汽车用新型合金有耐磨铝合金、抗蠕变镁合金及高强度/韧性镁合金.在工艺前沿方面,开发了真空辅助压铸和高真空压铸技术,用于生产高整体性的车体和底盘零件.用低压金属型铸造工艺生产结构用薄壁空心铸件.包覆铸造技术不断得到发展,使用混合材料设计汽车的子系统,例如发动机支架、仪表板梁成为可能.开发的模拟工具用来预测,不同组分之间的界面相互反应和包覆铸造系统的结构完整性,并且已被铸造实验证实.     

AlSi7Mg合金半固态压铸件热处理强化机理研究

对AlSi7Mg合金(A356)半固态压铸件和液态压铸件进行了不同工艺的固溶与时效热处理，分析了其显微组织与疏松度，测定了硬度、拉伸强度及延伸率等力学性能。实验得出，铝合金半固态压铸件原始态的力学性能优于液态压铸件，并且半固态压铸件时效强化效果尤其明显，拉伸强度可达330MPa以上，延伸率10％以上。这主要是由于半固态压铸件比液压件具有更加致密，且为球状的非树枝晶组织。铝合金半固态压铸件时效强化，机理主要归于弥散析出Mg2Si强化相。     

镁合金压铸用模具的应力场和变形数值模拟

通过建立有限差分/有限元集成应力分析系统,模拟了镁合金压铸用模具在压铸过程承受的应力场和变形.首先采用有限差分法模拟压铸系统的三维温度场,然后利用温度载荷转换接口将温度载荷转换到模拟对象有限元模型,再计算应力场和变形.应力计算中能够处理压铸过程的合模和开模过程中的边界约束条件变化.通过分析模具在合模过程及开模时刻的应力变化和变形趋势,对铸件尺寸精确度进行了预测,对压铸过程工艺参数的优化提出了见解.     

铝合金超低速压铸工艺参数对铸件性能的影响

应用具有不同浇道尺寸的简单圆形拉伸试样研究压铸工艺参数对ADC12铝合金超低速压铸件性能的影响,以优化超低速压铸工艺及其参数。试验结果表明,各种超低速压铸工艺条件下铸件的密度都比普通压铸高,影响铸件性能的主要因素不再是气孔,而是合金的凝固组织及飞溅凝固片和氧化夹杂等缺陷。在超低速实验条件下,浇道截面尺寸越大,对铸件性能影响越大,不同浇道尺寸对应有最佳浇道速度,在试验的三种浇道条件下,最佳浇道速度均低于0.6m/s;模具预热温度、浇注温度、铸造压力都有最佳值;在无增压条件下,仅采用较大的压射压力也可使铸件获得较好的力学性能。     

铸造Al-Si合金熔体处理——晶粒细化

对亚共晶Ａｌ－Ｓｉ铸造合金进行细化处理已成为一种基本操作。中间合金（Ａｌ－Ｔｉ,Ａｌ－Ｔｉ－Ｂ和Ａｌ－Ｂ合金）在亚共晶Ａｌ－Ｓｉ铸造合金中与在工业纯铝和变形铝合金中的晶粒细化行为存在较大的差异。Ａｌ－３Ｔｉ－３Ｂ,Ａｌ－３Ｂ中间合金在Ａｌ－Ｓｉ铸造合金中表现出优异的晶粒细化效应,Ｓｉ与晶粒细化剂的交互作用在其中扮演着重要的角色。通过炉前对熔体进行快速热分析可以对晶粒细化效果和变质程度进行评价和预测,继而控制熔体处理的质量。对于亚共晶Ａｌ－Ｓｉ铸造合金,归纳起来有四种晶粒细化机理：包晶反应理论、共晶反应理论、硼化物颗粒理论和超形核理论。仅对Ａｌ－Ｓｉ铸造合金细化处理的最新进展、Ｓｉ与晶粒细化剂的交互作用和晶粒细化机理进行综合评述     

基于有限元的镁合金、铝合金压铸用模具热机耦合分析

基于PROCAST压铸模块热-机耦合分析系统,分别针对A356和AZ91B两种铸件材质,采用H13模具钢,对比分析了铝合金和镁合金压铸件及压铸模具温度场和应力场,得出了压铸镁合金模具温度场及应力场的分布特征,对指导镁合金压铸模具设计及生产提出了见解。     

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。     

Effects of cooling rates on microporosity in DC casting Al-Li alloy

During the direct chill(DC)casting process,primary cooling from the mold and bottom block,and secondary cooling from the waterjets produce a concave solid shell.The depth of this liquid pocket and mushy zone not only depends on the solidification range of the alloy but also the boundary conditions such as cooling rates.Al-Li alloys solidify in a long solidification range increasing the susceptibility of porosity nucleation in the semi-solid region.In this study,the effects of cooling rate on the porosity formation were quantified for the large ingot casting using X-ray computed tomography(XCT).By characterizing pore size distributions at four different cooling conditions,the correlation between the mechanical properties at both room and high temperatures and the microstructure features was identified.The constitutive equations were constructed.It is found that increasing the cooling rate reduces the grain size,increases the number density of micropores,and minimizes the number of large pores,thereby improving the mechanical performance.Therefore,long mushy zones and deep liquid pockets in Al-Li alloys can be effectively controlled by controlling the boundary conditions of the DC casting solidification process,thereby obtaining castings with excellent mechanical properties.     

真空压铸工艺参数对AM50镁合金力学性能的影响规律

采用阶梯试验模具及AM50合金,进行了系统的真空压铸试验,实测了不同厚度的阶梯试样在不同工艺条件下的密度及力学性能,研究了高真空压铸工艺参数对AM50镁合金力学性能的影响规律.结果表明,随着型腔真空压力的降低,铸件密度、抗拉强度和伸长率均随之提高;铸造压力对力学性能的影响在真空压铸和常规压铸中遵循基本相同的规律,即增大铸造压力可以使铸件的致密程度、抗拉强度、屈服强度和伸长率得到提高;随着高速速度的增大,薄壁铸件的抗拉强度、屈服强度和伸长率均表现出明显的增加,这一点与常规压铸的规律相反.结合高真空和高速工艺,可以使薄壁铸件的抗拉强度和伸长率得到较为明显的提升.     

Advanced casting technologies for lightweight automotive applications

This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications.Wear-resistant aluminum alloys,creep-resistant and high strength/ductility magnesium alloys have been developed for automotive applications.On the process front,vacuum-assisted die casting and high vacuum die casting technologies have been developed for high-integrity body and chassis applications.Thin-wall and hollow casting components are being produced by low-pressure die casting processes for structural applications.Overcasting technology is gaining traction and has enabled mixed material designs for automotive sub-systems such as engine cradles and instrument panel beams.Simulation tools developed to predict the interfacial interactions of the dissimilar components and the structural integrity of the overcast systems are being validated in the casting trials.     

铝合金半固态压铸工艺参数及性能研究

应用具有不同厚度的简单板材模具来系统研究压铸工艺参数对A356铝合金半固态压铸件性能的影响,以优化半固态压铸工艺及其参数.试验结果表明,对A356铝合金半固态压铸,其性能随压射压力的增大而提高,当压射压力大于100 MPa,则性能基本上不再提高.压铸速度过小或过大会降低压铸件的性能.另外建压时间、坯料加热温度、模具预热温度以及脱模剂等参数对半固态压铸件性能也有明显的影响.     

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。     

Modeling of high temperature- and diffusion-controlled die soldering in aluminum high pressure die casting

Soldering of cast alloys to the dies has been a continuing source of die surface damage in the aluminum die-casting industry. To reduce the repair and maintenance costs, an approach to modeling the damage and predicting the die lifetime is required. The aim of the present study is the estimation of the die lifetime based on a quantitative analysis of die soldering in the framework of the numerical simulations of the die-casting process.Full 3D simulations of the process, including the filling, solidification, and the die cooling, are carried out using the casting simulation software MAGMAsoft. The resulting transient temperature fields on the die surface and in the casting are then post-processed to estimate the die soldering.The present work deals only with the metallurgical/chemical kind of soldering which occurs at high temperatures and involves formation and growth of intermetallic layers. The die-soldering model combines two approaches available in literature, describing the two aspects of die soldering: the growth of the intermetallic layer, and the thermal and metallurgical conditions in the layer that lead to the die soldering. The theoretical model is then extended with the treatment of the intermetallic layer growth controlled by the idealized effective diffusivity and with the treatment of solder strength dependent on the temperature and liquid fraction within the layer. The solder strength locally on the die surface is calculated as a function of the number of die-casting cycles. This also provides the estimation of the die lifetime defined as the number of cycles until the critical solder strength level is reached.Proper validation of the model is required, and the model parameters (the critical solder strength value, among others) need to be calibrated by measurements and data from the die-casting industry.As an example, the model is applied to several cases of high pressure die casting (HPDC) where A380 alloy parts are cast in the H13 steel die. The predicted locations of the higher strength of soldering appear in the “hot spot” areas of the die surface in agreement with the reports in literature. The influence of several casting process parameters such as cooling/spraying efficiency and other parameters that control the thermal history of the die and the casting is in agreement with the expected behavior.