铝合金拉伸试样金属型模具优化

设计了一种采用不同浇注系统的铝合金拉伸试样金属型模具,以减少铸件的缺陷、提升铸件的质量。利用Pro CAST对铸造过程进行模拟,对拉伸试样充型凝固过程中的各物理场进行分析,预测其铸造缺陷和二次枝晶臂间距。确定优化模具的合理性后进行实验验证。实验结果表明:优化模具能够有效阻止前沿含有氧化薄膜的金属熔体进入型腔;优化模具的扇形流道,使充型过程平稳,避免型腔内出现卷气现象;试样能够实现顺序凝固,成功消除试样中的缩松、缩孔缺陷;优化模具试样的二次枝晶臂间距为33. 2μm,抗拉强度为215 N·mm-2,屈服强度为173 N·mm-2,断后伸长率为4. 5%。优化后的模具能有效地减少拉伸试样中的铸造缺陷并减小二次枝晶臂间距,提升了拉伸试样的力学性能。     

TiAl基合金连杆件底漏式真空吸铸数值模拟

利用ProCAST数值模拟技术对TiAl合金汽车发动机连杆铸件底漏式真空吸铸过程的充型过程、凝固过程、缩孔缩松缺陷形成进行了模拟。研究了底漏式真空吸铸的几个主要参数,如吸口直径、浇注温度、浇注速度,对连杆铸件充型凝固过程和缩孔、缩松缺陷的影响规律,得到了TiAl合金底漏式真空吸铸的优化工艺参数图。     

1.5MW风力发电机组轮毂球墨铸铁件的浇注系统设计

为了解决1.5 MW风力发电机组轮毂球墨铸铁件在铸造过程中容易产生缩松缩孔缺陷的问题,采用计算机数值模拟技术对轮毂的浇注系统进行优化设计分析。研究了轮毂球墨铸铁件的凝固特点,明确了铸件产生缺陷的原因,利用三维造型软件和铸造模拟软件对风力发电机轮毂铸件凝固过程的温度场进行模拟,得出了铸造风机轮毂的优化工艺方案。模拟结果显示,优化工艺可以明显地改善风机轮毂在铸造过程中产生的缩孔缺陷。     

Optimization of investment casting process for K477 superalloy aero-engine turbine nozzle by simulation and experiment

In order to reduce the shrinkage porosity of nickel-based superalloy castings in the investment casting process, the effects of different gating systems on mold filling, solidification process, and prediction of shrinkage porosity of aero-engine turbine nozzle castings were investigated by simulation and experimental methods. Results show that the design of the vertical runner would cause greater turbulence of the melt in the riser during the mold filling process, and the outer runner is not necessary. With the decrease in number of runners, the hot spot moves down towards the casting, and the shrinkage and porosity defects are formed in the casting below the riser. In the original designs, a certain tendency of shrinkage and porosity defect is found in the vanes, inner rings, and outer rings of the castings by both simulation prediction and experiment. Finally, based on the processing optimization, the aero-engine turbine nozzle casting with no shrinkage and porosity defects is obtained.

     

镁合金轮毂低压铸造数值模拟及缺陷预测

以某镁合金汽车轮毂为研究时象,运用专业铸造模拟分析软件,进行低压铸造数值模拟,研究了填充和凝固过程中温度场的分布,预测了在此过程可能出现的缺陷.模拟结果显示.轮毂中心部位也可能产生缩松,并发现通过降低或者提高充型速度并不能有效解决问题,通过在模具上模增加局部冷却水道,能够较好地改善整体冷却顺序,有效减小轮毂中心的缩松现象.     

低碳合金钢引导轮的V法铸造工艺

分析了V法铸造的浇注充型过程,介绍了引导轮铸件的技术要求,设计了V法工艺的浇注系统和冒口,确定了铸件浇注温度以及造型和浇注过程等参数。生产结果表明,采用V法工艺生产的引导轮铸件性能达到技术要求,其内部无缩孔、缩松、砂眼、夹砂等缺陷,铸件表面质量显著提高,生产成本降低,产品得到客户认可。     

设计合理的浇注方案以保证充填和补缩--熔模铸件铸造方案设计系列讲座之一

合理的浇注速度和静压头、型壳透气性、浇注时的金属液温度和型壳温度、避免浇注时型壳憋气、避免浇注中途停顿以及保证充填平稳等是保证充填的重要影响因素。避免铸件出现缩孔(松)的措施有缩孔转移和缩孔分散两种措施，应根据不同铸件结构合理应用。     

Melt flow in a mushy zone – barrier effect of intermetallic phases

Abstract

Iron and manganese are common impurity elements in cast aluminium alloys, especially in secondary aluminium. During casting Fe/Mn-containing intermetallics are formed between the aluminium dendrites, which cause porosity and shrinkage defects. In this paper an experimental study on the influence of controlled convection during solidification on the spatial arrangement of intermetallic phases and their interaction with the dendritic microstructure in Al–7Si–1Fe (AlSiFe) and Al–7Si–1Mn (AlSiMn) alloys (wt-%) is presented. Forced convection is induced by a rotating magnetic field. The alloys are solidified directionally over a range of constant solidification velocities (0·015–0·18 mm s^–1) at a constant temperature gradient G of 3 K mm^–1. The results indicate that the primary spacing and the secondary dendrite arm spacing are affected by the presence of Fe and Mn intermetallic phases. In samples solidified under forced convections the primary dendrite arm spacing did not depend on the solidification velocity and no obvious fluid flow effect on the secondary spacing could be detected. These observations are in contrast to Fe and Mn free alloys. It seems that the intermetallics act as a barrier for the flow into the mushy zone.     

太阳轮的熔模铸造工艺

对一种太阳轮铸件采用硅溶胶制壳工艺,通过设计合理的浇注系统,确定合理的脱蜡工艺、型壳焙烧工艺和浇注工艺,有效解决了该太阳轮铸件浇口根部热节处缩孔缩松严重的问题,成功浇注出该系列太阳轮铸件。     

铝合金轮毂连接盘挤压铸造数值模拟

采用ProCAST软件对6061铝合金轮毂连接盘挤压铸造过程进行模拟。研究了浇注温度、模具预热温度、比压对铸件缩孔缩松的影响。结果表明,浇注温度700℃、模具预热温度300℃、比压50 MPa为最佳铸造方案。     

New filling system design for bolster casting and computer simulation

The new filling system is smooth filling without gas gap.It works well in avoiding the generation of defects such as porosity and inclusion.The pouring basin,sprue,runner and the gate of the bolster casting were designed according to the principle of the new filling system.The filling and solidification process of the bolster casting were also simulated.It was found that the filling process was smooth,and air entrapment and shrinkage were avoided.Finally,a further validation of the new filling system of bolster casting was carried out in a foundry.     

镁合金发动机缸体压铸充型和凝固过程的数值模拟

在对镁合金发动机缸体压铸件进行工艺分析的基础上,通过应用正交试验方法,并使用模拟软件对金属液的充型和凝固过程进行数值模拟。结合各组试验所得的不同数据,确定了压铸件生产的优化工艺参数:模具预热温度为220℃,浇注温度为670℃,压射速度为8.5m/s,并确定了工艺参数对铸件缺陷的影响顺序。且在该组优化的工艺参数下,通过对金属液的充型和凝固过程的动态观察,预测充型时间、凝固时间和可能存在的缩松、缩孔及气孔缺陷的分布与体积分数。实现了发动机缸体压铸工艺参数的优化。     

影响消失模铸造Al-Si-Cu合金薄壁铸件质量的显著性工艺参数

通过控制消失模铸造工艺参数可以制备出无缺陷的形状复杂的铸件产品。对Al-Si-Cu合金消失模铸造进行研究,考察浇注温度、涂料黏度、振动时间、型砂粒径以及它们之间的交互作用对铸件表面质量、孔隙率和共晶硅间距的影响。采用两水平全因子实验设计方法考察影响铸件性能的显著性影响工艺参数。结果表明,浇注温度和振动时间对铸件共晶硅间距和孔隙率的影响最明显。在细型砂模和较高的浇注温度下,铸件的表面质量几乎保持稳定不变,而在粗型砂模下铸件的表面质量较低。涂料黏度对铸件性能没有显著影响。     

高温合金燃机叶轮铸造工艺数值模拟

本文介绍了在高温合金燃机叶轮铸造过程中采用数值模拟技术,模拟了不同浇注温度条件下凝固过程中可能出现的缺陷。结果显示：采用数值模拟技术能够比较准确的预测缩孔疏松缺陷产生的部位,提供了工艺改进的方向。通过采用球形浇冒口、合适的径高比、局部保温措施等方法,解决了涡轮轴疏松的问题,获得了冶金质量优异的涡轮叶轮,很好的满足了设计和使用的要求。     

Numerical Simulation Research of Investment Casting for TiB2/A356 Aluminum Base Composite

研究了TiB2/A356铝基复合材料的某航空零件熔模精密铸造性能。根据该复合材料的各热物性参数和TiB2体积分数的关系,结合Pro CAST软件对其数据库进行二次开发,建立了体积分数为10%的TiB2/Al铝基复合材料的热物性参数随温度变化的关系。对某航空薄壁零件进行熔模铸造模拟,模拟结果显示:通过提高A356浇注温度、浇注速度和在浇口与冒孔周围添加保温材料措施,使零件表面的缩孔、缩松缺陷得到解决。     

汽车铝合金缸盖铸件缺陷分析及控制

铝合金缸盖的应用是目前轿车工业发展的必然趋势,其结构和工艺都很复杂,质量要求非常高,废品率也较高。通过对汽车铝合金缸盖铸件废品部位的观察和检测,发现针孔、缩孔、缩松和夹渣是造成铝合金缸盖铸件失效的主要铸造缺陷。针孔由气体和枝晶疏松共同作用形成的,通过采用合理的浇注温度、细化晶粒和改进浇注系统等方法来控制;缩孔、缩松主要是铸造工艺不合理形成的,通过采用合理的浇注温度、模具温度和浇注系统等方法来控制;夹渣主要是涂料的粘附力不强造成的,通过改进涂料等方面来控制。     

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。     

充型散热对缩孔缩松缺陷预测的影响

充型过程所伴随的热量传播交换与散失,导致铸件凝固过程初始温度场分布的不均匀性,进而影响缩孔缩松缺陷的形成。为了更加准确地预测缩孔缩松的位置与大小,凝固模拟应建立在充型过程传热计算的基础上。用实例说明充型散热对缩孔缩松缺陷的影响。     

Volume change during the solidification of grey cast iron: its relation with the microstructural variation,comparison between experimental and theoretical analysis

The expansion/contraction during the solidification of grey cast iron was studied using Linear Variable Differential Transformer (LVDT). The experiments were conducted with and without melt treatment. Two types of inoculant used for melt treatment: ASSC (Si, Ca, Sr & Al) and MBZCAS (Si, Ca, Zr, Ba, Mn & Al). Microstructural investigations carried out to quantify the eutectic cells, undercooled graphite, primary austenite and secondary dendritic arm spacing (SDAS). It was found that the casting shows hardly any shrinkage during early solidification but in the eutectic region, the casting expands until the end of solidification. The measured and the calculated volume changes are close to one another, but the former shows more expansion. The addition of MBZCAS promotes more flake graphite, and ASSC does not increase eutectic cells much. In addition to that, it lowers the primary austenite fraction, promotes more eutectic growth, decreases undercooled graphite and SDAS. As a result, the volume expansion changes in the eutectic region.     

Effect of cooling rate on solidification parameters and microstructure of Al-7Si-0.3Mg-0.15Fe alloy

The effects of cooling rate on the solidification parameters and microstructure of Al-7Si-0.3Mg-0.15Fe alloy during solidification process were studied. To obtain different cooling rates, the step casting with five different thicknesses was used and the cooling rates and solidification parameters were determined by computer-aided thermal analysis method. The results show that at higher cooling rates, the primary α(Al) dendrite nucleation temperature, eutectic reaction temperature and solidus temperature shift to lower temperatures. Besides, with increasing cooling rate from 0.19 °C/s up to 6.25 °C/s, the secondary dendritic arm spacing decreases from 68 μm to 20 μm, and the primary dendritic volume fraction declines by approximately 5%. In addition, it reduces the length of Fe-bearing phase from 28 μm to 18 μm with a better uniform distribution. It is also found that high cooling rates make for modifying eutectic silicon into fibrous branched morphology, and decreasing block or lamella shape eutectic silicon.