压力对ADC12铝合金超低速压铸件组织及力学性能的影响

采用光学显微镜、扫描电镜、X射线衍射和能谱等显微分析技术,结合力学性能检测,研究超低速压铸条件下压力对ADC12铝合金铸件组织及力学性能的影响。试验结果表明,在超低速试验条件下,持压时间越长、增压延时时间越短,铸件性能越好;铸造压力导致初生α-相形态发生变化,但铸造压力有最佳值,压力较小时,增大铸造压力可使α-相细化,铸件性能升高,过大的铸造压力将导致α-相粗大,使铸件性能下降;在无增压条件下,仅采用较大的压射压力也可使α-相组织细小,获得较好的力学性能。     

The effect of die casting machine parameters on porosity of aluminium die castings

The primary objective of this research is to investigate the effect of machine related parameters on porosity formation in the aluminum die casting process. The amount and distribution of porosity in die castings was examined in relation to plunger velocity during the 1st phase, fast shot set point, plunger velocity during the 2nd phase, die cavity filling time and multiplied pressure during the 3rd phase.

Standard statistical analysis was performed in order to identify the effect of each of the considered parameters and parameter interactions on porosity formation. It was found that, among the parameters considered, multiplied pressure, plunger velocity in the 2nd phase and die cavity filling time have the most significant effect on porosity formation. Using optimal die casting machine parameter levels, the optimum porosity value of aluminum alloy die-castings was predicted. The results were confirmed by further experiments.     

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。     

压铸镁合金缺陷带的组织特征及形成机理

研究了压铸镁合金缺陷带的组织形貌及分布特征,建立缺陷带与压室预结晶(ESCs)、气缩孔及压铸工艺参数之间的对应关系,在此基础上探讨了缺陷带的形成及演化机理。结果表明,压铸镁合金截面凝固组织以缺陷带为界可划分为3个有明显组织特征差异的区域。随着压铸低速速度提高,镁合金凝固组织中ESCs含量逐渐降低,而缺陷带组织愈加明显并向压铸件中心靠拢,缺陷带宽度减小,其内部孔洞更加聚集;高速速度越大,压铸镁合金凝固组织中ESCs越分散,缺陷带向压铸件中心靠拢,压铸在无高速速度情况下,镁合金凝固组织横截面出现双缺陷带现象。压铸充型过程中金属液流的形态决定了缺陷带的分布位置和发展趋势,在高速金属液的剧烈冲刷及增压压力的作用下,靠近金属液流外轮廓的晶粒发生破碎或转动,在晶粒间形成大于剩余金属液体积的间隙,随着凝固的进行,形成沿液流轮廓分布孔洞聚集的缺陷带组织。     

Effects of process parameters on morphology and distribution of externally solidified crystals in microstructure of magnesium alloy die castings

During the cold-chamber high pressure die casting(HPDC) process, samples were produced to investigate the microstructure characteristics of AM60B magnesium alloy. Special attention was paid to the effects of process parameters on the morphology and distribution of externally solidified crystals(ESCs) in the microstructure of magnesium alloy die castings, such as slow shot phase plunger velocity, delay time of pouring and fast shot phase plunger velocity. On the basis of metallographic observation and quantitative statistics, it is concluded that a lower slow shot phase plunger velocity and a longer delay time of pouring both lead to an increment of the size and percentage of the ESCs, due to the fact that a longer holding time of the melt in the shot sleeve will cause a more severe loss of the superheat. The impingement of the melt flow on the ESCs is more intensive with a higher fast shot phase plunger velocity, in such case the ESCs reveal a more granular and roundish morphology and are dispersed throughout the cross section of the castings. Based on analysis of the filling and solidification processes of the melt during the HPDC process, reasonable explanations were proposed in terms of the nucleation, growth, remelting and fragmentation of the ESCs to interpret the effects of process parameters on the morphology and distribution of the ESCs in the microstructure of magnesium alloy die castings.     

V型槽皮带轮成形方法研究

皮带轮外壁带有V型环槽,在压铸模上采用对分组合滑块成型,同时用斜销延时抽拔滑块,使铸件留在动模上,工件底部面积太小,故采用推件板推件,有效解决了该类铸件的成型和出模问题。分析了铸件的工艺性,论述了模具工作原理和工作过程。     

降低塑料直尺残留应力的优化分析

针对塑料直尺注射成型容易产生翘曲变形的问题,对其注射成型过程进行了优化分析,以降低注射成型中塑件的模内残留应力,提高塑件质量。采用正交优化方法和Minitab统计分析软件,将塑件的模内残留应力作为优化目标、对成型过程中影响塑件模内残留应力的模具温度、熔体温度、注射速率、保压压力与注射压力比和保压时间等5个工艺参数进行了优化分析。在此基础上,选取熔体温度、注射速率和保压时间这3个对优化目标有显著影响的工艺参数进行了二次优化,得到最优组合。最后进行试验,验证了数值模拟的合理性和优化分析的有效性。     

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.     

Influence of die casting process parameters on castability and properties of thin walled aluminium housings

Abstract

The objective of this study is to clarify effects of high pressure die casting process parameters for castability and mechanical properties. So the optimal die casting conditions for producing for thin walled Al component was conducted computational solidification simulation and actual die casting with three different venting systems, four straight, checker and full checker vent. Furthermore, the die casting process parameters, such as die controller temperature, high injection speed and die open time, were experimentally evaluated. The results of computational solidification simulation were found that the control of process parameters could lead to soundness of surface and no defect and improvement of mechanical properties. As increasing the high injection speed from 2˙0 to 4˙0 m s^?1 and die temperature, the castability was increased. The full checker venting system had best castability with good surface quality among the three cast specimens.     

Influence of intensification pressures on pores in die-cast ADC12 alloys

Die casting process is widely applied in making Al parts. However,due to high speed of liquid metal flow in the die cavity,gases are prone to be entrapped in the filling,resulting in porosity defects. The X-ray computed tomography scanning technique was used to detect the pores in die-cast ADC12 alloys with different intensification pressures. The three-dimensional features of pores including pore size,number,sphericity have been obtained. The effect of different intensification pressures on two different kinds of pores,namely gas-pores and shrinkage pores,was analyzed. The results show that with increasing the pressure,the pore fractions and quantity gradually decrease. When the pressure increased to 85 MPa,the pores from gas entrapment during the mold filling were compressed,leading to a lower porosity fraction. The pressure cannot affect the pores in the samples with a thin wall(2 mm) due to a great solidification rate.     

低压铸造中充型过程的水模拟研究

采用水模拟试验研究了工艺参数对低压铸造充型品质的影响。结果表明,随着加压速度的增大,升压-保压阶段拐点处液面波动振幅增加;而动力粘性系数增大,波动振幅反而减小。随着加压速度的增加,无论排气孔的面积有多大,液面上升延迟时间都有增加的趋势;型腔内背压逐渐增大,液面上升延迟时间逐渐增加。液面上升延迟时间随进气阻力增加而增加,进气阻力过大明显降低充型质量。     

基于响应面法的铝合金间接挤压铸造工艺研究

为研究间接挤压铸造工艺,选取ZL101铝合金,以孔隙率为指标,首先通过单因素实验,分析了挤压压力、模具温度与比例系数3个因素对孔隙率的影响。然后采用Box-Behnken实验设计方法来设计响应面实验,建立了间接挤压铸造工艺参数与孔隙率相互关系的预测模型,方差分析结果表明,实验结果和数学模型拟合良好。通过对各个因素交互作用的响应面进行分析,得知模具温度和挤压压力对孔隙率的影响存在显著的交互作用,模具温度和比例系数、比例系数和挤压压力对孔隙率的影响不存在显著的交互作用。通过对环形件浇注系统的直浇道边缘部位进行金相检测分析,得知由于压力的施加,会使已经凝固的金属壳层发生不均匀的塑性流动。     

低压铸造铝合金车圈若干技术问题的讨论

结合国内若干车圈厂低压铸造实践 ,参考国外低压铸造技术 ,对低压铸造设备、铝合金车圈模具设计和制造以及低压铸造工艺中较深层次问题提出了自己的观点     

汽车壳体低压铸造工艺与模具设计

介绍了汽车壳体零件低压铸造工艺与模具设计.内容主要有低压铸造工艺参数的设计,包括升液压力与升液速度、充型压力和充型速度的计算、浇注温度的确定、结晶压力和保压时间的计算等;模具设计,包括模具结构与壁厚的确定、型腔尺寸的计算、型芯和抽芯的计算、模具的三维造型.     

工艺参数对汽车用盒形件半固态压铸过程的影响

采用半固态成形技术(SSM)代替传统铸造来生产汽车用盒形件。基于Power Law Cut-Off(PLCO)模型和有限元模拟软件ProCast2008对盒形件半固态压铸过程建立模型并进行数值模拟,揭示了主要工艺参数对成形过程的影响规律。结果表明,在盒形件半固态压铸过程中,浇注温度、冲头速度、模具加热温度有明显的影响,并进一步获得了半固态压铸的合理工艺参数。     

Determination of temperature distribution in squeeze cast aluminium using the semi-empirical equations’ method

The effects of parameters such as applied pressure, die pre-heat temperature, delay time and retention time of applied pressure on the temperature distributions within the casting have been considered. The results using this method were compared with those of experimental and heat transfer differential equations’ methods and found to be about 1.7% higher in value. The semi-empirical equations’ method can be used to predict the temperature distribution of other metals and alloys at any location, if the empirical equations relating the heat transfer coefficients to applied pressures and solidifying temperatures for their three stages of solidification are known.     

箱体低压铸造过程的数值模拟

以计算流体力学和计算传热传质学作为理论基础,利用大型模拟软件ANSYS对箱体的低压铸造过程进行了数值模拟,分析了铝合金在低压铸造充型过程中的流场以及凝固过程中的温度、固相分数的分布情况,预测铸件可能出现的缺陷,为优化铸造工艺和模具设计提供参考。     

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.     

充填速度与浇口对半固态AlSi7Mg合金成形过程的影响

确定半固态触变成形的边界条件,在半固态表观粘度耦合于流场的动量方程上,建立半固态AlSi7Mg充型过程的计算模型.对不同充填速度、浇口形状以及浇口设置位置下半固态成形过程进行模拟分析.结果表明:半固态合金的充填速度对流态及成形质量具有明显影响,与压铸相比,半固态浇口形状、设置位置等因素对充填流态影响相对较小,所以半固态工艺设计较为灵活.半固态压铸机的充填流量及充填压力取决于浇口面积、充填速度以及合金种类.充填速度决定半固态浆料流动形态,进而影响半固态制件的成形质量.     

Gas content in high pressure die castings

This paper presents the results of a quantitative study of the gas level in various types of castings from the high pressure die casting (HPDC) process using a vacuum fusion method. It was found that the major part of the gas was from the air entrapment during cavity filling. Other sources such as air entrapment during ladling, residual die lubricant and quenching water were also noticeable. Measurements of a large casting and castings from a multi-cavity die showed that the gas content was unevenly distributed. The modified vacuum fusion method has been proved to be a valuable tool for evaluating and quantifying the level of gas in castings as well as for an assessment of the influence of different process parameters on gas evolution in castings.