大高径比铸件挤压铸造技术研究

用试验和计算机模拟的方法,研究了高径比为7的铸件凝固过程中的温度分布;研究了铸件中的缩松和铸件力学性能分布特点.结果表明,增加大高径比铸件挤压铸造的比压、提高铸型的预热温度不能有效地减少铸件内的缩松缺陷;采取措施使铸件顺序凝固,并使挤压力有效地作用在液体金属上,可以消除大高径比铸件内的缩松,获得高力学性能的铸件.     

挤压铸造ZA27合金大高径比铸件

通常挤压铸造仅适用于高径比小于3.5的铸件,研究大高径比铸件的挤压铸造将扩大这种先进铸造技术的应用范围.用试验和计算机模拟的方法,研究了高径比为7的ZA27合金铸件的力学性能、凝固过程中铸件内的温度、压力以及缩松的分布.结果表明,增加挤压铸造的压力不能有效地减少大高径比铸件的缩松缺陷;合理控制浇注温度和铸型预热温度能有效地消除大高径比铸件内的缩松,获得力学性能高且均匀的铸件.     

比压对大高径比挤压铸造ZA27合金杯形铸件的组织与性能的影响

研究了挤压铸造比压对大高径比(M=7)ZA27合金杯形铸件组织与不同部位性能的影响。随着比压的增大,ZA27合金杯形铸件的显微组织中α-Al枝晶发生破碎,枝晶逐渐细化,性能显著提高。     

铸造铝合金中氧化夹杂物的研究进展

就铸造铝合金中氧化夹杂物的来源和形成过程、对铝液吸氢、铝铸件中孔洞形成和铸件力学性能的影响进行了分析,并对国内外铝合金铸件中氧化夹杂的研究进展进行了综述.在熔铸过程中形成的氧化夹杂物,是铝液中夹杂物的主体,对铝液吸氢和铝合金铸件中孔洞的形成有着不可忽视的影响.铝合金铸件的力学性能与铝液中的氧化夹杂密切相关,夹杂物可作为显微裂纹的发源地,严重削弱铝合金铸件的力学性能.     

挤压铸造大高径比杯形铸件组织

研究大高径比铸件的挤压铸造将拓宽挤压铸造技术的应用范围。研究了挤压铸造ZA27合金大高径比杯形铸件的凝固组织。结果表明,铸件中压力分布极不均匀,铸件的上部边缘和底部压力较大,中下部压力较小;增大压力导致晶粒细化并发生塑性变形;ZA27合金大高径比杯形铸件的下部组织中出现分界面,界面两侧组织明显不同,后凝固一侧晶粒较细,含有较多共晶体。     

灰铸铁件表面缩松缺陷的防止

采用控制碳当量,提高硅碳比,并与成形冷铁技术相配合。实践表明,这些措施有效地防止了灰铸铁件的表面缩松缺陷     

Effect of vacuum on porosity and mechanical properties of high-pressure die-cast pure copper

Pure copper tensile bars were produced by conventional die casting(HPDC) and vacuum-assist die casting(VADC) processes. Porosity and mechanical properties were investigated by using optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), X-ray computed tomography(XCT) and tensile tester. Results show that porosities including gas porosity and shrinkage porosity could be observed in copper castings. Since the application of vacuum could reduce filling related gas entrapment and facilitate solidification due to the increased heat transfer between metal and die, both number and size of the entrapped gases, as well as shrinkage porosities were significantly reduced in vacuum-assist die castings of pure copper. The porosity fraction decreased from 2.243% to 0.875% compared with that of the conventional die casting. Besides, mechanical properties were improved significantly, i.e., by 15% for ultimate tensile strength and three times for elongation.     

Optimization of casting conditions for heat and abrasion resistant large grey iron castings

Numerical simulation technology was applied for optimizing the casting design and conditions in large cast iron castings for marine engine. By the simulation of mold filling and solidification sequences the problems of the previous casting conditions were analyzed and marked improvements for large cylinder liner parts were derived from these results. Especially the amount and positions of chills were optimized to increase the mechanical properties and to minimize the shrinkage and microporosity in the castings. Ultrasonic testing, penetration testing and mechanical property testing were carried out for the parts with the modified casting conditions. It showed that no defects in the castings were found and the productivity could be distinctly increased. The mechanical properties satisfied also the specification demanded.     

合成铸铁生产缸体铸件的工艺技术

考虑到大量使用生铁使铁液收缩倾向增大且使铸件性能降低,以及为解决铸铁熔炼所需原材料生铁价格不断上涨等问题,在缸体类铸铁产品的生产中,采用合成铸铁,即废钢加增碳剂增碳的方式进行铸铁生产。此工艺采用增硫防止石墨长成粗大片状,适当的合金化和孕育处理,可以使铁液的收缩倾向得到明显改善。采用合成铸铁生产的缸体类产品力学性能和金相组织均优于传统熔炼工艺生产的铸铁产品。     

Section thickness-dependent tensile properties of squeeze cast magnesium alloy AM60

The development of alternative casting processes is essential for the high demand of light weight magnesium components to be used in the automotive industry,which often contain different section thickn...     

AZ80镁合金挤压铸造工艺参数的形态学矩阵优化(英文)

运用形态学矩阵对AZ80镁合金挤压铸造工艺参数进行优化。采用 L9(33)田口方法中的正交列对不同挤压压力、模具预热温度和压力持续时间进行组合。采用一个3水平正交阵列确定信噪比,通过方差分析确定影响力学性能最重要的工艺参数,并利用多变量线性回归分析确定拉伸强度、伸长率和硬度,获得了最佳的挤压铸造工艺参数。     

A METHOD OF AS-CAST CRACK PREDICTION BASED UPON NUMERICAL SIMULATION OF SOLIDIFICATION

Based on the numerical simulation of solidification of castings, a thermal stress formula and a thermal crack initiation criterion are established, which suggest that the cracks initiate at the two-thirds thickness of solidified layer from outside of castings. Cast steel wheels whose diameters are 800mm are employed to testify the positions of cracks through thermal elastic-plastic analyses and low magnifying structure observations conventionally. The results show that the numerical prediction of cracks coincides with the measured result, and the cracks do not necessarily follow where the defects such as shrinkage holes and porosities occur. It is also found that surface temperature control is an effective factor to avoid the crack formation.     

湿型砂工艺铸件缩松缺陷的消除

采用黏土湿型砂射压造型生产线,铸件存在缩松和硬度过高的缺陷.从浇注温度、冒口颈和碳当量对铸件缺陷的影响进行了分析,发现铁水高温保温时间过长造成碳烧损是引起铸件缺陷的主要原因.为减少铁水的碳烧损,随其保温时间延长添加增碳剂,铸件缩松和过硬的缺陷彻底消除,从而保证了铸件质量.     

压铸工艺参数对ADC12Z压铸件孔洞和抗拉强度的影响

研究了铸造压力、料柄厚度、低速速度和高速速度对ADC12Z压铸件孔洞和抗拉强度的影响。结果表明:铸造压力和料柄厚度对密度、孔洞面积分数、孔洞平均尺寸及抗拉强度的影响较低速速度和高速速度显著。随着铸造压力和料柄厚度增大,压铸件孔洞面积分数和孔洞平均尺寸减小,密度和抗拉强度增大。     

均衡凝固技术在高铬白口铸铁衬板上的应用

运用均衡凝固技术进行高铬白口铸铁球磨机衬板压边冒口的设计及应用,收到了比按照顺序凝固技术进行设计更为理想的效果:铸件无缩孔、缩松现象,操作简单,工艺出品率最高可达到80%以上,大大降低了生产成本,取得了较好的经济效益.近十年来已稳定生产衬板类铸件5000余吨,为探索白口铸铁的生产工艺开辟了新的途径,同时也表明均衡凝固技术作为工艺设计的理论和方法对铸件生产具有普遍意义.     

Microstructure and tensile properties of squeeze cast magnesium alloy AM50

High-pressure die cast magnesium alloy AM50 is currently used extensively in large and complex shaped thin-wall automotive components. For further expansion of the alloy usage in automobiles, novelmanufacturing processes need to be developed. In this study, squeeze casting of AM50 alloy with a relatively thick cross section was carried out using a hydraulic press with an applied pressure of 70 MPa. Microstructure and mechanical properties of the squeeze cast AM50 with a cross-section thickness of 10 mm were characterized in comparison with the die cast counterpart. The squeeze cast AM50 alloy exhibits virtually no porosity in the microstructure as evaluated by both optical microscopy and the density measurement technique. The results of tensile testing indicate the improved tensile properties, specifically ultimate tensile strength and elongation, for the squeeze cast samples over the conventional high-pressure die cast parts. The analysis of tensile behavior show that the strain-hardening rate during the plastic deformation of the squeeze cast specimens is constantly higher than that of the die cast specimens. The scanning electron microscopy fractography evidently reveals the ductile fracture features of the squeeze cast alloy AM50.     

有限元模拟预测铸钢件的宏观缩孔缺陷

本文使用商品化有限元软件ProCAST模拟预测了铸钢件砂铸工艺中产生的宏观缩孔缺陷，并进行了相关的实验验证，发现铸件中确实存在模拟预测的宏观缩孔缺陷，这为下一步工艺方案改进奠定了基础。     

Grain size refinement through gas bubble stirring in AC4CH cast aluminium alloy

A comparison has been made of the mechanical properties of gravity and squeeze cast aluminium alloys that have been grain refined using gas bubbling and those that have not. To find the optimum gas bubbling conditions, the alloy melt temperature, the gas flow rate and the gas bubbling times were varied over wide ranges. The microstructure of the gas bubbled gravity and squeeze cast materials is fine, equiaxed and non-dendritic with an average primary α size of 52 μm and 163 μm respectively. However, gas bubbling has no effect on the morphology of the eutectic Si. There seems to be no noticeable difference between the measured mechanical properties of the gravity and squeeze cast materials with or without the gas bubbling. The lack of improvement in the mechanical properties of the gravity cast alloy is due to casting defects and porosity, which offset the effects of the grain refinement. The crystal separation and showering mechanisms are operative for the formation of equiaxed grains.     

Influence of rare earths on shrinkage porosity in thin walled ductile cast iron

Abstract

Ductile cast iron has been cast in test bars with thickness from 2 to 10 mm. The rare earth elements La and Ce have been added to some of the castings to evaluate their influence on microstructure and shrinkage tendency. Both La and Ce increased the graphite nodule count, especially for thickness of 6 mm and below. La gave the best nodule size distribution with many small nodules. La had less shrinkage tendency than Ce in the 10 mm test bars. This tendency was less pronounced for the 6 and 4 mm test bars and other factors may have a large influence at these thicknesses. Increasing the temperature T ₁, which is controlled by the growth of off-eutectic austenite dendrites, increased the shrinkage tendency.     

DISA造型线生产带盘的轴类零件均衡凝固铸造工艺优化设计

在垂直分型无箱挤压造型线上,每型12件,生产带盘的轴类铸件,其材质HT200,垂0.6 kg.应用均衡凝固理论,采用等流率设计浇注系统,在内浇道厚度应保证液态传输通道畅通的条件下,取内浇道厚度3mm,设置排气槽,加强型腔排气,经生产验证,成功完成了该件批量生产的工艺设计.