Physical Simulation of Mold-Filling Processing of Thin-Walled Castings under Traveling Magnetic Field

Mold-filling process of thin-walled castings under the condition of traveling magnetic field has been studied by physical simulation method using gallium melt and fast speed photography. Flow morphology and its formation mechanism were obtained and discussed for thin-walled casting. The influences of magnetic field density on the filling ability, filling velocity and mold filling time have been studied. The differences in filling capability between gravity casting and casting under the traveling magnetic field have been compared. The results indicate that the mold filling ability of the gallium melt increases greatly under the condition of traveling magnetic field; the filling time is shortened from 18 s under gravity field to 3 s under the traveling magnetic field and average flow rate of the melt increases from 1.6 to 8.68 cm3/s; the change law of the cross-section morphology of the gallium melt during the mold filling is that at first, the cross-section area does not change, then it decreases gradually. When the front of the melt reaches the end of the mold cavity, the front melt will backfill the mold; the wider the width of mold cavity, the better the mold filling ability. The mold filling ability of gallium melt in mold with upper magnetic conductor is better than that without upper magnetic conductor.

Eliminating shrinkage defects and improving mechanical performance of large thin-walled ZL205A alloy castings by coupling travelling magnetic fields with sequential solidification

ZL205 A alloys with large thin-walled shape were continuously processed by coupling travelling magnetic fields(TMF)with sequential solidification,to eliminate the shrinkage defects and optimize the mechanical performance.Through experiments and simulations,the parameter optimization of TMF and the influence on feeding behavior,microstructure and properties were systematically studied.The results indicate that the magnetic force maximizes at the excitation current of 20 A and frequency of 200 Hz under the experimental conditions of this study,and increases from center to side-walls,which is more convenient to process thin-walled castings.TMF can break secondary dendritic arm and dendrites overlaps,widen feeding channels,prolong the feeding time,optimize the feeding paths,eliminate shrinkage defects and improve properties.Specifically,for as-cast state,TMF with excitation current of 20 A increases ultimate tensile strength,elongation and micro-hardness from 186 MPa,7.3%and 82.1 kg/mm^(2) to 221 MPa,11.7%and 100.5 kg/mm^(2),decreases porosity from 1.71%to 0.22%,and alters brittle fracture to ductile fracture.

Numerical simulation for mold-filling of thin-walled aluminum alloy castings in traveling magnetic field

The numerical simulation for mold-filling of thin-walled aluminum alloy castings in horizontal traveling magnetic field is performed. A force model of Al alloy melt in the traveling magnetic field is founded by analyzing traveling magnetic field carefully. Numerical model of Al alloy mold-filling is founded based on N-S equation, which was suitable for traveling magnetic field. By using acryl glass mold with indium as alloy melt, the experiment testified the filling state of alloy in traveling magnetic field. The results of numerical simulation indicate that the mold-filling ability of gallium melt increases continually with the increase of the input ampere turns.

Effect of RE on Cast Structure and Properties of High Manganese Aluminium Bronze

The effects of various amount of Y and La on the cast structure.the fluidity,the wearability and corrosion resistance of the high manganese aluminium bronze have been investigated.The results have shown that a proper content of rare earth elements is able to refine the cast structure of the alloy,and furthermore to enhance its wearability and corrosion resistance.The reasons for these phenomena have also been discussed.

Solidified structure of thin-walled titanium parts by vertical centrifugal casting

The solidified structure of the thin-walled and complicated Ti-6AI-4V castings produced by the vertical centrifugal casting process was studied in the present work. The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains, compared with the microstructure of the thick-walled section. The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius. The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts, and the profile of inter-lamellar space is not susceptible to the centrifugal radius.

Die Casting Mold Design of the Thin-walled Aluminum Case by Computational Solidification Simulation

Recently, demand for the lightweight alloy in electric/electronic housings has been greatly increased. However, among the lightweight alloys, aluminum alloy thin-walled die casting is problematic because it is quite difficult to achieve sufficient fluidity and feedability to fill the thin cavity as the wall thickness becomes less than 1mm. Therefore, in this study, thin-walled die casting of aluminum （Al-Si-Cu alloy： ALDC 12） in size of notebook computer housing and thickness of 0.8 mm was investigated by solidification simulation （MAGMA soft） and actual casting experiment （Buhler Evolution B 53D）. Three different types of gating design, finger, tangential and split type with 6 vertical runners, were simulated and the results showed that sound thin-walled die casting was possible with tangential and split type gating design because those gates allowed aluminum melt to flow into the thin cavity uniformly and split type gating system was preferable gating design comparing to tangential type gating system at the point of view of soundness of casting and distortion generated after solidification. Also, the solidification simulation agreed well with the actual die-casting and the casting showed no casting defects and distortion.

Filling mode and regularity of vertical centrifugal casting process of titanium alloy in thin-walled cylinder cavity

The mold filling process of titanium alloy in a thin-walled cylinder cavity under vertical centrifugal casting process was studied by means of the hydraulic simulation experiments. Results show that the filling mode of the melt in the cylinder cavity varies with casting wall-thickness. When the casting wall-thickness is less than or equal to the thickness of the first layer during the filling process, the melts fill the cavity from the bottom to the top.When the casting wall-thickness is greater than the thickness of the first layer during the filling process, the melts first fill the largest radius parts of the cavity with a certain thickness of the first layer from the bottom to the top of the cavity, and then they fill the cavity from the larger radius part to the smaller radius part. The melt filling ability increases with the increment of the mold rotational speed and the pouring temperature. In another aspect, the melt filling ability rises with the decrement of the melt viscosity, and the melt with the better filling ability is prone to fill the cylinder cavity layer by layer.

Microstructural characteristics and mechanical properties of bronze/steel bimetallic laminated composite prepared by protective atmosphere casting process

The bonding quality of bronze/steel bimetallic laminated composite is the key factor to whether it can be used in poor working conditions.In this study,bimetallic billets were prepared by the protective atmosphere casting process.The microstructural characteristics,mechanical properties and interface bonding mechanism of the bronze/steel bimetallic composites were analyzed comprehensively through a series of microstructure analysis(inicluding OM,SEM,and EDS)and mechanical properties tests.The experimental results demonstrate that the vaporization of lead(Pb)element in the bronze is only 0.4%in weight,and alloy elements are diffused into both sides at the interface.Moreover,the hardness in the bronze region exceeds 100.0 HV which indicates excellent wear resistance.Tensile and shear tests indicate that the fractures mainly occur on the bronze side with the interaction of the brittle fracture of Pb particles and the ductile fracture of Cu-Sn solid solution.The maximum tensile strength and shear strength reach 204.0 MPa and 211.0 MPa,respectively.These results demonstrate that the protective atmosphere casting process is applicable for the preparation of bronze/steel bimetallic laminated composite with high quality.

Corrosion Characteristics of As-Cast Aluminium Bronze Alloy in Selected Aggressive Media

This research work investigated the corrosion characteristics of aluminium bronze alloy in four selected aggressive media which are H2SO4, HCl, NaOH, and NaCl. Aluminium bronze alloy was produced locally via sand casting method. Copper coils and aluminium materials which constitute waste to the environment were used in producing the alloy. Test specimens were produced from the as cast alloy and immersed in H2SO4, HCl, NaOH, and NaCl environment. The concentrations of the environment were varied as 0.1 M, 0.3 M and 0.5 M. The aluminium bronze produced from sand casting has mechanical properties that are closer to the standards proposed by CDA [1]. The corrosion rate was determined by weight loss method at an interval of 3 days. It was observed that the corrosion behaviour exhibited by aluminium bronze in acidic media followed similar trends in 0.1 M, 0.3 M and 0.5 M respectively. However, the corrosion rates increases with increase in the concentration of H2SO4 and NaCl media, but the attack was more aggressive in HCl medium. The aluminium bronze samples in NaOH and H2SO4 media show gradual decolouration from its as-cast yellow golden colour to brown and dark colour respectively. NaCl environment shows high resistance to corrosion and slight decolouration effect even at increased concentration.

Archaeologist-Led Studies on Bronze Casting in Ancient China: 1928–2000

Chinese bronzes are both valuable archaeological remains and significant objects of study in the history of art and technology due to their unique style,complex functions,and technological sophistication.In 1928,the archaeological excavation in Anyang was regarded as the symbol of the establishment of the field of Chinese archaeology.By 2000,tens of thousands of bronzes,and some bronze foundries had been excavated and studied.In archaeologist-led studies,the issues involved are generic,and their scope is restricted,while in multi-disciplinary studies involving both archaeologists and historians of technology,the research is more specific,indicating that research effectiveness and scientific collaboration are closely correlated.

Microstructure and mechanical properties of BFe10 cupronickel alloy tubes fabricated by a horizontal continuous casting with heating-cooling combined mold technology

A new horizontal continuous casting method with heating-cooling combined mold （HCCM） technology was explored for fabri- cating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microstructure and mechanical properties of BFe 10 cupronickel alloy tubes fabricated by HCCM and traditional continuous casting （cooling mold casting） were comparatively investigated. The results show that the tube fabricated by HCCM has smooth internal and external surfaces without any defects, and its internal and external surface roughnesses are 0.64 μm and 0.85 μm, respectively. The tube could be used for subsequent cold processing without other treatments such as surface planning, milling and acid-washing. This indicates that HCCM can effectively reduce the process flow and improve the pro- duction efficiency of a BFel0 cupronickel alloy tube. The tube has columnar grains along its axial direction with a major casting texture of {012}〈 621 〉. Compared with cooling mold casting （6 = 36.5%）, HCCM can improve elongation （3 = 46.3%） by 10% with a slight loss of strength, which indicates that HCCM remarkably improves the cold extension performance of a BFe 10 cupronickel alloy tube.

Effect of depressurizing speed on mold filling behavior and entrainment of oxide film in vacuum suction casting of A356 alloy

The effect of depressurizing speed on mold filling behavior and entrainment of oxide film of A356 alloy was studied. Themold filling behavior and velocity fields were recorded by water simulation with particle image velocimetry. The results show thatthe gate velocity first increased dramatically, then changed with the depressurizing speed: the gate velocity increased slowly atrelatively high depressurizing speed; at reasonable depressurizing speed, the gate velocity kept unchanged; while at lowerdepressurizing speed, the gate velocity decreased firstly and then kept unchanged. High gate velocity results in melt falling backunder gravity at higher speed. The falling velocity is the main factor of oxide film entrainment in vacuum suction casting. The designcriterion of depressurizing rate was deduced, and the A356 alloy castings were poured to test the formula. The four-point bend testand Weibull probability plots were applied to assessing the fracture mechanisms of the as-cast A356 alloy. The results illuminate amethod on designing suitable depressurizing speed for mold filling in vacuum suction casting.

电磁参数对宽幅锡磷青铜水平连铸坯组织和铸造性能的影响

采用电磁水平连铸技术制备了650 mm宽幅锡磷青铜合金铸坯,研究电磁参数对其水平连铸组织和铸造性能的影响。利用光学显微镜、扫描电镜、能谱仪和密度测试等研究了施加电磁前后锡磷青铜铸坯组织和性能的变化。结果表明:当电磁参数为20 A、20 Hz时,能有效地抑制锡磷青铜铸坯的锡元素偏析,使锡元素偏析标准差由0.5%下降至0.12%;施加电磁场后,铸坯晶粒组织由柱状晶向等轴晶转变,结合弱面消失,疏松、缩孔等微观铸造缺陷减少,铸坯致密度增加,从而有利于提升锡磷青铜铸坯表面和内部质量;施加电磁场后,铸坯的晶粒组织细化,微观偏析得到一定程度抑制,使得均匀化退火更充分,均匀化退火后铸坯的平均晶粒尺寸由未施加电磁场的700μm下降至260μm。

陕西西安赤栏桥商代遗址发掘简报

陕西省考古研究院于2021~2022年对西安市长安区赤栏桥遗址进行了发掘,获得了一批商文化遗存,遗迹主要包括灰坑、灰沟、陶窑、房址、灶坑、墓葬及较丰富的铸铜遗存,遗物包括陶器、石器、骨器、卜骨等。赤栏桥遗址商代遗存具有典型的商文化特征,同时兼具一定的本地特点。该遗址的发掘丰富了关中地区商文化遗存,为研究关中地区商时期文化谱系和了解中商王朝对西土地区矿产资源的掌控、利用提供了重要资料。

锡青铜阀体铸造工艺的数值模拟研究

目的针对薄壁阀体难以通过加工的方式精密成形的问题,研究锡青铜薄壁阀体的铸造成形工艺,探究不同浇注方案下的充型、凝固规律,提出合理的铸造工艺方案。方法基于锡青铜(C83600)的热物理性能和薄壁阀体铸件的几何特征,设计了顶注雨淋式浇注系统,通过改变散热方式、利用正交试验等方法研究铸造工艺参数、优化浇注系统,探究不同浇注工艺的铸件质量。结果本铸件在顶注式浇注系统下呈现良好的顺序凝固特征,但不均匀的薄壁恶化了铸件质量,通过调整浇注工艺和浇注系统设计,铸件质量得到有效改善。对正交试验的试验结果进行极差分析,发现浇注温度对铸件质量的影响最大,浇注速度次之,砂型预热温度的影响最小。将内浇道调整到6个厚内角区域,增设冷铁后,以浇注温度为1140℃、浇注速度为1.0 kg/s、砂型预热温度为150℃的浇注参数组合进行浇注,铸造完成后空冷的铸件质量最好。结论优化浇注系统设计,调整合适的浇注温度、浇注速度和砂型预热温度能有效提高铸件的质量,便于铸件一次成形。

水下搅拌摩擦加工对铸态镍铝青铜空蚀行为的影响

为了进一步提高铸态镍铝青铜抗空蚀性能,采用水下搅拌摩擦加工技术对其进行表面改性。观察并测试了加工前后材料的微观组织和力学性能,对比讨论了铸态和水下搅拌摩擦加工后镍铝青铜在蒸馏水和人工海水中的空蚀行为,分析了微观组织与空蚀机理的关系。研究结果表明,水下搅拌摩擦加工后,镍铝青铜组织细化,各相分布均匀,加工区中心平均显微硬度约为400 HV,是铸态样品的2倍。在2种介质空蚀试验中,水下搅拌摩擦加工镍铝青铜累计空蚀质量损失均较低,空蚀18 h后SFSP态NAB在蒸馏水和人工海水中的质量损失分别是2.55 mg和4.85 mg,约为铸态NAB质量损失的50%和44%,具有更好的抗空蚀性能。晶粒细化和小尺寸晶粒κ相弥散强化是提高铸态镍铝青铜的抗空蚀性能的主要原因。

基于砂型3D打印的双吸叶轮铸造工艺研究

C95820铝青铜双吸叶轮具有尺寸较大、壁厚不均、结构复杂等特点,在铸造时会容易产生集中缩松缩孔、氧化物夹杂和气孔等缺陷,采用传统铸造方法生产有一定的困难。本文结合砂型3D打印的技术优势,采用ProCAST软件优化设计了该铸件的浇冒口系统,实现了金属液的平稳充型,缩松缩孔缺陷也主要分布在浇冒口中。对影响叶轮精度的关键叶片砂芯采取一体化设计和打印成形,并且在内部开设了随形气道,保证了树脂砂受热后产生的气体能迅速排出。将3D打印的砂型组型浇注,成功生产出了质量良好的铝青铜双吸叶轮铸件。

山东邹城两孟南西周遗址发掘简报

2023年,山东省文物考古研究院对邹城市两孟南遗址进行了发掘。遗址主体年代是西周早中期,发现房址、墓葬、灰坑、灰沟等遗迹,出土遗物丰富,包括陶、石、骨角器,以及铜硫渣、残铜块、废弃炉壁等冶铸相关遗物。两孟南遗址发掘为鲁中南地区周代考古学文化的研究提供了重要材料。

关于青铜刻刀在青铜器上錾刻铭文的可行性研究

文章分析了不同锡(Sn)含量的青铜刻刀(12%、16%、20%、23%、26%、30%)在青铜板(含锡12%)上的刻铭试验,发现其均能刻铭成功,差异体现在刻铭的效果和刻刀的磨损上,含锡20%的刻刀刻字效果明显且刻刀持久耐用,低于此值的刻刀出现卷刃,高于此值的刻刀出现磨平或崩刃,且刻字效果不太理想。随着含锡量的增加,青铜的硬度先升后降,在加入铅(Pb)后,青铜的硬度普遍降低,为錾刻的实施提供了良好条件。此外,通过考察宏观的力学性能和微观的金相组织,本文分析了上述试验现象产生的原因,并在扫描电镜和XRD的配合下,更深入地讨论了硬度先升后降的机理。从技术角度看,青铜时代早期的刻铭并不难实现,无需借助铁质工具,这为西周时期晋侯苏钟以及更早的商代刻铭提供了试验和理论依据。

中国冶金考古研究五十年:回顾与展望

20世纪70年代开始,中国冶金考古进入大发展时期.多学科学者纷纷参与中国冶金考古研究,在冶铜术起源与青铜冶铸体系形成、钢铁技术形成与发展、金银铅锡锌等有色金属冶炼技术、古代金属流通与国家治理等方面取得了一系列重要成果,但在田野冶金考古与信息采集标准规范、古代金属材质与工艺及其流通研究关键技术、古代冶金与文明和国家起源发展机制等方面的研究仍具有极大空间,有待于今后开展更多的冶金考古理论与方法、关键科学问题研究.本文对1974年以来的重大成果进行简要回顾与总结,分析存在的问题,提出未来发展建议.