Numerical simulation of melt flow and temperature field during DC casting 2024 aluminium alloy under different casting conditions

Casting speed,casting temperature and secondary cooling water flow rate are the main process parameters affecting the DC casting process.These parameters significantly influence the flow and temperature fields during casting,which are crucial for the quality of the ingot and can determine the success or failure of the casting operation.Numerical simulation,with the advantages of low cost,rapid execution,and visualized results,is an important method to study and optimize the DC casting process.In the present work,a simulation model of DC casting 2024 aluminum alloy was established,and the reliability of the model was verified.Then,the influence of casting parameters on flow field and temperature field was studied in detail by numerical simulation method.Results show that with the increase of casting speed,the melt flow becomes faster,the depths of slurry zone and mushy zone increase,and the variation of slurry zone depth is greater than that of mushy zone.With an increase in casting temperature,the melt flow rate increases,the depth of the slurry zone becomes shallower,and the depth of the mushy zone experiences only minor changes.The simulation results further indicate that the increase of the flow rate of the secondary cooling water slightly reduces the depths of both slurry and mushy zone.

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.

LATERAL STABILITY OF ALTERNATIVE HORIZONTAL LEVITATION ELECTROMAGNETIC CONTINUOUS CASTING OF ALUMINIUM SHEET

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Numerical microstructure prediction for an aluminium casting and its experimental validation

Virtual manufacturing based on through-process modelling becomes an evolving research area which aims at integrating diverse simulation tools to realize computer-aided design, analysis, prototyping and manufacturing. Numerical prediction of the as-cast microstructure is an initial and critical step in the whole through- process modelling chain for engineering components. A commercial software package with the capability of calculating important microstructure features for aluminium alloys is used to simulate a G-AISi7MgCu0.5 laboratory casting. The simulated microstructure, namely grain size, secondary dendrite arm spacing and diverse phase fractions are verified experimentally. Correspondence and discrepancies are reported and discussed.

Influence of T6 heat treatment on A356 and A380 aluminium alloys manufactured by thixoforging combined with low superheat casting

The effects of T6 heat treatment on thixoforged A356 and A380 aluminium alloys were studied.Low superheat casting(LSC)technique was carried out to prepare proper specimens for thixoforging process.The samples were poured at 20°C above their liquidus temperatures which provided the formation of equiaxed grains instead of dendritic growth.Produced billets were reheated for varied time from 20 to 80 min and thixoforged with 50%deformation rate.After thixoforging process,the samples were T6 heat treated for both A356 and A380 alloys.The microstructural evaluation and hardness alteration of thixoforged,solution treated and aged specimens were examined comparatively by using optical microscopy,scanning electron microscopy with energy-dispersive X-ray spectroscopy and Brinell hardness equipment.T6 heat treatment provided relatively uniform microstructure with newly formed precipitates that are Mg2Si and Al2Cu for A356 and A380 billets,respectively.Accordingly,hardness after artificial aging was increased considerably and reached HB 93 for A356 and HB 120 for A380 alloys.

Continuous cooling precipitation diagram of cast aluminium alloy Al-7Si-0.3Mg

The precipitation behaviour during quenching of cast Al-7Si-0.3Mg aluminium alloy was investigated by DSC in the cooling rate range of 0.01 K/s to 3 K/s and by quenching dilatometry for higher rates. Two main precipitation reactions were observed during cooling, a high temperature reaction starting almost directly with quenching from 540℃ and a low temperature reaction starting at about 400℃. Quenching with 3 K/s already significantly suppresses precipitation during quenching. Hardness after T6 ageing increases with increasing quenching rate, due to the increasing content of supersaturated solid solution. By dilatometry and hardness results the critical cooling rate can be estimated as about 60 K/s. Quenched Al-7Si-0.3Mg microstructures have been investigated by light microscopy. The microstructures consist of an aluminium-silicon eutectic structure, aluminium solid solution dendrites and precipitates inside the aluminium dendrites, depending on quenching rate.

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.

Study of the Coarse Blocky Compounds in the As－cast 7075 Aluminium Alloys Containing Rare Earth Elements

The coarse blocky compounds in the as-cast 7075 aluminium alloys containing rare earth elements, neodymium, cerium or mischmetal were investigated by means of transmission electron microscope with EDX and scanning electron microscope. The blocky compounds in these alloys were identified as rare earth compounds, (Cr, Ti)2 RE (Al, X)20 (X is magnesium, copper and zinc),body-centred cubic, with 184 atoms to the unit cell , lattice parameter 1.453￣1. 458 nm, Vickers hardness 4000￣5600 MPa and calculated density 3400 kg/m3. The results show that the amount of blocky compounds in the alloys decreases with decreasing of Ti and Cr content or with increasing of cooling rate during solidification.

Effect of electromagnetic field on microstructure and macrosegregation of flat ingot of 2524 aluminium alloy

Low frequency electromagnetic casting （LFEC） process with the application of an induction coil outside the conventional direct chill （DC） casting mould was used to prepare the flat ingot of 2524 alloy and the effect of electromagnetic field on the microstructure and macrosegregation of this alloy was systematically studied. The results show that the fiat ingot prepared by the LFEC process has a finer and more uniform as-cast microstructure and the grain morphology is transformed from dendrite and rosette-like to equiaxed structure. The LFEC process also shows a significant effect on macrosegregation, and with the application of electromagnetic field during casting process, the segregation in the centre of the ingot is obviously reduced. The mechanism of these effects was also discussed.

拉伸试棒模具结构对铸造铝合金组织的影响

针对现有的国家标准铝合金的试棒浇注模具,浇注的试棒存在夹渣、气孔、缩松、冷隔等铸造缺陷,无法合理反映合金的真实力学性能的现状,本文使用ANSYS等软件,利用流体静力学和传热学原理科学的分析了直浇道的倾斜角度和内浇道与集渣腔连接的位置铝合金组织的影响,设计了一种铝合金拉伸试棒的铸造模具。模拟结果表明,直浇道的倾斜角度为70°时,流体流速波动范围最小;内浇道与集渣腔连接的位置为集渣腔压心时,集渣腔集渣过滤效果最佳。浇注实验结果表明,本模具成型的ZL205A和ZL101试棒平均晶粒和枝晶间距均优于GB/T1173-2013模具成型试棒组织。分析认为,合理的流速控制(直浇道的倾斜角)和集渣腔高度设计有利于试棒获得晶粒细小,铸造缺陷少的组织。

超声与氩气冷却对2219铝合金组织及偏析的影响

2219铝合金作为一种广泛应用于航天、汽车制造等领域的重要合金,其在一般重力铸造条件下生产的铸锭容易出现孔缩、第二相聚集、宏观偏析等问题。本研究在高纯气氛保护条件下,采用超声辅助处理熔体与氩气冷却相结合的方法制备了2219铝合金铸锭。通过光谱仪、光学显微镜(OM)、扫描电子显微镜(SEM)等手段研究了超声波、氩气冷却对改善2219铝合金凝固组织及宏观偏析的影响。结果表明,在高纯气氛保护下,超声作用对2219铝合金铸造具有良好的细化晶粒、均匀化第二相的效果,组织内无疏松缩孔缺陷。当超声与氩气冷却共同作用时,铸锭晶粒细化及第二相均匀化效果更佳,平均晶粒尺寸减小69.4%。超声空化效应促进了更多溶质元素在铝熔体中的均匀分布,提高了晶粒形核率,同时在空化破碎与声流的扰动效应作用下,第二相组织更为细小均匀,宏观偏析显著改善。

铝合金铸造性能及相关参数数据库研究

铸造性能数据的实时检测和分析处理能够对合金的铸造性能做出评估。基于铝合金铸造性能的实际需求分析,在铸造合金凝固特性检测系统的基础上,采用C++Builder的面向对象设计开发一套铝合金铸造数据库系统。通过铸造合金凝固特性检测仪对铝合金在凝固过程时的传热、线收缩、热裂和应力等特征参数进行采集,结合数据库中有关铸造铝合金材料的相关信息,分析铸造工艺设计过程中参数的形式和特点,从而实现铸造铝合金材料的数据采集、查询、分析、维护和打印等综合功能。

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。

基于集成计算平台的高强韧铝合金半连铸工艺优化

基于集成计算材料工程(ICME)思想,使用数字化集成计算平台依托ProCAST仿真模拟软件、MATLAB数值分析软件,并使用最优化方法中序列(逐步)二次规划法(SQP),优化了半连续铸造制备直径254 mm的7050铝合金圆锭工艺,得到较优铸造温度为690℃,所得铸锭的残余应力值最小。与传统优化方式,即逐步调整工艺参数并分析模拟结果的方法相比,数字化集成平台迭代进行工艺寻优的效率提高了1倍。在此优化工艺下得到铸锭的屈服强度为218 MPa,抗拉强度为336 MPa。

基于ProCAST的箱体盖铸造浇注系统优化

针对传统砂型铸造工艺生产效率低以及铸件精度差的弊端,采用负压实型铸造法成型了铝合金箱体盖铸件。本文通过对比研究了两种铸造浇注系统。结果表明,与单通道式浇注系统相比,多通道式浇注系统的充型速率更均匀,铸件质量更好。并基于多通道式浇注系统研究了耐火涂层厚度、耐火涂料的透气指数等工艺参数对充型过程的影响。

铝合金副车架环保型制芯工艺研究及应用

针对整体式铝合金副车架树脂砂芯体积大,浇注过程烟雾大、环境污染严重等难点,试制开发无机砂芯工艺。通过制芯设备选型、水平分模射芯方式确定,再对芯砂组份配比、混砂时间、芯盒温度、保存温度及湿度等工艺参数进一步试验研究。试验结果表明,整体式副车架铸造采用无机制芯工艺砂芯更容易成型,浇注过程中不仅没有明显的热分解产物、无任何凝聚物,还易溃散去砂效果好、发气量低等优点,有效降低气孔类缺陷提高产品质量,促进绿色低碳铸造技术发展。

金属型低压铸造铝合金裂纹分析及改进

从宏观特征、微观形貌、成分性能及金相组织等方面,分析了金属型低压铸造铸铝件的铸造裂纹特征。对裂纹进行了原因分析,并通过制定针对性改进措施,从源头彻底解决了铸造裂纹,大大提高了产品的铸造成品率。

铝合金套筒铸件仿真分析与工艺优化

通过AnyCasting铸造模拟软件对一种铝合金套筒原金属型低压铸造工艺进行仿真分析,研究了铸造缺陷出现的原因,并开展工艺优化。结果表明,原工艺内浇道不能较好补缩法兰,以及下法兰一字浇道没有起到补缩作用,却加大局部热节,导致法兰背面加工槽出现缩孔、缩松缺陷;初步优化工艺将原工艺内浇道扩大,并取消一字形内浇道,缺陷明显减小,但仍存在;对初步优化工艺进一步采取降低充型速度,与采用风冷铜镶块两种优化方案,都实现了法兰由远离内浇道端向内浇道顺序凝固,铸件缺陷消除。按照初步优化工艺并降低充型速度,开展试制与批量生产,铸件合格率达98%以上。