Assessing efficacy of standard impregnation techniques on die-cast aluminum alloys using X-ray micro-CT

Utilizing lightweight Al alloys in various industrial applications requires achieving precise pressure tightness and leak requirements.Vacuum pressure impregnation(VPI)with thermosetting polymers is commonly used to address leakage defects in die-cast Al alloys.In this study,the efficacy of the VPI technique in sealing alloy parts was investigated using a combination of nondestructive micro X-ray computed tomography(micro XCT)and a standard leak test.The results demonstrate that the commonly used water leak test is insufficient for determining the sealing performance.Instead,micro XCT shows distinct advantages by enabling more comprehensive analysis.It reveals the presence of a low atomic number impregnates sealant within casting defects,which has low grey contrast and allows for visualizing primary leakage paths in 3D.The effective atomic number of impregnated resin is 6.75 and that of Al alloy is 13.69 by dual-energy X-ray CT.This research findings will contribute to enhancing the standard VPI process parameters and the properties of impregnating sealants to improve quality assurance for impregnation in industrial metals.

Microstructure and mechanical properties of Mg-6Gd-3Y-0.5Zr alloy processed by high-vacuum die-casting

GW63K （Mg-6Gd-3Y-0.5Zr） magnesium alloys were prepared successfully by high-vacuum die-casting. Effects of fast shot speed and vacuum level on the grain size and mechanical properties of this alloy were studied. Microstructure of the alloys was analyzed by SEM, EDX and optical microscope （OM）. The effect of heat treatment on high vacuum die-casting （HVDC） GW63K alloy was also studied. The results indicate that with the increase of fast velocity, the tensile yield strength hardly changes, but the elongation first increases, then decreases. The optimum heat treatment process is solution treatment at 748 K for 2 h and aging at 473 K for 80 h. Under this condition, GW63K magnesium alloy exhibits a maximum tensile strength and elongation of 308 MPa and 9.45%. There is significant correlation between ductility and the presence of external solidified cells （ESCs）. The as-cast GW63K alloy consists ofα-Mg and Mg24（Gd,Y）5 particles. After heat treatment, Gd and Y atoms dissolve intoα-Mg matrix.

A review of magnesium die-castings for closure applications

Vehicle mass reduction in the automotive industry has become an industry-wide objective.Increasing fuel efficiency and greenhouse gas emission targets for engine-powered vehicles,and ambitions for extended range electric vehicles have motivated these reductions in vehicle mass.Mass reduction opportunities in structural automotive applications are increasingly realized through lightweight alloy castings,such as magnesium,primarily due to the ease of component substitution.The traditional benefits of magnesium die-castings including lightweighting and associated compounded mass savings,excellent strength-to-weight ratio,part consolidation,near net-shape forming,dimensional repeatability,and integration of additional components can be realized in closure applications.One recent example is the application of a magnesium die-casting for the structural inner of the liftgate in the 2017 Chrysler Pacifica,replacing nine parts in the previous generation and resulting in a liftgate assembly weight reduction of nearly 50%.The work presented here reviews past and current developments of magnesium die-castings in closure applications and discusses the benefits and challenges of magnesium alloys for these applications,including casting design,corrosion and fastening strategies,and the manufacturing design and assembly methodologies.

Development of vacuum die-casting process

The vacuum die-casting process,started 25 years ago in Japan,has been widely applied.This technology contributes very much to improvement of castings quality.The main factor causing the defects of die castings is the trapped air in the mold cavity,while the key technology of vacuum die-casting process is to avoid the trapped air effectively by evacuating the cavity before casting.At the same time,due to the shot speed and the casting pressure reduced in half,the service life of the die is prolonged and the productivity is enhanced,as well.Vacuum die-casting process is of great signif icance in improving the die castings quality and making up the shortcomings of super-high-speed shot casting.

Simulation of α-Al grain formation in high vacuum die-casting Al-Si-Mg alloys with multi-component quantitative cellular automaton method

Al-Si-Mg alloys are the most commonly used material in high vacuum die-casting(HVDC),in which the morphology and distribution ofα-Al grains have important effect on mechanical properties.A multi-component quantitative cellular automaton(CA)model was developed to simulate the microstructure and microsegregation of HVDC Al-Si-Mg alloys with different Si contents(7%and 10%)and cooling rates during solidification.The grain number and average grain size with electron backscatter diffraction(EBSD)analysis were used to verify the simulation.The relationship between grain size and nucleation order as well as nuclei density was investigated and discussed.It is found that the growth of grains will be restrained in the location with higher nuclei density.The influence of composition and cooling rate on the solute transport reveals that for AlSi7Mg0.3 alloy the concentration of solute Mg in liquid is higher at the beginning of eutectic solidification.The comparison between simulation and experiment results shows that externally solidified crystals(ESCs)have a significant effect for samples with high cooling rate and narrow solidification interval.

Thin-Wall Aluminum Die-Casting Technology for Development of Notebook Computer Housing

Silicon-based aluminum casting alloys are known to be one of the most widely used alloy systems mainly due to their superior casting characteristics and unique combination of mechanical and physical properties. However,manufacturing of thin-walled aluminum die-casting components,less than 1.0 mm in thickness,is generally known to be very difficult task to achieve aluminum casting alloys with high fluidity.Therefore,in this study,the optimal die-casting conditions for producing 297 mm×210 mm×0.7 mm thin-walled aluminum component was examined experimentally by using 2 different gating systems,tangential and split type,and vent design.Furthermore,computational solidification simulation was also conducted.The results showed that split type gating system was preferable gating design than tangential type gating system at the point of view of soundness of casting and distortion generated after solidification.It was also found that proper vent design was one of the most important factors for producing thin-wall casting components because it was important for the fulfillment of the thin-wall cavity and the minimization of the casting distortion.

Mold Filling and Prevention of Gas Entrapment in High-pressure Die-casting

This paper presents some results of direct observation of mold filling in a specially designed die-casting by X-ray diffraction, including comparison with numerical simulation. Based on such work the authors discuss how to prevent gas entrapment and propose new methods.

Opportunities and challenges of Chinese die-casting market

The present status and perspectives of Chinese die-casting market were commented. In 2003, the total output of die castings in the whole country was 708000 tons, in which the outputs of Al-alloy, Zn-alloy, Mg-alloy, Cu-alloy die castings were 474600 tons, 222000 tons, 5800 tons, 5600 tons, respectively, each accounted for 67%, 31.35%, 0.85%, 0.8% of the total. The annual sale volume of die-casting machines was approximately 1800. And the gross output value of dies approached RMB 38 billion, in which die-casting dies accounted for about 10%. In the die-casting industry of the entire country, the foreign capital enterprises, public-run enterprises, township and village enterprises, private enterprises accounted for over 80% of the total die-casting enterprises. Super huge die-casting groups are forming.

Development and Application of Die-Casting High Speed Steel Rolls

Due to its high hardness,good red hardness and excellent wear resistance at high temperature,high speed steel(HSS)is fit for the roll manufacture.In order to overcome the segregation of centrifugal casting of HSS roll,die-cast processes were developed and its effects on the properties of the HSS roll were investigated.It was found that pressure,pressing time and speed are three important factors affecting shrinkage cavity.For pouring temperature of 1 400-1 450 ℃,pressure of 150-160 MPa,pressing time of 120-150 sand pressing speed of 14-16mm/s,a compact HSS roll was obtained,which has no segregation and small working allowance.In the high speed wire rod rolling mill,service life of the HSS roll is 5to 8times longer than that of high nickel chromium infinite chilled cast iron roll.

An Improved Elite Slime Mould Algorithm for Engineering Design

The Swarm intelligence algorithm is a very prevalent field in which some scholars have made outstanding achievements.As a representative,Slime mould algorithm(SMA)is widely used because of its superior initial performance.Therefore,this paper focuses on the improvement of the SMA and the mitigation of its stagnation problems.For this aim,the structure of SMA is adjusted to develop the efficiency of the original method.As a stochastic optimizer,SMA mainly stimulates the behavior of slime mold in nature.For the harmony of the exploration and exploitation of SMA,the paper proposed an enhanced algorithm of SMA called ECSMA,in which two mechanisms are embedded into the structure:elite strategy,and chaotic stochastic strategy.The details of the original SMA and the two introduced strategies are given in this paper.Then,the advantages of the improved SMA through mechanism comparison,balance-diversity analysis,and contrasts with other counterparts are validated.The experimental results demonstrate that both mechanisms have a significant enhancing effect on SMA.Also,SMA is applied to four structural design issues of the welded beam design problem,PV design problem,I-beam design problem,and cantilever beam design problem with excellent results.

Code generation and recognition using a modified ejection system in die-casting process

A code-generation and recognition technology that uses a modified ejection system in the diecasting process is presented.To achieve the highest level of quality management,the first requirement in the manufacturing process is to establish a product management system according to the specific product unit.Thus,a method to individually identify each product,such as a barcode or QR code,is required during the production process.Products manufactured in the die-casting process always have ejector pin(EP)marks.Herein,an ejection system was modified to generate a unique code using EP marks.This ejection system has two features:an EP with a modified head to show the direction of rotation,and a function to dependently rotate EPs(five or six EPs)with a constant angle.The EPs are numbered according to the rotation angle.Thus,the EP marks can be viewed as a five-or six-digit code.A program was also developed to individually identify the products by automatically detecting and reading the EPs using deep learning-based object detection and classification technology.

Two semi-solid die-casting production lines of Xuzhou Die- casting Technology Co., Ltd. officially put into operation

The two production lines for the first phase of the semi-solid die-casting high-end parts project were put into production in this October, and can monthly produce more than 30 thousand die casting parts.

基于UG的拖拉机大灯注塑模具设计

以拖拉机大灯为例,分析了UG注塑模具建模的设计方法和工艺方案,建立了拖拉机大灯模型,并完成了拖拉机大灯注塑模具的设计。研究结果表明:经过UG模拟开模出来的塑料件没有出现气泡、变形、缺料和银线等缺陷,整体也没有发现熔合条纹,设计的拖拉机大灯注塑模具满足设计需求。

基于改进黏菌算法的光伏多峰值MPPT控制

针对传统最大功率点跟踪技术在局部遮阴等天气条件下存在无法追踪到全局最大功率点的问题,提出一种基于改进黏菌算法的MPPT控制。首先,对太阳电池模型及多峰值特性进行分析;其次,在黏菌算法中引入领导者策略和基于最优个体的凸透镜反向学习策略,在提高算法计算精度、收敛速度的同时克服了算法易“早熟”现象;最后,根据光伏阵列最大功率输出特性分别确定算法优化模型、初始化位置及重启机制。仿真与实验结果表明:基于改进黏菌算法的MPPT控制能快速、准确地跟踪到全局最大功率点,有效规避陷入局部最优问题,提高了光伏系统的转换效率。

基于改性PP成型的工控机电路板支撑架注射模设计

针对工控机电路板支撑架大型塑件的成型,选用了一种玻纤改性增强聚丙烯(PP)复合材料用于塑件的注射成型。模具结构为三板模结构,分3次开模打开。为保证塑件模腔充填均衡性、饱满性而设计了两个点浇口用于模腔的浇注。针对塑件二级子特征较多,特别是异型螺柱深筋位较多的特点,设计了多个局部镶件用于这些局部特征的成型,在提高局部成型镶件强度的同时,降低了这些成型件的加工难度。针对模腔局部位置排气难点,设置了多个透气镶件以增强排气。设置了锁扣机构、定距拉杆机构用于模具的开模闭模控制;设计了弹料机构用于流道废料的可靠脱模、定位机构以确保塑件的成型精度和模具工作寿命;3个滑块机构用于塑件侧壁直壁及直壁上侧孔的成型与脱模。模具结构形式合理,成型件便于加工且实用可靠,能为同类模具设计提供有益借鉴。

基于Polyflow正压防护面罩吸塑成型过程

为探究正压防护面罩吸塑成型过程中不同工艺参数组合对其影响。结合实际设计的要求,采用PET材料作为面罩吸塑材料,基于Ployflow,分析不同压力、温度组合的工艺参数及初始板材厚度对面罩吸塑成型的影响。结果表明,利用面积延伸率、厚度均匀性及面罩成型深度综合分析面罩的吸塑成型质量发现,温度和压力对面罩成型质量的影响较显著。由于板材厚度与成型深度呈负相关,再结合面罩成型深度的要求可知,在符合设计要求的条件下,当工艺参数组合为温度114℃、压力0.65 MPa、PET板材初始厚度为1 mm时,面罩质量最佳。

鞍钢8m弧半径小方坯连铸机提速实践

针对8 m弧半径小方坯铸机拉速低不能满足生产要求的问题,分析了影响铸机提速的主要原因,采取了增加结晶器长度,更新结晶器供水泵,更新二冷水嘴,增大二冷管径以及优化系统温度等措施,铸机拉速由2.8 m/min提高到3.5 m/min,铸坯质量合格率达到99.95%,实现了小方坯铸机高速稳定生产。

汽车空调控制面板双色倒装热流道注射模设计

汽车空调控制面板作为人机交互界面不可或缺的操作零件,设计时为了集成使用功能和外观美感等多重要求,一般设计为双色注塑件。以某汽车内饰空调控制面板为例,设计了一副双色倒装热流道注塑模,并详细介绍了零件结构特征、模具结构设计方案及工作原理。由于零件结构特殊性和注塑材料成型温度差异,塑件在成型过程中采用传统正置成型方案时表面易出现串色、印痕等缺陷,成型良品率较低,故模具采用倒装结构设计方案,即第一色先成型茶色透明的聚碳酸酯(PC)外观部分,再成型第二色黑色的PC/丙烯腈-丁二烯-苯乙烯塑料(ABS)基体部分。基于模具的倒装结构,其第一、二色均采用热流道系统进料,同时为了确保零件顺利生产、顶出顺畅,在第一色子模内设置拉料柱和预压型推出机构,第二色子模具的定模侧设计了斜顶和顶针联合顶出机构,利用油缸驱动实现塑件脱模。实验证明,该倒装双色热流道注塑模整体结构稳定可靠,塑件批量生产质量满足设计要求。

半预制预应力UHPC-S-NC盖梁静力性能试验及理论分析

为解决大悬臂盖梁吊装重量大且难以实现预制拼装的技术难题,利用超高性能混凝土(Ultra-High Performance Concrete,UHPC)优异的力学性能,提出了采用由UHPC、钢板和型钢(Steel,S)制作的槽形组合结构作为永久模板,架设就位后浇筑普通混凝土(Normal Concrete,NC)的新型半预制预应力UHPC-S-NC盖梁.为研究其抗裂性能、刚度并对其安全性进行评估,结合实际工程,设计一片1∶2.5的大比例缩尺模型并进行全过程静力加载测试,获得了试验梁的变形特征、开裂荷载、裂缝开展、分布规律和应变等关键试验数据.分析了试验梁裂缝分布和应变发展规律;考虑材料塑性应力-应变关系,提出了结构UHPC层和NC层的开裂弯矩计算模式和计算方法;并根据截面平衡条件提出了组合结构的抗弯承载力计算模式,同时,依据规范对结构抗剪承载力的计算模式进行了探究.结果表明:新型组合盖梁结构具有施工快捷、装配化程度高等特点;开裂弯矩的计算结果与试验值吻合较好;采用平衡条件和叠加法评估结构的承载力,新型盖梁结构具有足够的承载能力,结果偏于安全;针对实际工程提出了一些具体的结构设计和施工的建议.研究成果可为半预制盖梁的应用提供参考.

汽车侧裙板数值成型分析及模具设计

汽车侧裙板长度约为1 m,宽度约为0.1 m,卡扣、加强筋、嵌件孔等复杂结构较多,属于大型细长复杂塑件。大型细长复杂塑件成型难度较大,需要采用数值仿真与模具设计相结合的方法,仿真、设计和验证交叉进行、相互渗透。根据产品的特点拟定了3种进浇方案,仿真结果表明,方案Ⅲ(9点进浇)翘曲变形量最小,其值为4.51 mm。通过验证方案Ⅲ的缩水性、填充时间、填充等值线、填充末端时间差及压力差等参数可知,方案Ⅲ填充均匀、末端压力一致、产品无缩水,表面无质量缺陷,为可行方案。根据方案Ⅲ进行模具设计,包括浇注系统、成型零部件、推出机构、冷却系统等。模具设计完毕后对冷却系统进行验证,结果表明,凸凹模的模温温差小于10℃,模温趋于一致,无翘曲变形风险。基于方案Ⅲ的模具设计可作为最终方案,为模具制造和生产提供方向。