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.

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.

Modal Test/Calculation Correlation Study on the Lower Crankcase of High-Duty Diesel Engine

To set up the dynamic FEM model of a high-duty diesel's lower crankcase with sufficient precision, modal correlation research on tested and calculated modes have been fulfilled. MACs between each mode pairs, CoMACs and ECoMACs on each node of modal testing model have been calculated. On the assistant of modal shape comparison, MACs could afford information about correlating relations between tested and calculated mode groups. CoMACs and ECoMACs have pointed out the direction of structure modification to FEM model. The results of the study show that the analytic model built has a certain degree of accuracy.

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.

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.

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.

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.

开架发电机组冷却系统性能评估及结构改进

发电机组冷却系统流场分析及冷却性能评估有助于确认冷却系统总流量大小、冷却风量分配比例和冷却风流速分布特性,确保风道流量分配均匀和高温区域冷却良好。以某开架发电机组为研究对象,根据冷却系统设计要点对其冷却系统进行了初始布局结构设计,采用流体分析软件STAR-CCM+搭建了开架发电机组冷却系统流场分析模型。结果表明,缸头风道风量占发动机风道总风量的48.77%,箱体底部风量占比为6.7%,不利于发动机缸头和机油的冷却。通过调整导流罩与散热片间距、风扇罩更改为渐扩线形式、箱体开孔与散热片形状及导流的匹配改动、拉盘开孔增大等方式形成了开架发电机组冷却系统结构改进方案。改进后该机组缸头风道风量占发动机风道总风量的61.83%,箱体底部风量占比为13.04%。缸头风道风量及箱体底部风量基本满足发动机缸温及油温的冷却需求。发动机各风道冷却风速度分布均匀,电机冷却较好,空滤器进风均来源于外界冷却风;消声器表面风速分布均匀,不存在流动死区且靠排气管处风速较大。该发电机组冷却系统可对机组实现较好的冷却,保障机组正常且长时间运行。研究结果可为发电机组冷却系统布局设计及结构改进提供参考。

Study on Key Joining Technology and Test Method of Steel/Al Hybrid Structure Body-in-White

Green and low carbon promote the application and development of light-weight materials in body-in-white. Large-scale die-casting Al alloy (DCAA) and high-strength thermo-formed steel sheet (TFSS) have put forward higher requirements for the application of joining technology of high-strength steel/Al dissimilar materials. Taking the new die-casting Al alloy body as an example, this paper systematically studies the progress of the latest joining methods of steel/Al dissimilar material with combination of two-layer plate and three-layer plate. By analyzing the joining technologies such as FSPR, RES, FDS and SPR, the technology and process characteristics of steel/Al dissimilar material joining are studied, and the joining technical feasibility and realization means of different material combination of the body are analyzed. The conditions of material combination, material thickness, material strength, flange height, preformed holes and joint spacing for achieving high-quality joining are given. The FSPR joining technology is developed and tested in order to meet with the joining of parts with DCAA and TFSS, especially for the joining of three-layer plates with them. It finds the method and technical basis for the realization of high quality joining of dissimilar materials, provides the early conditions for the application of large DCAA and TFSS parts in body-in-white, and meets the design requirements of new energy body. .

High Cycle Fatigue Properties of Die-Cast Magnesium Alloy AZ91D with Addition of Different Concentrations of Cerium

The effect of addition of different concentrations of Ce on high-cycle fatigue behavior of die-cast magnesium alloy AZ91D was investigated. Mechanical fatigue tests were conducted at the stress ratio of R = 0.1, and fatigue strength was evaluated using up-and-down loading method. The results show that the grain size of AZ91D alloy is remarkably refined, and the amount of porosity decreases and evenly distributes with the addition of Ce. The fatigue strength of AZ91D alloy at room temperature increases from 96.7 up to 116.3 MPa （ 1% Ce） and 105.5 MPa （2 % Ce）, respectively, at the number of cycles to failure, Nf = 1 × 10^7. The fatigue crack of AZ91D alloy initiates at porosities and inclusions, and propagates along grain boundaries. The fatigue striations on fractured surface appear with Ce addition. The fatigue fracture surface of test specimens shows mixed-fracture characteristics of quasi-cleavage and dimple.

Low-cycle fatigue behavior of permanent mold cast and die-cast Al-Si-Cu-Mg alloys

Fatigue failure is one of the main failure forms of Al-Si-Cu-Mg aluminum alloys.To feature their mechanical aspect of fatigue behavior,the low-cycle fatigue behavior of permanent mold cast and die-cast Al-Si-Cu-Mg alloys at room temperature was investigated.The experimental results show that both permanent mold cast and die-cast Al-Si-Cu-Mg alloys mainly exhibit cyclic strain hardening.At the same total strain amplitude,the die-cast Al-Si-Cu-Mg alloy shows higher cyclic deformation resistance and longer fatigue life than does the permanent mold cast Al-Si-Cu-Mg alloy.The relationship between both elastic and plastic strain amplitudes with reversals to failure shows a monotonic linear behavior,and can be described by the Basquin and Coffin-Manson equations,respectively.

150BS基础油空间位阻和自氧化效应对柴油机油清净性的影响

采用曲轴箱模拟试验法考察了150BS基础油对柴油机油清净性能的影响,利用^(13)C NMR和凝胶渗透色谱对柴油机油组分进行了结构表征。实验结果表明:加入1%150BS基础油时清净性效果最优,加入5%150BS基础油时清净性效果最差。150BS基础油与柴油机油所用Ⅱ类基础油相比,其分子粒径更大。低含量150BS基础油空间位阻效应降低了机油组分自由基碰撞结合的概率,进而提高了柴油机油清净性能;而高含量150BS基础油在空间位阻效应抑制机油组分自由基碰撞概率的同时,自身产生更多自由基,反而提高了自由基碰撞结合概率,致使柴油机油清净性变差。

蠕墨铸铁轻量化曲轴箱的工艺研发与应用

介绍了蠕墨铸铁轻量化曲轴箱的结构和技术要求,详细阐述了采用SinterCast两步法蠕化处理工艺生产轻量化曲轴箱的熔炼工艺及过程控制,实现了蠕墨铸铁在线智能预测与调控,稳定了蠕墨铸铁件的质量。同时,使用自主研发的智能蠕化率自动评定系统,实现了蠕化率的自动测量和准确评级。经检测,生产的轻量化曲轴箱铸件材料质量稳定,铸件本体的蠕化率达到90%以上,珠光体体积分数达到95%,铸件本体的抗拉强度≥430 MPa,硬度为210~240 HB,符合技术要求。

农用柴油机活塞环组机油消耗和窜气的灰色关联分析与预测

活塞环组的润滑和密封性能直接影响柴油机的动力性、经济性和排放特性,机油消耗量(lube oil consumption,LOC)和窜气量(crankcase blow-by,CB)是评估活塞环组润滑和密封性能优劣的主要指标。为探究影响农用柴油机活塞环组LOC和CB的影响因素及LOC和CB对影响因素的敏感程度,该研究提出农用柴油机活塞环组LOC和CB的多影响因素系统分析及预测方法。以YNF40农用柴油机为对象,首先搭建柴油机LOC和CB测试台架,建立活塞环组运动学与动力学仿真模型并验证模型的精确度和可靠度,然后采用灰色关联分析(grey relation analysis,GRA)得到不同影响因素的灰色关联度(grey relational grade,GRG),并基于此进行影响因素敏感性分析,最后基于BP神经网络建立不同转速工况下LOC和CB瞬态变化的时间序列预测模型。多因素GRG分析结果表明:对活塞环组LOC和CB影响最敏感和最不敏感的因素分别是活塞第一环槽下边缘倒角和活塞第三环槽背隙,其对应的GRG分别为0.89279和0.58361,得到目标与影响因素敏感程度的降序排列为:第一环槽下边缘倒角、顶环开口间隙、第一环槽下侧环岸间隙、第二环槽侧隙、第二环槽下边缘倒角、第二环开口间隙、第三环槽上边缘倒角、油环开口间隙、第二环槽上边缘倒角、第一环槽背隙、顶环切向弹力、第三环槽上侧环岸间隙、顶环环槽下侧轮廓倾角、第二环槽下侧环岸间隙、第一环槽上侧环岸间隙、配缸间隙、第三环槽侧隙、第一环槽上边缘倒角、顶环环槽上侧轮廓倾角、第一环槽侧隙、第二环槽上侧环岸间隙、第三环槽下边缘倒角、第二环槽背隙、第三环槽下侧环岸间隙、顶环上端缩减量、第三环槽背隙。LOC和CB随活塞第一环槽下边缘倒角和活塞第三环槽背隙变化的平均标准差分别为2.81、3.90和0.003、0.209。各影响因素与LOC和CB的GRG越大,LOC和CB随影响因素变化的平均标准差越大,对影响因素越敏感。BP神经网络时间序列预测结果表明:预测值与真实值的变化趋势较一致且都分布在95%置信带以内,模型具有较高的预测精度。研究结果可为农用柴油机提高热效率、减少和控制碳排放提供有效指导。

球铁内燃机机身缩松缺陷的工艺改进

重点讨论了球墨铸铁机身在铸造过程中冒口根部的缩松缺陷。通过降低铸件浇注温度上限,即由1360~1380℃变为1360~1370℃范围内,同时将冒口颈尺寸为φ60 mm的φ120 mm保温冒口更改为冒口颈尺寸为30 mm×60 mm×25 mm的φ150 mm木质冒口以解决铸件冒口根部缩松缺陷。生产结果显示缩松问题得到彻底解决,为解决其他机身缩松缺陷提供了参考依据。

某型柴油机曲轴箱压力误报警原因分析与改进技术研究

针对某型柴油机在使用过程中多次出现曲轴箱压力过高报警停车问题,对柴油机自身运动件进行检查,重新起动无故障发生,可排除柴油机运行故障及零部件质量问题。另出现曲轴箱压力高报警时,油气分离器指示装置未出现变色,说明曲轴箱压力高报警问题的出现不是来自柴油机本身,而是报警系统及相关线路出现故障,造成误报警。造成误报警的原因是报警装置连接管路积油导致堵塞,引起控制系统误判并出现误报警。

发动机曲轴箱内腔脉纹成因分析及对策

介绍了发动机曲轴箱铸件的结构及生产中出现的铸件内腔脉纹问题,分析了曲轴箱油道内腔脉纹缺陷的形成机理,并采取多种措施进行改进,试验结果表明:(1)采用特种砂能解决脉纹问题,但显著增加铸件成本;(2)选择有机或无机防脉纹剂都会降低砂芯的强度,增加了铸件粘砂或烧结的风险,影响尺寸精度,造成铸件尺寸超差;(3)D381防脉纹涂料对铸件脉纹缺陷有着显著的抑制作用,并具有操作简单等综合成本上的优势。

An Industrial Perspective on Magnesium Alloy Wheels: A Process and Material Design

Light weights wheels improve vehicle performance with respect to road handling, cornering as well providing fuel economy and reduced greenhouse gas emissions. Aluminum wheels are currently used in many models and are produced usually by low pressure assisted gravity casting. Important property requirements are fatigue strength, pressure tightness, tensile strength, impact resistance, and corrosion resistance. Many attempts have been made to convert aluminum road wheels to magnesium. Race cars and some of the high end models (Porsche, Ferrari, etc.) have used magnesium wheels. These wheels have been gravity cast or forged. Viable corrosion protection systems have been developed and magnesium wheels have been used with success on these models. To use magnesium on more modest models is a challenge due to cost issues. Higher productivity casting processes or more cost effective coating systems need to be utilized. The project consists of selecting magnesium alloys for road wheels, examining the possible cost effective casting processes and corrosion protection systems, evaluating the cost per one wheel and comparing it to aluminum wheel costs. The wheels will also be compared with respect to fatigue and impact properties, pressure tightness, and corrosion.