水基涂料对冷芯盒法砂芯强度影响的研究

冷芯盒法砂芯浸涂水基涂料后强度会明显下降。砂芯脱盒至浸涂料的放置时间、浸涂料后不同的干燥方法及不同涂料对砂芯的强度都有不同程度的影响。混砂时加入适量二甲苯等抗湿剂，可以有效地抑制砂芯浸涂水基涂料后强度的降低。     

铸造涂料在灰铸铁缸体上的选配及应用

从组芯工艺和砂芯复杂程度、铸件缺陷、芯砂类别及粒度方面介绍了铸造涂料的研配及选型,详细阐述了铸造涂料在不同系列轿车发动机缸体砂芯上的应用情况.最后指出:涂料的选择应根据不同铸件和砂芯的质量要求,选用适合铸件或砂芯特点的专用涂料,使涂料的性能与铸件质量相得益彰,既不使涂料性能过度优异造成成本浪费,又能满足铸件质量需求;供...     

中等功率柴油机缸体和缸盖制芯工艺

总结了中等功率柴油机缸体、缸盖制芯工艺的要点,包括:缸体缸筒砂芯设计应尽量避免实心制芯;在湿砂造型生产线大批量生产缸盖的情况下,应尽量采用底座砂芯;水套砂芯应尽量设计成整体;缸体、缸盖砂芯一次涂料一般用水基涂料,特别部位的二次涂料一般用醇基涂料;缸体、缸盖砂芯必须采用组芯胎具和夹具来完成组芯和下芯工序;等。最后指出:近精确制芯技术是中等功率柴油机铸造业的发展方向。     

电动汽车水冷机壳螺旋砂芯自动涂覆系统设计

应用现代控制技术设计低压铸造电动汽车机壳水道砂芯表面涂料自动化涂覆设备,通过步进电机驱动悬挂在导轨上的砂芯连续进入带有搅拌装置的涂覆箱内,并经传感器反馈信号调节控制涂覆系统自动运转过程和速度,改变以往运用手工逐个进行砂芯涂料涂刷的方法,达到快速均匀地涂料涂覆目的,加快生产效率,提高和稳定砂芯生产质量。     

柴油机气缸盖进、排气道脉纹铸造缺陷研究及预防

研究认为，柴油机气缸盖进、排气道脉纹的产生主要是由硅砂高温发生相变膨胀导致砂芯开裂引起的。通过改进浇注系统，特别是采取在进、排气道芯砂中添加特殊抗脉纹添加剂及在砂芯表面涂刷烧结型涂料等工艺，有效地预防和消除了脉纹缺陷。     

全气动化砂芯浸涂涂料槽

传统的砂芯浸涂涂料槽装置的运转较多地采用电动的方式来实现.本文简要介绍了全气动砂芯浸涂涂料槽的配置及原理,为仅可使用压缩空气作为动力源的特殊场合涂料槽的使用提供了可行的手段.     

气缸盖组芯浸涂夹具的改进

详细介绍了柴油机缸盖砂芯浸涂夹具的改进经验。缸盖砂芯夹具的主要功能是:从砂芯预装座夹起盖板芯和底座芯组,运送到浸涂工位进行涂料浸涂,然后将多余涂料甩除,将砂芯放在烘干板上。原浸涂夹具的翻转动作由2个电机和2套链轮机构完成,有时会发生不同步情况,为此改进为由1个电机驱动的夹紧翻转系统,消除了不同步问题。砂芯侧面夹紧系统原采用气囊夹紧方式,砂芯容易被夹坏,气囊管口容易被涂料侵蚀,烘干板清理工作量大,生产率低,为此改进为气缸夹紧方式,避免了上述问题。叙述了甩除多余涂料的最佳夹具摇摆速度和最佳摇摆角度;最后还介绍了夹具水平限位器的设计和材料选择。     

水分对三乙胺法冷芯盒砂芯强度及断裂的影响

研究了水基涂料和环境湿度对三乙胺法冷芯盒砂芯强度的影响,并利用扫描电镜分析了砂芯断口。结果表明：（1）水基涂料使砂芯24h终强度显著下降,下降幅度随树脂加入量的增加而减少;存放1~6h后浸涂的砂芯强度低于即时浸涂强度和24h浸涂的砂芯强度。（2）在常温高湿环境下,随着砂芯存放时间的延长,砂芯强度出现显著的下降;在40℃、RH100%的环境下,砂芯的强度在5h达到最大值,随后砂芯的强度随放置时间的延长迅速下降。（3）低湿环境树脂粘结桥断口为以内聚断裂为主的复合断裂;而高湿环境里存放的砂芯,水分使树脂粘结桥出现裂纹、砂芯呈附着断裂。     

发动机缸体油道芯的冷芯盒工艺

详细介绍了采用冷芯盒工艺生产油道芯的过程,得出以下结论:(1)采用冷芯盒工艺生产壁薄砂芯的关键在于保证强度。制芯过程中射砂压力的选取应尽可能比厚壁砂芯略大,吹胺过程注意低压和高压的结合;使用水基涂料时,砂芯制完后应尽快上涂料,减小水分对砂芯强度的影响;砂芯储存过程中要关注环境的湿度。(2)冷芯的脉纹问题可通过添加宝珠砂和防脉纹剂,并结合防脉纹的保温涂料来解决。根据砂芯的不同,建议特种砂的加入量控制在30%以上。(3)采用冷芯盒工艺生产薄壁砂芯时,只要能解决好强度和脉纹问题,该工艺在生产节拍、生产质量控制、人员投入、能源消耗等方面均优于热芯盒工艺。     

自由基团树脂砂砂芯强度的研究

对自由基团树脂砂制芯新工艺进行了砂芯存放时间、吹气、芯盒温度、砂芯加热温度、不同混砂方式对强度的影响试验.分析了工艺方法对砂芯强度和表面强度的影响以及周围环境湿度和涂料对砂芯性能的影响,得出适用于生产的工艺参数.     

New sol-gel refractory coatings on chemically-bonded sand cores for foundry applications to improve casting surface quality

Foundry refractory coatings protect bonded sand cores and moulds from producing defective castings during the casting process by providing a barrier between the core and the liquid metal. In this study, new sol-gel refractory coating on phenolic urethane cold box (PUCB) core was examined. The coating density, viscosity, moisture content and wet and dry weight of the coating were evaluated on cores that had been coated at three different dip-coating times. The coating coverage, surface appearance and depth of penetration into the cores were examined with a Stereomicroscope. Gray iron castings were produced with sol-gel coated and uncoated cores and the results were related to the coating properties. The casting results were also compared with castings made with cores coated with commercial alcohol-based and water-based foundry coatings. The analyses show that castings produced with sol-gel coated cores have better surface quality than those from uncoated cores and comparable surface quality with the commercial coatings. Therefore, the new sol-gel coating has a potential application in the foundry industry for improving the surface finish of castings thereby reducing the cost of fettling in the foundry industry since the raw materials and technology are easily affordable.     

Prediction of burn-on and mould penetration in steel casting using simulation

Abstract

Burn-on and penetration defects in steel casting are principally caused by localised overheating of the sand mould or cores. Such overheating can cause liquid metal to compromise the mould surface and entrain onto the surface of the mould. A method has been developed to predict likely burn-on and penetration defect locations as part of a standard casting simulation. The method relies on determining, from simulation results, the locations where the mould is above a certain critical temperature. The critical temperature is generally above the temperature at which the steel is fully solidified. By measuring the time periods during which these locations in the mould are above the critical temperature, burn-on and penetration defects can be predicted. The method is validated through comparison with previous experimental data. Several parametric studies are conducted to investigate the sensitivity of the predictions to the choice of the critical temperature, the interfacial heat transfer coefficient between the steel and the mould, the pouring temperature, and the mould material. The results of one case study are presented where burn-on or penetration defects observed on a production steel casting are successfully predicted.     

便携式扫描仪在3D打印砂芯精度测量中的应用

为确保能快速测量、分析3D打印砂芯从而得出合适的打印工艺参数,本文分析了原砂粒度与粒形、黏结剂覆膜与渗透对打印砂芯精度的影响,介绍了扫描仪测量误差的影响因素。通过对便携式扫描仪所测量的砂芯精度尺寸的分析,提供合适的修正参数,从而生产出符合要求的高精度砂芯,也印证了便携式扫描仪能够在砂芯精度测量中广泛使用。     

醇基防渗透砂状涂料替代锆英粉涂料的研究应用

介绍了一种用于铸钢件的可替代锆英粉涂料的新型醇基砂状涂料,耐火骨料采用以70～200目为主的铬铝质砂状材料。这种涂料有着良好的悬浮稳定性,涂刷流畅,多次反复涂刷不起皮,附着强度高,发气量小。它与高温钢液接触时,有着很高的热稳定性,不与FeO等金属氧化物起熔蚀反应,抗钢液渗透能力强。在许多铸造厂应用表明:其防渗透粘砂效果优于锆英粉涂料。当涂刷达到5～6遍,可以部分替代铬铁矿面砂工艺而应用于厚大铸钢件热节处。     

Mechanical properties and multi-scale modeling of nanocrystalline materials

A generalized self-consistent scheme based on the coated inclusion method and using interfacial operators is developed and used to describe the grain-size-dependent viscoplastic behavior of pure fcc nanocrystalline materials. The material is represented by an equivalent three-phase material composed of coated inclusions embedded into an equivalent homogeneous medium. Inclusions represent grain cores and behave viscoplastically via dislocation glide while the coating represents both grain boundaries and triple junctions. A recently introduced constitutive law accounting for grain boundary dislocation emission and penetration is used to model the behavior of the coating. The model is applied to pure copper and enables the quantification of the macroscopic effect of interface dislocation emission. The analysis is completed with a set of finite element simulations revealing high stress concentrations at triple junctions.     

湿砂型冷芯铸造缸体的缺陷分析及对策

对大众系列发动机缸体开发过程中遇到的铸造缺陷进行了原因分析,并提出了相应的解决措施：（1）解决水套内腔局部断芯的措施有：使用特种砂替代硅砂、改进水套砂芯涂料工艺、严格控制原材料工艺参数、保证砂芯具有足够强度;（2）解决缸体顶面水套外壁夹砂的措施有：应用天然钠土替代部分人工活化土、缩短水套外壁受热辐射时间、减少砂芯发气量、增强铸型排气效率;（3）解决缸体外表面粘砂的措施有：细化型砂粒度、增加砂型孔隙阻力,增加砂型气体背压、阻止金属液侵入砂型孔隙,控制旧砂温度与水分、减少铸件热粘砂,优化型砂参数,等.     

带厚对FeCuNbSiB纳米晶铁芯性能的影响

采用标称成分为Fe73.5Cu1Nb3Si15.5B7(原子百分数)、带厚分别为18 μm、22 μm和26 μm的带材制成环形铁芯,经过560℃保温1h热处理后测试其性能,发现铁芯损耗随带材厚度的减小而降低,实验中用18μm和22 μm厚带材制备的铁芯与在共模电感方面处于国际领先地位的VAC公司生产的同规格铁芯在电感...     

空心涡轮叶片中残芯的定量评价

航空发动机空心涡轮叶片的铸造成形过程中的每个步骤都需要极其严格的质量控制,残芯评价也是必不可少的环节.基于浸泡法深入研究空心涡轮叶片中残芯的结构特征及其中子检测能力.结果表明:冷中子照相可以清晰分辨0.2 mm厚、经Gd元素标记的残芯,这种高灵敏度检测特性取决于残芯所吸收Gd元素的含量,与残芯的疏松多孔性、浸泡溶液的可...     

Fabrication of silica-based ceramic cores with internal lattice structures by stereolithography

Ceramic cores are widely used in investment casting, and ideal properties of cores are essential for high-quality castings. Under the circumstances requiring thick cores, solid cores are likely to encounter deformation and cracking defects due to the accumulation of shrinkage. Therefore, with the superiority of ceramic stereolithography in producing complex ceramic parts, hollow cores with lattice structures were designed and fabricated. The dimensional accuracy and properties of the green and sintered bodies were evaluated. Results show the dimensional accuracy of sintered cores is controlled within ±0.25 mm benefited from the precise green bodies. The mechanical properties are not obviously deteriorated. The bending strength reaches 11.94 MPa at room temperature and 12.87 MPa at 1,500 °C with a creep deformation of 0.345 mm. Furthermore, casting verifications prove that the hollow cores meet the requirements of investment casting. Smooth casting surfaces are obtained, at the same time, the core-removal efficiency is improved by over 3 times.