Permeability of coating in the lost foam casting process

This study measured the pressures developed during a filling experiment using molten grey iron in the lost foam casting (LFC) process. The measured pressures included back pressure and permeable pressure. The back pressure is created in-mould from the metal-foam interface. The permeable pressure was measured on the mould side of the coating, when gases introduced from the decomposing EPS were permeating through the coating. The permeable pressure reflected the permeability of the coating while filling molten iron. Variables, which included particle sizes, types of binders, weight per cent of binder in coatings, influenced the permeability of coating at room temperature and at casting temperature.

Coatings made from flaky alumina developed a greater total length of pore channels than those made from angular silica. Increasing the particle size of the refractory increased the permeability of the coating at room temperature. The highest permeable pressure was measured when the particle size was 74 μm and acrylic resin was used as a binder. The optimum binder content was less than 1% for flaky alumina and acrylic resin binder. The optimum coating thickness was less than 0.5 mm to develop a maximum permeable pressure associated with a minimum back pressure in the mould.     

消失模铸造用涂料

介绍了对消失模铸造用涂料的技术要求,包括透气性、强度、润湿性、粘着性、干燥速度等和水基涂料、醇基涂料、树脂涂料的特点及耐火材料、粘结剂、溶剂、添加剂等主要组成的作用与选配原则;同时介绍了常用的涂料配方,常用涂料搅拌机的参数与性能特点、涂料的主要性能测试方法和涂料的干燥工艺等。     

消失模铸造涂料强度的研究

试验研究了消失模涂料的组成对涂层常温强度和高温强度的影响。探讨了各组分对涂料强度影响的程度及原因。研究表明用聚乙烯醇作粘结剂涂料可获得较高的常温强度,用铝矾土作耐火填科涂料可获得较高的高温强度。     

铸钢湿型砂醇基喷涂涂料的研制和应用

对铸钢湿型砂醇基涂料进行了试验研究,得到一种合适的涂料配方。实际应用表明,本涂料喷涂后成膜性能好,不开裂、不起皮,常温和高温强度高,高温抗裂性好,发气量低。采用该涂料喷涂铸型并浇注铸钢摇枕和侧架,铸件无粘砂现象且表面光洁。     

压铸镁合金有机涂层的技术经济评价

对比测试了丙烯酸、环氧树脂、有机硅、陶瓷有机硅和氟碳树脂等5种有机涂层在镁合金压铸件上的附着力、铅笔硬度、光泽度以及耐盐雾性能,并对各涂层工艺进行了经济成本核算和技术经济评价。结果表明,不同的有机涂层具有不同的技术经济特性。环氧树脂涂层在腐蚀防护上具有显著的技术经济优势;陶瓷有机硅涂层和氟碳树脂涂层在硬度、光泽度方面性能突出,但耐蚀性一般且成本高,技术经济特性一般;有机硅涂层各项性能适中,且成本低廉,经济性能较好;丙烯酸树脂涂层成本低廉,但耐蚀性能差,制约了涂层的应用,缺乏技术经济优势。     

负压实型铸造涂料的试验研究

通过试验,研究不同粘结剂和耐火粉料对EPC涂料性能的影响,设计制作EPC涂料层强度和透气性测试装置.试验结果表明:用PVA作粘结剂可使涂料获得良好性能,且能很好地适用于铸铁件的生产.     

Effects of Particle Strength of Feedstock Powders on Properties of Warm-Sprayed WC-Co Coatings

Warm spray (WS) process, which can control the temperature of a combustion gas jet used to propel powder, has been successfully applied to deposit WC-Co coatings. Detrimental reactions resulting from dissolution of WC into Co binder and decarburization were suppressed effectively by keeping the WC-Co particles’ temperature below the m.p. of the binder phase. In this study, three nano-structured WC-12Co powders with different particle strengths were prepared by changing the sintering conditions of spray-dried powder and were deposited by WS. The deposition efficiency and porosity of the coatings decreased with increasing the particle strength. The coating deposited from the powder with very low particle strength showed significant phase changes, while those deposited from the higher particle strengths showed almost no change. Particle Image Velocimetry revealed significant disintegration of the weakest powder, which explains the changes observed. The hardness and wear properties of the former coating, therefore, were inferior to the other two.     

碳纳米管改性无机-有机水性富锌涂料的制备及其性能

在常见的水性无机硅酸盐富锌涂料中添加适量的硅丙乳液及碳纳米管,制成了无机-有机复合水性富锌涂料。对几种不同配比涂层的主要力学性能、电化学性能、耐盐雾性能及耐空蚀性能进行了测试分析,结果表明当硅丙乳液和碳纳米管分别占基料的20%和1%,颜基比为2:1时,涂料的基料稳定,喷涂粘度适中;同时涂层在保持了无机富锌涂料优异耐腐蚀性能的基础上,其耐空蚀性能也得到了很大提高。     

气体硬化水溶性砂芯的性能研究

以电熔刚玉为骨料、氢氧化钡为粘结剂、铝粉为添加剂的型芯混合料在吹入CO_2气体后即可实现硬化。本文研究了这种型芯的硬化工艺和常温特性,并采用X射线衍射分析、失重—示差热分析等方法,结合粘结膜的扫描电镜照片,对型芯的受热物理化学变化、高温强度、水溶性等行为进行了实验研究。     

耐火填料急热膨胀值与涂层高温抗裂性的关系

通过对耐火填料和砂基底的急热膨胀值的测定，证实了耐火填料与砂基底之间的膨胀值是否相匹配决定了涂料层在高温下开裂的程度。根据此法选出的耐火材料所组成的涂料在高温急热时不开裂，浇注出的铸件表面无缺陷，表面粗糙度达１８－Ｓ。     

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.     

碳纳米管复合水性丙烯酸涂层的腐蚀性能研究

目的制备碳纳米管复合水性丙烯酸涂层,探索分析碳纳米管含量对涂层力学和防腐性能的影响规律。方法采用高速球磨方式制备3%,1%,0.5%三种含量(以质量分数计)的碳纳米管复合涂层,对涂层附着力、耐冲击性、耐弯曲性等力学性能进行测试,以电化学阻抗技术来评价碳纳米管复合涂层的防腐性能。结果添加碳纳米管显著提高了涂层的附着力,并且随着碳纳米管含量的增加,附着力上升;其他力学性能,如耐冲击性、耐弯曲性,在不同含量下均保持良好。对改性和未改性的涂层进行了电化学阻抗测试,其中1%的碳纳米管涂层电化学性能最优,在浸泡36 h后,未改性涂层低频区阻抗模值|Z|0.01为2.5×103Ω·cm2,0.5%的碳纳米管涂层为1.1×106Ω·cm2,1%的为1.4×108Ω·cm2,3%的为7×102Ω·cm2。结论由于碳纳米管本身的纳米效应,在较低含量时即可提高涂层的性能,并存在最优含量,超过此含量后性能有所下降。     

Formation of Splats from Suspension Particles with Solid Inclusions Finely Dispersed in a Melted Metal Matrix

A theoretical model has been developed to describe the splats formation from composite particles of several tens of micrometers in size whose liquid metal binder contains a high volume concentration of ultra-fine refractory solid inclusions uniformly distributed in the binder. A theoretical solution was derived, enabling evaluation of splat thickness and diameter, and also the contact temperature at the particle-substrate interface, under complete control of key physical parameters (KPPs) of the spray process (impact velocity, temperature, and size of the particle, and substrate temperature) versus the concentration of solid inclusions suspended in the metal-binder melt. Using the solution obtained, the calculations performed demonstrate the possibility of formulating adequate requirements on the KPPs of particle-substrate interaction providing a deposition of ceramic-metal coatings with predictable splat thickness and degree of particle flattening on the substrate, and also with desired contact temperature during the formation of the first coating monolayer.     

氟改性和硅改性丙烯酸聚氨酯涂层的制备及环境行为

目的研究氟改性和硅改性丙烯酸聚氨酯涂层在不同环境中的失效行为。方法通过溶液聚合法制备具有一定羟基含量的丙烯酸酯树脂,再将丙烯酸树脂与多异腈酸酯固化剂配合,获得丙烯酸聚氨酯涂层。通过在丙烯酸酯合成中引入含氟丙烯酸酯单体,制得氟改性丙烯酸聚氨酯涂层;通过在固化过程中引入氨基硅油,制得硅改性丙烯酸聚氨酯涂层。利用傅里叶变换红外光谱(FT-IR)分析涂层的化学组成。对涂层试样进行温度环境实验(室温和100,150℃)、湿热环境实验和氙灯老化实验,分析涂层疏水性、光泽度等表面特性的变化。结果氟、硅改性有效提高了涂层的疏水性。未改性、氟改性和硅改性三种涂层在100℃以下的环境中服役时,疏水性和光泽度比较稳定。硅改性涂层在150℃的高温环境中较未改性和氟改性涂层失效慢。湿热环境对三种涂层的接触角和光泽度等性能影响不大。氟改性涂层在氙灯老化环境中的失效程度较另外两种涂层轻。结论氟改性涂层耐光老化性能较好,硅改性涂层耐温性较好。     

铸铁件消失模水基涂料的研制

选用石英粉与铝矾土做为耐火骨料、硅溶胶等为粘结剂 ,通过正交试验 ,确定了铸铁件消失模水基涂料的最佳配比 ,并考察了涂料的多种性能 ,进行了生产应用。结果表明 :该涂料性能优良、成本低廉、具有广泛的推广价值。     

Preparation of composite electroheat carbon film

1INTRODUCTIONThe electroheat carbon fil mis a newfunction-al electroheat fil m developed based on the electro-heat coating.Due to its good electroheat propertyand equivalent volume resistivity as nickel at roomtemperature,it can be widely used in electroheator relevant advanced technological fields such asportable low-voltage electric food warmer,ricecooker and heater,as a kind of lowvoltage electro-heat material[15].The existing electroheat coatingdeveloped by Acme chemicals&Insulating o…     

模拟风沙环境下混凝土防护涂层抗冲蚀性能的研究

目的 研究不同类型的防护涂层对风沙环境下混凝土抗冲蚀性能的影响规律及作用机理,从而选取适合风沙环境且综合性能良好的混凝土防护涂层.方法 以聚氨酯、丙烯酸及环氧树脂为研究对象,对三种混凝土结构防护涂层进行了研究.通过接触角和显微硬度对涂层的物理及力学性能进行了分析,并利用模拟风沙环境侵蚀实验系统,在不同冲蚀参数下,对混凝土结构防护涂层体系的抗冲蚀性能的变化规律进行测试.结合混凝土防护涂层风沙冲蚀实验及扫描电镜表征,探究风沙环境下混凝土防护涂层的冲蚀机理.结果 相同冲蚀条件下,不同防护涂层的冲蚀率大小为:聚氨酯防护涂层>环氧树脂防护涂层>丙烯酸防护涂层.喷涂丙烯酸防护涂层试样的抗冲蚀性能比喷涂聚氨酯防护涂层的试样提升了约57.56％,比喷涂环氧树脂防护涂层的试样提升了约33.57％.冲蚀表面分形维数(Ds)的变化在一定程度上反映了不同冲蚀阶段的变化,结合Ds及被冲蚀后涂层表面的微观形貌特征,发现在低角度冲蚀时,受粒子拉应力影响,涂层表面发生了撕裂及脱粘现象,冲蚀率较高.在高角度冲蚀时,受粒子压应力影响,涂层表面出现隆起及空穴等塑性变形,冲蚀表面Ds增加,且在材料屈服应力范围内未造成损伤界面的脱落,故冲蚀率较低,显示出典型塑性材料冲蚀损伤的特征.结论 聚氨酯、丙烯酸及环氧树脂防护涂层体系,均能提高混凝土的抗冲蚀性能.结合防护涂层的接触角及硬度测试结果,发现丙烯酸防护涂层作为风沙环境中混凝土结构防护涂层时,效果较好,适用于该环境下的混凝土防护.不同防护涂层在受到冲蚀时,不存在明显的塑性变形和脆性破坏阶段,而是随冲蚀分量变化,涂层由塑性变形向脆性破坏过渡,且该现象存在于整个冲蚀过程中.     

WP7缸盖内腔铸造缺陷的控制

针对我公司新开发的WP7缸盖铸件内腔出现的烧结、脉纹、残留砂等问题,从制芯覆膜砂材料、涂料等入手进行试验分析:最后确定采用高温低膨胀的覆膜砂和3861涂料有效解决了WP7缸盖内腔烧结和脉纹缺陷;并从制芯覆膜砂常温抗拉强度、溃散性及清理工艺方面进行分析试验,确定了适当的覆膜砂常温抗拉强度和铸件清理工艺方案,有效地解决残留砂的问题.     

消失模涂层透气性的研究进展

主要从消失模铸件气孔的形成原理、涂层透气性测试方法以及涂层透气性影响因素等方面进行了分析。总结了近年来关于消失模铸件气孔缺陷的研究进展,阐述了现阶段几种涂层透气性的检测原理,具体分析了涂料厚度、耐火骨粒以及有机添加剂对涂层透气性的影响。     

Emissivity of La1-xSrxMnO3/acrylic Resin Thermal Control Coating

Thermal control coatings were fabricated by mixing of La1-xSrxMnO3(LSMO)powder and acrylic resin and brushed on Al alloy substrate.The powders of La0.7Sr0.3MnO3 and La0.8Sr0.2MnO3 were prepared using sol-gel method.XRD results reveal the phase structure of LSMO powders are perovskite.The transition temperature from metal to insulator of La0.7Sr0.3MnO3 and La0.8Sr0.2MnO3 are 300 and 275 K,respectively.The emissivity evolution with temperature of the coatings was measured.For La0.7Sr0.3MnO3/acrylic resin coating,the emissivity increases from 0.56 to 0.88,and for La0.7Sr0.3MnO3/acrylic resin coating from 0.50 to 0.90.