Status quo and development trend of lost foam casting technology

Lost foam casting(LFC)technology has been widely applied to cast iron and cast steel.However,the development of LFC for Al and Mg alloys was relatively slower than that for cast iron and cast steel.The application of LFC to Al and Mg alloys needs more effort,especially in China.In this paper,the development history of LFC is reviewed,and the application situations of LFC to Al and Mg alloys are mainly discussed.Meanwhile,the key problems of LFC for Al and Mg alloys are also pointed out.Finally,the prospects for LFC technology are discussed,and some special new LFC technologies are introduced for casting Al and Mg alloys.In future,the development trends of green LFC technology mainly focus on the special new LFC methods,metal material,coating,heat treatment,new foam materials as well as purification technology of tail gas,etc.

Microstructural evolution of Mg9AlZnY alloy with vibration in lost foam casting during semi-solid isothermal heat treatment

The nearly equiaxed grains of Mg9AlZnY alloy were obtained by vibrating solidification in lost foam casting(LFC) and the microstructure of Mg9AlZnY alloy was analyzed.On this basis,the morphology and size of α-Mg grains fabricated by semi-solid isothermal heat treatment(SSIT) at 530 ℃ and 570 ℃ holding different time were studied.The results show that the main constituent phases of Mg9AlZnY alloy are α-Mg,β-Mg17Al12 and Al2Y,and the Y can greatly refine α-Mg grains.The distribution of α-Mg grains equivalent diameters between 20 and 100 μm is up to 87%,and the average roundness of α-Mg grains reaches 1.37 in the specimen obtained at 570 ℃ and holding time 60 min.According to the analysis of solidification kinetics and thermodynamic,binary eutectic with low melting point melts firstly on SSIT process.As the liquid fraction increases with the solute diffusibility,both of the shape and size of α-Mg grains change ceaselessly.When the liquid fraction reaches equilibrium,the α-Mg grains are gradually spheroidized under the interfacial tension,and then the α-Mg grains begin to combine and grow.Evolution of α-Mg dendritic grains on SSIT process is obviously different from that of equiaxed grains.

Investigation of carbon contamination in lost foam castings of low carbon steel

Lost foam casting(LFC) process is a special casting method in which polymeric foam patterns with refractory coatings are utilized as a mould component. In this work, four types of foam: expandable polyethylene(EPE), expandable polypropylene(EPP) and expandable polystyrene(EPS) foams with two different densities were employed as pattern materials. LFC and conventional green sand mould casting methods were used to cast a low carbon steel, A216 Grade WCB. Both casting processes were carried out at 1,580 °C. Chemical analysis results showed that the carbon contamination level was high and was influenced by pattern type. Metallographic investigations revealed a significant increase in the percentage of pearlite phase in all LFC samples. Densities of manufactured samples were calculated in order to evaluate porosity of the products. It was determined that the densities of the LFC samples were lower than the green sand mould cast reference sample(RS). Vickers hardness tests were also carried out and increments in hardness values with increased carbon content was observed.

Effect of manganese on the ferrum phases of B319 aluminum alloy in lost foam casting

By using ICP spectroscopy, energy dispersive spectroscopy (EDS) analysis, X-ray diffraction, SEM and microscope analysis, the effects of Mn on the structure of B319 aluminum alloy are studied. The results show that without the addition of Mn, there are coral-like Al_2Cu phase and needle-like β-Fe (Al_5FeSi)in the structure of casting with lost foam casting (LFC). Precipitation of Al_2Cu can take place along the long sides of the β needles. Under the rapid cooling rates, such as ones in metallic mold, the Fe phase appears in the form of Chinese script α-Fe. With the addition of Mn, there are Chinese script α-Fe phases(Al_(15) (Mn, Fe)_3Si_2)in the structure of LFC casting. When Fe/Mn≤1.5, the needle-like β-Fe phases transform to Chinese script α-Fe completely. With the decrease of Fe/Mn ratio, the tensile strength σ_b and elongation δ increase, especially the elongation δ increases greatly. When Fe/Mn ratio decreases from 2.5 to 1, the δ increases from 1.2% to 1.9% by 58%.

Recent Development of Lost Foam Casting Technology Comment on the 7th Chinese Lost Foam Casting Symposium

The 7th Chinese Lost Foam Casting (LFC) Symposium & the 1st LFC Technology Exposition were held on May 21-23 at Nanjing University of Aeronautics and Astronautics (NUAA), and the conference theme was "Recent development of lost foam casting technology". Prof. TAO Jie, the Executive Chairman of the conference and the Vice Director of LFC Committee of Foundry Institution of Chinese Mechanical Engineering Society(FICMES), chaired the inauguration. Prof. NIE Hong, the Vice President of NUAA, represented the host address and expressed welcome and gratitude to all the guests from home and abroad. He said the development of the technologies, environmental protection and the trade globalization require to continually improve the performance of products, and accurately select proper material and the manufacturing technology. As the revolutionary technology in casting development history, LFC technology has brought a brand-new change for the machine design and casting production. He hoped the conference would be beneficial to the development of Chinese LFC technololy and wished the symposium a complete success! Prof. YE Sheng-ping, the Executive Chairman of the conference and the Director of LFC Committee of FICMES, gave the opening address and read out the congratulations of F. J. Woestmann (Director of Germany LFC Technology Council), Wolfgang (General Manager of Storopack Hans Reichenecker Group), G Sedlmair Heiko (LFC project director of Teubert Maschinenbau GmbH), etc. Patrice Juton, the Sale Manager of Storopack Group, gave a speech on behalf of the conference delegates.

基于ProCAST消失模铸造磨球的工艺优化

通过采用ProCAST软件对消失模铸造中碳钢磨球的充型及凝固过程进行了数值模拟,预测其缺陷产生的部位,并分析其产生的原因。在此基础上,对生产磨球的工艺进行了优化,有效地避免了缩松、缩孔在其重要部位的产生,大大降低了废品率,提高了磨球的使用寿命和质量。

Microstructure and Mechanical Properties of Ductile Cast Iron in Lost Foam Casting with Vibration

The microstructures and mechanical properties of the ductile cast iron （DI） specimens obtained by lost foam casting （LFC） with and without vibration were investigated. The results indicate that the number of the graphite nodule increases from 175 mm 2 of the specimens produced by LFC without vibration to 334 mm^-2 of the specimens produced by LFC with vibration, and the thickness of the ferrite shell increases. Meanwhile, the amount of the carbides decreases in the specimens produced by LFC with vibration and the granule structure then forms. These are mainly attributed to the ＂crystal shower＂ caused by the vibration. In addition, the tensile strength and elongation of DI specimens produced by LFC with vibration are improved due to the dispersion-strengthening of refined carbide and Dearlite colonv, uniform distribution of the graphite nodule, and increase of the amount of dimples and tearing edges.

Al-Si-Mg-Y合金消失模铸造振动压力凝固的组织与性能

应用消失模铸造振动压力凝固成形技术制备了Al-7Si-0.8Mg-0.3Y(ASMY)合金。通过SEM、XRD、DSC和TEM等测试方法对其铸态和T6组织进行分析,研究其对力学性能的影响。结果表明:在ASMY合金铸态组织的晶界处生成有少量Al3Y短棒状颗粒相;在T6热处理过程中,稀土Y或Al3Y阻碍Mg2Si相的析出和扩散聚集,使析出相Mg2Si呈弥散分布;Mg2Si相与晶界稳定相Al3Y对合金同时起到钉扎强化作用;采用消失模铸造振动压力凝固技术后,铝合金的孔隙率显著降低,从1.1%降低0.18%;ASMY合金消失模铸造振动压力凝固试样T6态的抗拉强度达到308MPa,比A356普通消失模试样T6态的抗拉强度提高29%。

凸轮轴消失模铸造涂料的研制

以凸轮轴为例,配置了性能优良的水基消失模铸造涂料,配方采用铝矾土90%(质量分数,下同),石英粉10%,钠基膨润土3%～4%,水玻璃2.5%～4%,白乳胶2.5%～4%、CMC0.25%～0.5%,其他适量。此配方适合在凸轮轴消失模铸造生产中使用,具有良好的触变性和透气性,且具有高的表面强度和抗弯强度。

镶铸双金属复合锤头铸造工艺的研究

双金属复合锤头锤端复合层采用高铬铸铁,锤柄采用碳素结构钢。采用型内感应加热工艺进行镶铸复合。造型时锤柄预先放置在砂型中,锤端和浇注系统内浇道的成型采用消失模。复合时将包含有锤柄的砂型整体放入到感应圈内采用中频感应原理对锤柄进行预热,锤柄温度升高,锤端消失模受热汽化,锤柄达到预定温度后浇注并继续进行加热,复合层熔液将锤端部分锤柄包覆后停止加热并继续浇注,使金属液充满冒口。所得到的双金属复合锤头结合界面为完全冶金结合。经过热处理后,复合层组织为断续分布的Cr7C3 共晶碳化物+马氏体+少量残余奥氏体,硬度HRC≥58,冲击韧度≥12 J/cm2。基体组织为珠光体+铁素体。破碎石灰石和炼焦用原煤,镶铸双金属复合锤头使用寿命分别是高锰钢锤头的3倍和5倍左右。

镁合金消失模铸造的优势及关键

对常见镁合金铸造工艺作了分析和总结 ,对镁合金消失模工艺的优缺点作了客观分析 ;提出了可控气氛、可控压力镁合金消失模铸造新工艺 ;认为该工艺是一种非常适合镁合金液态成形的新的精密铸造方法 ,具有设备投资小、铸件成本低、内在质量好、精度高、生产率高的优势 ,同时可以较好地解决镁合金液态成形过程中易氧化燃烧的问题。

铝(镁)合金消失模铸造近净成形技术研究进展

阐述了铝(镁)合金消失模铸造技术的研究现状,着重介绍了铝(镁)合金消失模铸造在金属液充型、振动凝固、压力凝固以及消失模壳型铸造等技术方面的最新研究进展。研究表明,铝(镁)合金在消失模铸造过程中,需重点解决针孔、缩松等缺陷,提高液态合金的充型能力和铸件的力学性能;通过采用振动凝固和压力凝固的手段,可以提高金属液充型能力、细化组织、提高组织致密性,明显提高铸件力学性能。真空低压消失模壳型铸造技术,可以解决普通消失模铸造易于出现的孔洞和夹杂等缺陷以及浇不足和浇注温度高等问题,是一种生产复杂薄壁高质量铝、镁合金精密铸件的新方法。

消失模铸造充型速度和流动前沿温度的数值模拟研究

采用数值模拟方法,通过模拟板形灰铸铁件的消失模铸造充型过程,分析了各种工艺因素对充型过程中金属液前沿的流动速度和温度的影响规律。结果表明,液态金属充型速度随浇注温度、负压度和涂层透气性的增大而增大,随模样密度和涂层厚度的增大而减小;金属液流动前沿温度随模样密度和涂层厚度的增大而下降,而随负压度的增大而提高。

浇注温度对球墨铸铁消失模铸造组织及性能的影响

在不同浇注温度下制备了消失模铸造球墨铸铁Y型试块,对比分析了球墨铸铁的石墨形态、基体组织及力学性能的区别。结果表明:当浇注温度较高时(约1 510℃),由于碳、硅烧损严重,在球墨铸铁的基体组织中生成大量的碳化物;浇注温度较低时(约1 410℃)不利于球墨铸铁的球化,降低了球墨铸铁的球化率及球化级别,由于球墨铸铁的球化效果不良,导致球墨铸铁的抗拉强度及伸长率降低;而1 460℃的浇注温度对于消失模铸造球墨铸铁比较适宜。

Al-Ti和Al-Ti-C中间合金对消失模铸造AZ91镁合金显微组织的影响

A l-Ti和A l-Ti-C中间合金对消失模铸造AZ91镁合金组织的试验研究表明,与常用变质剂C2C l6相比,加入A l-Ti和A l-Ti-C中间合金对消失模铸造AZ91镁合金具有更好的组织细化效果和更高的力学性能,而加入A l-Ti-C中间合金的作用效果最佳。A l-Ti-C及A l-Ti中间合金的加入提高了共晶反应的离异化程度,晶界上的β相由连续网状变为不连续块状和孤立的粒状结构且分布均匀。A l-Ti-C中间合金对消失模铸造AZ91镁合金晶粒细化是其晶粒生长抑制作用和引入形核质点综合作用的结果。

双金属复合锤头的研制及生产

分别采用高铬铸铁和碳素钢作为锤端和锤柄。造型时锤端和浇注系统内浇道的成型分别采用消失模模型。复合时将砂型整体放入感应线圈中感应加热,加热过程中消失模受热汽化。当锤柄升到预定温度(800℃左右)时,开始浇注复合层金属液。所得的界面为完全冶金结合。复合部分经热处理后组织为Cr7C3共晶碳化物+马氏体+少量残奥,HRC≥58,ak≥12 J／cm2。锤头使用寿命是同等工况下高锰钢的5倍左右。

双电机消失模铸造振实台振动模式及效果

试验研究了不同振动模式下双电机激振消失模铸造振动紧实台的振动特性。在分析双电机振动数学模型的基础上 ,测试了多种振动模式下的振动效果 ,结果表明 ,在不同振动模式下 ,双电机振动特性差距较大。为了较好地实现复杂消失模模样振动紧实的目的 ,紧实过程中 ,可根据铸件消失模模样的形状特点 ,进行振动模式的不同组合与变换 ,以求得满意的紧实效果。

镁合金消失模铸造新技术研究

消失模铸造属于颇有特点的精密绿色铸造技术。但镁合金消失模铸造中存在充型能力差、孔洞缺陷严重、凝固组织粗大及力学性能偏低等问题。针对以上问题,国内外开发了几种镁合金消失模铸造新技术,本文主要介绍这些新技术的最新研究进展。真空低压消失模铸造技术,可保证金属液充型平稳,提高镁液充型和补缩能力,保护其充型过程,适于镁合金铸造成形。振动凝固消失模铸造技术,可提高镁合金充型能力、细化组织、明显提高铸件力学性能。消失模壳型铸造技术,可消除或减少消失模铸造易于出现的孔洞、夹杂等缺陷,能生产高质量复杂镁合金精密铸件。镁/铝双金属消失模铸造技术,可低成本直接成形复杂镁/铝双金属铸件。以上新技术都有其自身特点和应用前景。

美国铝合金消失模铸造现状及我国铝合金消失模铸造技术攻关建议

结合2007年第二届美国消失模铸造研讨会,报道了美国铝合金消失模铸造历程和最新资讯,针对我国铝合金消失模铸造的现状,提出技术攻关建议。

利用消失模铸造工艺制造双金属复合锤头

介绍了消失模铸造工艺制造高铬铸铁-高锰钢双金属复合锤头的材质选取、工艺设计。通过对结合区的微观组织分析．表明采用该工艺生产的双金属锤头界面结合良好，组织致密。实际使用结果表明，双金属复合锤头比高锰钢锤头的耐磨性提高了3-4倍。