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should be as low as possible, particularly if the furan resin system is to be used.


Grain Shape


Tere are four main grain shapes, rounded, subangular, angular and compounded. Te best type of grain shape is rounded, and as long as the correct type of equipment is used, this should be the shape of the sand grain after processing. It also is useful to note that the cavities of the natural sand grain become filled with resin, again leading to the more rounded shape, therefore requiring less resin absorption at the mixer.


Options Tere are three main options for sand reclamation, pri-


mary attrition, secondary attrition and thermal. Primary attrition can be further broken down into three


main types: primary attrition–low level, primary attrition- high level and combined shakeout/attrition. High level refers to the loading height of the attrition


unit. Tis type typically would be positioned in a pit and fed via a separate shakeout and vibratory feeder. It would not have it’s own shakeout deck and would be used where heavy castings or high throughputs would be processed. Low-level units are floor mounted requiring no special


foundations and can be used as a shakeout as well as attri- tion unit. Tis type of plant usually is more compact, easier to maintain has a low investment cost. Te main limitation is the maximum load capacity of 3 tons and a maximum throughput of 15 tons per hour (Fig. 1). Combined shakeout/attrition units usually are mounted in


a pit but can take much higher load capacities. All three types of primary attrition units will consist of a heavy-duty shakeout grid, a secondary perforated plate screen made from mild steel with 6mm diameter apertures, a third screen usually of stainless steel with 1.6mm apertures with a wedge cross section to enable a certain amount of self cleaning and a 1.6mm square aperture mesh screen for final sand classification. The actual attrition process takes place between the shake out grid and the area prior to the final mesh screen. Here there should be sufficient retention to enable grain scrubbing and binder removal. With any type of Attri- tion unit, there should always be the facility to remove flash metal, chills, reinforcing bars and other non-sand contami- nation. Therefore a clean-


砂的二氧化硅含量应该尽可能地高,酸耗值(ADV) 应该尽可能的低,特别是使用呋喃树脂工艺。


颗粒形状


有四个主要的颗粒形状,圆形,多角形,尖角形和 复合型。最佳类型的颗粒形状是圆形的,所以只要使 用正确类型的设备,这应该是加工就可满足再生后沙 砂粒的形状。另一个需要注意的益处是,天然砂粒的 空腔已被树脂填充,再生导致更圆的形状,因此,在 混砂系统器中,它需要添加较少量的树脂。


选项 砂再生有3种主要选项,初次摩擦,二次摩擦和热法 再生。


初次摩擦可以进一步细分为三种主要类型,初次摩 擦–低强度的,初次摩擦–高强的和振动/摩擦组合型。 高强度是指磨擦单元安装强度,此类型的通常会被安 装在一个基坑内,并通过一个单独的摇摆和振动送料器 馈送。它不会有它自己摇摆栅格板,将用于大型铸件或 高生产能力的处理。


低强度的单元安装在车间地面,无需特殊的基础, 可以作为一个振动以及摩擦单元的使用。这种类型的设 备通常通常更紧凑,更易于维护,且投资成本低。主要 的限制是最大负载能力3吨,最大生产能力为每小时15 吨。 (图1)


组合振动/摩擦设备通常安装在一个基坑内,以获得 更高的负载能力。


所有这三种类型初次摩擦单元将包括一个重型振动 格栅,由低碳钢制成的直径为6mm的孔的多孔板的次 级板,第三层板通常用不锈钢与1.6mm毫米具有楔形 横截面的孔来确保一定量的自清洁功能,最后由终一个 1.6mm的方孔网筛进行最后的沙砂子分类。实际的磨 擦过程中发生在振动格栅和最终网筛之前的区域之间。 这里应该有足够的停留,使 砂粒摩擦和粘结剂清除。任 何类型的磨损单元,应配有 装置以去除金属披缝,、冷 铁,、钢筋和其他非砂污染 的装置。因此,而检修门应


Fig. 1. Low-level units are floor mounted requiring no special foundations and can be used as a shakeout as well as attrition unit.


February 2013 FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION | 33


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