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粘土砂是以粘土作粘结剂的型砂

网址:www.zaoxingji.com.cn  2020-05-13  作者:admin    阅读:

粘土砂是以粘土(陶土)作粘结剂的型(芯)砂。粘土砂造型由于其成本低廉,适合于批量大规模生产,所以目前仍然作为铸件生产的最主要方式。粘土砂旧沙由于在循环使用过程中各组份的热分解,发生物理性能的变化,如未经再生就加以使用,将使型砂质量不稳定。据统计铸件废品率中30~40%为型砂质量引起,因此型砂质量的控制在粘土砂造型中起十分重要的作用。随着目前对铸件要求的提高,对型砂质量的要求也越来越高。
Clay sand is a kind of core sand with clay (clay) as binder. Clay sand molding is still the main way of casting production because of its low cost and suitable for mass production. Because of the thermal decomposition of each component in the process of recycling, the physical properties of old clay sand change. If it is used without regeneration, the quality of molding sand will be unstable. According to statistics, 30-40% of the scrap rate of castings is caused by the quality of molding sand, so the quality control of molding sand plays an important role in clay sand molding. With the improvement of casting requirements, the requirements of molding sand quality are higher and higher.
粘砂
Sand sticking
无效粘土(死黏土)部分约占整个砂型重的2~5%,无效粘土的一部分在高温作用下包裹在砂粒表面上,烧结形成一层牢固的膜,不能用水洗掉,成为砂粒的一部分,这层膜又称为惰性膜。型砂经过无数次循环混制和浇铸受热,惰性膜将多层重叠包裹,这个过程又叫鱼卵石化现象。适当的鱼卵石化降低了石英含量,减轻型砂的热膨胀性,减少膨胀类缺陷。当鱼卵石化过度惰性膜太厚时,由于惰性膜溶点低,降低了型砂总体的sio2含量,使型砂耐火度(仅有1150度)降低,如果浇铸温度高于1400~1450度时易引起铸件表面粘砂,产生机械粘砂,造成铸件表面不光洁。
The part of invalid clay (dead clay) accounts for about 2-5% of the weight of the whole sand mold. A part of invalid clay is wrapped on the surface of sand particles under the action of high temperature, which is sintered to form a solid film, which can not be washed away with water and become a part of sand particles. This film is also called inert film. After countless cycles of mixing and casting, the sand is heated, and the inert film will overlap and wrap the sand. This process is also called fish egg fossilization. Proper roetization reduces the quartz content, reduces the thermal expansion of molding sand and reduces the defects of expansion. When the inert film is too thick, due to the low melting point of the inert film, the total SiO2 content of the molding sand is reduced, and the refractoriness of the molding sand (only 1150 degrees) is reduced. If the casting temperature is higher than 1400-1450 degrees, it is easy to cause sand sticking on the surface of the casting, resulting in mechanical sand sticking, and the surface of the casting is not smooth.

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