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3.粘土湿型砂所用的主要原材料 (1)原砂 绝大多数用粘土湿型砂的铸造厂都用天然硅砂。粒度方面,为使铸件产品的表面粗糙度较低,一般不宜采用太粗的原砂。具体说来,铸型的尺寸愈大,则浇注时铸型中的静压头愈高,为减轻粘砂倾向,反而应采用稍细一些的原砂。我国铸造工人往往持一种似是而非的观点,以为铸件大些就应该用较粗的砂,实际上是不合适的。 对于尺寸较小的铸型,建议采用平均粒度为0.15～0.212mm的原砂。按GB9442—88,相当于15组偏粗一些。若仍用JB2488—78标准筛筛分,
3. Clay wet sand used by the main raw materials (1) the original sand most of the clay wet sand used in the foundry of natural silica sand. Particle size, in order to make the castings of low surface roughness, the general should not be too coarse sand. Specifically, the larger the size of the mold, the higher the static pressure head in the mold during casting, to reduce the tendency of sticking sand, instead, the smaller the original sand should be used. China’s foundry workers often hold a paradoxical view that larger castings should be used thicker sand, in fact, is not appropriate. For the smaller size of the mold, the proposed average particle size of 0.15 ~ 0.212mm of the original sand. According to GB9442-88, which is equivalent to 15 groups of partial thicker. If still using JB2488-78 standard sieve screening,