铸型中使用外冷铁,常因潮型放置时间较长冷铁吸潮锈蚀,或干型烘烤过程中冷铁表面氧化,以致浇注时氧化物会分解出气体。由于冷铁处冷却速度快,又无透气性,产生的气体来不及逸出而产生气孔和皮下气孔。为克服这一缺陷,我们采取在冷铁上钻排气孔眼的办法,一般一寸见方内钻一个φ10毫米的孔,孔眼内填充透气性好的粗型砂,刷上涂料,这就完满地解决 External use of cold-type iron mold, often due to the tide-type place for a long time cold iron rust moisture corrosion, or cold-type baking process during the oxidation of chrome, resulting in pouring oxide will decompose gas. Due to the chill iron at the cooling speed, but also no air permeability, resulting in gas escape too late to produce stomatal and subcutaneous pores. In order to overcome this defect, we adopt the method of drilling the vent hole on the chill iron. Usually, a hole of 10 mm in diameter is drilled. The hole is filled with coarse sand with good air permeability and the coating is painted, which is solved satisfactorily