铁模覆砂工艺设计和操作的注意事项：

 

Points for attention in process design and operation of sand covering for iron mould:

 

铁模覆砂：在加热铁模及砂型时，要控制其加热温度及整体温度的均匀性。

 

Sand coating for iron mould: When heating iron mould and sand mould, the uniformity of heating temperature and overall temperature should be controlled.

 

砂箱设计：砂箱壁厚激冷效果好，但铸件易硬度高，砂箱壁薄急冷效果差。铁模型及砂箱的壁厚一般在12~25㎜。铁/砂=1:6~7（即铸件重量与其所消耗覆膜砂重量之比）。

 

Sandbox design: Sandbox wall thickness quenching effect is good, but the castings are easy to harden high, sandbox wall thin quenching effect is poor. The wall thickness of iron models and sand boxes is generally 12-25. Iron/sand = 1:6-7 (i.e. the ratio of casting weight to the weight of coated sand consumed).

 

铁模覆砂：在设计分型面时，尽可能的使上下型（砂箱）高度均匀，减少充砂路程，便于使覆膜砂充实铸型。

 

Sand covering for iron mould: When designing parting surface, make the height of upper and lower moulds (sand boxes) as uniform as possible, reduce the sand filling distance, and make the sand covered to enrich the casting mould.

 

覆砂的厚度：覆砂的厚度对铸件质量和生产成本都很重要。覆砂的厚度过厚，不但影响其激冷效果，也加大了生产成本，另外由于发气量大，铸件易出现气孔缺陷，且不易均匀热固化。覆砂的厚度过薄，激烈过重，铸件的硬度高，不便精加工。一般情况下，精加工面覆砂较厚，非加工面覆砂较薄；珠光体基体材质的铸件覆砂较薄，铁素体基体的铸件覆砂较厚；热节点覆砂较薄（可少至3~4㎜），非热节点覆砂较厚;距射砂口近处覆砂要厚，远离射砂孔处覆砂适当薄；铸件大而且形状复杂时，覆砂要厚，否则影响砂的流速，途中固化，致使铸型下部充砂不实。覆砂厚度一般控制在5~8㎜。

 

Sand thickness: Sand thickness is very important for casting quality and production cost. The thickness of sand coating is too thick, which not only affects the chilling effect, but also increases the production cost. In addition, due to the large amount of gas, the casting is prone to porosity defects, and is not easy to uniform thermal curing. The thickness of sand coating is too thin, intense and heavy, the hardness of castings is high, and it is inconvenient for finishing. Generally, the sand coating on the finishing surface is thicker than that on the non-processing surface; the sand coating on the pearlite matrix is thinner, and the sand coating on the ferrite matrix is thicker; the sand coating on the hot joints is thinner (up to 3-4_), and the sand coating on the non-thermal joints is thicker; the sand coating near the nozzle should be thicker, and the sand coating should be thinner far from the perforation. When the parts are large and complex in shape, the sand coating should be thick. Otherwise, the flow rate of sand will be affected, and the sand will solidify in the way, which will lead to the inadequate filling of the lower part of the casting mould. Sand cover thickness is generally controlled at 5 to 8 inches.

 

铁模覆砂：如果铸件的高（深）度大，在下部要设“气塞”，防止起模时下部产生真空区不能进气，吸伤铸型。

 

Sand-covered iron mould: If the casting is of high (deep) degree, a "gas plug" should be set at the lower part to prevent the vacuum zone in the lower part from being unable to breathe in and suck up the casting.

 

射砂和排气：即在往砂箱和铁模型之间，形成的型腔中射充砂的同时，要使型腔中的气体顺利排出，否则将会产生覆砂不实或覆砂层不完整的现象。如：砂箱与铁模底版的接触面，砂箱上要开设排气道，排气道开设的大小，以只能充分排气而不能跑砂为准则(一般是用手锯开槽即可)。

 

Sand shooting and exhaust: that is to say, when injecting sand into the cavity formed between the sand box and the iron model, the gas in the cavity should be discharged smoothly. Otherwise, the phenomenon of improper sand coating or incomplete sand coating will occur. For example, the contact surface between the sand box and the bottom plate of the iron mould, the exhaust duct should be set up on the sand box, and the size of the exhaust duct should be set up according to the criterion that only enough exhaust gas can be exhausted and sand can not be run off (usually the groove can be cut by hand saw).