- 本站编辑：财神888电玩发布日期：2019-08-07 12:04 浏览次数：
Points for attention in process design and operation of sand covering for iron mould:
Sand coating for iron mould: When heating iron mould and sand mould, the uniformity of heating temperature and overall temperature should be controlled.
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).
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.
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.
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.
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).