Mechanism of mixing sand action of Machinery Castings four points:
The main function of the sand-mixing of Machinery Castings is to mix the powder of each group evenly, it is the moisture and moist clay, and the clay paste is coated on the sand surface, which is the performance of the sand type to adapt to the shape. There are several types of clay sand mixer used in foundry Enterprises in China: Roller type, rotor type, balance wheel type and continuous type. Large-scale production of automotive castings foundry, requirements of fast sand mixing, good quality sand. The rotor-type mixer also satisfies both requirements. and many manual production batches are not very large foundries, still a large number of roller-type sand mixer.
Adding quality coal powder to the wet sand of Machinery Castings can prevent the casting from producing sticky sand, but also can reduce the surface roughness of castings significantly.
The mechanism of its action is mainly as follows.
(1) The theory of air-film isolation the pulverized coal in the moulding sand produces a lot of reducing gas, which is formed by the sand/metal interface to form a layer of gas film, which prevents the molten iron from drilling into the sand grain pores of the type sand.
(2) The colloid body sealing theory T-groove table-type sand of the coal powder becomes solid, liquid and gas three-phase gel, the expansion of the glial body can block sand grain pores, Machinery Casting prevent molten iron drilling into the sand grain pores.
(3) Gas oxidation theory the volatile fraction of pulverized coal is pyrolysis at high temperature and gas phase, resulting in a large amount of reducing gases, which can prevent the oxidation of iron liquid and avoid chemical reaction between iron oxide and quartz sand.
(4) Bright carbon anti-wetting theory pouring when the coal powder in the test platform sand precipitates the bright carbon of fine grains, deposits on the sand grain surface, Machinery Casting so that the sand grains are not wetted by the iron liquid, and the molten iron is prevented from penetrating into the sand grain pores by the surface tension. From the mechanism of cast iron platform, it is known that the volatile, bright carbon and coke slag are the main influencing factors of the effect of coal powder on sand control.
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