Aluminum Casting Sticky Sand And Its Solution

  Aluminum castings sticky sand not only affect the appearance of the casting quality, and even cause scrapped. Therefore, it is necessary to give enough attention to the sticky sand of the casting.

  First, sticky sand phenomenon

  Sticky sand with chemical sticky sand and mechanical sticky sand, its simple way of identification is that the former sticky sand layer often does not contain metal iron.

  1. mechanical sticky sand

  Department of metal infiltration of sand or sand core sand gap, and sand sintered and adhere to the casting surface. It can be a thin layer, it may be a few millimeters thick layer. Metal liquid sometimes penetrate into the entire cross section of the sand core, resulting in obstruction of the cavity, this sticky sand is often impossible to remove the castings had to be scrapped.

  2. Chemical sticky sand

  Department of metal chemical reaction generated by the formation of metal oxides and modeling materials to form a strong adhesion of ferric silicate scum.Aluminum castings It is produced in the casting gate or thick wall, especially when the sand or sand core is thin and the casting is more likely to produce.

  Second, the reasons for sticky sand

  1. Adequate pressure causes the molten metal to penetrate the sand between the higher metal liquid static pressure head. Ie the casting height and the pressure formed by the casting system. Such as the pressure exceeds the resistance of the capillary formed between the sand gap. That is, corpse hair = QcosO / r, where P hair is capillary pressure; For the metal liquid surface tension; e for the metal liquid capillary wetting angle; r for the capillary radius. It will form a mechanical sticky sand. Static pressure head more than 500 mm, casting sand and thick, most will produce mechanical sticky sand, unless the paint.Aluminum castings The above formula also shows: the bigger, that is, the thicker the sand grain size, the smaller the dead body, that is more prone to mechanical sticky sand.

  2. The dynamic pressure that the molten metal flows in the mold.

  3. Mold "burst" or "choke". That is, when the mold is cast, the combustible gas is mixed with the air and is ignited by the hot metal liquid.

  4. mechanical sticky sand once started, even if the pressure is reduced, the metal liquid penetration will continue until the penetration of metal liquid before the solidification. That is, the metal liquid temperature is lower than the solidus temperature, the infiltration can stop.

  5. Chemical sticky sand The most common reason is the wet type and core with the refractory material, sintering point is low;Aluminum castings quartz sand is impure; coal or substitutes add enough; no use of paint or improper use; pouring temperature is too high; Improper pouring caused by slag into the mold and other factors.