What are the causes of slag inclusion in lost foam casting?

The slag inclusion defect refers to the defect formed by the molten iron entering the casting during the pouring process of dry sand, paint and other inclusions. On the surface of the casting after processing, white or dark gray inclusion spots can be seen, distributed individually or in pieces, and white is quartz sand particles. Black and gray are residues and other inclusions after pyrolysis of slag, paint, foam model. This kind of defect is commonly known as "sand-in" or "slag inclusion", which is a very common defect in the production of lost foam casting. Factories that almost use lost foam casting are ubiquitous and difficult to eradicate completely. Only by adopting various measures and careful operation in each process can the "slag inclusion" be reduced to the lower limit and a satisfactory result can be achieved.

Before the lost foam castings are cooled and unboxed and not cleaned, according to the surface conditions of the castings and the pouring system, it can be judged whether there is sand entry and slag inclusion missing. If the gate cup, sprue, cross runner, gate and gate surface or connection and casting surface are severely sticky or have crack-like sticky sand, it is basically certain that the casting has slag inclusion and sand entry defects. If you smash the sprue bar or the sprue of the sprue, you can see white spots on the fracture. In severe cases, the fracture forms a circle of white spots. Such castings, especially plate-shaped, cake-shaped castings will be processed on the processing surface. There is white. Black and gray speckle defects. If the process operation rules are not strictly controlled. The castings produced seriously affect the quality of castings and the progress of order completion.

Causes of slag inclusion and sand entry defects

After long-term observation in the production practice, it has been proved that from the gate cup, the sprue, the cross-runner, the in-runner to the casting, all parts may cause sand ingress, especially the joint between the pouring system and the casting. During the production process, the paint peeling and cracking on the surface of the white mold of the casting system, the paint peeling and cracking of the joint part of the white mold, the paint peeling and cracking of the foamed white mold surface, and the tightness of the direct sprue are not tightly closed. The main reason.

Secondly, the selection of process parameters, such as the size of the net head of the casting system, the pouring temperature, the size of the negative pressure, the dry sand particle size, and the model transportation process and packing operation, etc., are all very important for casting slag inclusion and sand entry defects. Big impact. Only by taking systematic measures and careful operations in these links can the slag inclusion defects of castings be reduced and basically eliminated, and high-quality castings can be obtained.