Why Does The Box Collapse Phenomenon Occur In Lost Mold Casting?

In the process of production and processing, foundry manufacturers generally encounter a common casting defect - collapse box, even for experienced large foundries, it is often encountered. Box collapse defects, also known as collapse defects, mainly occur in the production of large parts, closed or semi-closed parts. So, why will the collapse of the box occur in the production of lost mold casting?

 

 

1. In the production of lost mold, the casting of high temperature metal liquid will cause the lost mold to decompose rapidly and produce a large amount of gas. If the exhaust speed of the mold cannot keep up with the speed of the gas generated by the decomposition of the lost mold, the mold will collapse, resulting in the collapse of the box.

 

2. During the pouring process, part of the molten metal flowing into the filling position of the lost mold is transferred to other parts under the external action, so that the original displacement position is not occupied by the molten metal or metal filling, and collapse defects will also occur. This "flash stream" is called molten metal. This problem mainly occurs in top injection, large surface casting, and multiple patterns of a mold.

 

3. The fire resistance and high temperature strength of the coating are not enough, and it is easy to produce box-like collapse defects of lost mold casting. The lost mold pattern has the function of buffering the filling and cooling of molten metal during the pouring process, and can reduce the erosion of molten metal on the mold. Dry sand is primarily supported by the coating as molten metal replaces the disappearing foam pattern and fills the mold cavity. When the coating strength is not enough or the fire resistance is not enough, the local cast will collapse, especially the collapse above the large inner runner.