Casting and pouring may seem simple, but there are many details. Remember to pay attention to these points in production!

There are certain specifications and requirements for lost foam casting. The following aspects should be paid attention to in the molding process: silica sand is generally used in lost foam casting, and its silica content is required to be more than 85%~90%. In terms of air permeability and refractoriness, cast steel and cast iron parts generally use silica sand with a particle size of 0.850~0.300mm. First, put a layer of dry sand with a thickness of about 100mm on the bottom of the sand box, then place the painted EPS mold and the pouring riser in the center of the sand box, fill the sand while shaking, until the dry sand is about 50mm away from the top surface of the sand box Stop adding sand, cover the dry sand with plastic film, then place the sprue cup on the top of the sprue, and remove a layer of loose sand on the film to prevent molten iron from splashing during pouring, burning through the film and causing air leakage and collapse box.

Pouring in the lost foam casting process, the entire process includes seven links, each link has a great impact on the quality of the lost foam casting, of course, the pouring process is also a crucial part of the entire lost foam casting process, Mastering the precautions of the pouring process and strictly controlling every detail in the pouring process is the key to producing high-quality lost foam castings.

The pouring process of lost foam casting is a process in which molten steel is filled and the foam mold evaporates and disappears. The things to keep in mind throughout the process are:

(1) The runner should be filled with molten steel from beginning to end. If it is not satisfied, due to the limited strength of the coating layer, it is easy to cause sand collapse and air intake, resulting in casting defects.

(2) When pouring molten steel, it must be grasped to ensure that it is stable, accurate and fast. Instantly fill the pouring cup, and achieve rapid and continuous flow, ton of molten steel in about one minute. If the molten steel of the castings in the same box is interrupted, air will be sucked in, which may cause the phenomenon of sand collapse or the increase of pores in the castings, resulting in the scrapping of the castings.

(3) Lost foam casting adopts negative pressure closed type, and it must be closed below the pouring cup. When the molten steel enters the molding die, it begins to liquefy and burn, and then vaporizes and disappears. The front end of the molten steel forms a temporary cavity in a short distance, so the designed speed of the molten steel filling and the disappearance of the foam model are roughly the same. In order to prevent the molten steel from high temperature radiation melting other models in the same box, the runner should be a little farther away from the casting model. The position of the vertical runner selects the lowest position of the whole box of castings. When pouring, pay attention to adjust and control the vacuum degree of negative pressure within a certain range. After pouring, keep it in a certain negative pressure state for a period of time. After the negative pressure is stopped, the molten steel is condensed out of the box.


Prevent back spray

Lost foam casting is one of the casting processes. There will be various casting defects in the casting process, which will lead to the defects of castings. Lost foam casting is no exception. Back-spray is a common phenomenon in lost foam casting. When the back-spray is serious, it may endanger the personal safety of the pourer. It must be paid attention to. In order to reduce the spray phenomenon, the following measures can be taken: