Process control for lost foam casting

The lost foam casting process includes riser system design, pouring temperature control, pouring operation control, negative pressure control, etc.
The gating system plays a very important role in the lost foam casting process and is a key to the success or failure of casting production. Due to the wide variety and shape of castings, the specific production process of each casting has its own characteristics and is very different. These factors directly affect the accuracy of the gating system design results.
The gating system design is different from traditional sand casting. In the design of the gating system, the particularity of this process should be taken into account, and the cross-sectional size of each part of the gating system is related to the size of the casting, the combination of model clusters and the number of pieces per box.
The combination of model clusters can basically reflect the characteristics of the casting, as well as the form of the casting. Due to the presence of model clusters, the behavior of molten metal after pouring is very different from sand casting. Model gasification needs to absorb heat during the pouring process, so the pouring temperature of lost foam casting should be slightly higher than that of sand casting.
When designing the cross-sectional dimensions of each part of the casting system, the resistance caused by the presence of the model during the casting of molten metal in lost foam casting should be taken into account, and the minimum resistance flow area should be slightly larger than that of sand casting.
Negative pressure is a necessary measure for ferrous alloy lost foam casting. The negative pressure is an important guarantee measure to increase the strength and stiffness of the molding sand, and it is also the main measure to eliminate the model gasification products. The size and holding time of the negative pressure are related to the casting material and model cluster structure and the coating.
The most taboo thing about the lost foam casting pouring operation is intermittent pouring, which is easy to cause cold partition defects in castings, that is, the temperature of the molten metal poured first decreases, resulting in a cold separation between the molten metal poured later. In addition, the lost foam casting pouring system mostly adopts a closed pouring system to maintain the smoothness of pouring. In this regard, the form of the gate cup is closely related to whether the gating operation is stable. When pouring, the liquid level in the gate cup should be kept stable, and the dynamic pressure of pouring should be stable.