The casting process of the lost foam casting involves the filling of molten steel while the foam mold vaporizes and disappears. Throughout the process, it is important to note:

① Ensure that the runner is continuously filled with molten steel. Failure to do so can easily lead to sand collapse and air intake due to the limited strength of the coating layer, resulting in casting defects.

Ensure a firm grip during the casting process to achieve stability, accuracy, and speed. Instantly fill the sprue cup and maintain a continuous flow without interruption, with approximately one ton of molten steel in about a minute. If the molten steel in the same box stops flowing, it may draw in air, potentially causing sand shrinkage or an increase in casting porosity, leading to the rejection of the casting.

③ The Shell Molding Casting uses a negative pressure enclosed design, and it must be sealed below the sprue cup. As the molten steel enters the mold, it begins to liquefy, burn, and vaporize, forming a temporary cavity at the front end of the steel flow. Therefore, the design ensures that the filling speed of the molten steel is roughly similar to the rate at which the foam mold disappears. To prevent the high-temperature radiation of the molten steel from melting other models in the same box, the runner is appropriately spaced further from the casting model. The riser is positioned at the lower end of the entire casting box. During casting, attention is paid to adjusting and controlling the negative pressure vacuum degree within a certain range. After casting is complete, maintain a certain negative pressure state for a period of time, then remove the steel after the negative pressure stops and the molten steel solidifies.

2. Shell molding is a type of casting process, where various casting defects can occur, leading to defects in the castings, with shell molding being no exception. Flashing is a common occurrence in shell molding, and in severe cases, it may pose a risk to the safety of the caster. It is essential to pay attention to this issue. To mitigate flashing, the following measures can be taken:

The foam model should have a low density. To ensure the quality of the foam surface and the strength of the model, the foam should be as light as possible to reduce the gas generation during casting.

Ensure the foam models are dried completely before applying paint. Each batch of foam models should have its weight changes during the drying process inspected, and a weight change curve chart should be made. Only when there is no further weight change can paint be applied.

③ The casting system, particularly the straight and horizontal runners, should not be coated. This allows the gases produced during casting to be quickly and fully extracted. Moreover, not applying coatings saves on material consumption. At the end, place a挡板 on top of the sprue cup to prevent the backflow of molten steel, thus avoiding splashes that could endanger on-site workers.

Employing these methods effectively prevents back-pouring during the lost foam casting process, significantly reduces casting defects, enhances the quality of castings, and also improves production safety.