The core elements of the casting industry include the "Three Excellences": high-quality molten iron, suitable molding sand, and exquisite craftsmanship. The casting process, as one of the three major elements in casting manufacturing, is self-evidently important. It involves studying how to determine the path and method by which molten iron flows into the mold cavity, thereby ensuring the quality of the castings.

The mold system is a key component of the casting process, including parts such as the pouring cup, runner, ingate, vents, and risers. The pouring cup is the entry point where molten iron is poured from the ladle into the mold; its design must consider uniform filling and slag removal. The runner is the channel through which molten iron flows from the pouring cup to the mold cavity. The ingate, where molten iron enters the mold cavity, is crucial in its design and directly affects the quality of the casting. Vents are used to expel air from the mold cavity. Risers serve to remove inclusions from the molten iron and debris from the mold, while also providing a feeding (compensating for shrinkage) function.

In the casting process, smooth and rapid pouring is key. To achieve this, the positioning of the cope and drag must be properly arranged, ensuring that machined surfaces are located in the drag to reduce shrinkage porosity and improve material density. Simultaneously, selecting the appropriate gating method is essential. Top gating, although it can easily cause erosion (washing), is used less frequently. The position and type of ingates are also important factors affecting casting quality, requiring consideration of their number, shape, and the cross-sectional area ratio relative to the sprue and runner. Through reasonable process design, the quality and performance of the castings can meet the expected requirements.

Although there are different viewpoints regarding the specific proportions of the gating system, the design philosophy is clear. Molten iron first enters through the pouring cup into a wide runner, then flows into narrower ingates. In the runner, the flow velocity of the molten iron decreases, allowing time for lighter inclusions to float up, thereby preventing them from entering the casting interior. By grasping this key design point, we need not overly dwell on minor details, just remember the principle of "Medium [Sprue], Large [Runner], Small [Ingate]".

In the practical design of the gating system, to reduce the impact of molten iron on the bottom of the sprue, both the sprue base and the end of the runner are often designed with a hemispherical shape. Furthermore, to ensure casting quality, the solidification process of the molten iron in the mold should be completed in the shortest possible time. Therefore, we establish pouring time standards as follows.

For castings weighing 10-25 kg, the pouring time is typically controlled within 4 to 8 seconds; for castings weighing 25-50 kg, the pouring time is set at 7 to 10 seconds. When the casting weight reaches 50-100 kg, the pouring time needs to be extended to 9 to 14 seconds. For heavier castings of 100-200 kg, the pouring time is further increased to 16 to 28 seconds.

Additionally, the design of feeder heads (feeders) and risers is crucial. The main function of a feeder head is to supply additional molten iron to compensate for shrinkage during solidification and cooling within the mold. It should be positioned at the thick sections of the casting, with a diameter approximately 1 to 2 times the wall thickness of the casting. The design of risers aims to allow inclusions that enter the mold cavity to float out, and their placement also requires careful selection.

Special techniques are required when pouring for feeder heads. When the feeder head is upright, pouring should first be done through the sprue until the molten iron rises to half the height of the feeder head, then stopped. Subsequently, high-temperature molten iron is poured again from the top of the feeder head to ensure the temperature of the iron in the feeder head is higher than that in the casting. This effectively prevents shrinkage cavity formation. If the feeder head cools too quickly, it might draw in molten iron from the casting, having a counterproductive effect. Therefore, special attention must be paid in the design to controlling the cooling rate of the feeder head.