The speed concept and control requirements of die casting speed of casting mold

In the die-casting process of casting molds, there are two different concepts of die-casting speed, namely injection speed and filling speed. The injection speed refers to the linear speed of the injection punch driven by the pressure oil in the injection cylinder of the die casting machine; and the filling speed refers to the linear speed of the liquid metal entering the cavity through the gate under the action of pressure.

The main function of the filling speed of the casting mold is to quickly send the liquid metal into the cavity before solidification. Obtaining castings with sharp contours and high surface quality is an important factor. Speed and pressure are two closely related process parameters. Therefore, in addition to the proper injection specific pressure, the low-pressure mold should select the correct speed.

The filling rate is determined according to the characteristics of the alloy and the structural characteristics of the casting. When the filling speed is low, the contour of the casting is unclear or even cannot be formed. When the filling speed is high, even with a low injection pressure, castings with high surface quality can be obtained. But too high filling speed will cause many technical defects, resulting in unfavorable die casting conditions.

Because the high-speed molten metal flows in front of the air, the low-pressure mold blocks the exhaust passage, and the air is wrapped in the cavity to form bubbles. The molten metal is atomized into the cavity and adhered to the wall of the casting mold, so that the molten metal cannot fuse with the molten metal to form surface defects, thereby reducing the surface quality of the casting.

The high-speed metal flow generates eddy current, which first wraps the air and cold metal entering the cavity, so that the casting produces pores and oxide inclusions; the high-speed metal flow scours the mold wall and accelerates the wear of the die-casting mold. Therefore, casting mold parts have high precision, high complexity, good consistency, high productivity and low consumption.