In die casting, die casting speed has two different con […]
In die casting, die casting speed has two different concepts: injection speed and filling speed. The injection speed refers to the linear velocity of the injection punch driven by the pressure oil in the injection cylinder of the die casting machine. Filling speed refers to the linear velocity of liquid metal entering the cavity through the gate under pressure. The main function of casting mold filling speed is to quickly send liquid metal into the cavity before solidification. Obtaining castings with clear contours and high surface quality is an important factor.
Speed and pressure are two closely related process parameters. Therefore, in addition to proper injection pressure, the low-pressure mold must 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 unable to form. 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 and cause unfavorable die casting conditions, mainly as follows:
First, 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.
Second, the molten metal is atomized into the cavity and adhered to the mold wall, so that the molten metal cannot fuse with the molten metal to form surface defects (cold beans or cold partitions), thereby reducing the surface quality of the casting.
Third, the high-speed metal flow generates eddy currents. First, the air and cold metal entering the cavity are wrapped, so that the casting produces pores and oxide inclusions.
Fourth, the high-speed metal flow washes the mold wall and accelerates the wear of the die-casting mold.
The above are the decisive factors of the casting speed of the casting mold. The casting mold has high precision, high complexity, good consistency, high productivity and low consumption. The manufacturing method of casting mold has unique innovative value. The quality, efficiency and development capabilities of the product depend to a large extent on the casting mold.