We believe that technical key points of lower cylinder blocks
are mainly as the following according to experimental analyses.
1. Scientifically design gating systems of cylinder block die casts
; inserts which are placed in the middle of lower cylinder blocks have thin walls; the upper and the lower parts of the lower cylinder block are the thick parts; therefore, we choose the unilateral pouring; by doing this, the aluminum liquid will flow from the bottom side of the cavity to the middle of the insert and then to the top of the cavity.
2. We use the tooth-shaped chilled exhaust block vacuum die casting; tooth-shaped chilled exhaust blocks and vacuum machines can improve bad mobility caused by thin walls of the two sides and ensure good quality of die casts.
3. We preheat inserts in order to improve wetness of aluminum alloy liquids and cast iron inserts, which not only ensures that cast iron parts are not separated from aluminum alloy after molding processes, but also improves mobility of aluminum liquids.
We can obtain the lower cylinder block with the compact structure and good appearance after the test. Scientific and reasonable technological parameters are guarantees of obtaining lower cylinder blocks with high quality in die casting processes. We believe that the following technological parameters are the key factors affecting the moldings of the die casts.
1. Die casting temperatures
Temperatures of aluminum liquids should be well controlled in die casting processes, because too high or too low temperatures can not achieve good die casting effects; too high temperatures will easily cause the shrinkage cavity and the shrinkage porosity; too low temperatures will easily cause poor fillings. Generally speaking, the reasonable temperature of the aluminum liquid should be from 650 to 665℃ and the temperature of the mold after being sprayed should be between 150 and 200℃.
2. Inserts' temperatures
When the temperature of the insert reaches from 120 to 140℃, the aluminum liquid will overflow one side of the overflow launder, which can improve the internal quality.
3. Fast injection speed, slow injection speed and pressure of die casting
Fast injection speed and slow injection speed should be controlled at about 4 m/s and 0.22 m/s and the pressure under about 70MPa.
4. Aluminum liquid's quality
As the basic material for the die cast, the quality of the aluminum liquid determines the quality of the die cast; therefore we need to ensure the quality of the aluminum alloy liquid; every bag of aluminum alloy liquids must have refining treatments to degas aluminum alloy liquids and to avoid pollution.