Die-casting pot die casting production technology requirements and control


Any production process requirements are selected according to the product quality requirements, and the die casting pot blank has high quality requirements. It is mainly reflected in the surface roughness, high temperature baking, no bubbles, no pinholes after adding I, and no peeling of castings after shot blasting. This quality requirement is higher than that of ordinary automobile die castings, so its process requirements also have certain particularity. Next, the non stick pot export manufacturers, die-casting pot manufacturers and non stick pot manufacturers will talk about the process requirements and control of die-casting production of die-casting pots.

(1) Vacuum die casting

That is to say, before fast injection, first seal the feeding port through the injection punch, and at the same time, the mold parting surface is sealed with a sealing strip. The vacuum pump starts to pump air, and then fast injection is carried out. The negative pressure of vacuum die casting is generally controlled at 600~800mmHg. In fact, there is no sealing device at the push rod of the mold, so the vacuum negative pressure is generally only about 600mmHg. Through vacuum die casting, it is hoped to obtain castings with high density, high strength and no porosity. Some factories do not need vacuum die-casting for small pots below 160mm, but can also obtain castings with high qualification rate, which requires a certain degree of assurance in the pouring and exhaust system.

(2) Pouring temperature

This refers to the temperature at the discharge port of the die-casting machine holding furnace. Generally, the pouring temperature of aluminum alloy die castings is controlled at 650~680 ° C. From the production practice, it is better to control the pouring temperature of die casting pots at 630~650 ° C. This is also related to the use of vacuum die casting.

(3) Mold temperature

The die-casting die needs to be preheated before production, and the production should be started at about 150 ° C. Through continuous production of die casting, the mold temperature will gradually increase, but excessive temperature will affect the quality of castings. Therefore, it is appropriate to keep the mold temperature within 180~230 ° C by cooling and coating.

(4) Die casting speed

Die casting speed can be divided into injection speed (moving speed of punch) and liquid aluminum filling speed (ingate speed). The casting speed mainly affects the surface quality of the casting. The casting speed is fast, and the casting surface is relatively smooth, but not too fast. It is easy to entrain air and erode the mold. Generally, the filling speed of die castings is 25-35 m/s. Due to the high requirements on the surface quality of the die-casting pot, the longer process distance and the thinner average wall thickness (2-2.5 mm), the filling speed can be faster, about 35-45 m/s.

(5) Specific pressure

Specific pressure can be divided into injection specific pressure and boost specific pressure. The selection principle of specific pressure is: high specific pressure shall be selected for thick wall castings, castings with complex shape and high strength requirements, castings with high internal quality requirements, castings with high filling speed requirements, and castings with large runner resistance. In addition to the thin wall of the die-casting pan, all other parts meet the above conditions. Therefore, the specific pressure should be selected higher, which is close to the requirements of automotive pressure castings, about 800~1000Kg/cm2. Adjust the specific pressure. On the same die-casting machine, in addition to adjusting the injection ratio or boost pressure, it can also be achieved by adjusting the diameter of the pressure chamber.

(6) Injection stroke

It refers to the distance that the punch moves during injection. According to the general requirements of the die-casting process, when the slow injection is over, the position of the metal liquid flow should be at the inner gate. Once it is converted to fast injection, the aluminum liquid can be rapidly injected into the cavity without resistance, which is an ideal state. Obviously, it is not allowed to carry out rapid injection without aluminum liquid reaching the inner gate. Is it allowed to conduct rapid injection after the aluminum liquid flows through the inner gate? This scheme is available. Generally, it can be used in two cases. One is that the casting quality at the end far from the inner gate is poor, and the other is that the resistance of the cavity at the inlet of the inner gate is large. Technically, the aluminum liquid is intentionally allowed to exceed a certain distance from the inner gate before entering the injection. For example, for a large die-casting pot, the distance between the inner gate and the opposite side is long, which is easy to produce patterns and cold shuts. This scheme can be used. However, the actual amount of aluminum liquid entering the inner gate should be completed through actual commissioning.