Holding and mold opening and filling time method of investment castings

H2. 1. Holding time.

The length of holding time depends on the investment casting material and wall thickness. For castings with high melting point, high crystallization temperature range and thick wall, the holding time is longer. For the casting of small and thin wall of crystallization temperature, the holding time can be shorter. If the holding time is insufficient, it is easy to cause shrinkage.

But the holding time is too long, it can not be very effective, easy to cause the vertical die-casting machine to remove the residual material difficulty. When the liquid metal filling cavity is completely solidified in the inner gate, the duration under the action of the injection is called the holding time.

The effect of holding time is to have enough time to pass the pressure to the solidified metal, to ensure that the casting is crystallized under pressure and to strengthen the retraction to obtain the dense tissue.

H3.2. Mold opening time.

After holding pressure, the mould should be opened to remove investment casting products. The time from the end of the injection to the casting die is called the opening time. Enough opening time can make the precision casting in the mold to have certain strength, the mold and the ejection will not produce deformation or crack.

When the meat is too short, it will die when the casting strength is low and the casting is easy to deform. Low - strength alloys may also cause surface blistering due to the expansion of internal pores.

But investment casting mould time is too long, product temperature is too low, contraction, the core pulling and ejection of the casting is also big, the resistance of the alloy can also cause the casting of large heat brittle cracking, but also reduces productivity of casting.

H4.3. Fill time.

The time required for the liquid metal to enter the cavity in the die casting cavity is called the filling time. The length of filling time depends on the size and complexity of the investment casting.

For large and simple products, the filling time is relatively long, and the filling time of complex and thin-walled castings is a little bit. The adjusting method of filling time is similar to that of filling speed.