Five Major Defects In Mold Casting

- Aug 17, 2018-

1.Casting shrinkage hole


The main reason is that the alloy solidification shrinkage produces casting shrinkage cavities and the alloy absorbs a large amount of oxygen, nitrogen, etc. in the air. When the alloy solidifies, gas is released to cause casting shrinkage.


The solution


(1) Place the gold ball.

(2) Thicken the diameter of the casting track or shorten the length of the casting path.

(3) Increase the amount of metal used.

(4) The following method is used to prevent the formation of depressions in the direction of the casting path.

1) Place a cooling channel at the root of the casting path.

2) In order to prevent the molten metal from vertically impacting the cavity, the casting path should be curved.

3) Place the casting path diagonally.


2. The surface of the casting is rough and not clean


The rough surface of the cavity and the molten metal reacted with the surface of the cavity, mainly reflecting the following conditions.


(1) The embedded material particles are coarse and not delicate after stirring.

(2) After the embedded material is solidified, it is directly placed in a Maofu furnace for roasting, and the water is excessive.

(3) The heating rate of the baking is too fast, and the difference in expansion occurs in different positions in the cavity, so that the inner surface of the cavity is peeled off.

(4) The maximum temperature of the baking is too high or the baking time is too long, so that the inner surface of the cavity is too dry.

(5) The melting temperature of the metal or the calcination temperature of the casting ring is too high, causing the metal to react with the cavity, and the surface of the casting is burned with the embedding material.

(6) The calcination of the mold is insufficient, and when the molten metal is cast, the decomposition of the embedding material is caused, and a large amount of gas is generated to cause pitting on the surface of the casting.

(7) After the molten metal is cast, the local temperature in the cavity is too high, and the surface of the casting is locally rough.


The solution


(1) Do not excessively melt the metal.

(2) The baking temperature of the mold should not be too high.

(3) The calcination temperature of the mold should not be too low (the calcination temperature of the phosphate embedding material is 800 to 900 degrees).

(4) Avoid the phenomenon that the structure is concave toward the direction of the casting path.

(5) Apply a liquid to prevent sticking on the wax type.