Defects in die-casting parts

Flow mark

Other names: Stripes.

Feature: The casting surface presents locally sunken smooth patterns that are consistent with the flow direction of the molten metal and can be felt by hand. This defect has no development direction and can be removed by polishing method.

Reason for occurrence: 1. Traces left by two asynchronous metal flows filling the cavity. 2. Low mold temperature, such as zinc alloy mold temperature below 150 ℃ and aluminum alloy mold temperature below 180 ℃, are prone to such defects. 3. The filling speed is too high. 4. Excessive use of paint.

Exclusion measures: 1. Adjust the cross-sectional area or position of the sprue. 2. Adjust the mold temperature and increase the overflow groove. 3. Adjust the filling speed appropriately to change the flow state of the metal liquid filling cavity. 4. The coating should be thin and uniform.

Cold water barrier pattern

Other names: Cold connection (docking), water pattern.

Characteristic: A gap that occurs when metal flows at lower temperatures collide but do not fuse with each other, presenting an irregular linear shape with both penetrating and non penetrating types, and showing a tendency to develop under external forces.

Causes: 1. Low pouring temperature of molten metal or low mold temperature. 2. The alloy composition does not meet the standards and has poor fluidity. 3. Metal liquid is filled in separate strands, resulting in poor fusion. 4. The gate is unreasonable and the process is too long. 5. Low filling speed or poor exhaust. 6. The pressure is relatively low.

Exclusion measures: 1. Increase the pouring temperature and mold temperature appropriately. 2. Change the alloy composition to improve fluidity. 3. Improve the pouring system, increase the speed of the sprue, and improve the filling conditions. 4. Improve the overflow conditions and increase the overflow volume. 5. Improve injection speed and exhaust conditions. 6. Increase the specific pressure.

Scratches and abrasions

Other names: tensile strength, tensile marks, adhesive mold scars.

Characteristic: Along the demolding direction, due to metal adhesion, the mold manufacturing slope is too small, resulting in scratches on the surface of the casting, and in severe cases, it becomes a scratch surface.

Reason for occurrence: 1. The casting slope of the core and wall is too small or there is a reverse slope. 2. There are pressure marks on the core and wall. 3. Alloy adhesive mold. 4. Casting protrusion deviation, or core axis deviation. 5. The surface of the wall is rough. 6. Paint often cannot be sprayed. 7. The iron content in aluminum alloy is less than 0.6%.