The crack defect on metal surface caused by flow of lower temperature butts with each other but does not coalescence, showing irregular linear shape, there are two kinds of penetrating and non-penetrating, and there is a development tendency under the action of external force.
1. Metal liquid pouring temperature is low or mold temperature is low;
2. The alloy composition does not meet the standard and has poor liquidity;
3. Sub-unit of molten metal fill, poor fusion;
4. Unreasonable gate and too long flow passageway;
5. Low filling speed or poor air exhaust;
6. Shooting pressure is lower than general pressure;
Analyze judgement and solution
1. Product is black with flow mark. increase casting temperature and mold temperature appropriately.
2. Change alloy composition to improve fluidity.
3. Hot die parts to see the direction of aluminum liquid, metal liquid collision produced cold shuts with vortex shape, accompanied by flow marks.Improve pouring system and filling direction of inner gate. in addition, slag collecting bag can be set at the edge of casting to improve filling conditions.
4. Not compaction of distal area.Change the gate position and cross section area, improve the discharge condition and increase the flow volume.
5. The product turned dark, often accompanied by surface bubbles. Increase the velocity of injection.
6. Not compaction of a whole part. Increase pressure rate (not preferred).