Analysis of the reasons of 10 common defects in die casting

With the development of die-casting technology, people's requirements for castings are getting higher and higher. However, the production process is affected by many factors, resulting in defects in castings. We have analyzed and compiled the following reasons for the top ten common defects in die-casting.

1. Reasons why castings have flow marks and patterns

(1) The mold temperature is too low;

(2) Poor runner design and poor location of the inner gate;

(3) The material temperature is too low;

(4) The filling speed is low and the filling time is short;

(5) The pouring system is unreasonable;

(6) Poor exhaust;

(7) The spray is unreasonable.

2. Reasons for cracks in castings

(1) There are cracks on the surface of the die-casting mold cavity;

(2) The die-casting mold is not evenly preheated.

3. Causes of cold insulation in castings

(1) The two metal streams are connected to each other, but they are not completely fused and there is no inclusion between them, and the bonding force between the two metal streams is very weak;

(2) The pouring temperature or die-casting mold temperature is low;

(3) The sprue position is wrong or the flow path is too long;

(4) The filling speed is low.

4. Causes of shrinkage (dents) in castings

(1) Improper design of die-casting parts caused by shrinkage; too large wall thickness difference; improper runner position; low injection pressure and short holding time; local temperature of the die-casting mold is too high.

(2) The cooling system design is unreasonable;

(3) Open the mold too early;

(4) The pouring temperature is too high.

5. Causes of imprints on Castings

(1) The end face of the ejector rod is worn due to the ejection component; the adjustment length of the ejector rod is inconsistent; the splicing part of the die-casting model cavity does not match well with other parts.

(2) The inserting part is loosened due to splicing or movable parts; the movable part is loosened or worn; the side wall surface of the casting is formed by the inserts of the moving and fixed molds interpenetrating each other.

6. Reasons why castings are accompanied by traces of adherents

(1) There are metal or non-metallic residues on the surface of the die-casting model cavity;

(2) During pouring, impurities are first brought in and attached to the surface of the cavity.

7. Reasons for skinning and peeling of castings

(1) The mold is not rigid enough and the template will vibrate during the filling process of molten metal;

(2) The punch crawls during the injection process;

(3) Improper design of the runner system.

8. Causes of friction ablation in castings

(1) Improper position, direction and shape of the runner caused by the die-casting mold;

(2) Insufficient cooling of the parts where the molten metal is eroded violently in the inner runner caused by the casting conditions.

9. Causes of erosion in castings

(1) Improper setting of the gate position;

2) The cooling conditions are not good.

10. Reasons for cracks in castings

(1) The iron content in the alloy is too high or the silicon content is too low; the content of harmful impurities in the alloy is too high, which reduces the plasticity of the alloy; aluminum-silicon alloys and aluminum-silicon-copper alloys contain too much zinc or copper; aluminum-magnesium alloys contain Too much magnesium;

(2) The mold retention time is too short and the pressure holding time is short; the wall thickness of the casting changes drastically;

(3) The local tightening force is too large and the force is uneven during ejection.