Aluminum alloy die casting refers to the liquid aluminum alloy in high temperature and high pressure at a very high speed from the pressure chamber into the die cavity, after cooling to form the casting method. Especially in recent years become the industry trend of ultra-large integrated die casting is new energy automobile parts production of advanced technology. Aluminum alloy die casting has the advantages of high dimensional accuracy, good mechanical properties, high production efficiency, etc. It has a broad application prospect in the field of automobile, motorcycle, internal combustion engine, electronics, instrumentation, aerospace and so on.

Although this production method has a variety of advantages, but in the production process, aluminum alloy die casting molding is affected by many factors, very easy to cause the final casting defects, aluminum alloy solution in the flow process is easy to get involved in the gas, casting process temperature distribution imbalance, will lead to casting produce flow marks, cracks, shrinkage of the cavity, burns, and many other defects.

1, Castings with flow marks and patterns

Castings symptoms:

There are streaks on the surface of the casting that are consistent with the direction of the flow of the metal liquid, and there are clearly visible non-directional lines that are different from the color of the metal matrix, and there is no development trend.

Generate cause analysis:

1) Mold temperature is too low;

2) Poor sprue design and poor location of inner gate;

3) Material temperature is too low;

4) Low filling speed and short filling time;

5) Irrational pouring system;

6) Poor exhaust;

7) unreasonable spraying.

2, The castings appear cracks

Casting symptoms:

There are traces of net-like hairline-like bulging or depression on the surface of the die casting, which expand and extend with the increase of the number of die casting.

Produce cause analysis:

(1) Cracks on the surface of die-casting mold cavity;

2) Uneven preheating of die-casting mold.

3, Castings produce cold segregation

Symptoms of castings:

Die casting surface has obvious, irregular, sagging linear pattern pattern (there are penetrating and not penetrating two kinds) fine and narrow shape, sometimes the intersection edge is smooth, in the external force under the action of the possibility of disconnection.

Produce cause analysis:

(1) two streams of metal docking each other, but not completely fused and no inclusions exist between them, the two metal bonding force and very weak;

(2) Pouring temperature or die casting mold temperature is low;

3) Incorrect location of sprue or flow path is too long;

4) low filling speed.

4, Castings appear shrinkage (dent)

Symptoms of castings:

Comparatively thick aluminum casting, most of the surface has a smooth dent (like a disk dish).

Generation cause analysis:

(1) caused by shrinkage die casting design improper wall thickness difference is too large; sprue location is not appropriate;

Pressure injection ratio pressure is low, holding pressure time is short; die-casting mold local temperature is too high.

(2) cooling system design is unreasonable;

(3) Open the mold too early;

4) pouring temperature is too high.

5, Castings produce marks

Castings symptoms:

Traces left by the contact between the surface of the casting and the surface of the cavity of the die-casting mold or the appearance of step marks on the surface of the casting.

Generation cause analysis:

(1) Caused by the ejector element the top rod end surface is worn out; the top rod adjustment length is inconsistent; die-casting mold cavity splicing part and other parts are not well coordinated.

(2) by the splicing or movable part caused by the splicing part of the loosening; movable part of the loosening or wear; casting side wall surface, by the movable and fixed mold interspersed with each other inlays formed.

6, Castings accompanied by traces of adherents

Castings symptoms:

Small flakes and metal or non-metallic and metal matrix partially fused, under the action of external forces peeling off small flakes, peeling off the casting surface some shiny, some dark gray.

Produce cause analysis:

(1) in the die-casting mold cavity surface metal or non-metallic residues;

(2) pouring first brought into the impurities attached to the cavity surface.

7, Casting skinning and spalling

Symptoms of casting:

There are obvious layers of metal in the casting locally.

Produce cause analysis:

(1) Mold rigidity is not enough in the liquid metal filling process, the template produces jitter;

2) Crawling phenomenon of the punch in the process of compression injection;

(3) Improperly designed sprue system.

8, Castings occur friction ablation

Castings symptoms:

The surface of the die casting produces rough surfaces in some positions.

Produce cause analysis:

(1) by the die casting type (mold) caused by the location of the inner sprue direction and shape is not appropriate;

(2) caused by the casting conditions of the inner sprue at the metal liquid scouring intense parts of the cooling is not enough.

9, Castings appear erosion

Symptoms of castings:

Die casting localized position with pockmarks or bumps.

Produce cause analysis:

(1) Improperly set up position of inner sprue;

2) Poor cooling conditions.

10，Cracks appear in castings

Castings Symptoms:

Put the casting in alkaline solution, the crack is dark gray. The destruction and cracking of the metal matrix is in a straight line or wave line, the grain is narrow and long, and there is a trend of development under the action of external force.

Produce cause analysis:

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

(2) The time of leaving the mold is too short, and the pressure holding time is short; where there is a drastic change in the wall thickness of the casting;

(3) The local packing tightness is too large, and the force is uneven when ejecting.

Conclusion

Integration die casting can be the original design of a number of separate fragmented parts after re-design highly integrated, and then use a large die casting machine for one-time molding, omitting the process of welding, directly get a complete large parts. Because of this kind of production process innovation can simplify the production process, improve production efficiency, and reduce the weight of the body, effectively and significantly reduce production costs.

Previously, the market using integrated die casting process is mainly rear bottom plate, with the optimization of the process, integrated die casting application scope is also expanding. At present, the integrated die-casting technology gradually applied to the automobile front cabin, center bottom plate, battery tray and other parts. A professional organization estimates that by 2025, China's integrated die casting parts market space will reach 34.84 billion yuan, the compound annual growth rate from 2021 to 2025 is 230.9%.