The punch is usually used to clean and remove the sprue, overflow groove and burr of copper die-casting parts. Generally, manual operation is no longer required after punching. When the punch is difficult to remove, it can be removed manually, but it shall not cause meat shortage and deformation. When the product needs finishing, it can be polished with a grinder, grinding wheel grinder or polishing machine. The parts that are not in place can be trimmed with a scraper or file. In case of deformation of die castings, special molds and equipment can be used for correction, and annealing or aging treatment shall be required after correction. This is the guide that shares pros, cons and defects and solutions of copper die casting.

Advantages of copper die casting:

1. Good product quality: high dimensional accuracy of castings, generally equivalent to grade 6 ~ 7, or even grade 4; Good surface finish, generally equivalent to grade 5 ~ 8; The strength and hardness are higher. The strength is generally 25 ~ 30% higher than that of sand casting, but the elongation is reduced by about 70%; Stable size and good interchangeability; It can die cast thin-walled and complex castings.

2. High production efficiency: high machine productivity. For example, the domestic J Ⅲ 3 horizontal cold air die casting machine can die 600 ~ 700 times in eight hours on average, and the small hot chamber die casting machine can die 3000 ~ 7000 times in eight hours on average; Long service life of die-casting mold, one pair of die-casting mold.

3. Excellent economic effect: due to the accurate size of die castings, the surface is bright and clean. Generally, it is not directly used for machining, or the processing volume is very small, so it not only improves the utilization rate of metal, but also reduces a large number of processing equipment and working hours; Casting price is easy; Combined die casting can be used to other metallic or non-metallic materials. Save both assembly time and metal.

 

Disadvantages of copper die casting:

1. During die casting, due to the high filling speed of liquid metal in the mold cavity and unstable flow state, the general die casting method is adopted, which is easy to produce pores and cannot be heat treated;

2. For castings with complex concave, die casting is difficult;

3. High melting point alloys (such as copper and ferrous metals), with low service life of die casting mold;

4. It is not suitable for small batch production. The main reason is that the manufacturing cost of die-casting mold is high, the production efficiency of die-casting machine is high, and small batch production is uneconomical.

 

Defects and solutions of copper die casting:

1. Mold spots are often found on the surface of die castings, which seriously affect the appearance quality of castings, mainly caused by release agent. At present, there are a large number of large and small manufacturers of release agent on the market, many of which have various quality problems, the most important of which is the corrosion effect on die castings. Generally, the die-casting factory does not pay much attention. If the die-casting is put for a long time, there will be white spots (frost like, black after removal)) on the surface, which has actually been corroded. The main reason is that there are corrosive components in the release agent. Therefore, the choice of release agent must not only pursue low price, but also pay attention to cost performance.

Generally, the release agent will not penetrate into the die casting. However, the inferior release agent will corrode the surface of die castings and penetrate into the interior; In addition, if the air volume of release agent is large, it will be drawn into the die casting to form pores. If the coating such as release paste is not used properly, defects such as slag inclusion will occur.

 

2. The surface peeling of die castings often occurs after shot blasting. Generally, the mold or injection chamber (molten cup) is not cleaned up due to the following reasons; Insufficient injection pressure (pay attention to whether the moving die gives way during injection); There are some problems in the setting of gating system, and there is turbulence when the alloy liquid enters the mold cavity; Mold temperature problem; Liquid metal splashes seriously during injection.

 

3. Zinc alloy electroplating foaming. Poor electroplating can be caused by electroplating process and surface quality of die castings. The surface quality of die castings shall be good, and there shall be no defects such as porosity, cracks, pores, bubbles, shrinkage cavities, cold lines, pinholes, etc. otherwise, the surface of castings is easy to blister after electroplating, and the electroplated coating is separated from the substrate. When grinding and polishing before electroplating, be careful not to grind too much. Because in the solidification process of die castings, a dense cold hard layer is formed on the surface due to rapid cooling, while the internal structure may have defects such as pores and shrinkage cavities. Do not remove this good surface layer during grinding, otherwise pitting and bubbles will appear during electroplating. In addition, the polishing wheel should not be pressed too tightly and overheated to prevent adhesion between the abrasive and the product, resulting in poor electroplating of the product.

 

There are pores in the die casting, and the causes are as follows:

1. The metal flow direction is incorrect, which has a frontal impact with the casting cavity, resulting in eddy current, surrounding the air and generating bubbles;

2. The inner gate is too small and the metal flow rate is too large. Before the air is removed, the exhaust hole is blocked prematurely, leaving the gas in the casting;

3. The cavity is too deep and ventilation and exhaust are difficult;

 

Unreasonable exhaust system design, difficult exhaust and adjustment methods;

1. Correct the size and shape of the shunt cone to prevent the front impact of metal flow on the cavity

2. Appropriately increase the inner gate;

3. Improve mold design;

4. Reasonably design the exhaust slot and increase the air hole.

 

Metal liquid splashed out during die casting. Causes:

1. The clamping between movable and fixed molds is not tight and the gap is large;

2. Insufficient clamping force;

3. Die casting machine, fixed die mounting plate is not parallel;

4. Large span of support plate. The injection force causes the sleeve plate to deform. Produce spraying.

 

Adjustment method:

1. Reinstall the mold;

2. Increase the clamping force;

3 adjust the die casting machine to keep the moving and fixed die mounting plates parallel to each other;

4. Add support plate on the moving die to increase the stiffness of the sleeve plate.