Cold shut means that two or more strands of liquid metal are not fully fused during convection. What is the reason for cold shut of zinc alloy die castings? How to solve it?

Cause:

1. The two metal streams are connected with each other, but they are not fully fused and there is no impurity between them. The bonding force between the two metals is very weak;

2. Low pouring temperature or mold temperature;

3. Incorrect alloy composition and poor fluidity;

4. The gate is incorrect and the flow path is too long;

5. Low filling speed;

6. Low pressure;

resolvent:

1. Properly increase the pouring temperature and mold temperature;

2. Increase injection pressure;

3. Increase the thickness of the inner gate appropriately while increasing the injection speed;

4. Improve exhaust conditions;

5. Properly configure alloy composition to improve fluidity;

There are many problems in the process of zinc alloy die casting, and cracks are one of them. How to solve them? First of all, we should understand the causes of cracks.

The main reasons for cracks in zinc alloy die castings are as follows:

1. The harmful impurities lead, tin, iron and cadmium in the alloy exceed the specified range;

2. The casting is taken out of the mold too early, and the metal strength is insufficient;

3. The pulling out or pushing out force of the core is uneven, resulting in a small force on one side and a large force on the other side, causing cracks and deformation of the product;

4. The junction of casting wall thickness changes violently;

5. The melting temperature is too high, resulting in coarse grains;

resolvent:

1. The proportion of alloy materials shall not be too high;

2. Extend the mold opening time;

3. Adjust the core and push rod to ensure uniform force;

4. Change the non-uniform section of wall thickness;

Flow marks and patterns are one of the defects of zinc alloy die castings. To eliminate the defects of zinc alloy die castings, the causes of defects in zinc alloy die castings must be analyzed first, and then effective measures can be taken quickly and accurately.

Causes of flow marks and patterns:

1. The trace left after the metal liquid entering the mold cavity first forms an extremely thin and incomplete metal layer, which is made up by the later metal;

2. Low model temperature, such as zinc alloy mold temperature less than 150 and aluminum alloy mold temperature less than 180, will cause such defects;

3. High filling speed;

4. Excessive amount of paint;

5. The cavity back pressure is large;

resolvent:

1. Adjust the sectional area or position of the inner gate;

2. Properly adjust the filling speed to change the flow pattern of the metal filling cavity;

3. Increase the model temperature;

4. Properly select and improve coatings;

The die castings made of zinc alloy die castings have the advantages of smooth surface, wear resistance and high precision. The most common defect of zinc alloy die castings in the production process is blistering on the surface of the castings. What is the reason for the bubbles on the surface of zinc alloy die castings?

1. The mold release agent or mold oil water is too much, and the design air vent of the mold is too small or too little, so that when the high-temperature zinc alloy slurry is injected into the mold, the gas generated by the film release agent cannot be eliminated, thus producing bubbles on the product;

2. The pressure of the die-casting machine is not adjusted sufficiently, making it difficult to remove the gas in the mold;

3. The nozzle is broken or not aligned;

4. The hammer in the furnace is broken;

Source: Changjiang Nonferrous Metal Network

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