When using die-casting molds, you need to pay attention:

(1) Characteristics of use of die-casting molds;

(2) the temperature of the alloy melt;

(3) temperature of mold work;

(4) Lubrication of die casting molds;

(5) Adjustment content of die casting mold.

First, the use of die casting mold features

In the die-casting production process, the forming conditions of the parts of the die-casting mold are extremely harsh, and they are subjected to mechanical abrasion, chemical erosion, and repeated effects of thermal fatigue.

1. The molten metal enters the cavity of the mold under high pressure and high speed, causing fierce friction and impact on the surface of the cavity of the mold, causing corrosion and wear on the surface of the mold.

2. Molten metal is inevitably brought into the slag during the casting process. The slag has a complex chemical effect on the surface of the formed part. The compound of aluminum and iron, like a sharp turn, accelerates the formation and development of cracks in the die casting mold.

3. Thermal stress is the main cause of cracks on the surface of mold forming parts. In the production process of each die casting, in addition to the high-speed and high-pressure flushing of the molten metal on the surface of the formed part, there is also the heat released by the absorbing metal during the solidification process, resulting in heat exchange. In addition, due to the thermal conduction of the mold material, the temperature of the surface layer of the molded part rises sharply, and there is a large temperature difference with the inside, so that internal stress is generated. When the molten metal fills the cavity, the surface of the cavity first reaches high temperature and expands, while the inner layer has a lower mold temperature, and the relative expansion is small, so that the surface layer generates compressive stress. After the mold is opened, the surface of the cavity is in contact with the air, and the tensile stress is generated by the chilling of the compressed air and the paint. This alternating stress increases with the continuation of production. When the fatigue limit of the mold material is exceeded, the surface layer of the mold is plastically deformed to generate a crack.

In order to maintain the durability of the profile, the surface is required to have thermal fatigue resistance, wear resistance, non-sticking properties, and easy-to-remove parts. Therefore, a 4Cr5MoSiV1 (H13) material, which is currently used well, is used to form parts.

Second, the temperature of the alloy melt

During the production process of the die-casting mold, in order to better fill all the recessed holes and depths of the die-casting mold and to ensure that the metals flow into each other, when the die-casting mold is used, the metal pouring temperature should be properly selected. Alloy casting liquid casting temperature is as follows:

Material Name: Die Casting Fluid Temperature/°C

(1) Zinc alloy: 420-500°C;

(2) Aluminum alloy: 620-690°C;

(3) Magnesium alloy: 700-740°C;

(4) Copper-zinc alloy: 850-960°C.

Die casting alloy temperature selection principle:

1. The lower the temperature of the poured metal, the longer the life of the die casting mold;

2. Using low-temperature die-casting, it is possible to reduce the increase of the depth of the exhaust groove and reduce the risk of splashing of molten metal.

3. The use of low-temperature die-casting can reduce the chance of the pressure chamber and the top rod engaging;

4. The use of low-temperature die-casting can reduce shrinkage holes and cracks in the casting.

In short, under the conditions of process conditions, the temperature of the die-casting alloy is better than low-temperature die-casting.

Third, the mold working temperature

The working temperature of the die-casting mold is different according to the die-casting alloy. The following are the recommended values ​​for several alloy molds for selection:

Mold Name: Operating Temperature/°C

(1) Zinc alloy mold: 150-180°C;

(2) aluminum alloy mold: 180-225 °C;

(3) Magnesium alloy mold: 200-250°C;

(4) Copper-zinc alloy mold: 300°C.

Die casting mold working temperature selection principle:

1. The mold temperature is too low, the internal structure of the casting is loose, and the air is difficult to mold;

2 mold temperature is too high, the internal structure of the casting is dense, but the casting is easy to "weld" attached to the mold cavity, stick mold, not easy to discharge the casting, at the same time, high temperature will cause the mold itself to expand, affecting the casting size accuracy;

3. The mold temperature should be selected within a suitable range. Generally, after the test is suitable, the constant temperature control is good.

Fourth, the die casting mold lubrication

1. Purpose of lubrication

Lubrication is used as a parting agent for die-casting molds and die castings to facilitate die-casting mold unloading. As a lubricant for the die-casting mold and the movable part of the press, friction is reduced, and the service life of the die-casting mold is increased. In addition, it can also be used as a cooling mold for die-casting molds. Agent, and reduce the thermal fatigue of the mold due to long-term work, extending the life of the mold.

2. Lubricant requirements

For the selection of lubricants, the following needs should be met:

(1) The die casting cannot be adhered in the cavity;

(2) It is not possible to corrode the steel material of the mold surface;

(3) Do not produce toxic gases;

(4) No ash can be generated when heated;

(5) After lubrication, it should be evenly attached to the cavity and working surface without being washed away by the high pressure metal.

3. Preparation of lubricant

(1) Total loss system oil 85%-90% + graphite 10%-15%;

(2) 100% heavy oil;

(3) Paraffin wax 30% + yellow wax 30% + vaseline oil 14% + graphite 26%;

(4) Graphite 25% + glycerin 20% + water glass 5% + water 50%.

4. Matters needing attention when using lubricants

(1) The lubricant can be used on the surface of the cavity and the movable part;

(2) The amount of lubricant to be sprayed is small every time, and it should be uniform. It is better to form a thin film on the molding surface after spraying.

Fifth, the adjustment content of die casting mold

After the completion of the die-casting molds, it is necessary to make trial adjustments. The correct die casting conditions and process parameters are selected to achieve stable die casting and produce qualified castings.

Before the test mode, the test mode personnel should do a preliminary inspection of the alloy raw materials for die casting to understand the characteristics of alloy materials and die casting characteristics; also should understand the die structure, die casting machine performance, die casting conditions, die casting process and operation methods .

The correct choice of die casting forming conditions is the key to the adjustment of the trial die. Often encountered such problems, even if the mold design and manufacture are very correct, but due to the improper selection of die-casting conditions, the same pressure can not be qualified castings. On the contrary, in some cases, the disadvantages of the mold can be overcome by adjusting the conditions of the die-cast molding, and a qualified casting is extruded. To this end, the test mode personnel must be familiar with the role and relationship of the die casting forming conditions, the principle of the die movement, etc., in order to correctly select and reasonably adjust the die casting molding conditions.

Die casting molding conditions include: melting temperature of material, temperature of mold during injection and temperature of melt; determination of injection pressure, clamping force, mold opening force of die casting machine, and injection ratio and pressure required according to the condition of the part Shooting speed and so on. Finally, the conditions of die-casting products must be modified to obtain a complete die casting.

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