When using die-casting molds, attention should be paid to: the usage characteristics of the die-casting mold, the temperature of the alloy melt, the working temperature of the mold, lubrication of the die-casting mold, and the adjustment of the die-casting mold.

I. Usage characteristics of die-casting molds
During die-casting production, the molding conditions for die-casting mold components are extremely harsh, as they undergo repeated mechanical abrasion, chemical corrosion, and thermal fatigue.
1) The molten metal enters the mold cavity at high pressure and high speed, causing intense friction and impact on the cavity surface, leading to erosion and wear.
2) During pouring, slag is inevitably carried into the molten metal, causing complex chemical reactions on the forming surface. Compounds of aluminum and iron act like wedges, accelerating crack initiation and growth in the die-casting mold.
3) Thermal stress is the main cause of crack formation on the surface of forming components. In each production cycle, the forming surface not only undergoes high-speed, high-pressure erosion by the molten metal but also absorbs heat released during solidification, resulting in heat exchange. Additionally, due to the thermal conductivity of the mold material, the surface layer temperature rises sharply, creating a large temperature difference between the surface and interior, which generates internal stress. When molten metal fills the cavity, the surface layer reaches high temperature and expands, while the inner layer remains cooler with relatively less expansion, causing compressive stress on the surface. After mold opening, the cavity surface contacts air and is rapidly chilled by compressed air and coatings, generating tensile stress. This alternating stress increases with continued production, and when it exceeds the fatigue limit of the mold material, plastic deformation and cracks occur on the surface layer.

To maintain the durability of the molding surface, it must have thermal fatigue resistance, wear resistance, non-stick properties, and easy release. Therefore, forming components are commonly made of 4Cr5MoSiV1 (H13) steel, which is currently well-suited for this application.

II. Temperature of the alloy melt
To ensure proper filling of all cavities and deep sections of the die-casting mold and to guarantee good fusion of the metal flow, the pouring temperature of the alloy should be correctly selected. Recommended die-casting temperatures for different alloys are as follows:

| Material | Die-casting temperature / °C |
| :--- | :--- |
| Zinc alloys | 420–500 |
| Aluminum alloys | 620–690 |
| Magnesium alloys | 700–740 |
| Copper-zinc alloys | 850–960 |

Guidelines for selecting die-casting alloy temperature:
1) Lower pouring temperatures generally extend mold life.
2) Low-temperature die-casting helps reduce vent depth increases and lowers the risk of metal splashing.
3) Low-temperature die-casting reduces the chance of sticking between the shot sleeve and plunger tip.
4) Low-temperature die-casting reduces shrinkage porosity and cracks in castings.
In general, as long as process conditions allow, lower pouring temperatures are preferred.

III. Working temperature of the mold
The recommended working temperatures for die-casting molds vary with the alloy being cast:

| Mold type | Working temperature / °C |
| :--- | :--- |
| Zinc alloy molds | 150–180 |
| Aluminum alloy molds | 180–225 |
| Magnesium alloy molds | 200–250 |
| Copper-zinc alloy molds | 300 |

Guidelines for selecting mold working temperature:
1) If the mold temperature is too low, the casting may have internal porosity, poor venting, and difficulty in forming.
2) If the mold temperature is too high, the casting may have dense structure but tends to "solder" to the cavity, making ejection difficult. Excessively high temperature may also cause thermal expansion affecting dimensional accuracy.
3) The mold temperature should be kept within a suitable range, ideally controlled by a constant-temperature system after initial testing.

IV. Lubrication of die-casting molds
1. Purpose of lubrication
Lubrication serves as a release agent between the mold and the casting, facilitating ejection; as a lubricant for moving parts of the mold and press, reducing friction and extending mold life; and also as a coolant to reduce thermal fatigue and extend mold service life.
2. Requirements for lubricants
Lubricants should meet the following requirements:
a. Prevent casting adhesion to the cavity.
b. Not corrode the mold steel.
c. Not produce toxic gases.
d. Not form residue upon heating.
e. Form a uniform film on the cavity and working surfaces, not washed away by high-pressure metal.
3. Formulations of lubricants
a. 85%–90% total-loss system oil + 10%–15% graphite;
b. 100% heavy oil;
c. 30% paraffin + 30% yellow wax + 14% petroleum jelly + 26% graphite;
d. 25% graphite + 20% glycerin + 5% water glass + 50% water.
4. Precautions when using lubricants
a. Apply lubricant to the cavity and movable surfaces.
b. Spray small amounts each time, uniformly, ideally forming a thin film on the surface.

V. Adjustment of die-casting molds
After the die-casting mold is manufactured, it must be trial-run and adjusted to select the correct die-casting conditions and process parameters to achieve stable production and produce qualified castings.

Before trial runs, personnel should inspect the raw alloy materials, understand their characteristics and die-casting properties, and also understand the mold structure, press performance, die-casting conditions, process parameters, and operating methods.

Correctly selecting die-casting forming conditions is key to trial adjustment. A common issue is that even with correct mold design and manufacture, improper forming conditions may still fail to produce qualified castings. Conversely, in some cases, adjustments to forming conditions can compensate for minor mold deficiencies and yield qualified castings. Therefore, trial personnel must be familiar with the functions and interactions of each condition and the mold's operating sequence to properly select and adjust them.

Adjustment of die-casting conditions includes: melting temperature of the material, mold temperature and melt temperature during injection; injection pressure, clamping force, and mold opening force determination; and based on the part requirements, injection ratio and speed settings. Finally, the castings may require post-processing to obtain finished die-cast parts.