What Are the Effects of Cooling Rate During Solidification in the Die Casting Process

What Are the Effects of Cooling Rate During Solidification in the Die Casting Process

Cooling casting is a very complicated process. The most important part is the rate at which a casting cools down. Many properties of the casting are affected by this rate, which eventually determines the quality of the finished products.

Introduction

In die casting processes, the quality of aluminium parts is greatly influenced by the temperature control of the mold. Nevertheless, cooling also has a decisive impact on the efficiency and speed of casting. You will learn how to minimize scrap rates and maximize product quality by optimizing and customizing cooling line control in this blog.

Cooling Process Challenges

Cooling rate may seem like a trivial factor in the die casting process, but in reality, it has considerable effects upon the:

  1. Mechanical Properties of Casting
  2. Microstructure of the casting
  3. Final Dimensions of the Casted Products.

The cooling or control of the temperature influences the structure of the material, i.e. the microstructure and the surface of the metal. Errors, failures, or inaccuracies that occur during cooling have a direct effect on the quality of the cast product. Temperature control imperfections are not uncommon:

For example, flow fluctuations can occur – especially in systems with more than one cooling section running at the same time or with multiple die casting machines that are continuously supplied by the same central control system. It is essential that the cooling system calculates differences and compensates accordingly. Because heat must be dispersed uniformly across the final product, dissipation must be uniform at all points. 

The cooling section must not only be fast in reaction but also be aligned and adjusted accurately to ensure the exact amount of cooling is applied where it is required: less cooling is needed at narrower areas of the product, while more cooling is needed at the wider zones to reduce internal thermal stress.

Another example, if a composite molded piece has uneven thickness on some areas, uneven cooling may occur, leading to undesirable microstructures and mechanical properties, these cause defects and weak spots to be scattered across the casting substrate.

The Omnidex solution accommodates the specific needs of foundries with its comprehensive solution. The modular system can be readily configured and customized to meet any requirements based on application, pressures, temperatures or flow rates.

Effect of Solidification Cooling Rate

Furthermore, the solidification cooling rate has far-reaching effects on the production and development cost of the product. Unexpected changes in microstructure and mechanical properties means additional processing (such as heat treatment or straightening processes) is needed on the product to meet the specifications. 

As well as cost, additional processes may lead to more issues, such as the need to replace a non-heat-treatable alloy, excessive heat treatment causing surface blistering, and mechanical treatment inducing excessive residual stresses in the metal parts.

die casting operation

A professional die casting manufacturer will consider all these factors early in the development process. As an example Al-Si-Cu-Mg-Ni is an alloy that is very popular in the automotive industry, and is used to make die casted pistons and many other parts. let’s use this to explore the effect of cooling rates upon the mechanical properties and microstructure of die casting parts.

At lower cooling rates, the phase formed during the solidification is mainly M-Mg2Si phase, γ-Al7Cu4Ni phase, δ-Al3CuNi phase, ε-Al3Ni phase, and Q-Al5Cu2Mg8Si6 phase. When the solidification cooling rates are increased from 0.15 to 15°C/s, hardness increases from 80 to 125 HB, and tensile strength increases from 190 to 280 MPa.

If we increase the cooling rate still further, the alloy will solidify into a uniform structure and micro-hardness will increase from 130 to 196 HV.

For a complex cast product, more cooling channels will be required for cooling the mold. The sequence of the individual cooling channels is determined by the cooling strategy. Depending on the cooling channel, coolant time and quantity can be set separately. Liquid aluminum can be controlled very precisely regarding the direction of solidification. In this way, holes or cracks caused by uncontrolled shrinkage are reduced.

Conclusion

The solidification cooling rate has a great impact on the die casting process, as it may affect the alloy’s mechanical properties and dimensions, and subsequently the product quality.

The ability of a die casting system to regulate its internal temperature is vital to its success. 

In order to avoid defects, different metals require different temperatures at which they will be properly forged, and a deviation outside these given temperature ranges will affect the final product. Furthermore, excessive temperatures can damage the less resistant components within a die casting system, resulting in equipment failures and costly maintenance downtimes.

Having a die-cast cooling system in place is the best defense against poor temperature regulation caused by casting. As a result, these devices will optimize process efficiency, protect critical equipment, and ensure high-quality parts.

Our Services

Here at Omnidex, our casting engineers work tirelessly on casting simulation to optimize the cooling rates for every die casting product. Drawing upon our experience and expertise in metal casting, we will continue to deliver quality products to our valued customers. Get in touch with our casting engineers today to learn more about our cutting-edge die casting process.

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Customized solutions for precise cooling and temperature control.

The know-how of the Omnidex experts allows not only an individual adaptation to the respective casting situation but also guarantees a comprehensive and custom metal casting service and design in which the respective components can be easily exchanged.

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