Cooling

Cooling is becoming increasingly important in connection with the heat treatment of products. A distinction is essentially made here between two different types of cooling:

• Cooling as quickly as possible, predominantly without tolerance, for further handling or for further processing of the products/materials
• Targeted, controlled cooling in a relatively narrow temperature tolerance field to achieve desired product properties or to avoid material stresses in sensitive products/materials

The following are selected practical examples to illustrate this process.

The cooling of different products as a follow-up process to the heat treatment in our industrial furnaces or after independent processes must be designed in a similar way to heating over the surface and the appropriate heat transfer value. The temperature difference, namely the difference between the cooling medium and the temperature of the products to be cooled, as well as the inflow velocity, play an important role here. For example, the cooling time can be adjusted through the inflow velocity of the cooling medium onto the product, especially when the temperature difference is decreasing.

For some processes, slow cooling or even cooling controlled by several temperature ramps is required to bring the workpieces to the core temperature equalisation (relaxation).

In this case, cooling is usually carried out by means of different temperatures over a longer period of time, namely over hours or days.

Similarly, when tempering plastic parts, for example, it is necessary to maintain the product temperature at approx. 50 °C for a period of less than one hour, even after the tempering process, before the products are cooled to temperatures for packaging or for subsequent work steps, so that they can be handled safely, for example, by people without the risk of burns or further protective measures.

The cooling medium, mostly process air, can be pre-tempered with cooling water to achieve reproducible cooling rates (summer/winter).

In order to prevent condensate from forming at these process air temperatures, these cooling zone housings must be adequately insulated to avoid falling below the dew point.

In other processes in turn, quenching processes with very low cooling rates of up to 2–3 K/s at temperatures from 530 °C to 200 °C are required, for example, to freeze structural changes in the component.

For quenching processes, in particular for the heat treatment of aluminium castings, quenching in tempered water or in polymer solutions is common, but especially for the “milder” quenching of “so-called” structural components, which are increasingly used in the automotive industry, also with air. For these quenching processes, air discharge speeds are sometimes required beyond a speed of 100 km/h, which are generated accordingly by fans. In addition, particularly with these mostly large-volume components, it is important to ensure uniform, namely homogeneous cooling by means of an appropriate technology. As a side effect, a very effective air technology can also save manufacturing space by reducing the cooling area to almost a third, in contrast to conventional cooling processes.

Cooling: a process which represents a challenge and which is implemented and handled reliably and efficiently by the Airtec technology.