Setting cooling intensity a little differently

Setting cooling intensity a little differently

The correct cooling of metal surfaces in the manufacturing of semi-finished products is not that easy. It requires finding a suitable type of nozzle while setting the correct flow rate and nozzle distance from the surface to be cooled. In addition, an important role is also played by the material and the shape of the cooled surface. Nevertheless, finding the optimal parameters for a specific cooling section is quite a complicated science. At the Brno University of Technology, this issue is being studied by the Heat Transfer and Fluid Flow Laboratory. Up until now, they have been trying to adjust the amount of falling water by varying types of nozzle and their distribution around the cooled surface. This time, however, they have tackled the problem a little differently.

In the manufacturing of semi-finished products, in addition to cooling the semi-finished product itself, it is necessary to cool the rollers that form the material and which are heated by it. However, in this article we will focus on the semi-finished product alone. Incorrect cooling may cause the profile to deform and develop various cracks. So the aim is to cool the surface as evenly as possible to eliminate the undesirable deflection of the semi-finished product. But it is not easy to set up such cooling. It can differ from one production line to another, as well as between various sections of one production line, where the temperatures of the semi-finished product are different. In addition, what might be optimal for steel, may not work for aluminium at all. And what if the semi-finished product has a more complicated shape? For example, aluminium hollow section which has walls with variable thicknesses (see the figure below).

The task – to design cooling for extruded alloy sections, mainly aluminium-based – was solved by staff and students at the Heat Transfer and Fluid Flow Laboratory. In their quest they tried using existing cooling to avoid extensive unnecessary adaptation of the cooling system. In this way the procedure differed significantly from their work to date.

Designing optimal cooling for a homogenous material is now for them no longer a problem. But how to do it for an extruded section which has two or three different wall thicknesses on one side? Surprisingly, the answer to this question is simple – to insert a screen between the nozzle and the cooled surface, in parallel with this surface. The screen then lets through less or no water where the section is thinnest and more water where it is thicker. The whole idea is shown in the figure below.

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(1) The figure shows the nozzles out of which water or some other coolant flows (3) onto the section surface (2). This moves under the screen (4). The aperture size (5) then specifies how much water will flow onto the cooled surface. The screen can be designed universally by means of movable plates. This solution is patent protected.


Source of the pictures: the archives of the patent authors

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