New quenching technologies all about control.

It sounds like a simple matter to cool down hot aluminum profiles after they’ve come through the press. Anything will cool down if you let it sit long enough, right?

But the truth is, the quenching process is actually a very scientific one, and it has a great deal to do with overall line productivity, both in terms of the speed at which the line can operate, and the amount of waste generated in the process. The more attention paid to proper quenching, the more useable product will exit the line, and in turn, the more profitable it can be.

This helps explain, no doubt, why the quenching process has generated some significant interest and advances in technology recently.

Trickier for some profiles than others.

Many factors go into determining the proper type and amount of quenching required on a given line at a given time. For many light-duty and “architectural” profiles, and with certain alloys, the needs are relatively minimal. Profiles can be allowed to simply cool naturally, or with air provided by an overhead duct system.

For profiles requiring more intense air cooling, ducts may be integrated with the run-out table, providing air cooling immediately below the extruded profiles. This is a particularly efficient use of space and time, as profiles are cooled as they are handled through the system.

Heavier profiles make heavier cooling demands.

Heavier “industrial” profiles are a different matter. First, of course, comes the fact that they are generally thicker, requiring a greater amount of cooling. As any extruder knows, that immediately suggests the use of water rather than simply air for cooling.

For modern heat transfer needs, a “water wall” or flood quench maybe adequate. In this design (of which there are several variations) the lead-out table converts to a trough, into which water is pumped to wash over the moving profiles. But for many industrial profiles, due to their weight and the types of alloys utilized, the only appropriate choice is high-pressure spray quenching.

Metallurgical concerns become critical with industrial profiles. This is because, while more cooling is required, it can’t necessarily take a longer time to accomplish. For an aluminum profile to make its optimum metallurgical properties, it must receive not only the proper amount of cooling, but also the proper rate of cooling.

If it spends too much time within a certain predetermined critical temperature range, magnesium and silicon elements can precipitate and begin to form grains within the profile. (Proper growth and distribution of fine grains need to occur in the controlled environment of the age oven; if it begins to happen during quenching, larger and more inconsistent grain size can weaken the profile and prevent it from making properties.)

This is why a longer quenching unit or a slower profile speed as it moves through the quench are not always suitable answers.

Increasing pressure without increasing waste.

Given all this, the immediate tendency would be to move toward ever-more powerful spray quenching units, in the interest of bringing about the fastest possible heat transfer and causing the profile temperature to fall across the critical zone as quickly as possible. But this, too, brings potential complications.

Immediately upon extrusion, profiles are vulnerable to distortion. Because along with the optimal “cooling rate” every profile needs to achieve its desired metallurgical properties; each one also has a “critical temperature gradient.” This means that if one section of the profile is cooled more rapidly than another, this can cause mechanical stress that can create distortion in the profile.

This is where the true metallurgical challenges arise. How do you deal with that “minefield” in which quenching can be too slow (jeopardizing the profile’s metallurgical integrity) or too fast (risking distortion) — and in which each change in alloy, profile shape, or type can change the equation completely?

There are, indeed, situations in which the maximum cooling rate necessary to prevent distortion may be below the minimum cooling rate required for the alloy to make properties. To pose the question in decidedly non-metallurgical terms: then what? Is the answer simply to make the best compromise possible and hope for the best? Hardly.

Quenching control.

This situation calls for control; the precise control that takes into full account the variables that affect the cooling process, including alloy, profile weight and shape, the profile’s critical temperature zone and critical temperature gradient. But it requires not only awareness of all these things, but the technology that allows the extruder to do something about them.

That is why recent advances in quenching technology are geared, almost exclusively, to providing a greater degree of control, with more sophisticated nozzle patterns and more “customizable” quench settings.

Because most profiles can accept a higher rate of temperature as their actual temperature is reduced, there is an answer: sequential cooling. The most advanced high-pressure spray quenches deliver an unprecedented degree of precision, not only in conforming the spray pattern to the specific profile shape, but also in varying the amount of pressure as the profile travels through the quench.

Flex2.

Granco Clark has taken a strong step in that direction with a unique new technology that delivers incredible control and flexibility with its new Flex2 Combination Quench. To be sure, a combination quench promises a certain efficiency, in that it provides the ability to quench with air or water in the same “footprint” along an extrusion line. That in itself is not new.

The important aspect of the Flex2 is its actual performance. Unlike earlier combination quenches that compromised high-end performance in order to offer flexibility, the Flex2 is capable of delivery truly high-pressure spray quenching.

The Flex2 is designed with carefully positioned blowers and nozzles to make quick and even quenching simple; and virtually all are totally adjustable, to meet the specific metallurgical requirements of almost any type of profile.

The optional high-velocity spray capability is even selectable within zones, allowing for the cooling of profiles gently at first, then faster, by using an increased spray pressure in the second zone, once the profiles are sufficiently stabilized to withstand the force.