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Flat Rolled Aluminum: Advantages and Disadvantages of Hot and Cold Rolling

A sweltering foundry illuminated by the glows of molten metal poured from crucibles, is the default image of a metal working for most people. While this view is rooted in history that isn’t too far back, it has little to do with modern metalworking and almost nothing to do with aluminum—which is worked with mechanical force or a combination of mechanical force and heat more often than it is worked via heat alone. This is a process that yields a type of aluminum properly called wrought aluminum. The most common type of wrought aluminum is flat-rolled aluminum or rolled aluminum.

As the name implies, flat-rolled aluminum is created by a process that uses rollers to flatten an aluminum ingot. This process is used to create both aluminum plates and aluminum sheets. The difference between the two is simply the amount of rolling of the metal. However, making flat-rolled aluminum is a little more complicated than breaking out a roller and pressing it flat, like rolling out the dough for a pastry. It involves substantially more pressure and may involve heating the metal multiple times.

In this article, we explore some of the advantages of flat-rolled aluminum when compared to aluminum produced by other types of working.

The Advantages and Disadvantages of Flat Rolled Aluminum

Aluminum comes from the foundry as gigantic billets that weigh several tons and measure several feet in width, length, and height. Looking at this initial material, one wouldn’t assume it was destined to end up as a plate a few eighths of an inch thick or the even thinner skin of a beverage can. Rolling this aluminum flat can be done in two different ways: hot rolling or cold rolling.

  • Hot rolling or hot working is the standard way of making nonstructural flat-rolled aluminum. The aluminum is first heated to a temperature that softens it. The heating changes the microstructure of the final aluminum, and its resulting properties.
  • Cold rolling aluminum seems more straight forward at first. A large aluminum billet is simply run through rollers repeatedly until it reaches the desired dimensions. However, the mechanical deformation of the aluminum at room temperature changes the microstructure of the aluminum in a different way than heating it does. It makes it substantially stronger and harder.

Flat rolled aluminum has substantially different properties depending on how it was made. A general comparison of hot vs. cold rolled aluminum can be seen in the table below:

Hot Rolled vs Cold Rolled Aluminum
Hot Rolled Aluminum Cold Rolled Aluminum
Cost-effective Yes No
Faster production Yes No
Improved surface finish No Yes
Increased strength No Yes
Rougher surface finish Yes No
Greater Dimensional Variation Yes No
Higher hardness No Yes

 

When understanding the advantages or disadvantages of flat-rolled aluminum, or any wrought aluminum versus cast or extruded aluminum, it comes down to the strain from the rolling process. The degree of strain, whether it was stress relieved using heat during rolling, or after rolling, and how it compares to aluminum plate that was created via a non-mechanical process.

How Flat Rolled Aluminum Compares to Other Aluminum

The biggest advantage of flat-rolled aluminum is that it is a relatively cost-effective means of creating an engineered aluminum product. It makes more efficient use of the material than the extrusion process used to make extruded aluminum pieces, and frequently rolled aluminum can be formed or drawn into the shapes that are produced through extrusion. However, they lose some of the stiffness across their length compared to extruded aluminum due to the different orientations of the internal stresses within the metal. This additional strength due to the strain hardening of the material is the second great advantage of flat-rolled aluminum.

These internal stresses can be a disadvantage as well as an advantage when using flat-rolled aluminum or another wrought aluminum type. One of the reasons that these internal stresses enhance the strength of the material is that they press against each other within the material. They are, in effect, perfectly balanced and this is what makes the aluminum resistant to any further deformation or changes.

When material is altered or removed during metalworking, it can disrupt the balance of forces within the material, resulting in potential distortion of the final product. If you’ve ever come across aluminum profiles made from flat-rolled aluminum that appear twisted without apparent cause, it is likely due to these internal stresses. Similarly, when machining removes a portion of the material, the remaining aluminum lacks counteracting forces and can curl as a result. This stress is inherent to flat-rolled aluminums whether hot or cold-rolled. This has led to the creation of cast aluminum plates that do not have the same internal stresses.

The internal stresses of cast aluminum tooling plate vs   or other flat-rolled or extruded aluminum are vastly reduced. This means that they remain dimensionally stable as machined. As a bonus, cast aluminum like MIC-6 cast aluminum plate or 5080 aluminum tooling plate is also far more dimensionally stable under changing temperature environments than wrought or extruded aluminum. This dimensional stability makes cast aluminum a preferred substance for molds or other precision devices, while wrought or extruded aluminum 6061 or a similar aluminum is preferred for applications where structural strength is the major priority.

 

At Industrial Metal Service, we have been supplying new and remnant flat rolled aluminum 6061 plate, extruded bar stock and round stock as well as cast aluminum like MIC-6 and alternatives to machine shops and fabricators nationwide. This aluminum arrives ready to process thanks to our state-of-art aluminum cutting equipment. Call us today to discuss your requirements for MIC-6 alternatives. We will get the job done — quickly.  

 

Published by IMS Team

Industrial Metal Service has decades of experience and over 1.1 billion pounds of metal sold and recycled. Our founder, Jeff, has spent his life in the industry and prides himself on offering fair, efficient, trustworthy, knowledgeable, outstanding customer service. We offer metal salesmetal recycling pickup service, and other associated services, such as precise metal sawing, machinery teardown, and warehouse cleanupGive us a call and we’ll get it done.