Hot vs Cold Rolled Steel processing – What’s The Difference

If you’re considering hot vs cold rolled steel processing, how do you know which is best for you? Let’s take a closer look…

When it comes to metal fabrication one of the most common forms of metal processing is known as rolling. This is carried out to make a sheet or piece of metal uniform in thickness and/or to stretch it and make it slimmer.

You could say that this fabrication method is akin to a gigantic pasta machine whereby instead of dough, metal is placed between one or more heavy rollers in order to create the correct uniform thickness needed for a particular job.

While that sounds pretty straight forward – and indeed is – it’s worth pointing out that there are two types of metal rolling. The question is…, what are they and when should they be used?

Hot vs cold rolled steel processing

In metal fabrication terms, stock metal – the term to describe metal before it’s been through any type of fabrication process – can either be hot or cold rolled.

As the name suggests, hot rolling involves rolling metal at a temperature of around 926 degrees Celsius.  This is the point at which deformed crystals are replaced by newer and stronger crystals – known as the recrystallisation point.

Conversely, when the temperature of metal is rolled at a point below its re-crystallisation level – usually on or near room temperature – it is classified as cold rolling.

In essence, they are one in the same processes except one is carried out using heat and one isn’t.

So why would you use one process over another?

While steels of differing grades and specifications can be hot or cold rolled, it’s worth remembering that some types of steel respond better to different types of rolling. For instance, many metals – including carbon and alloy steels – become pliable and easy to work with when rolled to 926 degrees Celsius. This process is both cheaper and less time-consuming.

However, some metals when cooled can shrink more than others, meaning that you have less control over the final shape and size of your steel. For this reason, the hot rolling process is best used when minutely specific details or dimensions aren’t required. These include the manufacture of railway tracking and for metals used in a variety of construction projects.

Conversely, if absolute pinpoint precision is what you need, then metals are best processed via cold rolling. Cold rolling produces an end product that is true and square, has a great finish and has well-defined corners and edges – perfect if you need precision engineering.

One of the disadvantages of this process, however, is that after cold rolling the steel needs to be subjected to further processing, including temper rolling to provide the best accuracy and surface finish. While adding on extra processes can extend the life of a product, it also makes for a more expensive process – This is a cost that needs to be passed on to the customer. 

Hot rolling vs cold rolled steel processing – Which is best?

In reality, it all depends on purpose…

While cold rolling provides more technically precise applications, the process is usually more expensive because it takes longer. For instance, cold-rolled steel should be stress relieved prior to cutting, welding, or grinding otherwise it can be prone to unpredictable warping.

That said, provided all other processes have been carried out, the end result is a harder and stronger product.

Hot rolling, on the other hand, requires far less processing making the production less expensive. In addition, because hot rolled steel is worked then allowed to cool to room temperature, the inner structure becomes better stabilised. However, the finish usually comes with a scaled surface and tiny distortions as opposed to beautifully proportioned angles.

If you would like to find out more about hot and cold rolling and which process is best for you, then you can always talk to the experts here at Metro Steel. Alternatively, we can undertake your entire fabrication process giving you the final product you need in a time that suits.

If you’re passing our Kabi Circuit location, then come and talk to our friendly team. Alternatively, if you prefer, you can always call us on 07 3204 1000, Either way, we’d love to hear from you!