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Hot Or Not? Understanding The Differences Between Hot And Cold Rolled Steel

27 July 2017

Lucille Palmer

If you're new to the metal fabrication industry, you may be considering many different types of steel and other metals for your production system. When it comes to working with steel, you have two options. You can use either hot or cold rolled steel. Before you make a final determination of which is right for your operation, you should understand the features and differences between them. Here are some key facts you should know about both.

How Are They Made?

The biggest single difference in the production of hot and cold rolled steel is the temperature at which it's rolled. As the name suggests, hot rolled steel is heated to a temperature that's beyond the recrystallization temperature. Recrystallization is the formation of new grains in the metal that essentially consume the old ones, replacing deformed grains with new, flawless ones, and it happens at very high temperatures. Cold rolled steel, on the other hand, is kept at nearly room temperature when it's rolled, which prevents the recrystallization process from occurring.

What Difference Does The Temperature Make?

Heating steel to temperatures beyond the recrystallization point will actually make the metal more pliable. That means it's easier to shape and mold to the forms that you need. In addition, making it more pliable makes it easier to work in larger sizes, so if you're dealing with large dimensions for your fabrication needs, it may be a better way to go.

With cold rolled steel, working at room temperature makes the metal somewhat less pliable, which may reduce your options for fabrication. However, you'll get more consistency out of your final product with cold rolled steel because there's no temperature change to lead to shrinking. As a result, what you see when you're done is what you'll get. When you heat steel, it will shrink some as it cools, which is expected from the standard expansion and contraction caused by temperature changes.

Finally, the process of recrystallization actually weakens the steel, so if your fabrication process puts the steel under pressure, or the final product will be under pressure, you should consider cold rolled steel instead. It maintains its strength throughout fabrication so that you get a more durable product.

Is There A Difference In Appearance?

When you alter the temperature of steel, it changes more than just its structural attributes. It also changes the physical appearance. Hot rolled steel has a somewhat scaly surface finish to it as a result of the temperature shift, and you lose some of the sharpness in the edges and corners. It results in rounded corners. That means that you won't want to use this kind of steel for anything where you need precise edges and dimensions. It also may not be the best choice for end products where the appearance matters.

As an alternative, cold rolled steel features a much smoother surface finish. When looks matter, this may be the option that's best for your needs. In addition, fabricators are able to get more precise edges and sharper corners with cold rolled steel, so when precision counts, consider opting for cold rolled instead of hot rolled steel.

What's The Bottom Line?

Cold rolled steel (CRC) can often cost over $100 more per metric tonne than hot rolled steel (HRC). Although fabricators sometimes opt for hot rolled steel simply because it's cheaper to invest in, it's not the right product for every application. If you're dealing with fabrication in construction or welding, hot rolled steel may be a viable option. But when you're working with machining, producing parts, or something similar, cold rolled steel is definitely worth the added investment.

For more information, contact companies like A & C Metals - Sawing.

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