What’s the difference when it comes to hot formed vs. cold formed hollow sections?
By most appearances, not much.
As both types of hollow sections are indeed unique, it’s important to understand their differences when selecting the right type of processed steel for a project.
Hot Formed Vs. Cold Formed Hollow Sections
When evaluating hot and cold formed hollow structural sections, there are three main considerations to keep in mind:
- Manufacturing
- Strength
- Price
1. Hot Rolled Vs. Cold Rolled Steel: Manufacturing
Determining which type of hollow section is right for your project starts with how each is manufactured.
Hot Formed Hollow Sections
Hot formed hollow pieces are created by superheating sheets of steel up to temperatures of up to 1,700° F, making it more malleable. While heated, the steel is processed through a series of rollers to form it into a desired shape.
Hot formed steel is cooled slowly back to an ambient temperature. While cooling, the steel reconfigures to have a consistent microstructure.
Cold Formed Hollow Sections
Cold formed hollow sections start out exactly the same as hot formed hollow sections.
The key difference between is that their shaping doesn’t occur until after the steel is cooled.
Like hot rolled steel, cold rolled steel is processed through rollers to create form. However, because cold rolled steel is less malleable, it requires additional pressure and several passes through shaping elements.
2. Hot Formed Vs. Cold Formed Hollow Sections: Strength
Comparing the strength of hot formed vs. cold formed hollow sections, cold formed is the clear winner.
The additional strength is attributed to strain hardening, which increases cold formed hollow sections’ resistance to bending by up to 20%.
While able to withstand great amounts of stress, hot rolled steel products are more apt to bend if there are any impurities within the metal.
3. Hot Formed Vs. Cold Formed Hollow Sections: Price
Comparing hot rolled vs. cold rolled steel production methods, hot formed hollow sections cost less.
Though hot formed steel requires extreme heating, it’s much easier to shape and work with once it reaches a suitable temperature. This reduces production and labor expenses.
Because cold formed hollow sections undergo several additional layers of production, that means longer lead times and increased labor costs.
Hot Formed Vs. Cold Formed Hollow Sections: The Pros And Cons
Hot formed and cold formed hollow sections have distinct advantages and disadvantages.
Hot Formed Hollow Sections
The Pros: As heated steel is much easier to shape, hot formed hollow steel sections require less processing. The heating process also eliminates a steel sheet’s inconsistencies or internal stresses. Having undergone intense processing, hot formed hollow sections stand up to stress from additional fabrication, such as welding and riveting.
The Cons: Hot formed hollow sections shrink somewhat during cooling and corners become rounded, making tolerances a concern. In addition, the cooling process causes surface scaling. Because of its formability during processing, it’s also difficult to maintain a precise thickness along an entire length.
Cold Formed Hollow Sections
The Pros: Despite taking more effort to create, cold formed hollow sections can be manufactured to tighter tolerances. Unlike hot rolled steel, cold rolled holds its shape after processing, providing a more dimensionally accurate finished product. Cold rolled steel pieces also have a uniform thickness and smoothness.
The Cons: With more additional steps in production, cold rolled steel pieces take more effort and time to produce. Because of its rigidity, cold rolled steel faces shaping limitations -- though your manufacturer’s skill level is also a factor. During shaping, the steel is stretched, making cold formed hollow sections prone to corner breaks.
Choosing Between Hot and Cold Formed Hollow Sections
Selecting the right type of steel hollow section has a big impact in the successful completion and functionality of a project.
Understanding the differences between hot formed vs. cold formed hollow sections saves time, money and effort. To learn more about creating a tube design that’s manufacturable and effective in the field, download our free e-book below:
