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Cold Formed Hollow Section
What is cold rolled steel and how is it different from hot rolled steel?
The key difference between hot rolled steel and cold rolled steel is the process with which they are made. You can probably tell from their names, but hot rolled steel is created with heat while cold rolled steel is crafted at around room temperature. It’s important to understand the difference between the two applications because they impact the performance of your steel products. Also, certain types of steel are better suited to a particular type of application.
Hot rolled steel
Hot rolled steel is a lot cheaper than cold rolled steel as it needs less processing time. It’s created by roll-pressing steel over 1,700˚F, which makes it easy to mould into a final product. Also, because it’s allowed to cool naturally it’s not subject to internal pressure that can result from quick-hardening techniques.
Hot rolled steel is best used on products where material strength is more important than the dimensional tolerances or surface finish. However, if the surface finish is important to you, any scaling can be removed and then we can apply a mirror or brush finish for a nicer overall look.
Hot rolled steel has the following characteristics:
- Minor distortions due to natural cooling
- Mildly rounded corners and edges on some products from shrinkage and natural cooling
- A slightly scaled finish that occurs as the hot temperature cools
Cold rolled steel
Cold rolled steel is essentially a finishing process used to modify hot rolled steel into a more exact or refined state. Once hot rolled steel is completed, it can then be re-rolled at normal room temperature to create more exact dimensions and finishes. This further process is more expensive, however it also provides a more refined product. Cold rolled steel is also generally harder and more durable than hot rolled steel. Cold rolled steel has the following characteristics:
- Smooth, oily surfaces
- Refined finish with closer tolerances
- Uniform tubes with better concentric straightness
- Well-defined bars
LSAW steel pipes vs SSAW steel pipes
Longitudinal Submerged Arc-Welding pipe (LSAW), also known as SAWL pipe, is made through the process of raw steel plates being machine moulded and then undergoing double-sided submerged arc welding. LSAW steel pipes gain weld strength, plasticity, great ductility and excellent sealing from this process. LSAW pipe diameter ranges are larger than ERW steel pipe (approx. 16–60 inches). Two benefits LSAW steel pipes offer are low-temperature erosion resistance and high-pressure resistance.
Spiral Submerged Arc-Welding Pipe (SSAW), also known as HSAW pipe, is created using the same welding technique as the LSAW pipe. However, while LSAW pipes are longitudinally welded, SSAW steel pipes are spiral welded to create a welding line shaped like a helix. SSAW steel pipe diameter ranges are about 20–100 inches and their key benefit is that they have a wide application and are stress-resistant.
Hot and Cold Rolled Steel FAQs:
Q: What is cold rolled steel used for?
A: Cold rolled steel is used for projects where precision is essential because the metal can be formed to exact specifications.
Q: Is cold rolled steel stronger?
A: Yes, cold rolled steels are usually stronger and harder than standard hot rolled steels. The process of shaping at lower temperature increases the steel’s hardness and resistance capabilities.
Q: Can cold rolled steel be welded?
A: It depends on the thickness of the steel. Cold rolled steel is typically less malleable than hot rolled steel so it’s best to consult an expert on the cold rolled steel's ability to be welded.
Q: What is the difference between hot and cold rolled steel?
A: Hot rolled steel is formed at a high temperature and the surface finish is less exact. Cold rolled steel is shaped at room temperature and is more precisely finished.
Q: What is an ERW steel pipe and where are ERW pipes used?
A: ERW steel pipes are round pipes welded from steel plates with longitudinal welds. They are manufactured by low-frequency or high-frequency resistance and are used to transport oil, natural gas and other vapour-liquid objects.
Q: What is ERW pipe specification?
A: ERW pipe maximum OD is 24” (609mm). Larger dimensions pipe will be made in SAW.
Q: What is the difference between ERW and seamless pipe?
A: Seamless pipe is made by extruding the metal to the desired length while ERW steel pipes are manufactured by rolling metal and then welding it longitudinally across its length. ERW steel pipes have a welded joint on their cross-section but the seamless pipe has none.