Friday, December 14, 2018

Understanding the Hot Rolling Process



In metalworking, rolling is a fabrication process that consists of passing the metal through a pair of
rollers. Flat rolling creates a sheet, while profile rolling creates a bar or a rod. In addition, rolling
processes are temperature-dependent. Hot rolling is performed when the material is above its
recrystallization temperature, while cold rolling is performed below the recrystallization temperature.
Advantages of Hot Rolling
As you might suspect, hot rolling and cold rolling create products with very different characteristics,
meaning that each process has its place. Hot rolling requires less processing than cold rolling,
meaning that hot rolled products are significantly less expensive. In addition, hot rolled metals cool at
room temperature, avoiding the internal stresses of quenching or work-hardening. Hot rolling allows
metals to be easily manipulated into a variety of shapes, and it creates a denser finished product.
It is important to note that dimensional tolerances are not as precise with hot rolling as with cold rolling,
but the material strength is higher. Therefore, it is best suited to applications in which strength matters
more than minute distortions, such as construction projects and railroad tracks.
Hot rolled metals do not have the same smooth surface as cold rolled metals, as scaling is a byproduct
of the cooling process. However, this scaling can be removed through acid-bath pickling, sandblasting,
or grinding, and a new finish can be applied. In addition, descaled steel provides an optimal surface for
coatings such as paint.
How Is Hot Rolling Done?
The first step is to heat a large, rectangular billet of metal to an extremely high temperature based on
the temperature at which the molten metal recrystallizes (for example, more than 1700 degrees F for
steel), and then pre-process it by flattening it into a single large roll. While maintaining the temperature,
the metal is then pushed through a series of rollers at high speeds to create its finished shape and size.
To create sheet metal, the rolled metal is spun into coils before cooling. For bars, plates, or other
profiles, the material is sectioned, cooled, and then packaged. Note that hot rolled metal is allowed to
cool naturally, which will result in a bit of shrinkage and perhaps minute warping.
Each metal and each fabrication process has its own unique pros and cons, and each is best for
specific applications. Because there is no one size fits all solution, it is vital to work with an expert to
ensure that you choose just the right metal and fabrication process for your specific project.
Ready to Start?
Atlas Bronze is a leading U.S. distributor of bronze, copper, brass, iron, and more. Contact us today at 1-800-478-0887 to place an order or learn about our custom products.

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