It should be no surprise that steel has received more attention than almost any other material on earth. After all, the modern world has largely been built on this metal.
The massive amounts of investigative and experimental attention focused on steel has produced more than 3,500 grades of steel, allowing customers to receive exactly the correct steel-performance required for their application. For example, modern cars are a collage of different grade steels, each placed in different joints and systems of the car to produce minimum waste and top performance.
In addition to the plethora of steel grades, the detail applied to steel production has also generated different rolling techniques for steel. In contrast to creating different grades of steel which often involves changing steel’s chemical properties, steel rolling simply refers to the process by which steel is compressed through rollers and formed into a desired shape.
The variable element is whether heat is applied to steel as it undergoes the forming processes. The two types of rolling techniques, hot rolling and cold rolling, offer certain benefits. Both types of rolling are complex processes that require high levels of knowledge to reach desired outcomes.
- Hot Rolling
As you might imagine, heating steel to extreme temperatures – around 1,500 degrees Fahrenheit – makes the metal malleable and easier to form.
Throughout the rolling process, the steel is maintained at temperatures above the recrystallization temperature. Consequently, large quantities of shapeable steel can be produced simultaneously as less brute force is needed to form the steel. This in turn affects pricing: hot rolled steel sells for less per-pound than cold rolled steel.
During hot rolling, white-hot steel moves swiftly through rotating rolls – often through multiple passes— and is reduced in weight, width, and thickness as desired so that the steel can then be rolled into coils or sectioned off into bars or plates. As steel returns to room temperature and shrinks, it will warp slightly. Also, it will have a rough, grayish surface from the mill scale formed during the heated process. These imperfections (or perfection if you like the mill scale aesthetic, which is often sought after by modern designers) mean that hot-rolling is not ideal for projects that are looking for a certain aesthetic quality or need extreme precision in the steel shapes. Also, the steel will need extra work before it can be painted, as mill scale won’t allow paint to adhere easily.
- Cold Rolling
If you take a hot rolled strip of steel, return it to room temperature, and then continue rolling and a drawing process at room temperature, you’ll have cold rolled steel. The result is an end product with millimetric shape consistency and with a smooth finish.
In addition to increased precision, by cold rolling, the yield strength of steel will significantly increase as the cold rolled steel undergoes plastic deformation.
Should I Use Hot or Cold Rolled Steel For My Project?
Use hot rolled steel if very precise shapes and tolerances are not required, for example on railroad tracks or many parts used in the construction and welding industries.
Cold rolled steel can be formed in more precise shapes with precise tolerances and is perfect for moving parts, such as axles and automotive parts.
Hot and Cold Rolling in Mexico
National Material Mexico plays an important role in the Mexican steel industry. NMM has recently expanded their facilities to increase efficiency and capacity. The facility is a one-stop processing powerhouse, capable of processing all types of carbon, stainless and pre-painted steel, aluminum, AHSS automotive steel, and grain-oriented electrical steel starting from 0.007? thickness, with cut-to-length and leveling capabilities up to 72? wide. With their state-of-the-art slitters, cut-to-length lines, blanking lines, and warehousing capabilities, NMM can handle virtually any steel project.
National Material of Mexico (“NMM”) is a subsidiary of National Material L.P., operating 16 steel service centers and processing facilities in North America and shipping over 2,000,000 tons of steel annually. NMM specializes in supplying, servicing, and processing steel with unmatched efficiency and capacity due to the company’s substantial list of capabilities. Proud to be minority-owned, ISO-certified, and uncompromised in its safety standards for their employees, National Material is a leader through efficiency, innovation, and performance.