Formation and Uses of Rolled Steel
There are many different types of mechanical processes involved in forming steel, all of which achieve different physical properties. Choosing the right kind of steel for your project is essential to achieving the structural stability and quality of work that is required.
With so many different types of steel out there, it’s important to understand the materials that you are using and how they are made, so keep reading to learn all about rolled steel!
What is Rolled Steel?
As the name suggests, rolled steel is a type of steel that has been passed through rolls which squeeze the steel in order to flatten it into its rolled shape. There are several different types of rolling processes, including ring rolling, roll bending, roll forming and controlled rolling (to name a few!).
Ring Rolling: Ring rolling is a hot rolling process, designed to increase the diameter of the ring (the circular hollow section). As the rolling takes place, the thickness of the wall of steel decreases while the diameter of the circular hollow section increases.
Roll Bending: The manufacture process whereby steel metal parts are rolled into a circular arc.
Roll Forming: Roll Forming is popular method of producing large volumes of rolled steel. It’s a continuous bending operation, involving passing sheets of metal through a series of rollers, with each of the rollers adding shape to the metal as it passes through. The rolls work together to form a cross section.
Controlled Rolling: Controlled rolling is a closely monitored method of rolling steel, using computer models which calculate microstructure evolution. It involves improving the properties of the steel to equal an alloyed or heat treated steel; the improved strength of controlled rolled steels are commonly attributed due to their fine grain size which is formed during the rolling process. Controlled rolling is a thermomechanical process, which means that it involves controlled deformation and heat treating the steel.
Hot Rolled Steel Versus Cold Rolled Steel
Cold rolled and hot rolled steel offer different advantages to the user, but the main difference tends to be in the precision of the measurements of the steel. Keep reading to find out more about the key differences between hot rolled and cold rolled steel!
Hot Rolled Steel (HRS): Generally, hot rolled steel has been rolled at a temperature over 1,000 degrees Fahrenheit and as a result has a blue-grey finish and is rough to the touch. As the name suggests, hot rolled steel is more malleable, which means it can be reconfigured into many different shapes.
The only downside to hot rolled steel is that due to the fact that steel shrinks when it is cooled, there is less control over the final shape of the steel. It’s therefore not the best material for making precise structures. It’s also often a lot less expensive compared to cold rolled steel because it involves less processing to produce the finished product.
Hot rolled steel, for example hot rolled steel bars, is usually used in construction and welding processes where these precise shapes are not essential. It’s a good choice for structural beams and rail tracks as it’s great for making beams and cross sections – you’ll often seen hot rolled steel used for gates and railings.
Cold Rolled Steel (CRS): Cold rolling usually occurs at room temperature, after the steel has been heated and cooled. CRS refers to the cold rolling of flat rolled sheets and coil products. Cold rolled steel is renowned for being strong, resistant and with more refined tolerances that hot rolled steel.
Due to the fact that it is less malleable, cold rolled steel is limited in the amount of shapes that it can be rolled into; these include bars, rods, strips and sheets which are smaller than their hot rolled equivalents, nevertheless they are more precise and more tolerant.
Cold rolled steel involves further processing than hot rolled steel, which means that it can come in a much wider variety of surface finishes and a closer dimensional tolerance. You can usually identify cold rolled steel by its oily or greasy surface, smooth surface and/or very sharp edges.
CRS is commonly used in household appliances – filing cabinets, metal furniture, exhaust pipes, other automotive components and machine parts etc. because of the fact that it retains fewer surface imperfections. Because of the extended manufacturing process, cold rolled steel tends to cost a lot more than hot rolled steel.
So there you have it! There are a few key differences between the different types of rolled steel and we hope that this blog was useful in outlining them.