There are many terms when it comes to describing the processes used to shape steel into various forms, from hot rolled and cold rolled, to cold drawn and cold finished.
Let’s explore what each one means.
Hot Rolled Steel
The words say it all. First, the mill pours or produces a billet or slab of steel with a specific chemistry and alloys. After cooling, it’s reheated into a semi-molten state, which allows the steel to be formed into many different shapes and dimensions, including plates, sheets, and bars.
The semi-molten billet or slab of steel is rolled back and forth between large rollers in open air to reduce the slab to a desired thickness. When this is achieved, the wear plate is sheared to a desired length. The width however is “ragged” and must be further trimmed to achieve the desired width.
Some mills will sell the plate “as is” at a lower price compared to a trimmed plate. The plate also has surface scale known as “Mill Scale”, which may or may not be removed by the producing mill. Hot rolled steel requires less processing by the mill than cold rolled steel and is more affordable.
Cold Rolled Steel
In this process, the billet or slab is first hot rolled to a specific size and thickness and then cooled to room temperature. It’s further processed using different cold rolling techniques for benefits that include better mechanical properties, better dimensional tolerance, and a better surface finish. The three cold rolling processes are:
- Cold drawing – The billet, which is now a specific size and thickness at room temperature, is drawn through a sequence of reducing dyes that cold work the steel into a desired shape and size, including round, square, or flat. Cold drawing greatly improves dimensional tolerances and the surface finish.
- Cold finishing – The billet is turned, polished, or ground and polished producing a shiny, semi-finished and cost-effective product.
- Cold rolling – Once again, after the billet has been formed to a specific size and thickness and cooled to room temperature, it’s processed through a series of rollers that gradually reduce the thickness of the steel while removing some of the hot rolled mill scale. This process strain hardens the steel, producing mechanically stronger physical properties and a better surface finish, similar to that of a finished product.
Recommended Wear Plates
Our signature wear plate product offerings – ENDURA, ENDURA Dual and Titus Manganese – are all hot rolled but achieve their unique “work-hardening” and high-wear resistance through a heat treatment and quenching process.