Hot Rolled Steel vs. Cold Rolled Steel
Rolling is a key process in metalworking, one which can lead to the improved strength and grain orientation needed to accomplish different fabrication techniques and applications. The basic metal rolling procedure involves passing the metal through a pair of heavy rolls that give the metal the desired shape and thickness, but from there the process can be adapted based upon the metal’s application. There are two main types of steel rolling; hot rolling and cold rolling. As implied by the name, difference between the two depends on the rolled metal’s temperature at the time of rolling. Hot rolling works on metals heated beyond their recrystallization temperature while cold rolling works on metals whose temperature is below its recrystallization temperatures. Both of these methods lead to decidedly different outcomes, each of which will be better suited to a certain type of application.
Hot Rolled Steel
Steel’s recrystallization temperature stands at 1700 degrees Fahrenheit. As such, during the hot rolling process the temperature must exceed that level. It’s much easier to shape and form steel at such temperatures, hence most complex and bulky designs form better under high temperatures. Hot rolling steel has its advantages and disadvantages.
Some of the advantages of this process include:
- High rate of production.
- Suitable for large reduction.
- Production of a wide range of shapes like blooms, billets, sheets, slabs, tubes, bars, structural section, and others.
Some of the main disadvantages are:
- High cost of equipment.
- Poor finish and poor dimensional accuracy.
- Suitable for large sections’ production.
Cold Rolled Steel
Cold rolling is performed at room temperature, meaning that the steel is below its recrystallization temperature. Since the steel won’t be so malleable this technique might require stronger mills but will definitely be more accurate as the steel doesn’t will not change its shape and orientation upon cooling. Examples of cold rolled steel products include; bars, strips, rods and sheets. These products are normally smaller than hot-rolled ones.
Some advantages of this process include:
- High rate of production.
- Good finish and good dimensional accuracy.
- Suitable for among others, the production of foils, plates and sheets.
Disadvantages include:
- Deformation limited to small reductions
- It is limited to only a few shapes and their variations such like square, round, and flat.
- High cost of equipment
Hot rolled steel is usually cheaper to produce than cold rolled steel. This is mainly because the hot rolled steel is more malleable, hence you don’t need heavier rollers or more production cycles to form a product. However, because its shape can shift after the process is over hot rolled steel can lead to additional reshaping expenditures down the line.
Rollers in Rolling Mills
Rolls come in various sizes and geometries. In the course of their application they are made to endure strong forces, wear, thermal stresses, and bending moments along with other such conditions. The material used to make the roll is an important factor as far as their strength, wear resistance, and rigidity is concerned. Ductile Iron, cast iron, forged steel, and cast steel are among the most common.
Metal Rolling Defects
There is the possibility of a number of defects with metal rolling. They include;
- Surface defects arising from scale, dirt, rust, and other impurities in the material.
- Internal defects due to improper distribution of the material in final product
- Wavy edges, center cracks, and edge cracks
A good fabricator should leave you at liberty of choosing between hot rolling and cold rolling. Moreover, the steel fabrication shop should have the right tools and skill needed to give you the best quality product for each procedure. Choosing a company with the right equipment, personnel, and experience is essential. At Swanton Welding, we have the top quality rolling and forming equipment necessary to guarantee precision and high accuracy. We take pride in our ability to meet high-end contracts with finesse. Our highly skilled team and fully equipped production floor will be all you need to get the job done in record time, so contact us today.