If you are new to metalworking with steel, then you need to understand the differences between cold rolled steel and hot rolled steel. Since each type acts differently when cut and worked, using the right type of steel is essential to the success of your metalworking projects.
The following is some basic information about each type of steel and how each is best utilized:
Cold Rolled Steel Milling Basics
The difference between cold rolled and hot rolled steel is how they are milled. Cold rolled is made by heating raw steel and then cooling it at a low temperature. Once cooled, the steel is rolled flat or extruded into rods, and then it is heated briefly to create an annealing skin on its exterior surfaces.
Identification Characteristics of Cold Rolled Steel
You can identify cold rolled steel, like that from A & C Metals - Sawing, by these three characteristics:
- oily/greasy texture
- very smooth exterior
- very sharp edges
Advantages and Disadvantages of Cold Rolled Steel
Cold rolled steel is ideal for manufacturing parts for machines and automobiles. It is very strong and is better for tight tolerances. However, once you cut into pre-formed cold rolled steel, it will lose some of its strength and can be deformed from changes in temperature and humidity. This can be a serious problem if you are cutting custom shapes that need to adhere to very small tolerances.
Hot Rolled Steel Milling Basics
In contrast to cold rolled steel, hot rolled steel is heated and then milled at very high temperatures. Since the metal is more malleable at the higher temperatures, it can easily be formed into custom shapes, sheets, or extruded to form rods. Once it has been milled or extruded, the steel is cooled to anneal it. As the metal cools in a process known as annealing, it will shrink. This shrinking process adds to the steel's strength but also changes its shape.
Identification Characteristics of Hot Rolled Steel
Hot rolled steel can be easily identified by these three characteristics:
- scaly exterior surface
- non-oily surfaces
- rounded edges
Advantages and Disadvantages of Hot Rolled Steel
As long as hot rolled steel is case hardened, then it is ideal for use in applications such as railroad tracks and structural beams for buildings. However, hot rolled steel is not ideal for use when tight tolerances are necessary because it is hard to harden your finished product in such a way to accommodate them.