Hot-Rolled Steel vs Cold-Rolled Steel

Steel is available in a variety of finishes, grades, shapes, and specifications, making it one of the world’s most versatile alloys. One of the most common questions about these different types boils down to hot-rolled steel vs cold-rolled steel as when it comes to prefabricated steel products, this is a key distinction.

Read on to learn more about this distinction among BM Steel’s high-quality re-rolled products and make an informed decision for your project.

What is hot-rolled steel?

To put it simply, hot rolled steel is steel that has been roll-pressed at temperatures higher than 927°C (1,700°F). As this temperature is higher than most steel’s recrystallisation temperature, it makes the steel easier to form into products.

Hot-rolled steel is produced by heating and flattening a large rectangular length of steel (a billet) into a large roll. The roll is kept at a high temperature whilst being run through a series of rollers at high speeds. The steel will shrink slightly as it cools, making this option suitable for projects that do not require extremely accurate dimensions.

The characteristics of each type are an important factor in understanding hot-rolled steel vs cold-rolled steel. Hot-rolled steel has the following characteristics:

• A scaled surface due to cooling from extremely high temperatures
• Slight distortions due to cooling
• Bar and plate products have slightly rounded edges due to shrinkage
• Normalised – free from internal stresses associated with quenching or work-hardening processes
• Good malleability
• Enhanced ductility and toughness

Hot-rolled steel is an excellent choice for a wide variety of applications that do not require precise tolerances and shapes. Some of the many uses for steel that has been hot-rolled include:

• Agricultural equipment
• Automotive frames
• Metal buildings
• Stampings
• Structural components such as I-beams, sheet metal, and railway tracks

Hot-rolled steel types

There are three main types of hot-rolled steel. These types include:

• Low-carbon or mild steel with 0.3 % or less carbon by volume
• Medium-carbon steel with between 0.3% and 0.6% carbon by volume
• High-carbon steel with more than 0.6% carbon by volume

As mentioned, hot-rolled steel has a number of advantages and disadvantages.

The advantages include:

• Simple production process
• Better malleability
• Free from internal stresses
• Used to produce popular shapes
• More affordable than cold-rolled steel

The disadvantages include:

• Rough surface texture that must be removed and buffed before painting
• Slight distortions and dimensional imperfections

What is cold-rolled steel?

Cold-rolled steel is hot-rolled steel that has been through additional processing. After hot-rolled steel has been cooled, it is re-rolled at room temperature to produce products with exact dimensions and enhanced surface qualities.

While the term is commonly used for a variety of finishing processes, “cold-rolled steel” really applies only to sheets that are compressed between rollers. Pulled steel forms such as bars and tubes are referred to as cold-drawn steel so are slightly different.

As with steel that has been hot rolled, the characteristics of cold-rolled steel are an important factor in understanding hot-rolled steel vs cold-rolled steel. The characteristics of steel that has been cold rolled include:

• A smooth surface that’s often oily to the touch
• Surfaces with better finishing and closer tolerances
• Bars have well-defined corners and edges
• Tubes have greater straightness and concentric uniformity

Cold-rolled steel is the best choice for applications with specific concentricity, straightness, surface conditions, and tolerances. Some common applications include:

• Aerospace structural components
• Automotive parts
• Home appliances
• Metal furniture
• Visually appealing surfaces

Cold-rolled steel types

There are four main cold-rolled steel types. These include:

• Commercial steel
• Drawing steel
• Extra deep drawing steel
• Extra deep drawing steel plus.

Of these, drawing steels are the most ductile.

Cold-rolled steel has different advantages and disadvantages to hot-rolled steel.

The advantages include:

• Consistent, straight, and accurate shapes
• Smoother, shinier surface
• Extensive range of surface finishes

The disadvantages include:

• Fewer steel structural shapes available
• Additional processing can create internal stresses that could lead to warping
• More expensive than hot-rolled steel

When it comes to hot-rolled steel vs cold-rolled steel, the best choice for your project depends on the project itself. Hot-rolled steel is ideal if you’re looking for good malleability and your project doesn’t require precise dimensions. However, cold-rolled steel is best if you’re looking for steel products with precise dimensions and a beautiful surface.

Find all the steel products you need at BM Steel.