Hot rolled steel or cold rolled steel – which to choose? One of the crucial parts of an engineer’s job is picking the right materials for their application. There’s already a lot of types of metal to choose from. Each with its own advantages and uses. Some types of steel make an excellent fit for home appliances, others for the automotive or marine industry, gas tanks, constructions, etc.
Still, there’s one more distinction to make. A material grade with the same chemical composition may have varying qualities depending on the manufacturing method. Our customers have asked for the difference. So here it is.
Hot working is more widely used compared to cold working because it needs less force and energy. It is used in compressive forming methods like rolling, metal extrusion, forging, etc.
Hot Rolling Method
Hot rolling takes place in temperatures above the material’s recrystallisation temperature. In case of steel, the temperatures rise above 1000°C.
Heated metal in hot rolling process
The starting material is usually steel billets or slabs. First, they are heated above the aforementioned temperature. The next step is feeding them to the rolling machinery. Continuous rolling gives the desired final shape – a metal sheet (3 mm and upwards) or profile.
Hot Rolled Steel Properties
As it is easy to form metal in high temperatures without any extra delays, it is possible to produce it in larger quantities than cold rolled steel. This keeps the market price of hot rolled steel lower. The steel cools at room temperature. This is known as normalising. It changes the material’s microstructure in a way that results in increased ductility and toughness. Ductility is especially important when forming the material (e.g. sheet metal bending) to give it the required shape for your needs.
Hot rolled steel, though, doesn’t have the best quality. It shrinks slightly during the cooling process. This leaves the metal with internal stresses. The results are non-uniform measurements and some distortions. The material’s dimensional tolerances can vary between 2…5%. Also, the surface has a scaly finish. This is a kind of oxide that forms at high temperatures, known as mill scale.
It is easy to identify hot rolled products by touching the surface because of the uneven finish but it is also lacking an oily film. With steel bars, the corners are rounded.
Hot Rolled Steel Uses
I-beams find wide usage in construction
Hot rolled steel is a good choice when tight tolerances are not of utmost importance. There are many fields where that is the case. Its great advantage in price matters more than precision. Some common uses for hot rolled steel are:
Constructions
Pipes and tubes
Truck frames
Doors and shelving
Railroad tracks
Railroad car parts
Cold Rolled Steel
What’s the Difference Between Hot Rolled Steel & Cold Rolled Steel?
Hot rolled steel or cold rolled steel – which to choose? One of the crucial parts of an engineer’s job is picking the right materials for their application. There’s already a lot of types of metal to choose from. Each with its own advantages and uses. Some types of steel make an excellent fit for home appliances, others for the automotive or marine industry, gas tanks, constructions, etc.
Still, there’s one more distinction to make. A material grade with the same chemical composition may have varying qualities depending on the manufacturing method. Our customers have asked for the difference. So here it is.
Hot working is more widely used compared to cold working because it needs less force and energy. It is used in compressive forming methods like rolling, metal extrusion, forging, etc.
Hot Rolling Method
Hot rolling takes place in temperatures above the material’s recrystallisation temperature. In case of steel, the temperatures rise above 1000°C.
Hot rolling bars
Heated metal in hot rolling process
The starting material is usually steel billets or slabs. First, they are heated above the aforementioned temperature. The next step is feeding them to the rolling machinery. Continuous rolling gives the desired final shape – a metal sheet (3 mm and upwards) or profile.
Hot Rolled Steel Properties
As it is easy to form metal in high temperatures without any extra delays, it is possible to produce it in larger quantities than cold rolled steel. This keeps the market price of hot rolled steel lower. The steel cools at room temperature. This is known as normalising. It changes the material’s microstructure in a way that results in increased ductility and toughness. Ductility is especially important when forming the material (e.g sheet metal bending) to give it the required shape for your needs.
Hot rolled steel, though, doesn’t have the best quality. It shrinks slightly during the cooling process. This leaves the metal with internal stresses. The results are non-uniform measurements and some distortions. The material’s dimensional tolerances can vary between 2…5%. Also, the surface has a scaly finish. This is a kind of oxide that forms at high temperatures, known as mill scale.
It is easy to identify hot rolled products by touching the surface because of the uneven finish but it is also lacking an oily film. With steel bars, the corners are rounded.