Cold Roll Forming vs Hot Roll Forming: What's the difference?

What is steel cold roll forming?

First, the cold-rolled steel "term" describes the variety of finishing processes. Steel cold roll forming involves creating metal shapes just at above room temperature. This is rolled steel which has passed further processing through a cold roll forming machine. This means once the hot rolled steel has been cooled, it's re-rolled right at room temperature to eventually achieve better surface qualities and more exact dimensions.

Cold rolling is achieved when a metal is below there crystallization temperature. And this is a temperature where steel grain structure is altered.In simple terms, cold-rolled steel describes finishing process range, but technically the cold-rolled applied to sheet which undergoes compression between rollers only.

In most cases, cold-rolled steel applied only to sheet which is compressed right between the rollers. For example, when talking about the bar products, cold finishing the term used that consists of turning, polishing, grinding or cold drawing.

Applications

Overall, steel cold roll forming is utilized in the applications where surface conditions, tolerances, straightness and concentricity are factors. And it also provides a more visually appealing and aesthetic surface.The other applications comprise:

- Aerospace structural components

- Home appliances

- Automotive parts

- Metal furniture

Advantages of steel cord roll forming

Due to it, better surface characteristics compared to the rolled steel. Cold rolled steel is mostly utilized where aesthetics are crucial or preferably for technically precise applications.Cold rolled steel is stronger and harder compared to standard steel hot roll forming.

In this case, the metal is perfectly shaped in lower temperature. Below is list of steel cord roll forming advantages:

- Stronger and harder than steel hot roll forming- Aesthetically has pleasing finish

- Wider range of the surface finishes

-Can still be used in the precise applications

-Resistance over tension breaking, increased hardness and resistance over deformation because of work hardening

What is steel hot roll forming?

This is the process at which hot steel is formed; it is a combination of rolling and extruding using the molten steel under very high temperatures. A steel which has been fully roll-pressed at high temperatures. Steel roll hot temperatures are over1,700 Celsius F above the re-crystallization temperature of many steels.

In essence, this tends to make this steel simple to form, resulting in products that are straight forward to work with. When processing hot steel rolls, the manufacturers start first with rectangular, larger length of metal known as billet.Billet is fully heated and sent for the pre-processing to get flattened to a larger roll.

Next, its kept at a very high temperature then run through rollers series to eventually achieve better finished dimensions. In this case, white-hot steel strands are pushed via rollers at very high rates.To achieve sheet metal,the rolled steel is spun to coils then left to cool.When this steel cools, it shrinks, giving less control right on shape and size of finished products compared to the cold rolled.

Hot rolled products such as steel hot roll bars are utilized in construction and welding trades to make I-beams and railroad tracks. Basically, steel hot roll is useful in the situations where exact tolerance sand shapes are not needed.

In addition, hot rolled steel have a scary finish that can only be removed by grinding, picking or sand-blasting. It is essentially normalized, which means free it from the internal stresses which arise from work-hardening and quenching processes.

Characteristics of steel hot forming

- Increases toughness and ductility

- Slight distortions

- Slightly rounded corners and edges for the plate products ( And this due to less precise finishing and shrinkage)

- More malleable and can be turned to various shapes

-It's a scaled surface meaning it a remnant of cooling right from extreme temperatures

-Slight distortions,cooling might result in low trapezoidal forms

What are the differences between steel cold roll forming & steel hot roll forming?

Before going into deep differences between cold rolled steel and hot rolled steel, it is important to first note the major difference between them is one of their process. Cold rolling is the process done near or at room temperature, while hot rolling is done with extreme heat.

1. Structural uses

Cold roll has many industrial and commercial uses. And they include elevators & escalators, solar, refrigeration, guard rails and signposts. Hot rolls are harder and ductile, making them tougher to eventually bend cold. So, they are mostly used for the structural shapes which carry much weight.

2. Surface quality and appearance

The surfaces and edges of the hot rolled steel are rough.And this is because of cooling right from high temperatures leaves remnants into steel surface to make it look scaly. So, such surfaces might need decarburization and other surface treatments to typically prepare steel for the subsequent operations.

Talking about the cold-rolled steel, they have shiny and smooth surfaces because they don't involve high temperatures. In short, cold-rolled steels are ideal to be used in the production operation even without surface treatments.

3. Recrystallization point

Cold rolling happens when a metal material can form new grains, where bending and rolling of a metal is able to destroy old grains. Besides, the cold work on the steel can reduce its strength. As a result, manufacturers add annealing, which is the final step.

Besides, this is a heating steel process with heat ranging from 1400-1,333 degrees Fahrenheit. Steel cooling happens at a slow rate and without bringing it into room temperature rapidly. And this way, a metal can effectively create a uniform micro structure to typically reset it grains.

On the other side, hot rolled steel happens above1700 degrees F. Also, it's higher compared to recrystallization steel point and an essential condition for easy shaping and forming of metal.

4. Size limits

The steel sheet is hot rolled up only to a certain thickness. For example, you cannot purchase 20gauge of hot-rolled sheet because, at this point, cold-rolled will be required. And because roll-formed parts usually it produced from the coiled fabric, the product length seems to be limited by amount of fabric right in the coil only and handling of finished part.The hot-rolled shapes still are limited but only by the equipment capability.

5. Internal stress

Steel hardness and strength significantly impact the internal stresses on the fabric. As a result, cold-rolled steel has greater internal stresses due to greater hardness and strength than hot rolled steel. Essentially, it recommended to relieve the stress before your process the material to eventually prevent warping of your final product.

6. Steel hardness and strength

The process at which cold roll steel is formed gives a uniform micro structure.Cold rolled metals are stronger compared to hot rolled due to work hardening. Besides, this process aids to create metal with hardness and higher strength. It's not extremely hard but a process that makes the metal easily malleable.

On the other side, the hot rolling process involves rapid cooling and extreme heat to prevent stress from regaining the metal grains. And as a result,this type of metal got much liver hardness and strength compared to rolled steel.

7. Distortions

The hot rolled steel tends to experience just slight distortions, for example, via sheet metal bending. And this is because the cooling process offers slightly trapezoidal forms and shapes.

On the other side, cold-rolled steel got a perfectly squared angle that has well-defined edges and corners. Additionally, the tubes formed in cold rolled steel have better straightness and perfect concentric uniformity.