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Let’s talk about hot rolling.

We should begin be defining four important terms:

- Hot rolling
- Cold rolling
- Induction bending
- Induction coils

HOT ROLLING: Hot rolling is the process of heating a large tract of steel (rarely any other type of metal) and using weighted rollers to shape the metal, typically to make it thinner. The heat is fairly substantial, between 800 and 2,200 degrees Fahrenheit. The rollers are calibrated to place just the right amount of pressure on the steel to meet the thickness and other specifications of the client.

COLD ROLLING: Cold rolling differs from hot rolling, primarily because it doesn’t use heat. Yes, that is obvious. But the heat is needed for bulkier and less-finished material. Cold rolling would more typically be used on sheet metal, steel rods, bars and the like. Cold rolling’s main advantage is that the metal retains its strength more than hot rolling does.

INDUCTION BENDING: Induction bending is a totally different process with a totally different purpose. It is used to bend almost any metal, but typically pipe and tube forms. It is a highly energy-efficient process, because only a small section needs to be heated - just the section that requires a bend. So a long pipe that would typically remain straight, such as a petroleum or natural gas pipelinet, needs to be heated only at those select points that require a bend.

INDUCTION COILS: These are coils used to heat through a process called “induction”. Really they are transformers that convert DC power into very high heat. It consists of two insulated copper wires coiled around an iron core. A vibrating interrupter creates a faster pulse from the low-voltage DC power, creating a higher voltage pulse for more heat. Induction coils are used to heat the tubes and pipes in induction bending.

So the processes are quite different and so are the goals. However, there can be overlap and there are times when a decision must be made between induction bending, hot rolling and cold rolling.

Here are six advantages of induction bending over hot or cold rolling, reasons why a metal tube rolling company would prefer induction bending over other methods when it is appropriate for the job:

To begin with, induction bending is more cost-effective, saving the client money in three key areas:

- Labour
- Energy
- Overhead

Labour costs are lower simply because the induction bending process is faster. It is a highly time-efficient process. It takes less time to complete, so the labour costs are less. Simple math.

Energy costs are lower simply because less heat is required. It is a highly energy-efficient process. Keep in mind that where hot rolling required heating a huge piece of metal, the heat in induction bending is laser-targeted to just the specific spots where a bend is needed. One big caveat to report - when cold rolling can be applied, it has an obvious energy-saving advatahge over any heated process, including induction bending

Overhead costs are lower simply because the induction bending. No sand filling needed. No internal mandrel. The whole equipment set-up is smaller and cheaper.

Although more cost-effective, induction bending does deliver a final product that is superior in at least three ways:

- smoother finish
- fewer imperfections
- minimal distortions

Induction bending leaves no joints to weld together. Fewer joints not only means a stronger product than if it has been hot rolled, but also a smoother finish.

Cold rolling isn’t perfect. “Wall thinning” and warping are among the imperfections that can happen, in part due to the thinner nature of the metal used. Induction bending tends to create a more even and predictable quality than cold rolling.

And induction bending created the fewest distortions in the metal, for one very obvious reason - most of the metal is not touched. Since heat is very localized and bending is equally localized, the integrity of the rest of the pipe remains intact.

It should be noted that these methods of bending and forming metal are not mutually exclusive. For instance, hot rolled steel often ends up as coiled sheet metal. This sheet metal ifs often then fed through the cold rolling metal process, where it becomes thinner sheet metal, metal foil and metal plates.

So it is not always just a choice between induction bending, hot rolling and cold rolling that needs to be made. Sometimes it is a decision of just exactly how to best combine two of the methods for the highest quality result, meeting the specifications of the client while minimizing possible weaknesses and imperfection, all the while keeping costs as low as possible. This is not a simple task.

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