First, a couple definitions. Hot rolling and induction bending are sometimes carelessly used interchangeably, just because both involve heating steel to a very high temperature. But there are major differences.
Induction bending is a energy-efficient way to create a bend in a pipe or tube when only a specific area requires a bend. For example, if an angle needs to be added to an otherwise straight pipe or tube. For induction bending, only that specific area needs to be heated to render just that section of steel (or other metal) easier to bend to the prescribed radius. An induction coil, sometimes called a “spark coil” or by metal-working highbrows a “Ruhmkorff coil “, is used to apply the heat. Induction coils are electrical transformers that create high-voltage pulses based on a low-voltage DC current, repeatedly interrupted by a vibrating interrupter.
Hot rolling steel differs from induction bending primarily in that the entire metal object is heated - the whole slab or billet, in fact - typically to between 800 and 2,200 degrees Fahrenheit. While in heat, the steel is pliable…and without further puns, it is sent through rollers that are weighted to specifications required to change the metal to the desired size or thickness. The steel is then quenched by blowing air or spraying water on it, to bring back down the temperature. Note that it is usually steel, iron or alloys used in hot rolling. Non-ferrous metals would generally be cold rolled.
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 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:
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 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.
