Annealing is one of the best-known heat treatments for metals. Induction, on the other hand, is a heating method based on the diffusion of an electromagnetic current transmitted by an inductor to the surface of parts. The combination of these two technologies is ideal for applying a localized annealing treatment to products. Induction annealing involves treating parts one by one, but rises to temperature more rapidly than traditional methods, making it particularly suitable for parts with more or less complex geometries in series production.
How induction annealing works
Induction annealing actually combines two processes: annealing, which is a heat treatment heat treatmentLike nitriding, for example, annealing is a heat treatment, and induction is a heating process. In practice, annealing involves heating a part to modify some of its properties. The main aim of this method is toimprove the machinability of products, particularly if they are to undergo riveting, turning or drilling afterwards. This solution can also be used to soften and defragilize a particular area of the part.
In the case of induction annealing, the workpiece is placed in a coil (inductor), and induction heating takes place through the diffusion of an electromagnetic current between an inductor, often made of copper, and the surface of the workpiece. This method is primarily used to treat very specific areas of parts, and ensures that their geometry is respected. In this way, only the parts located within the inductor receive heat, making it an ideal process for heating only certain well-defined parts.
Why use this solution?
Induction annealing is a very practical way of treating only certain areas of a product, and is therefore used on finished, hardened, tempered or case-hardened parts in their entire volume, as part of the finishing process. In some cases, additional treatment is required only in very specific areas, where the inductors are placed so as not to heat the rest of the surface.
Induction annealing offers several advantages. First of all, it's an excellent way of applying localized treatment to parts. For example, if a product is 10 centimetres long, and only one centimetre needs to be heated, simply place the inductor specifically in this area. This makes it easy to adjust the thickness, length and diameter of the treatment zone. It is also possible to treat the entire workpiece in this way.
What's more, while induction annealing involves treating products one by one, it's still possible to automate the process and thus save a great deal of time. In the case of furnace annealing, processing can take between 8 and 10 hours, compared with just a few seconds for induction annealing. This technique also guarantees faster heating, as parts can reach over 850 degrees Celsius in just a few moments. Hourly output can therefore be very attractive.
Examples of induction annealing applications
Induction annealing makes it possible to treat only certain areas of finished parts, which is particularly useful for products such as rivets or those with fine threads. In fact, induction annealing makes it possible to defragilize and soften parts or certain zones of them, making them easier to machine or deform. In the case of a rivet, a part of which is bound to be crushed and deformed, induction annealing ensures that this part becomes softer and, as a result, performs its function better. The technique is also ideal for parts with threads. The treatment can be applied only to the thread, which is often thin and brittle in its natural state.
Induction annealing is based on a combination of annealing heat treatment and induction heating. By inducing an electromagnetic current between an inductor and the surface of a part, this process offers the possibility of applying an extremely localized treatment, ideal for rivets and threaded fasteners. Although products have to be processed one by one, automating the passage of parts saves a great deal of time: since inductors can diffuse heat of over 850 degrees Celsius in a matter of seconds, induction annealing guarantees excellent productivity.
