What are Induction Preheat and Postheat?
Induction heating is a non-contact heating method where the heat is induced directly into the workpiece electromagnetically. Induction heating coils are placed onto or around an electrically conductive part. The alternating magnetic field created by the coil current induces eddy currents inside the part, exciting the material’s molecules and generating internal heat. As a result, the workpiece itself becomes the source of the heat, not the heating element.
Industries and Processes
Induction heating for preheating, post heating, and stress relieving have been used for decades in manufacturing and construction welding applications in industries such as mining, oil and gas refineries and pipelines, structural welding, shipbuilding, transportation, precision casting, and injection molding.
Preheating before welding or Post-weld stress relieving involves heating the base material before or after welding (typically the area surrounding the weld joint) to a specific temperature determined by the welding process.
Induction preheating is used in many other manufacturing processes, such as preheating casting molds or injection molding tools and dies.
Benefits of Induction for Preheating/Post Heating
Preheating of the welding zone minimizes the temperature difference between the welding arc and the base material. Preheating also slows the weld cooling rate and lowers hydrogen which helps reduce the risk of cracking and failed welds.
Induction heating is very fast and saves time when preheating is required. The setup time for the induction heating equipment is also much faster compared to other methods. Easy to wind, flexible induction coils can be used on many shapes, sizes, and types of parts.
Providing temperature uniformity and consistency of the weld quality are also some of the numerous benefits. In addition, induction offers safety benefits compared to resistance and open flame heating methods.
Induction is a clean and energy efficient heating method, where the heat is directly induced in the part, resulting in significant energy costs savings.