Induction heating is a non-contact type method. It works on the principle of electromagnetic induction in which heat is directly produce in the workpiece. Induction heating coils are placed around the electrically conductive part. The position of metal body or workpiece in an alternating current induces eddy currents inside the part. These currents are concentrated in the outer layer of metal body due to the skin effect. These eddy currents excite the material's molecules and generate the internal heat. As a result, the workpiece itself becomes the source of the heat, not the heating element. The depth of heating is influenced by the amplitude of AC frequency, concentration of flux capacity, material of work piece and property of materials. Induction heating for preheating, post heating and stress relieving have been used in manufacturing and construction welding application in industries such as mining, oil and gas refineries and pipelines, structural welding, shipbuilding, transportation, precision casting and injection molding.
Induction heating mainly used for 1) Melting of steel, stainless steel, and other non-ferrous materials 2) Heating of ferrous and non-ferrous billets for forging extrusion and piercing. 3) Through heating of the wire, tube, pipe, rods, flats etc. 4) Induction Hardening, tempering, annealing, stress relieving & softening.
Benefits of Induction heating are, 1) Uniformity and Quality- Provides the highest degree of temperature control across the heat affected zone (HAZ). 2) Reduced Cycle Times- Significantly faster time-to-temperature than resistant methods. 3) Cost Reduction- No fuel cost and minimum insulation costs; reusable insulation reduces disposal. 4) Power Efficiency- Operates at maximum efficiency transferring more energy to the part, decreased heating times. 5) Ease of Use- Simple set-up using preheat blankets or flexible heating cables. In some cases, how to use the induction equipment can be taught in one day. 6) Reliability- Induction heating system components make cycle uninterrupted. The cabling for induction is simple, making it less likely to fail. Also, no contactors are used to control the heat input to the part. 7) Versatility- Pipe preheat and stress relief; weldolets, elbows, valves, I-beams, complex shape. Induction coils have ability to adjust during the heating process to accommodate unique parts and heat sinks. 8) Safety- Fewer fumes, eliminate fuel gases; no exposure to flame, gases or hot elements. 9) Environment- Less airborne particulate; improved work environment results in higher work productivity.