Metal tubing is used in many different products, which requires a wide range of process concepts including induction heating. Although there are many similarities, several process features and physical phenomena distinguish induction heating of tubular products from induction heating of solid cylinders, especially for selective induction heating of tubes and pipes. The ability of induction heating to concentrate heat in a specific area of a workpiece makes it useful in many applications including localized stress relieving, brazing, bending, annealing of welds, and preheating prior to hot forming and Spinduction welding. The figure below shows the results of FEA computer modeling of preheating the ends of an 11-in. diameter by 0.5 in. thick wall (280 by 13 mm) carbon steel pipe prior to Spinduction welding.
Induction preheating is a critical part of this technology, providing the required heat input quickly and efficiency. The unique inductor design allows retracting it within a fraction of a second after completion of the heating stage, and the two pipes are rapidly pressed together. One pipe is rotated (typically 90 to 180 degrees depending upon application specifics) to produce the weld. The figure below shows zoomed view of a dynamics of induction preheating of pipe ends.
The ability of induction-heating manufacturers to shorten the learning curve and minimize development time through efficient computer modeling is critical to a company’s success.
• V. Rudnev, D. Loveless, et al., Handbook of Induction Heating, Marcel Dekker, NY, 2003.
• V.Rudnev, D.Loveless, C.Ribeiro, J.Boomis, Unleashing a superior induction-heating design with computer modeling, Industrial Heating, August 2009, p 43-47.