Numerical computer modeling is a major factor in the successful design of induction heating systems. Induction heating is a complex combination of electromagnetics, heat transfer, and metallurgical phenomena involving many factors. Heat transfer and electromagnetics are nonlinear and closely interrelated because the physical properties of heated metals depend strongly on both temperature and magnetic field intensity. The metallurgical phenomenon is also a nonlinear function of temperature, heating intensity, cooling severity, chemical composition, prior microstructure, and other factors. Computer modeling provides the ability to predict how different interrelated and nonlinear factors may impact the transitional and final thermal conditions of the workpiece, and what must be accomplished in the design of the induction heating system to improve the effectiveness of the process and guarantee the desired temperature profiles helping to optimize technical pioneering ideas.
Consider the example of computer modeling SpinductionTM Welding of piston halves. This welding process combines friction welding and induction pressure welding . An advantage of the process is that it produces consistently flawless welds at very low rotational velocities; well below the minimum forging velocity for friction welding with minimum or no flash projection.
Induction preheating is a critical part of this technology because it provides over 95% of the weld energy input. Induction provides the required heat input quickly and efficiently. The ability to achieve the required temperature uniformity is imperative for the process to work successfully. Immediately after the part is heated, the inductor is retracted within the fraction of second, and the two piston halves are rapidly pressed together.
The figure above shows a finite element mesh (right) and the variation of temperature profiles (left) during induction preheating of the top and bottom halves of the piston using 30 kHz. Total heating time is 6 seconds. A novel inductor concept made possible a retraction time of less than 1 second.
The figure below shows a magnified view of the temperature variation within the right half of modeled induction preheating system.
1. V.Rudnev, D.Loveless, C.Ribeiro, J.Boomis, Unleashing a superior induction heating design with computer modeling, Industrial Heating, August, 2009, p.43-47.
2. V. Rudnev, et al., Handbook of Induction Heating, Marcel Dekker, NY, 2003, 800p.
3. V. Rudnev, Simulation of Induction Heating Prior to Hot Working and Coating, ASM Handbook, Vol. 22B: Metals Process Simulation, editors D.U. Furrer and S.L. Semiatin, ASM International, 2010, p.475-500.