The majority of billets and bars have round, square, or rectangular cross sections. However, special applications require heating components with complex cross sections including triangular, trapezoidal, hexagonal, parallelogram, polygonal, and others.
Induction heating such geometries and, in particular, those with a combination of obtuse and acute corners and holes, as well as polyhedral corners, could introduce certain challenges in obtaining the required temperature uniformity end-to-end, top-to-bottom, and side-to-side.
To illustrate, the figure below shows the results of FEA computer modeling of induction heating of titanium alloy (Ti-6V-4Al) bar with a rhomboid transverse cross section (6 in. by 8 in.) using a frequency of 1 kHz.
Computer modeling reveals that the region of the acute corner is noticeably underheated because the path of eddy currents in the transverse cross section does not match the contour of the rhomboid, and most of the induced currents close their loops earlier, without reaching the acute corner. The situation is quite different when heating the obtuse corners.
Various proprietary coil designs and process recipes were developed to ensure uniformly heated products and to accommodate geometrical features of the workpieces that are different compared to heating components of traditional shape.
Numerical computer modeling helps determine optimal recipe and process details that could be costly, time-consuming, and, in some cases, extremely difficult, if not impossible, to determine experimentally.
V. Rudnev, D. Loveless, et al., Handbook of Induction Heating, Marcel Dekker, NY, 2003.