Computer Modeling of Induction Forging Applications

The majority of commercial codes used for computer modeling of induction heating processes are all-purpose programs originally developed for modeling processes occurring in electrical machines, motors, circuit breakers, transformers, and magnetic recording systems, and later adapted to induction heating needs. Despite the capabilities of modern commercial software, many generalized programs have difficulty taking into consideration certain features of induction heating prior to warm and hot forming (including forging, rolling, and upsetting). This includes:

• The presence of a thermal refractory and the necessity of considering radiation factors
• The heated workpiece can simultaneously move, rotate, and oscillate with respect to induction coil
• The presence of nonuniform initial temperature distributions, such as reheating after continuous casting and billet holding stage
• The presence of end plates, guides, fixtures, liners, etc.

Results of computer simulation of the sequential dynamics of end heating of carbon steel bars utilizing an oval coil (top half is shown only). Bar OD=2”; required heated length = 5¼”; @ 112 bars per hour; 5 bars were progressively heated in oval inductor using 3kHz. Temperature variation “degree C” of four critical points is also shown there.

It is important to be aware that certain critical features of induction heating the workpiece prior to forging could be limiting factors for all-purpose software, dramatically affecting accuracy. This was the reason why some induction heating manufacturers developed several proprietary application-oriented programs, which allow taking into consideration process specifics and important subtleties.

Results of computer modeling of the dynamics of end heating a 2-in. (50-mm) diameter low-carbon steel bar using a solenoid multiturn coil are shown in the figure. The required heated length is 5in. (127 mm). Because the bar is symmetrical, only the top half was modeled using Inductoheat’s proprietary FEA software. Temperature variations at four selected areas of the bar are shown. A 0.5-in. thick thermal refractory is placed between the heated bar and a multiturn inductor (inductor is not shown). Prior to heating, the thermal refractory has certain nonuniform initial temperature distribution that remains from the previous heating cycle.

During the heating cycle, the temperature of both bar and refractory changes. Bar temperature increases due to Joule heat generated by induced eddy currents. The thermal condition of the refractory is a complex function of the heat radiated from the bar surface (due to thermal radiation and convection) and its cooling due to surroundings and water-cooled induction coil.

Computer modeling using appropriate software makes it possible to address all of the important process features, reducing the learning curve in the development of the most appropriate process recipe.

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References

1. V. Rudnev, et al., Handbook of Induction Heating, Marcel Dekker, NY, 2003.
2. 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, p 475-500, 2010.