In this work, the authors employ computer modeling to investigate a quenching process recently demonstrated at Karlsruhe Institute of Technology. A matrix of models was run to assess the effects of heat transfer and phase transformation kinetics on residual stress and microstructure in a relatively thick walled tube. The experiments at Karlsruhe were conducted using a high pressure water quench to produce martensite and residual compressive stress in the bore of a 4140 steel tube. Results show that the timing and rate of martensite formation and bainite kinetics have a significant effect on both the in-process and residual stress state.

The temperature profile in the Heat Affected Zone (HAZ) during induction welding is one of the most important factors determining the weld quality of High-Frequency Induction (HFI) welded steel tubes. In this work, numerical computation of the 3D temperature profile in the steel tube has been done by coupling the electromagnetic model with the thermal model. The high-frequency current and the magnetic fields in the tube, coil and impeder have been evaluated. The resulting power from the induced current is used to evaluate the temperature in the joining edges of the tube. The continuous tube movement has been implemented by considering an additional transport term in the heat equation. The simulations consider non-linear electromagnetic and thermal properties of the steel when it undergoes temperature rise to the welding temperature. The temperature profile from the resulting simulation gives information to control the subsequent process of joining the edges of the steel tube.

Requirements for greater product flexibility in the heat treating industry, driven by lean strategies, have resulted in growing global capacity for induction heating operations as well as the re-examination of processes to save production time and line space. However, there are important considerations to keep in mind when developing and modifying heat treat recipes whether for full-body, full-length heat treating, or seam normalizing applications. These include consideration of specialty alloy requirements and the presence of micro-alloying elements, the prior microstructure and presence of heavily banded structures, heating and cooling rates, and phase transformation kinetics especially with overheating and undercooling situations. This paper focuses on the intersection of theory and practical application for induction heating operations. Particular attention is paid to induction heating principles and fundamentals as well as new and proven methods for recipe generation.