This paper presents a computational approach for assessing the potential for distortion when using high pressure gas to quench steel parts. It explains how to account for component geometry, heat transfer coefficient, gas temperature and velocity, heating and cooling rates, and phase transformations. The authors employ finite element modeling methods to determine local phase fraction and displacement in a Ferrium C64 disk for different quench pressures. Simulations at timed intervals show how distortion and phase fraction progress in different areas of the disk and along the edges of an off-center bore. The causes of distortion are examined and explained using the model, with insights into why the cooling rate has a nonlinear relation with distortion.

Press quenching is often used to harden parts that are sensitive to distortion, but it is a difficult process to control due to the effects of tooling and the relatively large number of process parameters. In this paper, the authors show how they use finite element analysis to optimize the process and tooling design for a spiral bevel gear made of carburized 9310 steel. Several designs adaptations are assessed, one of which is shown to minimize radial shrinkage and taper distortion in the inner diameter of the bore.

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.

In single-shot hardening applications, heat treated components often feature a variety of geometric complexities including variable wall thicknesses, sharp diameter transitions, lightening holes, slots, etc. Due to the inherent 3D electromagnetic nature of single-shot coils and the complex geometry components which they must accommodate, the design and optimization of single-shot hardening coils is typically a demanding and intricate task. This paper presents combined electromagnetic-thermal and thermal-mechanical FEA simulation results for the single-shot induction hardening of a power transmission shaft. The simulation results, including electromagnetic, thermal, metallurgical, and mechanical data demonstrate the value of computer simulation in the design and development of single-shot induction hardening systems.

Quench hardening is a transient thermal stress process with phase transformations. It is inevitable that a component will go through plastic deformation due to phase transformations, which will lead to distortion in the hardened part. Understanding the sources of distortion is necessary in designing the heat treat process and component configuration to obtain a product with greater dimensional accuracy. It is worth mentioning that consistent distortion can be compensated by adjusting the part dimensions prior to hardening. The possible sources of distortion include residual stresses prior to hardening, heating rate, austenitizing temperature, soaking time, quenching rate and uniformity, and possible tooling constraints, etc. The significance of these effects varies according to the part geometry and heat treatment process. Characterization of material properties and the development of computer modeling made it possible to understand the material and component responses during quench hardening, which is the key to process improvement and part configuration optimization. In this paper, the hardening process of a simplified bevel gear with thin-wall feature made of AISI 9310 is analyzed using DANTE, and the effect of tooling used in a press quench on distortion is investigated. The causes of distortion are analyzed through the material response aspect using the modeling results.

Carburizing grades of high strength steels, such as Ferrium C- 64 alloy, contain strong carbide forming elements such as chromium and molybdenum. Alloys with high amounts of strong carbide formers can form stable carbides during carburization that effectively block carbon diffusion and retard the carburization process. This is especially true for low pressure carburization. To achieve the desired case depth, the low pressure carburization process consists of a series of rapid boost and longer time diffusion cycles. One problem is how to determine an acceptable carburization schedule. This paper will discuss a methodology used to develop the data for Ferrium C-64 so that a proper low pressure carburizing schedule could be determined. Integral parts of this methodology are experiments to determine carbon diffusion rates, carbide formation kinetics, and carbide dissolution kinetics, and use of these data in computer software to simulate the process and to determine the proper schedule.

Simulation of stresses during heat treating relates usually to furnace heating. Induction heating provides very different evolution of temperature in the part and therefore different stresses. This may be positive for service properties or negative, reducing component strength or even causing cracks. A method of coupled simulation between electromagnetic, thermal, structural, stress and deformation phenomena during induction tube hardening is described. Commercial software package ELTA is used to calculate the power density distribution in the load resulting from the induction heating process. The program DANTE is used to predict temperature distribution, phase transformations, stress state and deformation during heating and quenching. Analysis of stress and deformation evolution was made on a simple case of induction hardening of external (1st case) and internal (2nd case) surfaces of a thick-walled tubular body.