A patented DANTE Controlled Gas Quench (DCGQ) process was developed for high precision distortion control during quench hardening. The DCGQ process follows a recipe of quenching time and the ambient gas temperature designed by computer modeling, with a specified maximum allowed temperature difference in the part section during the martensitic transformation.

In this study, a single-sided carburized Almen strip made of Pyrowear 675 is used to investigate the effect of phase transformations on quench hardening distortion. Computer modeling is used to analyze the collected experimental data and demonstrate the underlying principles of distortions and residual stress.

Heat treatment of steels is a process of modifying the mechanical properties by solid-state phase transformations or microstructural changes through heating and cooling. The material volume changes with phase transformations, which is one of the main sources of distortion. The thermal stress also contributes to the distortion, and its effect increases with solidstate phase transformations, as the material stays in the plastic deformation field due to the TRIP effect. With the basic understanding described above, the sources of distortion from a quench hardening process can be categorized as: 1) nonuniform austenitizing transformation during heating, 2) nonuniform austenite decomposing transformations to ferrite, pearlite, bainite or martensite during quenching, 3) adding of carbon or nitrogen to the material, and forming carbides or nitrides during carburizing or nitriding, 4) coarsening of carbide in tempered martensite during tempering, 5) stress relaxation from the initial state, 6) thermal stress caused by temperature gradient, and 7) nonhomogeneous material conditions, etc. With the help of computer modeling, the causes of distortion by these sources are analyzed and quantified independently. In this article, a series of modeling case studies are used to simulate the specific heat treatment process steps. Solutions for controlling and reducing distortion are proposed and validated from the modeling aspect. A thinwalled part with various wall section thickness is used to demonstrate the effectiveness of stepped heating on distortion caused by austenitizing. A patented gas quenching process is used to demonstrate the controlling of distortion with martensitic transformation for high temperature tempering steels. The effect of adding carbon to austenite on size change during carburizing is quantified by modeling, and the distortion can be compensated by adjusting the heat treat part size.

High-alloy steels, like Ferrium C64, are used in powertrain components due to their corrosion resistance and high temperature resistance properties. These steels undergo a tempering temperature that is well above traditional steel, and during this process alloy carbides or compounds form, increasing the materials hardness, mechanical strength, and high temperature resistance properties. In the early stages of tempering, softening occurs due to the formation and coarsening of iron carbide, followed by a hardening as the alloy elements combine to form nano-scale dispersoids. These alloy carbides block the path of dislocations in the grain, strengthening the material. At longer tempering times or high temperatures, the coarsening of these alloy carbides and compounds can cause softening. A predictive material model for the high-tempering response of steels is needed to ensure peak hardening properties are met. For a robust heat treatment model, the material response for every step of the process needs to be modeled. These material properties include austenitization rates and thermal expansion during heating, carbon diffusivity and saturation limits for carburization, phase transformation rates and thermal contraction rates per phase during cooling and quenching, deep-freeze kinetics for further martensitic transformation, tempering kinetics for formation of the tempered martensite phase, and carbide kinetics for formation, coarsening, and size. Additionally, mechanical properties of each phase as a function of carbon need to be defined to ensure the proper mechanical response during and after heat treatment. After the material model is developed it can be used to design and optimize the high-temperature tempering process for any part using the same material.

A gas quenching method was developed by DANTE Solutions, in conjunction with the U.S. Army Combat Capabilities Development Command Aviation & Missile Center (DEVCOM AvMC), to control distortion in difficult to quench geometries. This new method addresses the nonuniform cooling inherent in most gas quenching processes. A prototype unit was constructed and tested with the aim of controlling the martensite formation rate uniformity in the component being quenched. With the ability of the DANTE Controlled Gas Quenching (DCGQ) unit to control the temperature of the quench gas entering the quench chamber, thermal and phase transformation gradients are significantly reduced. This reduction in gradients yields a more uniform phase transformation, resulting in reduced and predictable distortion. Being able to minimize and predict distortion during gas quenching, post heat treatment finishing operations can be reduced or eliminated, and as such, fatigue performance can be improved. This paper will discuss the prototype unit performance. Mechanical testing and metallographic analysis were also performed on Ferrium C64 alloy steel coupons and will be discussed. The results obtained showed that the slower cooling rate provided by the prototype did not alter the microstructure, hardness, strength, ductility, toughness, or residual stress of the alloy.

During the liquid quenching process, there are three main phases between the solid and the liquid interface: film boiling where vapor blanket covers the entire solid structure, transition or nucleate boiling, and single phase convection. The type of the quenching media, the agitation, and the flow pattern of a quench tank have significant effect on the cooling behavior during these three phases, which will affect the cooling rate, phase transformation, stress evolution and shape change of the quenched components. In this paper, transient CFD analysis using AVL FIRE is coupled with heat treatment analysis using DANTE to simulate an oil quench hardening process of a test gear made of Pyrowear 53. The gear is carburized prior to quench hardening. During the coupling analyses, the heat flux between the gear and the oil calculated in the CFD model is applied to the solid heat treatment model, and the gear surface temperature predicted by the heat treatment model is passed back to the transient CFD model. The aforementioned CFD tool is capable of considering the entire quenching domains without considering phase transformations in the quenched components. In the present case the gear is treated with a finite element tool in combination with DANTE to account for the latent heat release, which slows down the cooling. The relations between carbon content, temperature field, phase transformation, internal stress, and shape change during quenching are explained from the heat treatment modeling results. The coupling of CFD and heat treatment analyses provides a more robust application of computer modeling in the heat treatment industry.

Press quenching is an effective method to improve the strength and control the distortion of auto gears. However, it can be challenging to understand, predict, and further minimize the deformation of circular-arc bevel gears in industrial applications because of multiple influencing factors. This paper reports on work to build a comprehensive model with phase changes to reproduce the gear quenching process with consideration of the quenching machine, process parameters, and variation of steel compositions. The phase content and temperature history predicted by the model agree with the gear-quenching experimental results.

This study employs computer simulation to predict residual stresses and distortion in a full-float truck axle subjected to induction scan hardening. Electromagnetic behavior and temporal power distributions within the axle are modeled using Flux2D, with these power distributions subsequently mapped into DANTE software for comprehensive thermal, phase transformation, and stress analysis. The truck axle has three key geometrical regions: the flange/fillet, shaft, and spline. Our study reveals that induction heating and spray quenching processes significantly impact distortion and residual stress distributions. We specifically investigate how spray quenching severity affects these outcomes by simulating varying quenching rates, which can be practically adjusted through spray nozzle design, polymer solution ratio, and quenchant flow rate. Three heat transfer coefficients (5,000, 12,000, and 25,000 W/m²·°C) were applied as thermal boundary conditions during spray quenching while keeping all other parameters constant. Understanding the relationship between heating/quenching parameters and resulting residual stresses and distortion enables optimization of the induction hardening process for enhanced part performance.

The induction hardening process has been widely adopted in the heat treatment industry due to its energy efficiency, process consistency, and clean environment. Compared to traditional furnace heating and liquid quenching processes, induction hardening is more flexible in terms of process adjustment for improved results. The commonly modified process parameters are frequency and power of the inductor, method and timing of power application, and spray quench rate. In this study, a scanning induction hardening process of a generic coupler made of AISI 4150 is investigated by heat treatment process modeling using DANTE. The corner of the non-axisymmetric bore experiences high tensile stresses during the hardening process, which leads to a high possibility of cracking during quenching. The model is used to explain why and how the high tensile stresses are generated. To reduce cracking potential, an innovative process is proposed that reduces the high tensile stresses at the corner, which is demonstrated and validated by modeling. This process modification not only reduces the magnitude of the tensile stress at the corner during induction hardening, but also converts the surface residual stresses at the corner from tension to compression. The residual compression on the bore surface provides improves fatigue performance for the coupler during service.