The Purdue Heat Treating Consortium works to advance the science of heat treating by turning new technologies into practice. Over the past three years, the consortium has delivered results on projects for new sustainable and environmentally friendly austempering oils and processes, as well as lifecycle analysis of carburization heat treatments.

A dilatometry test is an effective method for characterizing the phase transformation kinetics for heat treatment processing of steels. This study uses computer modeling to examine the root causes of inaccuracies in measured dilatometry displacement data using a quench dilatometer.

4D high-pressure gas quenching ensures uniform heating and quenching for precise, repeatable results while reducing distortion. This article describes the process and equipment for 4D high-pressure gas quenching and gives some examples.

Martempering involves cooling steel from the austenitizing temperature and rapidly cooling into either specially formulated petroleum oil or a molten salt bath with a specific composition to a temperature slightly above the martensite start (Ms) transformation temperature of the steel. Martempering is performed to reduce distortion problems that may be encountered with conventional quenching methods. This article, adapted from the latest ASM Handbook on quenching and quenchants, describes suitable steels for martempering and variables that influence the process.

Integral quenching (IQ) is a widely adopted heat treatment technique known for its efficient and rapid quenching capabilities. Vertical vacuum IQ furnaces give heat treaters a larger working zone for efficient and rapid quenching. This article describes the elements of a vacuum IQ furnace line and describes its operational workflow and process control.

This article compares heat treat processes and furnace types that are typically used to harden gears.

The second article in this series looks at materials testing, microstructural evaluation, mechanical testing, and residual stress and distortion using the DANTE Controlled Gas Quenching process.

A new method to control distortion in difficult-to-quench geometries addresses the nonuniform cooling inherent in most gas quenching processes. This article describes the development of a controlled gas quenching prototype unit design and its operation. The prototype unit constructed was able to achieve great control within the temperature range of 400 to 100°C, using varying rates of temperature change.

Precise controls are at the heart of today’s flame hardening processes and design, delivering consistent, measured, and accurate heat treatments.

A digital refractometer gives more accurate quench concentration readings thereby reducing maintenance, increasing productivity, and ensuring desired metallurgical properties.

Tests conducted on vacuum carburized and quenched shafts identify variables that increase distortion and the magnitude of residual stresses.

Application of heat treat simulation using the finite element method is ideal to troubleshoot, improve, and design heat treating processes. This article presents examples of heat treating simulation used in the design of a tooling component and in refining a low-pressure carburizing process.

As a regular contributor to the HTPro eNewsletter, Professor Induction answers a wide variety of questions regarding induction heating and heat treating. This column addresses control of quenching temperatures and affect on induction hardening results.

This article focuses on five common reasons for distortion and cracking during heat treatment and recommended remediations: (1) Nonuniform and uncontrollable heat transfer during heating and cooling; (2) Structural changes during phase transformation; (3) Residual stresses in the part that occur due to forming, welding, or machining before heat treatment; (4) Macro or micro steel structure; and (5) Fixturing and loading errors.

Using virtual tools to study aluminum cylinder head quenching processes delivers valuable information for process design and optimization. In this study, cooling curves and temperature gradients generated by air and water quench modeling methods were used to evaluate quenching performance for various quenching configurations.

Intensive quenching enables manufacturers to improve part performance at a lower cost than other available methods. This article describes how using direct-from-forge intensive quenching can significantly reduce the cost of manufacturing steel products when engineered into the lean part-making process.

This article describes a planned three-year research project at the Center for Heat Treating Excellence (CHTE) at Worcester Polytechnic Institute (WPI) to help the heat treat industry better understand process parameters related to austempering of steels. This research will enable the industry to identify the potential strength, toughness, and cost benefits of bainitic steels over martensitic steels and provide guidance on the design, validation, and control of heat treating processes to produce bainitic microstructures in steels.

New methods evaluate steel hardenability in a standard gas quench test and heat transfer coefficient variation within a furnace gas quench chamber.

Experimentally derived surface heat flux rate data and computational fluid dynamics (CFD) software are helping researchers more accurately simulate liquid quenching processes. This article describes an approach where surface heat flux rates are determined experimentally in a precisely controlled flow boiling test system. This data is then used to build CFD models that are proving to be quite accurate in quenching process simulations.

Because alloy steel hardenability is such an important factor in part manufacturing, the Center for Heat Treating Excellence (CHTE) is conducting research through simulations and laboratory testing aimed at learning more about the performance of gas quenching systems used to harden newer alloy steels. The primary goal of the study is to establish a standard method to evaluate gas-quench steel hardenability. Heat transfer coefficients will be determined for different gas pressures and during the cooling phase.