This work serves to expand upon the fundamental idea of high convection quenching (HCQ), examining alternative methods to destabilize vapor barrier formation in liquid quenchants. Namely, ultrasound in combination with a brine solution is applied to realize fast yet controllable quenching conditions.

This work aims to contribute to the optimization of the simulation process in the heat treatment industry. Cooling curves of a polyacrylate-based (ACR) polymer solution at a concentration of 9 and 12 %, using an axial flow rate of 1.30 L/min on an immersion system and a fluid temperature of 45 °C were acquired and analyzed. Air quenching was also used to compare the polymer quenching conditions.

Decarburization of steel parts during heat treating results in a lower surface hardness, undesirable residual stress profiles, and poor part performance. Significant effort has been made towards preventing decarburization and determining the impact of annealing time and temperature on decarburization rate. Much of the published research has focused on medium carbon steels, ranging from 0.3wt% C to the eutectoid composition. The goal of the current research is to determine decarburization rates for steels with carbon concentrations above the eutectoid concentration. AISI 52100 steel was heated in air for 12, 24, and 36 hours at three temperature ranges (below A 1 , above A cm , and between A 1 and A cm ). Optical microscopy was used to determine the carbon concentration as a function of depth from the surface. The diffusion coefficients of carbon in austenite and ferrite plus cementite phase assemblages were calculated. These diffusion coefficients can be used in a finite difference simulation to predict decarburization at different temperatures and times.

This study investigates the heat treatment response and microstructure evolution of high-carbon steels for additive manufacturing. Moreover, the role of nitrogen as an interstitial alloying element is addressed. Stainless steel 440C, cold-work D2, hot-work H13, and T15 high-speed tool steel overspray powders from spray forming were investigated. The thermal behavior of these materials was examined using a thermal analyzer that combines calorimetry and thermogravimetry. Additionally, interstitial alloying with nitrogen was performed in-situ to understand its influence on thermal behavior. The (near-)equilibrium nitrogen solubility in 440C and D2 in contact with flowing N 2 gas was recorded as a function of temperature through the interval 1200 to 800 °C. The microstructure of the steel powders was characterized by light optical microscopy and X-ray diffraction. The potential of nitrogen alloying and the importance of optimized heat treatment protocols are emphasized with respect to high-carbon steels in additive manufacturing applications.

The phase transformation model is coupled with the inverse heat conduction problem (IHCP) to estimate the steel/quenchant interfacial heat flux. Cylindrical steel probes having section thicknesses 25 and 50mm, respectively, and lengths 30mm were made from medium and high carbon steels (AISI 1045 and 52100). The probes were quenched in mineral, neem, and sunflower oils. The cooling curves at the centre and near the surface of steel probes were recorded. The near-surface cooling curve was used as a reference temperature data in the IHCP algorithm for the estimation of surface heat flux, whereas the cooling curve at the centre was used as the boundary condition of the axisymmetric model of the probe. The effect of phase transformation on the metal/quenchant interfacial heat flux was indicated by a kink and rise of heat flux. The increase in the section thickness of the probe from 25 to 50mm decreased the magnitude of the heat flux. Increasing section thickness increases the phase transformation, increasing the resistance to heat flow at the metal/quenchant interface.

AISI 52100 is a high carbon alloy steel typically used in bearings. One hardening heat treatment method for AISI 52100 is austempering, in which the steel is heated to above austenitizing temperature, cooled to just above martensite starting (Ms) temperature in quench media (typically molten salt), held at that temperature until the transformation to bainite is completed and then cooled further to room temperature. Different austempering temperatures and holding times will develop different bainite percentages in the steel and result in different mechanical properties. In the present work, the bainitic transformation kinetics of AISI 52100 were investigated through experiments and simulation. Molten salt austempering trials of AISI 52100 were conducted at selected austempering temperatures and holding times. The austempered samples were characterized and the bainitic transformation kinetics were analyzed by Avrami equations using measured hardness data. The CHTE quench probe was used to measure the cooling curves in the molten salt from austenitizing temperature to the selected austempering temperatures. The heat transfer coefficient (HTC) was calculated with the measured cooling rates and used to calculate the bainitic transformation kinetics via DANTE software. The experimental results were compared with the calculated results and they had good agreement.

Excessive distortion was observed in many small components made from 1080 steel that was neutral hardened following stamping. A study was then undertaken to determine how to reduce the distortion of the heat-treated parts while maintaining proper hardness and microstructure. A numerical simulation based on Simheat software was conducted to determine the effect of elevated temperature on the quenching oil used and its impact on distortion and microstructure. A second oil designed to operate at higher temperatures was also examined. Using Simheat software, the two oils were compared based on predicted distortion, hardness, and microstructure and the results were subsequently validated using empirical methods. It was concluded that a significant improvement in distortion could be achieved by using a different oil and higher quench temperatures.

This paper examines the causes of distortion in heat treated 1080 steel parts and the influence of quenchants and quenching temperature. A comparison of parts produced using a different oil and different quench temperatures shows that a significant improvement can be achieved in distortion with only minor grain growth and a slight reduction in hardness.

Dilatometry test systems are commonly used for characterizing the transformation behavior in steels and induction heating is commonly the heating source. In these systems, the steel test article is assumed to have a uniform temperature throughout the sample. This is a good assumption for slow heating rates with small samples, however, for induction hardening cycles this may or may not be accurate. Using computer models, it is possible to predict the temperature dynamics of the sample, both radially and axially, during the thermal processing cycle (heating and cooling). O1 tool steel was utilized to characterize and model heating and cooling temperature gradients. Specimens instrumented with multiple thermocouples were induction heated and gas quenched. The test data and geometry were evaluated with 1- D and 2-D models to characterize transient temperature gradients. The goal of the modeling is to better characterize temperature corrections required when rapid heating and cooling processes are used to determine transformation behavior in induction hardenable steels.

Press quenching is a specialized quenching technique used in heat treating operations to minimize the distortion of complex components such as spiral bevel gears and high quality bearing races. The quenching machine is designed to control the geometrical characteristics of components such as out-of-round, flatness, and (if the tooling is designed to accommodate it) taper. The achievement of final dimensional tolerances is accomplished through a trial and error process where the incoming machined sizes of the components are adjusted based upon measurement data taken from the initial sets of quenched and tempered components that have already been processed through the press quenching operation. Oil flow rates can be altered during the different stages of the quenching cycle, and through the use of specialized tooling the oil flow pathways can be selectively adjusted to meter the oil flow towards specific areas of the part surface while baffling it away from others in order to provide a more uniform overall quench. Complex metallurgical changes take place during austenitizing and quenching, resulting in corresponding mechanical property changes. Accompanying these changes are the generation of thermal and transformation induced stresses, which produce in-process and final residual stresses. During press quenching, dimensional restrictions add additional complexity to the combined effects of thermal and mechanical process sensitivities on these stresses. And if the stresses are severe enough, quench cracking can result. In this investigation the quench cracking of an asymmetrical AISI 52100 bearing ring is evaluated through physical experiments and through corresponding heat treatment process modeling using DANTE. The effects of quench rate, die load pulsing, and several other process variables are examined experimentally and/or analytically to illustrate how they can impact the resulting stresses generated during the press quenching operation.