In industrial applications, hot forging of aluminum alloy AA 6082 is carried out at 480 °C following a preheating process in an induction heater. The forged parts are then cooled down to room temperature, heated up again to apply conventional solution treatment followed by quenching and artificial aging processes. Repetitive heating/cooling steps are a significant cause of energy loss. The aim of this study was to provide time and energy efficiency by combining hot forging and solution treatment processes in a single high temperature process. To achieve this a new and improved heat treatment pattern was introduced. AA6082 parts were quenched immediately from a rather high forging temperature and artificially aged without any necessity for a second heating step and solution treatment. Mechanical properties of parts heat treated by this new pattern were than compared to the mechanical properties of parts heat treated conventionally. Heat treatment of AA6082 alloys were carried out for 30 minutes at three different temperatures (480, 510 and 540 °C) for comparison, followed by forging, water quenching and artificial aging (180°C, 8h). Mechanical properties of each sample were investigated using hardness and tensile tests. Elemental analysis and microstructural characterization were carried out using Energy Dispersive Spectrometry (EDS), Scanning Electron Microscope (SEM) and Optical Microscope (OM). Required minimum hardness for the samples after heat treatment was considered as 90 HB. This hardness value could not be obtained for the parts forged/solution treated at 480°C and 510°C. Hardness values of parts heat treated at 540°C, water quenched and aged at 180°C were higher than 90 HB.

A method of predicting tempered hardness of mixed microstructures has been formulated, which uses the quenched hardness and steel chemistry as independent variables. This calculation is based upon a method first proposed in 1947 by Crafts and Lamont for mixed microstructures and modified using the 1977 chemistry-based, tempered martensite hardness calculation of Grange, Hribal, and Porter. Tempered hardness predictions were examined using Jominy end-quench bars tempered between 204°C (400°F) and 649°C (1200°F). The measured Jominy hardness after tempering was used to make adjustments to the Crafts and Lamont parameters used in the hybrid model. Both plain carbon (SAE 1045) and low alloy (SAE grades 8620, 4130, 4142, and 5160) were used to evaluate the chemistry-based hardness prediction. In combination with a ASTM A255 Jominy hardenability calculation, the proposed calculation can be used to predict the quenched and tempered hardness profile of a round bar based upon chemistry, quench severity, and tempering temperature.

Aluminide diffusion coatings enhance carburization and oxidation resistance of iron and nickel based alloys by formation of iron and nickel aluminides which extends the life of furnace alloys and fixtures. As a part of a large project in the Center for Heat Treating Excellence (CHTE), an aluminized coating on RA330 was studied by a hot dip process followed by diffusion heat treatment. Samples of RA330 steel were dipped in pure liquid aluminum at 700 °C for 10 minutes. After dipping, four samples were given an additional diffusion treatment. To predict the developed phases, computational analysis was used and the results were compared with the experimental data.

Carburizing is a method of enhancing the surface properties of components, primarily made from low to medium carbon steels, such as shafts, gears, bearings, etc. Carburized parts are generally quenched and tempered before being put into service; however, after quenching of carburized parts further annealing and hardening treatments can be employed before final tempering. This work analyses the impact of the two aforementioned heat treatment approaches on the development of subsequent microstructures and mechanical properties of hot forged 18CrNiMo7-6 steel. Moreover, this study aims to understand the impact of normalizing treatments prior to the two aforementioned heat treatment routes. Microstructural and mechanical tests were conducted on four as forged flat cylinder components that received a combination of the abovementioned heat treatments. In general, better microstructure refinement, in terms of prior austenite grain size (PAGS), was obtained for carburized parts that received the intermediate annealing and hardening treatments after quenching and prior to the final tempering. Additionally, further refinement of the martensitic pockets/blocks was observed for parts that did not receive a normalizing treatment prior to carburization. The studied heat treatments appear to have a negligible effect on the mechanical properties of the hot forged flat cylinder components.

The evolution of Low Pressure Vacuum Carburizing in the automotive industry is well embedded in assembly plants with continuous batch loading. This batch loading, which causes a need for high cost WIP (work in progress), can now be reduced with the Low Pressure Vacuum Carburizing furnace equipment being sized to fit into single piece flow line with small batches. This presentation will look into the recent integration of heat treatment for in-line machining cells and the overall influences for the customer to provide equipment for heat treating in-line. These details will be compared to batch or continuous batch heat treatment as we know it today in the automotive industry. High Pressure gas quenching will be illustrated in both in-line and continuous batch integration.

As a result of research conducted by the Department of Materials Science and Metallurgy at the University of Cambridge and tests conducted in the calibration laboratory at CCPI Europe Ltd, a new mineral insulated (MI) thermocouple cable has been developed for sensor manufacturing. The use of both type K and type N base metal thermocouple combinations under operational conditions during extended and/or high temperature conditions have historically been shown to have a limited life operation. The test results on mineral insulated cable show that conventional type K mineral insulated thermocouple designs can maintain calibration limits and stay within IEC 60584 -1: 2013 class 1 and ASTM E230 special tolerances for a limited number of operations. However, when compared to the type K sensors, manufactured from the new designed mineral insulated cable, these new designs have been shown to maintain calibration values to meet both IEC 60584 -1: 2013 class 1 and ASTM E230 special tolerances for up to five times longer. This new mineral insulated cable can allow type K and N thermocouples to work longer and at higher temperatures with significantly reduced drift, offering greater measurement confidence. This paper will discuss how the new design will offer the opportunity for type K and type N MI thermocouples to work for longer and at higher temperatures under both continuous and cycling conditions with significantly reduced drift, giving increased confidence in measurement capability.

In 1999, ASM’s Heat Treating Society set forth a view of what the ideal future for the heat treating industry would be by the year 2020. Among the goals is to “Achieve zero distortion and maximum uniformity in heat treated parts.” Since heat treating is a crosscutting technology, it affects, and is affected by, many aspects of part design and manufacture. All the parties in the lean manufacturing value chain, including the heat treater, must realize that “everything matters” when trying to eliminate waste. Lean concurrent engineering teams must collaborate to integrate their innovations, they develop seamlessly, into the methods and equipment they use to make and to market their products. The author will review the 1999 ideals set forth in Vision 2020 and how far we have come as of 2017. The author combines his dual perspectives performing traditional commercial heat treating for over 35 years for over 1,200 different customers, as well as his work with many lean part making customers and “heat treat waste-fighting” colleagues commercializing advanced heat treat quenching methods and equipment since 1997.

While the induction heating of non-ferrous alloys is fundamentally no different than that of other metals, the unique physical properties of different non-ferrous alloys have a number of critical induction heating implications. This paper addresses a number of physical characteristics and practical subtleties associated with the induction heating of non-ferrous alloys, focusing particularly on the influence of electromagnetic and thermal material properties. A mathematical optimization routine for continuous induction heating processes is also presented. Utilizing coupled electromagnetic-thermal FEA computer simulation results and taking into account real-world process requirements, this routine is used to maximize induction heating quality and equipment performance.

Laser beam heat treatment has been established during the last years as a complementary technology for local hardening treatment tasks at tool manufacturing, automotive industry and many others. Recently developed new high power diode lasers and a lot of process supporting systems lead to an increase of industrial laser hardening applications. The presentation starts with information about the basics of laser heat treatment. After that a review about suitable lasers and recommended systems for reliable and well adapted laser heat treatment processes is given. Recent examples of the transfer of laser beam hardening into industry are presented and discussed.

Flash Bainite Processing employs rapid thermal cycling (<10s) to strengthen commercial off the shelf (COTS) steel sheet, plate, and tubing into AHSS. In a continuous process, induction technology heats a narrow segment of the cross section in just seconds to atypically high temperatures (1000-1300°C). Quenching substantially immediately follows. Flash Processing utilizes inherent heterogeneity of steel creating multi-chemistry, complex mixtures of approximately 20% bainite and 80% martensite. Carbide dissolution and carbon migration are controlled by limiting time in the austenite temperature range. Unlike conventional heat treating to create advanced high strength steels (AHSS), homogeneity is intentionally avoided and non-equilibrium conditions are created. The leanest prior ferritic regions transform to bainite while prior pearlite forms martensite. A 7-10% higher yield/tensile strength product results with the beneficial ductility of the bainite constituent. Flashed AISI1010 (1100MPa UTS) and AISI1020 (1500MPa UTS) have shown exceptional room temperature stamp-ability to 0T/1T bend radii. The 1500MPa formability of 3G-AHSS is achievable. Flash Bainite offers simultaneous weight and cost savings.

The development of residual stress in an induction hardened small spur gear is numerically simulated. A full scale 3D simulation is utilized to obtain the results, providing the possibility to evaluate the complete distribution of residual stress in the hardened component. Electromagnetic and thermal solutions under induction heating conditions are obtained with Cedrat Flux 3D, whereas EDF Code Aster software is used for thermal simulation during the quenching stage, phase transformation, and stress-strain simulations. The simulated induction heating isotherms and distribution of residual stress are compared with experimental investigations done by Larregain et al. and Savaria et al.

During heat treating in air, 400-series stainless steels suffer from significant oxidation. It will be shown that doping the surface with a small amount of reactive element effect (REE) material can minimize this oxidation. Examples of REE materials include aluminum, silicon and cerium. After this treatment, the thermal oxides that form are thin and protective rather than thick and flaking. The process can be done in the field without any hazardous materials or special equipment. Complex geometries can be protected. The reduction of heat treat warp has also been demonstrated. The net result of the very thin thermal oxide is significantly reduced secondary operations.

Austempering heat treatments of steels and cast irons are usually performed using salt bath quenching followed by isothermal transformation of austenite to bainite or ausferrite. High Pressure Gas Quenching (HPGQ) at 1-4 MPa gas pressures is increasingly used to replace oil quenching, but may also be used for austempering. However, to obtain sufficient heat transfer high gas speeds >25 m/s are required. Hot Isostatic Pressing (HIP) is widely used for densifying castings and powder-based materials. Recent equipment developments enable Uniform Rapid Quenching (URQ) under 200 MPa pressure and 0.3 m/s speed, providing uniform cooling. Superplastic conditions during austenitization and initially during URQ reduce residual stresses and eliminate internal porosity in castings and PM materials. Hardenability is increased due to stabilization of the close-packed austenite. The inherent freedom provided by HIP to select optimum levels and rates for temperatures and pressures has been shown to improve mechanical properties and reduce process duration.

Heat treatment response of a complex shaped cylindrical component with varying sections of thickness and length has been studied in a 15CDV6 bainitic steel. The effect of cooling rate at every location has been predicted using an FEM based simulation. The distortion associated with the experimental component was matched with the theoretical FEM based heat treatment model. The component distortion has been attributed to the strain associated with volume changes associated with thermal gradient and phase transformation at various locations. The heat flux on the surface was modelled to arrive at heat transfer by inverse technique. The study validates the definition of boundary conditions for such complex components.

The recently published ASM Handbook , Volume 4C is specifically devoted to meeting the needs of the induction heating and heat treating community. It is a long-awaited expansion of the ASM Handbook series to cover induction technology in depth. Heating by electromagnetic induction is a topic of major technological significance that continues to grow at an accelerated rate in a variety of thermal applications such as hardening, tempering, stress relieving, brazing, soldering, shrink fitting, melting, normalizing, annealing, coating, as well as re-heating ferrous and non-ferrous metallic materials prior to warm and hot working. The new ASM Handbook volume reflects an ambitious undertaking to compile an all-new, comprehensive resource on 21 st -century induction thermal processes. World-recognized experts from leading universities, national research laboratories, and industrial corporations from 10 countries contributed to this volume, making it a truly international work to address leading-edge induction technologies.

To experimentally investigate the effect of tempering temperature and time on the structure and composition of martensite, AISI 52100 was austenized at 1000°C for 40 minutes and quenched in agitated water at 21°C. The as-quenched steel contained body-centered tetragonal (BCT) martensite with 22% retained austenite. These samples were tempered at 100°C, 200°C, and 300°C with different holding times and then were characterized by x-ray diffraction (XRD) to determine the effect on the structure of the martensite. It was found that the content of retained austenite did not change after tempering at 100°C. Retained austenite decomposed after tempering for 40 minutes at 300°C. The changes in crystal structures and lattice parameters for tempered martensite with different holding times and temperatures were measured. The effect of sample preparation on retained austenite and the structure of martensite and tempered martensite was evaluated. An effective technique for carbide extraction and collection in steel is introduced.

Around 1970 it was discovered that quenching AISI 4340 steel from 1200 °C leads to much higher fracture toughness, in the as quenched state, than by conventional austenitizing at 870 °C. Further researches have ascertained that the apparent toughness increase is limited to fracture toughness tests (KIC), whereas Charpy-V impact tests do not show any betterment due to high temperature austenitizing, in respect to conventional heat-treating. Various explanations of these contradicting results were given on the basis of the then existing theories. It was further ascertained that the betterment of fracture toughness was limited upon tempering to a maximum temperature of 250 °C, making it useless for most applications. The puzzling phenomenon has been recently reconsidered for the validation of new Blunt Notch Brittle Finite Fracture Mechanics theories. Results are given and possible future applications to industrial cases presented.

Austempered Ductile Cast Iron (ADI) has emerged as an important engineering material in recent years. It has a combination of high strength, good ductility, good fatigue strength and fracture toughness. Because of these excellent properties, it is now extensively used in many structural applications such as automotive components, earth moving machineries etc. An investigation was carried out to develop ADI with a nano scale microstructure. This was achieved by high temperature deformation and subsequent austempering of ductile cast iron. The effect of processing parameters such as deformation temperature, strain rate, austempering temperature and austempering time on microstructural features such as volume fraction of phases, size and distribution of phases were examined.

Accurate assessment of heat treat (HT) growth on carburized ring gears is of critical importance when developing new gears or implementing various design/process changes on current production gears. The traditional approach has been to conduct expensive and time consuming HT trials with green and after- HT measurements on a case-by-case basis. An advancement of this process was to create an extensive database in order to develop a predictive model. Various statistical analyses were performed using Minitab. Ring gear HT growth on measurements between pins expressed in % growth gave better predicting power than delta (mm) growth. The best subset model with green hardness data utilizes 7 factors (material, key geometrical features) and yields 98.3% R 2 . The model developed from a larger dataset without green hardness yields 89.8% R 2 . On-going work includes continuously updating the database and refining the model. This work will help minimize the number of trials needed for new product launches and shortening of the development cycle.

This paper will address practical aspects of developing induction heat treatment processes – induction hardening processes in particular. Examples will be presented to illustrate methods of improving inductor and process designs utilizing computer simulation. A number of everyday challenges encountered by heat treatment practitioners will be addressed, specifically challenges related to metallurgical and mechanical quality. The value of utilizing computer simulation will be demonstrated in these real-world solutions through the revelation of subtle facets of induction heat treatment that cannot otherwise be physically observed or measured.