This paper examines the latest developments in energy management in heat treatment with a specific focus on electrical heating and tighter integration between the power supply and furnace control to maximize energy efficiency. It also discusses the use of IGBT (insulated-gate bipolar transistor) and SCR (silicon-controlled rectifier) based power supplies as energy-efficient alternatives to variable reactance transformers (VRTs) for powering electric vacuum furnaces.

This paper describes a furnace retrofit involving the replacement of a variable reactance transformer (VRT) with an IGBT-controlled mid-frequency direct current (MFDC) transformer. The two transformers are similar in size and all other variables remained essentially equivalent. A typical heating cycle was initiated with a ramp rate of 10°F/min to a soak temperature of approximately 1900°F. Cross-sectional data was taken during the ramp phase and soak phase. Based on power measurements and adjusting for differences in thermal loads, the retrofit achieved a 40% reduction in kilowatt consumption, a 14% reduction in peak current draw, and an improvement in power factor throughout the cycle.

High-temperature, energy efficient ceramic coatings are being used in heat treating and forging furnaces around the globe to rein in the high cost of refractory maintenance, reduce fuel consumption, and improve furnace efficiencies as well as product quality. These coatings also protect metal from high-temperature oxidation and corrosion. This paper shows how specialized ceramic coatings can provide an energy savings of up to 20% in industrial furnaces while reducing heat-up and turn-around times and extending refractory service life.

This paper revisits a case study presented at Heat Treat 2009, investigating the failure of induction coils used for heat treating automotive wheel hubs. At the time, computer simulation was beginning to allow for virtual prototyping of heat treat applications as an alternative to experimental testing. As explained in the original paper on p. 86 of the 2009 HTS conference proceedings, although simulation helped in the development of a more robust coil, it was not used to pinpoint the cause of failure. In this current work, the authors tackle the same problem aided by more than a decade of improvements in compute power and finite element analysis techniques. To highlight the leaps made in virtual prototyping, the induction hardening coil previously analyzed using an axisymmetric 2D model is now examined using more precise 3D electromagnetic and thermal models while accounting for the rotation of the part.

This paper presents four case studies documenting the time and money that heat treaters have saved with the help of predictive maintenance tools. In one case, a heat treater avoided potential catastrophic melting of a heating element and several hangers when predictive maintenance software guided the operator to a broken ceramic in a specific heating zone. In another case, a commercial heat treater was alerted to a low kW reading, indicating a heater failure on a diffusion pump, which would have led to the contamination of a vacuum furnace if not addressed in a timely manner. Situations involving a failing motor on a quench tank and the degradation of furnace insulation are also discussed. Cost comparisons, with and without predictive maintenance, are included in three of the four studies.

This study demonstrates the use of simulation in the design of induction hardening coils. It compares three coil geometries, two of which leverage the flexibility of 3D printing. The paper explains how to set up and run the simulations in order to predict temperature fields, hardness profiles, and microstructure distributions in the workpiece. Based on the simulations, the conventionally manufactured coil and one of the two 3D-printed coils do not achieve the desired martensitic microstructure everywhere along the surface of the workpiece. In the case of the 3D-printed coil, the simulations show that the workpiece overheats in an area where its diameter abruptly changes. To fix the problem, the coil was adapted with an additional winding that carries current in the opposite direction. Simulations show that the redesign reduces hot spot temperature by more than 200 °C, producing the desired microstructure in that area of the workpiece and a more uniform hardness profile.

This paper describes a new grade of 3D carbon composite materials that are more durable than alloys at high temperatures as well as lighter and stronger. Advantages over other materials in the construction of heat treat furnace fixtures are illustrated in several comparative case studies.