Industry 4.0 is here to stay. To remain competitive, heat treaters must take steps toward adopting automated and interconnected technologies, data analysis, intelligent systems, computer-based algorithms, machine learning, and autonomous decision-making. Predictive maintenance capabilities are particularly critical to heat treating operations. This paper provides background on Industry 4.0 and its relevance to the heat treating industry. It describes the small, incremental actions that can be taken to implement technologies for monitoring and managing heat treating operations, gathering and analyzing data sets, and fostering innovation among personnel.

Heat-treating industry is adopting more and more industry 4.0 techniques and solution packages, to improve production process and product quality. Proper specification, measurement, and control of heat-treating atmospheres are always critical to achieving the desired metallurgical and microstructural results. The combination of atmosphere measurements and other furnace operating parameters (e.g., furnace temperature and pressure) can provide a better view of the whole production. Thermodynamic calculations and field experiences can be integrated into the smart solution to provide process engineers more capabilities to manage and optimize production. In this article, our recent research and development work on smart solutions for the heat-treating industry will be presented and discussed.

For annealing, brazing or sintering, furnace atmospheres help ensure that metals thermal processors obtain the results they need. Hydrogen-containing atmospheres are used to protect surfaces from oxidation, and to ensure satisfactory thermal processing results. Hydrogen-containing atmospheres make thermal processing more forgiving because the hydrogen improves heat conduction and actively cleans heated surfaces – reducing oxides and destroying surface impurities. For powder based fabrication such as P/M, MIM or binder-jet metal AM, the use of a hydrogen-containing thermal processing atmosphere ensures the highest possible density of the sintered parts without necessitating the use of post-processing techniques. Users of pure hydrogen or hydrogen-containing gas blend atmospheres often struggle with hydrogen supply options. Hydrogen storage may create compliance problems due to its flammability and high energy content. Hydrogen generation enables hydrogen use without hydrogen storage issues. Deployment of hydrogen generation can ease the addition of thermal processing atmospheres to new and existing processing facilities.

Heat treaters are adopting more and more Industry 4.0 techniques and solution packages to improve production processes and product quality. Proper specification, measurement, and control of heat-treating atmospheres are always critical to achieving the desired metallurgical and microstructural results. The combination of atmosphere measurements and other furnace operating parameters (e.g., furnace temperature and pressure) can provide a better view of the whole production. Thermodynamic calculations and field experiences can be integrated into the smart solution to provide process engineers more capabilities to manage and optimize production. In this article, our recent research and development work on smart solutions for the heat-treating industry will be presented and discussed.

Low pressure carburizing (LPC) is a proven, robust case hardening process whose potential is only limited by the style and size of vacuum furnace. Today, LPC is typically used in horizontal vacuum furnaces where the opportunity to carburize large parts is limited. In this paper we present a new adaptation of the technology in large pit type vacuum furnaces, capable of opening to air at elevated temperature. This underscores the potential of LPC to carburize larger, more massive parts in a clean, effective and efficient process. The result is quality casehardened parts without the undesirable side effects of atmosphere gas carburizing such as the use of a flammable atmosphere, reduced CO and NOx emissions, no intergranular oxidation, and limited retort life. Another significant advantage is decreased process time. The case study presented here shows that eliminating furnace conditioning and increasing process temperature can significantly reduce cycle durations by nearly three times and cut utility costs in half. Under these conditions, a return on investment (ROI) is in the neighborhood of 1 – 2 years is possible, making LPC in a pit style furnace a cost-effective solution than traditional atmosphere gas carburizing technologies.

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.

Decisions on capital equipment purchases are often based on the cost of the equipment and expected revenue. Although these are important, they do not provide a full financial picture of the value involved. This paper identifies the many aspects of heat treating that impact the value of a furnace purchase. It discusses hidden costs associated with installing, operating, and maintaining new equipment, the effect of depreciation and inflation, and the influence of unevaluated risk. It presents an analysis framework and tools that can help heat treaters not only make better purchasing decisions, but also know what to charge for services to stay competitive and still hit target breakeven timelines.

This paper discuss recent developments in mesh belt heat treating systems used in the production of automotive fasteners. Methods for heat treating threaded fasteners have evolved significantly over the last 20 years as low-capacity shaker hearth, rotary hearth, and plate-belt systems are replaced by soft handling mesh belt heat treatment systems. Design innovations for improving the accuracy of tempering furnace tolerance bands and integrating inline zinc phosphate removal systems are discussed along with their respective benefits.

This paper compares and contrasts heat treat processes and equipment typically used to harden gears. It discusses the basic design and operation of vacuum, controlled atmosphere, and hybrid furnaces and process techniques such as carburizing, carbonitriding, nitriding, nitrocarburizing, and neutral hardening. It also includes information on operating and maintenance costs, using batch integral quench furnaces as the base case for comparison. A discussion on when to consider continuous furnace types is included as well.

Induction hardening, although a safe repeatable process, can require a lot of tuning whenever an input parameter or inductor is changed. This paper discusses the nature of the problem and how it can be alleviated using 3D technology. It explains that long setup times and tedious adjustments after tooling changes are due to inaccuracies in the inductors and their positioning relative to the workpiece. It then describes how these inaccuracies are removed using 3D construction, production, measurement, and positioning technology, including FEA and CFD software, laser powder bed fusion, and optical scanning. To verify the approach, two inductors were additively manufactured and tested in a hardening system. The first inductor was used to harden a bearing seat on a shaft. The inductors were then swapped and another part was hardened without any adjustment to the process. The hardening depth and surface hardness of the two parts are identical within the scope of measurement accuracy.

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 paper discusses the growing use of automation in heat treating and some of the benefits that have been realized in early applications. It provides examples showing how articulated robots are used to load and unload parts on fixtures, how inline 3D cameras facilitate dimensional and distortion control, and how test coupons placed by robots at strategic locations throughout a load are weighed before and after heat treatment to determine if parts in different areas of the load are likely to be carburized to the same degree. It also includes an example of an automatically generated report and explains how binary codes on base trays can be used to automatically upload recipes for specific heat treatments.

This paper presents the results of a study examining the cooling rates of two vacuum high-pressure gas quenching furnaces: a large 10-bar furnace equipped with a 600-hp blower motor and a smaller 10-bar furnace with a 300-hp motor. In comparing critical cooling temperatures for H13 in the 1850°F to 1300°F range, the furnace that is almost three times larger in volume (110 vs. 40 ft 3 of hot zone) cooled the same workload almost identically to smaller unit. The test results clearly show that gas flow, or velocity, is more meaningful than pressure when it comes to cooling rate.

Carbon fiber reinforced carbon is a high-tech ceramic matrix composite consisting of very strong carbon fibers in a carbon matrix. This paper discusses the capabilities of carbon-carbon composites and their potential for use in fixtures and racks that support workpieces during heat treating operations.

Integral quench furnaces combine the benefits of low-pressure vacuum carburizing (LPC) with atmosphere oil quenching. This paper discusses key milestones in the development of integral quench furnaces and the advantages they provide in annealing, normalizing, and hardening applications.

This paper investigates the factors that influence quenching rates and temperature distributions in steel during dilatometry testing. In a prior study, the authors assessed the performance of the cooling system in a widely used dilatometer. The goal of the current work is to develop a cooling strategy that provides more uniform and possibly faster cooling in the same system. Several alternate quench concepts are analyzed, the most promising of which uses water-cooled tubes to deliver high velocity gas through a series of jets axially aligned with the test sample. The proposed cooling apparatus and its effect on the induction heating process are assessed using CFD, electromagnetic, and thermal analyses.

This paper reviews several recent advancements in high pressure gas quenching technology along with the impact of new higher hardenability steels. With design upgrades and improved gas flow and heat removal, a wider variety of materials, part geometries, and load sizes can now be gas quenched.

Furnace atmosphere circulation is at the heart of the heat treatment process. Without thorough circulation of gases, heat treatment processes cannot achieve consistent results in terms of parts surface quality and mechanical properties. The uniformity of the atmosphere plays a major role in maximizing performance of the heat treatment recipe. How well that is achieved translates directly into the quality of the actual process. Proper circulation helps the furnace heat the treatment atmosphere and promotes the thermochemical reactions that take place during the heat treat process. Convection, which is the main mechanism of stimulating atmosphere reactions to achieve surface properties as well as the combination of convection and radiation for heat transfer, are both determined by the efficiency of atmosphere circulation. The paper will discuss traditional atmosphere circulation, and compare this to new gas-mixing technology from Linde, highlighting data from recent installations and actual operating experience.