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.

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.

Dew point (DP) is a function of the furnace atmosphere composition. In a metal processing furnace, maintaining appropriate atmosphere composition is critical to achieving the desired gas/metal reactions and quality and consistency of the treated product. Continuous measurement of DP is always challenging because of particulates and vapor-phase contaminants in sampled gas stream which can potentially accumulate in filtering systems and on sensors. The DP measurement can also be affected by temperature variations within the sampling unit. Thus, DP readings can drift significantly, necessitating frequent cleaning, recalibration, and sensor replacement. Air Products has developed a DP monitoring system that addresses these issues and based on long-term testing at a customer site, drifts/changes of DP readings on calibration gas were not observed after more than one year of operation, without any maintenance. The contamination and drift issues have been mitigated by incorporating an automated self-cleaning and sensor calibration process after pre-set measurement periods. Temperature control of the sensor and the sampling system are also essential to maintain consistency, and can be achieved via various design features. Drifts/changes in DP that are reported through local monitoring/alarms or remotely through cloud server access can also help to address furnace operational issues quickly and efficiently.

The atmospheres used in a brazing furnace play a critical role in the final quality and metallurgical properties of the brazed component. Typically, exothermic, dissociated ammonia and nitrogen/hydrogen atmospheres are used for brazing mild steel, alloy steel and stainless steel components. The atmosphere composition, flow rates, pressures, and dew point are some of the key variables control final quality. Almost all brazing companies have quality issues that directly result from improper atmosphere application and control. Common problems include oxidation, flashing, inadequate braze flow, sooting, decarburization and carbon pickup. This troubleshooting presentation reviews years of field experience with nitrogen and hydrogen based atmosphere systems. It will help the heat treater or the brazing production engineer to identify these problems and apply appropriate corrective action.

A software simulation tool, CarbonitrideTool, has been developed by Center for Heat Treatment Excellence (CHTE) to predict the Nitrogen and Carbon concentration profiles in selected steels. In this paper, the introduction of the software will be presented. In addition, enhancements have been made to improve the CarbonitrideTool. The diffusion of nitrogen increases the amount of retained Austenite (RA) by changing the Ms temperature. In this paper, the modification has been made to calculate the RA fraction. The empirical prediction of microhardness profile will also be presented. The results of verification experiments will be presented and discussed.

Nitrogen (N 2 ) atmospheres with different, not always optimized levels of reducing and carburizing gases are often used to prevent decarburizing and oxidation of steel parts during annealing in continuous furnaces. The type and concentration of these additives in N 2 should correlate to the extent of air leakage into furnace, entrainment of air with loaded parts, steel composition, and complex reaction kinetics in the gradients of oxygen (O 2 ) and temperature existing between the entrance and hot zones of the furnace. This study explores the effect of small, 0.1 vol.% - 0.4 vol.% propane (C 3 H 8 ) additions on composition of air-contaminated N 2 atmosphere in the temperature range of 500°C - 860°C. Microstructures are presented for AISI 1045 steel exposed to the atmospheres produced. Atmosphere compositions compared include those produced by a new type of plasma activated, in-situ reformer for N 2 -diluted C 3 H 8 . The latter method extends the atmosphere protection to the lower range of annealing temperatures. Present results may assist heat treaters in optimizing their neutral hardening operations.

In the carbonitriding process, both carbon and nitrogen are diffused into the steel, can be carried out in a salt bath or in a furnace gas atmosphere. It is a modified carburizing process but is mostly done at a slightly lower temperature and for shorter time than carburizing. This process is one of the widely used heat treatments for surface hardening. Nonetheless, there are challenges associated with the process performance and reliability. In industry, numerical modeling can be an efficient approach with lower cost and less time to help determine and optimize process parameters.

Industrial carburizing parameter optimization traditionally relies on time-consuming and expensive trial-and-error methods, yielding suboptimal results. To address this challenge, the Center for Heat Treating Excellence developed CarbTool, a sophisticated simulation program designed to calculate carbon concentration profiles during gas and vacuum carburizing processes. The most recent version of CarbTool extends beyond previous capabilities by predicting hardness profiles and carbon saturation limits, offering a comprehensive tool for process optimization in terms of time and energy consumption.