FEATURE ADVANCED MATERIALS & PROCESSES | NOVEMBER/DECEMBER 2025 40 T he heat-treating industry is experiencing a rapid transformation, driven by the adoption of Industry 4.0 technologies. These advancements—interconnectivity, automation, machine learning, and real-time data—are reshaping how manufacturers optimize production and ensure product quality. In heat treatment, the ability to specify, measure, and control furnace atmospheres is essential for achieving desired metallurgical and microstructural outcomes. By integrating atmosphere measurements with other furnace parameters, such as temperature and pressure, engineers gain a holistic view of production, enabling smarter decision-making and process optimization. AI and machine learning further help to analyze heat treatment data to optimize parameters, improve quality control, and enhance energy efficiency. These smart solutions enable predictive maintenance, anticipate process issues, and streamline operations, moving the industry toward intelligent autonomy and away from outdated manual methods. HEAT TREATING ATMOSPHERES: CHALLENGES AND REQUIREMENTS In metal heat treatment, tailored atmospheres prevent unwanted surface reactions and help achieve specific mechanical properties. For example, carburizing and surface hardening often use endothermic gas atmospheres (N₂, H₂, CO), sometimes diluted with N₂. Key parameters— carbon potential (Cp), furnace temperature, and process time—must be measured and controlled. Annealing treatments require careful management to avoid surface oxidation and decarburization, which can result from impurities like O₂, H₂O, or CO₂. Hydrogen acts as a reducing agent, balancing oxidizing potential and ensuring a clean surface finish. Common annealing atmospheres include N₂-H₂ blends, and sometimes N₂-H₂-hydrocarbon mixtures to prevent decarburization. While control systems for endothermic atmospheres are well-established, N₂/H₂ or N₂/hydrocarbon blends are often managed with fixed ratios and flow rates, lacking real- time monitoring. This approach can lead to unexpected contamination, oxidation, and costly rejects or rework. SMART SOLUTIONS IMPROVE HEAT TREATING ATMOSPHERES AND PROCESSES Interconnectivity, automation, machine learning, and real-time data give manufacturers the ability to specify, measure, and control furnace atmospheres and optimize processes. Liang He,* Paulina Kus, and Guido Plicht Air Products and Chemicals Inc., Allentown, Pennsylvania Even small amounts of O₂ (e.g., 10 ppm in pure N₂) can cause surface oxidation. CLOUD-BASED ADVISOR SYSTEM: DESIGN AND FUNCTION To address these challenges, a cloud-based heat-treating atmosphere and process advisor system could help. Such systems enable real-time monitoring and control of furnace atmospheres and other process parameters. For N₂-H₂ or N₂-hydrocarbon atmospheres, it regulates H₂ and hydrocarbon flows based on thermodynamic modeling and active measurements, allowing recipe optimization and early identification of process issues. All required atmosphere information for the closed loop atmosphere control system is connected to the atmosphere control system, which is installed on site and handles the thermodynamic calculations to monitor and control the furnace atmosphere. Additional information like atmosphere flow rates, atmosphere composition, and supply pressure can be tracked directly by the cloud server. A list of examples for relevant furnace data is listed in Table 1. The key features of such systems could include: • Real-Time Alerts: The system provides immediate notifications when process deviations occur, based on historical data from installed sensors. • Preventive Maintenance: Scheduling is optimized, enabling proactive shutdowns and troubleshooting. • Custom Reports: Data stored on the cloud server can be used to generate tailored reports for production tracking and certification. The smart furnace atmosphere monitoring or advisor system can be retrofit to existing heat treatment furnaces. It combines closed-loop control on-site with cloud-based data analytics, offering advice for furnace operation and maintenance in line with Industry 4.0 trends. The system consists of: • Atmosphere Control System: Installed on-site, it handles thermodynamic calculations and controls the furnace atmosphere. *Member of ASM International 6
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