FEATURE ADVANCED MATERIALS & PROCESSES | NOVEMBER/DECEMBER 2025 42 dewpoint. To adjust the atmosphere inside the furnace to the desired parameters, the system can either control flow rates or gas composition by opening solenoid valves or mass flow controller. The control set-points can be put in to avoid surface oxidation and decarburization for the oxygen probe signal, KH= H2O/H2 ratio, and dew point. Figure 1 shows the installation of smart furnace atmosphere monitoring and control system for a N2/H2 roller hearth annealing furnace. The smart furnace atmosphere control system adjusts H₂ flow to maintain the desired H₂O/H₂ ratio, moisture content, and residual oxygen ppm level, ensuring a reducing atmosphere for different materials by reading different recipes which are built based on the process know-how and thermodynamics calculations from simulation tools. Since the installation of this smart control system, the operation of H₂ flow is regulated based on real-time measurements and hydrogen consumption is significantly reduced by approximately 35% compared to previous fixed flow operation. CASE STUDY: PROCESS IMPROVEMENT AND PRODUCTION MONITORING Pure H₂ atmospheres offer superior surface quality for bright annealing of stainless steel products, reducing heating and cooling times as well as lowering energy costs. Figure 2 shows that the addition of H2 into the furnace atmosphere helps the heating and cooling cycles. A cloud-based atmosphere and process monitoring system is installed on a continuous belt furnace that runs pure H2 atmosphere for annealing of stainless-steel parts. Figure 3 is a screen capture of the production overview. Users can access this webpage on a cloud server to watch how the furnace is running. This page also has information about the liquid level inside the LIN and LHY tanks. With this tank level information and averaged gas usage rate, the system can predict when the tanks need to be refilled and tell the customer how long the normal production can last with the left gas products in the tanks to ensure better production scheduling. During production breaks, pure H2 atmosphere is switched to N2/H2 atmosphere for cost reduction purposes. This dry N2/H2 flow builds up the furnace pressure to block Fig. 1 — Smart N2/H2 atmosphere control system. Fig. 2 — Effects of atmospheric composition on heat transfer rates. Fig. 3 — Overview of important production measurements. 8
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