When discussing furnace compliance, we might ask ourselves the following question:
“If my thermocouples and control instruments are calibrated, and my SATs are performed successfully, does that mean the temperatures inside my furnaces are correct?”
Your immediate response might be “Yes”, however the correct answer is “Not necessarily”. A successful calibration and SAT only tells us that our furnace’s temperature system is accurate at one location: the tip of our sensor. Unfortunately, we don’t yet know the temperatures of any other locations inside our furnace.
This is why we must evaluate temperature uniformity, meaning the temperature variation of several locations within the furnace work zone (expressed in ± degrees) with respect to the temperature set point. To do this we must perform Temperature Uniformity Surveys (TUS) A TUS is a test or series of tests where calibrated instrumentation and sensors measure temperature variations inside the furnace. By identifying where in the work zone these temperature variations exist, heat treaters can answer important questions such as:
Where are the cold and/or hot spots in my furnace? Why are there cold and/or hot spots, and how do I fix them?
You may like the article: Pyrometry, the key for reliable heat treat in Automotive and Aerospace
When discussing furnace compliance, we might ask ourselves the following question:
“If my thermocouples and control instruments are calibrated, and my SATs are performed successfully, does that mean the temperatures inside my furnaces are correct?”
Your immediate response might be “Yes”, however the correct answer is “Not necessarily”. A successful calibration and SAT only tells us that our furnace’s temperature system is accurate at one location: the tip of our sensor. Unfortunately, we don’t yet know the temperatures of any other locations inside our furnace.
Escrito por:
Victor Zacarias
Víctor Zacarías is a Metallurgical Engineer from the University of Queretaro with studies in Strategic Management from Tec de Monterrey. With over 15 years of experience in Heat Treatment Management, he is currently the Managing Director of Global Thermal Solutions México. He has conducted numerous courses, workshops and assessments in México, United States, Brazil, Argentina and Costa Rica. He has been member of the AIAG Heat Treat Work Group (CQI-9 committee) and the SAE Aerospace Materials Engineering Committee (AMS2750).