Conrad Kacsik Blog

How to Properly Perform Temperature Uniformity Surveys

Sep 25, 2018 9:17:44 AM / by Jason Schulze

Spartanburg Batch FurnaceEnsuring that a furnace can perform repeatable and accurate cycles is a cornerstone of AMS2750E pyrometry specifications as well as Nadcap and CQI-9 standards. The best way to measure and test any furnace is through a temperature uniformity survey (TUS).

These surveys are critically important, and when working to meet a specification or standard, it’s critical to follow the requirements of that standard.

Why a TUS Is so Crucial

Furnace temperature uniformity is important for any heat treating process. To help illustrate why, I’ll use an example of brazing because it vividly illustrates the need for consistent and reproducible results in a furnace.

Brazing bonds two materials together with filler via the eutectic reaction. Many things can influence this reaction, but I’ll focus on temperature uniformity as it applies to AMS2750E and Nadcap.

Brazing for aerospace applications requires particularly strict tolerances due to its sensitivities. Temperature tolerances for such brazing processes can be as little as ±5 degrees Fahrenheit.

For example, if we began a new diffusion braze process using a nickel braze filler, we might place five widgets at the corners and center of a flat ceramic plate to get five total samples. After the cycle, we would examine the samples in the laboratory to determine if they met the required diffusion depth.

If lab tests show that the samples located in the rear of the furnace have considerably less diffusion than the others, we will refer to the most recent TUS as a starting point for what went wrong. More than likely, it would show that the uniformity requirement cannot be met the way the furnace is performing.

This is just one illustration of why a TUS is not arbitrary. Customers have good reason to demand tight temperature tolerances. To meet their demands and adhere to AMS2750E, Nadcap and other requirements, it’s vital to keep furnaces in perfect operating order so they can pass any TUS and deliver the right outcomes.

In later posts, I’ll share more details about AMS2750E and Nadcap definitions and terms to help facilitate implementation of requirements.

If you have any questions about TUS, AMS2750E, Nadcap or other heat treating requirements, contact Conrad Kacsik.

To read more of Jason's articles related to Nadcap heat treat audits and pyrometry, you can visit his articles at as well as Thermal Processing Magazine.

Industrial Furnace Control System Guide

Jason Schulze

Written by Jason Schulze

Jason Schulze is a metallurgical engineer at Conrad Kacsik with over 20 years experience in the aerospace industry. He has been exposed to Nadcap in multiple commodities, although he often focuses on heat treat. Jason works with companies to insource and improve metallurgical processes, perform gap analysis and internal audits as well as gain Nadcap approval. He is a voting member of the Aerospace Metals and Engineering Committee (AMEC) B & D which provides the aerospace industry with the technical benefits that accrue from the ideas and experience of its members. Additionally, Jason is contracted by PRI as a PRI Training (formerly eQuaLearn) Instructor and teaches multiple courses, including pyrometry. He also writes articles for Heat Treat Today and Thermal Processing on specific subjects related to Nadcap heat treat audits and pyrometry.

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