Nadcap Heat Treating Standards for Aerospace

Posted by Chris Kielb on Jun 23, 2019 3:03:44 PM



Advance Welding has plans to provide comprehensive Nadcap heat treating services. We often get asked about Nadcap heat treating standards so we've written this blog to address those questions.

Nadcap Heat Treating Processes are:

Normalizing: This process involves heating steel above the critical temperature, holding for a period of time long enough for transformation to occur, and air cooling. Normalized heat treatment establishes a more uniform carbide size and distribution which facilitates later heat treatment operations and produces a more uniform metal.

Annealing: This process involves heating the metal above the critical temperature, holding long enough for transformation to occur, and slow cooling. The difference between annealing and normalizing is the temperature (annealing is about 150 to 200 degrees Fahrenheit lower). This creates a softer metal. Metals that can be normalized or annealed include steel, cast iron, copper, and brass.

Stress Relieving: Often, as weldments cool internal stresses increase as different parts were subjected to different temperatures during welding and thermal expansion rates dictate that parts will shrink proportionately to their original working temperature. Stress relieving metals is done by heating the part to a temperature at which the yield strength is low enough that internal stresses relieve themselves. Higher temperatures and longer times will often yield a part with lower overall stresses although temperatures are always maintained below a point at which the metal would change phase. Getting stress relieving correct can be important, particularly with parts that will be machined after welding, as machining metal away removes material that might be under internal stress or holding back other areas of the weldment that are under stress...and parts will distort sometimes beyond the machining tolerances.

Advance Welding offers Nadcap heat treating services including stress relieving, aging and normalizing.  Advance Welding has multiple ovens and furnaces in-house that include: L&L Argon Atmosphere Furnace, L&L Furnace, Blue M Oven and small electric furnaces. All heat treating equipment is calibrated per AMS 2750. AW has plans to become Nadcap accredited for heat treating.

To learn more about Nadcap, its origins, how standards are developed and more, visit our Guide to Nadcap here. To learn about Nadcap Welding and Brazing you can go here. To learn more about Nadcap NDT (Non-Destructive Testing) you can go here.


Topics: Nadcap

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