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I Forge Iron

Are there tests to determine double tempered?


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  • 2 months later...

Tempering twice is a pretty good practice so I would assume that it would be done. Testing the hardness isn't going to tell you if it was tempered once or a hundred times because after the transformations are done and your left with no un tempered martensite re-tempering at the same or lower temps will do nothing to the steel. Seeing that's its got such a small amount of carbon makes me think that either way its not really going to matter. With only .3% carbon the metal isn't going to be overly brittle even if it was not tempered.

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Since tempering is a function of time at temperature, with that big hunk of metal i would be more concerned with how long it was held at temperature rather than the number of times it was heated to temperature.

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you can read the whole thing here, http://en.wikipedia.org/wiki/Tempering this is just one excerpt from the article, but once again there is no memtion or repetition that most of the knifemaking world is caught up in. "Precise control of time and temperature during the tempering process is critical to achieve the desired balance of physical properties."

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In industry it is not uncommon to double temper, though that is very much a function of grade and desired mechanical properties. Some grades do in fact respond fairly dramatically to being double tempered at the same or even slighlty LOWER second tempering temperatures. Unfortunately, there really is no test that one can do to confirm that a second temper was performed. All you can do is confim that hardness and mechancal properties requirements have been met.

Patrick

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As a Certified Welding Inspector with just enough Non-Destructive Testing background to be dangerous: No.

No known test can determine the number of thermal cycles. The component either meets end user requirements for Rockwell Hardness/X-ray/Magnetic Particle/Eddy Current/UltraSonic/etc. tests or it does not. You are relying on vendor reputation and history here.

If you do *anything* else to it, you are assuming the blame for any later failures.

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  • 3 months later...
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