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09-30-2013, 03:48 AM #31
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- Sep 2013
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Thanked: 0Thanks for your addition TulaneBoy. I'm new here myself but if the new people don't post then they will always be new
What you described by heating in an oven is called Annealing. Tempering releases trapped carbon in the... I'm going to need a refrence here sorry:
"Tempering - The carbon trapped in the martensite transformation can be released by heating the steel below the A1 transformation temperature. This release of carbon from nucleated areas allows the structure to deform plastically and relive some of its internal stresses. This reduces hardness and increases toughness, but it also tends to reduce tensile strength. The degree of tempering is dependant on temperature and time; temperature having the greatest influence." (Metallurgy Of Carbon Steel)
Check the site refrenced out if you like. It has a nice description of Martensite too, which is when you rapidly cool steel to make it harder.
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09-30-2013, 04:22 AM #32
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09-30-2013, 04:38 AM #33
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- Aug 2013
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- Chalmette LA
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- 109
Thanked: 10Actually annealing and tempering are two different things. You can't anneal tool steel in a kitchen oven. Temper yes, but not anneal. For annealing you need basically the same heating capability that you use for heat treating. The main difference between annealing and heat treating is to anneal, you cool very slowly. Buried in slowly cooling ashes and coals, for instance, or sand or salt, or simply moderating the heat source in a slow and deliberate manner. Annealing makes steel soft enough to work. You can take hardened tool steel and anneal it and then you can stamp it, saw it, bend it even. You can file it and you can easily grind it. Try to cut hardendd steel with a file. It will mostly just skitter across the steel and not bite in. But anneal it, and you can work it with a file. In fact, speaking of files, I was shown a worn out file that had been annealed cause it is scheduled to some day be made into a couple of razors. We bent the tang in a vise. Okay, so some files you can do that. Well, we also bent the tip of the file. You can't do THAT with a file that has not been annealed! But the description in your link of tempering is interesting so thanks for posting. It has added to my knowledge base.
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09-30-2013, 07:01 AM #34
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- Sep 2013
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- 9
Thanked: 0Shoot, you're right. You need to heat beyond the A1 transformation temperature for annealing, preferably significantly exceeding the A3 line.
I read the page I referenced after I had copied the quote, plus read your posts with more scrutiny, and realize that I have been calling tempering by the wrong name. The procedure and noticable effects are very similar, however they work in fundamentally different ways.
On a side note, I find air cooling makes steel malleable enough for a drill or machine sanding (those are not 'malleable' actions, I realize). I have used sand before and it makes a small difference.Last edited by Nathanael; 09-30-2013 at 07:08 AM. Reason: Added a note on 'malleable'