Overheating aluminum

Sometimes when I'm deburring with the Scotch Brite wheel (and typically when I'm trying to remove excess material), I notice the aluminum gets hot enough to slightly burn me from the friction. At that point I stop until it cools down.

I was wondering if it's possible, like with hardened steel, to irreversibly weaken/damage the aluminum we use by getting it hot while working it in the shop.

bmellis11 said:

Sometimes when I'm deburring with the Scotch Brite wheel (and typically when I'm trying to remove excess material), I notice the aluminum gets hot enough to slightly burn me from the friction. At that point I stop until it cools down.

I was wondering if it's possible, like with hardened steel, to irreversibly weaken/damage the aluminum we use by getting it hot while working it in the shop.

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Yes, but the chance of you getting it that hot on the deburring wheel is smallish. You'll burn yourself ~150-200F. Removing the temper from aluminum (annealing it) requires ~775F. You can mark the aluminum with a sharpie marker in the area where you're deburring. If it changes color you can start to worry, but if it doesn't change color, you're below the annealing temperature and shouldn't affect the heat treatment in the metal in a significant way.

agent4573 said:

Yes, but the chance of you getting it that hot on the deburring wheel is smallish. You'll burn yourself ~150-200F. Removing the temper from aluminum (annealing it) requires ~775F. You can mark the aluminum with a sharpie marker in the area where you're deburring. If it changes color you can start to worry, but if it doesn't change color, you're below the annealing temperature and shouldn't affect the heat treatment in the metal in a significant way.

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Good to know, thank you for the response.

agent4573 said:

Yes, but the chance of you getting it that hot on the deburring wheel is smallish. You'll burn yourself ~150-200F. Removing the temper from aluminum (annealing it) requires ~775F. You can mark the aluminum with a sharpie marker in the area where you're deburring. If it changes color you can start to worry, but if it doesn't change color, you're below the annealing temperature and shouldn't affect the heat treatment in the metal in a significant way.

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Coming back to this, I was reading AC 43.13-1B last night and came across 4-54-b (attached) which says that temps above 212F tend to impair the original heat treatment of 2017 and 2024 alloys. Is the annealing process gradual up to a total loss of temper at 775F or am I reading this out of context?

These charts illustrate the permanent loss of tensile strength for different lengths of exposure at different temperatures.

So if 1/2 hour of exposure at 700 degrees, once cooled back to room temperature, the material has about 58% of its ultimate strength, and 40 percent of its yield strength.

If just 200 degrees you have basically no loss of ultimate strength, but a slight loss, maybe 98% remaining of yield strength.

Water handy

I keep a small tin of water beside and cool frequently….has secondary effect of some control over aluminum “ dust “ also

CATPart said:

These charts illustrate the permanent loss of tensile strength for different lengths of exposure at different temperatures.

So if 1/2 hour of exposure at 700 degrees, once cooled back to room temperature, the material has about 58% of its ultimate strength, and 40 percent of its yield strength.

If just 200 degrees you have basically no loss of ultimate strength, but a slight loss, maybe 98% remaining of yield strength.

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That's a very helpful chart. Is it safe to assume that a momentary spike in temperature to the 250-300F range, for instance from using a scotch brite wheel to grind a piece into its final shape, would have much less effect than the 30 minute exposure charted here?

bmellis11 said:

That's a very helpful chart. Is it safe to assume that a momentary spike in temperature to the 250-300F range, for instance from using a scotch brite wheel to grind a piece into its final shape, would have much less effect than the 30 minute exposure charted here?

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As a rule of thumb, coming from the perspective of a stress analyst, you would not extrapolate beyond the charted data, but you may interpolate within it. Since they did not chart below 30 minutes they probably did not test below it, therefore we do not know the effect, therefore we conservatively would use the 1/2 hour curve.

From a static strength perspective, your ultimate strength is not affected much at the temp range you specify. Ultimate strength is when the test coupon starts losing its strength. Your yield strength is affected a little bit more. Yield strength is when the coupon first starts to take a permanent deformation, stops acting like a linear spring. Please note this chart is only good for the specific aluminum series and heat treats and forms listed in the title blocks.