Straightening Alloy

By: QldSpitty - 30th December 2018 at 00:18 Permalink

Twist it back the other way past its springback point works.All depends on the material.7075 is a lot harder than 2024

By: 24 Threshold - 30th December 2018 at 01:01 Permalink

These alloys are heat treatable, i.e. their mechanical properties are created by a carefully controlled heat treatment: unless the mechanical properties of the structure are no longer important, heat treatment (annealing) should only be used if you understand the alloy type, so that its response to the temperature/time exposure can be predicted.

By: Whitley_Project - 30th December 2018 at 01:57 Permalink

A picture would help Julian

By: ZRX61 - 30th December 2018 at 02:22 Permalink

Airworthy or not?

If not:
Cover it with a black Sharpie, rub bar soap over it or use the gas wrench with just the Acetylene turned on & turn it black.
Turn the Oxygen on & burn off the sharpie ink or carbon from the acetylene... or heat it to the point the bar soap turns black.

It's now annealed.

Airworthy:
I'm not opening Pandora's box & putting my ticket on the line.

By: stuart gowans - 30th December 2018 at 10:17 Permalink

A problem with soap, is once it goes black, it cant get any blacker, and marker pens work the other way around disappearing at undisclosed temperature, softer aluminium melts at around 300, whereas the 2000, and 7000, series alloys are around 450 (figures are approximate), when working these alloys they are normally heated in a commercial oven, and quenched in a solution at a specific temperature;you may not have access to this equipment! I have found working with a small propane torch (plumbing type) in one hand and hammer in the other gives good results with dents, the advantage of the calor type torch, is that it wont easily generate enough heat to melt the metal; remember once you've wrecked it, it is all over!

By: 24 Threshold - 30th December 2018 at 16:48 Permalink

Pure aluminium melts at 660 C and the alloys somewhat lower, sometimes below 600 C. However, the problem is not really about melting it is softening, which occurs at much lower temperatures. Precipitation hardening alloys soften, rapidly, when heated above 200 C. Thus, as others have also mentioned, the issue becomes what the structure has to do: if it just has to be the right shape and look pretty, worrying about melting might be appropriate but, if it needs to perform as designed, you should only heat it, if you understand exactly what you are doing.

By: stuart gowans - 31st December 2018 at 07:40 Permalink

Indeed "melting" was the wrong use of the word, but it will melt if you use too much heat, in a localised area, and the point I was trying to make is that all of the "indicators" change colour, but once they have done that, there is no further warning (indication) as to what heat you have reached; to a larger extent it's not the melting that causes the problem (although when it drips on the floor you may think that) but, the lack of softening, which will cause a fracture when the metal is worked.

By: Mr Schmitt - 31st December 2018 at 11:15 Permalink

Hi,
If you can find a piece of scrap aluminium the same or similar grade then you you could experiment the different recommendations.
I have found that what has worked best for me when I have straightened Cast Aluminium, is first remove all old paint and any oil etc. Heat evenly using a plumbers hand blow lamp and watch as the aluminium starts to turn a tinge of an off light goldy colour and then dip into cold water as soon as it does. Hold in water until cool enough to hold, then bend back into position a little at a time. Gently though, as it starts to stiffen again as you bend it. Once it does stiffen and you can feel it with the resistance getting harder in the bending process. Heat again and continue this process. I have straightened control levers and cast Aluminium this way and in some cases it has taken upto ten times to get it completely back into shape. Note also that the heating is of the whole part and not localised. This has not been for flying purposes.

Happy New Year to all and all the best for 2019

By: ZRX61 - 31st December 2018 at 21:04 Permalink

The general idea is you stop heating the part/area when the indicator has changed color, not keep the gas axe pointed at it... so there's no danger of it becoming a puddle. Been using the soap method for 40+ years without issue.

By: stuart gowans - 1st January 2019 at 09:45 Permalink

I use soap from time to time (not in the bath though that's just wrong) but it's worth remembering that not everyone has done this before, and internet "how to's" are easily misunderstood; I find that the working the metal (sheet) in a tactile way you can feel the tension in the metal as it cools and try's to return to it's former shape (you may need gloves for this!)

By: dhfan - 2nd January 2019 at 06:02 Permalink

Do not rely on being able to spot aluminium alloys changing colour when heated because they don't. On my visits to extrusion mills I was told to never touch anything under any circumstances as it could be room temperature, just short of melting point or anywhere between, it never looks any different. I've no experience of casting alloys but I doubt a beginner would be able to detect any colour change and it's not relevant in this case anyway.
The soap method works. I was taught it as an 11 or 12 year old at school 50+ years ago and if kids that age are trusted with it, it's not rocket science.

Assuming it is a heat-treatable alloy, it "should" age-harden to a certain extent afterwards but unfortunately I've no idea how much or how long it would take. I could do with an idea myself as I've got a wavy length of strip I need to flatten.
I did know a bloke who could probably have told me but I haven't seen him for over 30 years and I think he was past retirement age then, or fast approaching it if not.

By: ZRX61 - 2nd January 2019 at 16:03 Permalink

Been 5 days & we still don't know if the part is for a flyer or something aircraft shaped & bolted to the planet.

By: dhfan - 2nd January 2019 at 20:51 Permalink

It would be safest to find out the original material spec first.
Personally, I've no idea about Hurricane wing structure but if it's stamped or pressed from sheet material it's quite possible it's a non-heat-treatable alloy. The soap trick still works but once you've annealed it that's your lot, it stays soft. It would get a bit harder as you straightened it but if it's only slightly distorted, not much.