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Strength of metals after heating and cooling

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Old 01-20-09, 12:00 PM   #16
ConSynX
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Other than TJ, i'm really confused why this forum is well informed about metals and manufacturing. . .

I was thinking I'd be the first to hit this...but either there is way more MEs on this forum that I thought, or you guys just know your shtuff.
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Old 01-20-09, 12:10 PM   #17
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Quote:
Originally Posted by tjschnei View Post
after spending many years studying mechanical engineering, vipsoarer is quite correct, but depending on how hot the metal gets changes the structure and how you cool it, but again just dont use super cold water, room temperature water should be fine and as long as the shifter isnt super narrow after you bend it, you shouldnt have to worry about it being brittle enough to "shatter" when you shift
Don't forget that in order to turn a metal into martensite you need to fully austenize the metal. I'm not sure that with a small heat up the metal will even reach is austenite stable state. Everybody loves properties of materials!

Just bend the thing!

+1 for MEs, lol
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Old 01-20-09, 12:21 PM   #18
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Without knowing the base alloy of the shifter, we really won't know what the best process is. I would not quench the part if it were me ( and I am a consulting metallurgical engineer with 30+ years of professional experience ) - loss of ductility is not worth the extra strength ( that's assuming the material is alloyed such that it really can attain a martensitic structure upon quenching ). You're better of playing it safe and letting it aircool after heating. This may reduce strength, but will not harm ductility, and I would rather have the ductility ( the part bends, instead of breaking ). I would also recommend using your oven to heat the part and not a torch - this way you'll have better control on what temp you are trying to achieve. Torch heating results in thermal gradients and this will result in residual stresses that are not desirable.

If you could do a hardness test, we would have an idea of how to process the shifter. A file test may suffice, too. If you're looking to do the job the easiest way - use the oven to preheat the part to 300F and then bend. If that does not allow you to bend the part without too much force - reheat to 400F and try again. Good luck.
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Old 01-20-09, 02:27 PM   #19
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teelex, the problem w/ the oven method is that the dampener portion of the shifter is rubber. i'd be afraid of melting that part in the oven.
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Old 01-20-09, 02:50 PM   #20
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I love how many informed people we have on here. Welding engineer here. Most of my suggestions are because the shifter is medium carbon steel and my work is usually done with oxy torches for bending. The dampener can be removed to help bend the part and replaced after the dampener has been trimmed to fit. Craaaazy, try the oven method, if that doesnt work then go torch and lastly try the oxy as we all know that will get the job done. Let us know how it works man.
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Old 01-20-09, 03:03 PM   #21
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Quote:
Originally Posted by TeeLex View Post
loss of ductility is not worth the extra strength ( that's assuming the material is alloyed such that it really can attain a martensitic structure upon quenching ). You're better of playing it safe and letting it aircool after heating. This may reduce strength, but will not harm ductility, and I would rather have the ductility ( the part bends, instead of breaking ).
Took the words out of my mouth. The same reason I said you are giving it the chance to break. The minimal gains of adding that extra tad of strength that you don't even need does not offset what could happen if it backfires on you on day. Good post.
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Old 01-20-09, 03:13 PM   #22
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After some thought ( and assuming the shifter is made from a medium carbon steel ), I would say that the risk of forming untempered martensite is low unless you get the shifter really hot ( above 1450F ). Thus, if you don't get the shifter cherry red ( about 1300-1400F ), you will not 're-harden' the alloy ( form the martensite ). What you will do is potentially 'temper' back the hardness/strength somewhat.

The oven method would be best for controlling temp, but your concern about the rubber degrading is understood ( I don't think you'll melt it, but it could deform or degradate the rubber ). So you could try the torch method and avoid getting it too hot ( don't let it get cherry red ), and just let it air cool to room temp.
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Old 01-20-09, 03:39 PM   #23
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dunk it in used motor oil, NOT WHEN ITS GLOWING ... BUT a few seconds thereafter.

i was told by a real "blacksmith" that, that is what old school rat rodders do for forging and increasing the strength of suspension parts the modify...

my $.02
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Old 01-20-09, 07:04 PM   #24
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vip, i've removed the dampener before in an old r154 shifter and it's not quite so easy. i can probably put it back together using some epoxy. i'll probably try the propane torch method as it'll be easier and let it air cool.
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Old 01-20-09, 07:22 PM   #25
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good input guys.

JDMparts: Thats exactly where I learned the methods... well before schooling. Old school way of bending shifters and split wishbones.

craaaazzy: the dampener, i have found, doesnt do too much. Its mostly to give the shift boot some girth IMO as it doesnt feel too different from having it on or off, but thats up to you. good luck!
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Old 01-20-09, 07:22 PM
 
 
 
 
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