Raptor Spindle Gussets

Discussion in 'Ford Raptor Suspension Discussion and Modification' started by Dan06, Oct 18, 2012.

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  1. Aidan

    Aidan Full Access Member

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    Do you have any evidence to support this? I would have to disagree. You'd be right if all stress came from thermal reasons but what about things like phase transformations? For example: we carburize parts. That means that the surfaces have more carbon and are therefore harder than the cores. When you quench this you get two separate causes for residual stress, one that the surface quenches faster than the core and transforms first and the other that it is higher carbon than the core, both lead to high compressive residual stress on the surface.

    I doubt either one would be relieved from taking the part to 0K but would like to see some actual evidence. I could try to do some experimenting at work but we're pretty backed up on residual stress in the first place and I could only get a couple of points (room temp, -120F, and liquid nitrogen ~-304F).
     
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  2. PropDr

    PropDr FRF Addict

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    Any motion is heat; any opposing forces (stress) generate more heat. Any working of metals creates chaotic stresses.
    Removing the heat will slow the motion and opposing forces will relax. As heat is allowed to return stresses build up more uniform (less chaotic)
    If you have a ‘feel’ for metal, get yourself a quality cryo treated blade; hold it in your hand… work the edge… you know the difference.
     
  3. Aidan

    Aidan Full Access Member

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    This is the kind of stuff I mean. I've read a lot of claims about cryogenic treatments improving metal in all kinds of ways but no one has any data to prove it from what I've seen. I haven't seen any data to prove you wrong either. It just doesn't make any sense to me.

    As I mentioned before, cold treating to around -120F does have some well documented benefits. I don't see cryogenics having any more effect though. Using the case of an induction hardened steel, like an axle shaft: only the surface is heated and quenched so you only get martensite transformation on the surface (and some depth as well but not through hardening). The metal crystals transforming to martensite also grow measurably on a microscopic level. This leads to fairly high compressive stresses since the surface layer grew and the core did not (it was not heated enough to transform at all).

    Now bring this steel down to -120F where standard cold treatments are performed. This completes the martensite transformation with any austenite that was left at room temperature, again with a volume increase and some residual stress. This is balanced out by a precipitation of fine eta carbides so as far as I know, you don't see any increases in residual stress when you bring the steel back to room temperature.

    The martensite phase transformation is only temperature dependant but even in the most highly alloyed steels it is complete by the time you reach -120F so you don't get any additional converted retained austenite by going lower.

    Now take that steel down to -340F or even absolute zero. The ferrite/pearlite core of the shaft and the martensite surface both have similar coefficients of thermal expansion so when you go down that low they shrink by comparable amounts. You're still left with those martensite crystals that were bigger than they had space for though and since everything contracted the same, they didn't gain any extra room. So you've still got that residual stress left from the phase transformation.

    I really would like to see anything showing benefits of cryogenics over standard cold treatment but I haven't and I can't think of any mechanisms that would make sense for it. I've heard and read a lot of apocryphal information but nothing with real supporting data. Lots of 'feel' and 'it's always worked' but no proof.
     
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  4. BRONCOBOY1

    BRONCOBOY1 Full Access Member

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    Damn you guys - were not building the space shuttle here. This stuff has been done in the Off Road industry for years go find some one who can handle the welding properly and don't look back.
     
  5. Nv Guy

    Nv Guy Full Access Member

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    Yeah, you break a spindle while off road only you crash. You break a spindle on the highway, slide across the road in front of a school bus or some innocent person & you will wish you looked back.
     
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