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Thread: Torch Hardening and Annealing Help

  1. #41
    Join Date
    Jan 2004


    Quote Originally Posted by Mcgyver
    Many of the commonly found diagrams would lead one to think its continuous spectrum of colours.
    There are enough to make the difference between what happens and a "continuous spectrum" of interest only to a person who wants to split half-hairs into microns.......

    Quote Originally Posted by Mcgyver
    you know this how?
    By observation..... there does not seem to be a sharp line, there is a "transition region".... Possibly that is due to microscopic interspersed areas changing. Possibly THAT is in turn caused by intermediate temperatures..... that is certainly what it looks like.

    By reasonable good sense..... it is a chemical reaction, so it is some form of equilibrium..... and typically will have some range of conditions over which the equilibrium "tilts" from one to the other..... Can of course be small, but apparently is not, since there is a visible transition region in most cases.

    Quote Originally Posted by Mcgyver
    I gave the ASM temps at which colour changes take place. The weren't to absurd decimal places. The info I presented suggests you will see peacock from around 540 to 590, at around 590 you start to see blue. You don't see some shade half way between peacock and blue at 565 is the point, you see peacock.
    The entire process is not one calculated to give a "slidebar" choice of colors..... that you can get any shade of...... The 8 different varieties you yourself posted is sufficient proof that there is a goodly range of color, never mind the "half and half" intermediates.

    Quote Originally Posted by Mcgyver
    Finally, I didn't mention this fact to go through the 20 pages of dribble and drivel that can happen here, only to encourage the newbie that its not that hard, and don't crazy looking for some specific shade some erroneous spectrum suggests is out there,there only a couple that you'll see.
    There are several, and some gradations of each..... Yellow-brown, purple, blue.......... with gradations of "light straw", "dark straw", etc..... your OWN picture and the H-D plaque picture both show that....

    The ASM list you yourself posted shows 8 different colors or gradations...... Should be enough for anyone, and DEFINITELY not "only a couple that you'll see", as you state in the quote.

    Perhaps, if there are only a "couple" that will be seen, you would like to point out which two of the eight choices in YOUR posted ASM list are the only "couple" you will (ever) see?

  2. #42
    Join Date
    May 2003
    Vancouver's Island


    Pixel mumbo jumbo doesn't cut it, my original appears the same as in my picture.
    "Pixel mumbo jumbo" is the only way to tell what colours are in there. That is why they use paint colour comparators to mix paint. By the time the image reaches your or my screen there isn't nearly the same colour gamut available to represent the colours. The printed colour charts have the same problem. It is entirely impossible to print a colour chart that looks the same as a hot piece of metal.

    Sure your original may appear to have steps but it doesn't look that way because of some sort of stepwise colour change with temperature. To start with there isn't a plausible explanation why it should be so as an inherent property of the metal.

    The colours are a result of progressively thicker oxide layers that act as an interference filter that traps most colors while reflecting on one small range of wavelengths. To produce a stepwise change in the layer thickness would require the formation of crystalline ordered arrays of Fe3O4 oxide molecules that would be far larger than the crystals on which they rest. The crystalline arrays would also have to remain ordered in 3 dimensions, one atop the other through thousands of layers to produce a range of colours. Then the layers thousands of molecules thick would have to avoid forming some thicknesses and prefer others. That simply doesn't happen.

    In reality the oxide layers are amorphous and form through a continuous range of thickness. That means all colours are both possible and present.

    The chances are good that there are colours present that you can't see, the same as most people. Having passed a standard eye colour test means nothing except that you can discern gross differences. The apparent match between the physical part and the image on the screen is entirely due to the adaptability of your eyes and brain. In objective reality, they don't even come close to matching.

    The digital analysis shows without a doubt that all the shades are present in the image and that isn't nearly as smooth as the actual part. If it really was stepwise then the colour curves would have notches dropping to the bottom of the graph.

    Your impression that not all the colours are present is also due in part to a lack of full saturation.

    This diagram below shows the colour gamut for various methods of displaying colour compared to what we can see with our eyes. Of course, the colours in the diagram are not accurate because it is impossible to show them on your screen accurately. It gives only a relative indication of how well colours may be represented. Also, the outside circle which contains the colours that a human can see is an average and does not represent what any one person can see. Any one person will have bumps and hollows around the outside curve that represents how they perceive colour. The RGB gamut is what your monitor can produce, at best. The Pantone gamut is what the best industry standard printing inks can produce and the CMYK gamut is the best your printer can do.

    At any rate, arguments about subjective colour start and end at the same point, the observers brain. No two people see colour exactly the same and no one person sees it the same all the time. Even one's eyes differ in colour perception. That is why colour tests are done one eye at a time. In particular, men have a large variability in the perception of red and green.
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  3. #43
    Join Date
    Mar 2005


    Quote Originally Posted by J Tiers
    Perhaps, if there are only a "couple" that will be seen, you would like to point out which two of the eight choices in YOUR posted ASM list are the only "couple" you will (ever) see?
    Couple was the wrong word, a hand full or finite number would be more exact. Minor semantics though, given i presented both images and list of how many i expect to see. I think they may well vary slightly by alloy, but you'll find a finite number for a given alloy. I found the results interesting when you try to get the progression of the zone of colours over a wide area, combined with the ASM's info contrasted against the rainbow view that appears on the back of say "Hardening and Tempering Engineers Tools" and other publications....again the intent was to simplify not obfuscate so some newbie trying his hand at it wasn't looking for things that don't seem to exist

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