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How To Knowl If Metal Is Stainless

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  • #16
    Copper sulphate solution will leave a copper deposit on iron and steel, but probably not on stainless steel.


    • #17
      Most stainless I have tried is atleast very lightly magnetic. I use rare earth (neodymium magnets) pressed into mold plates to hold various wire inserts in place for castings. A cheap magnet may have no noticeable magnetic affect, but a good quality neodymium will have enough pull to hold a thin wire in a half wire thickness slot until the mold is closed. There may be some stainless that is zero magnetic, but I have not run across it.

      X-ray guns will give you most of the composition of the alloy, but its my understanding that they do not give you any idea of the carbon content.
      Bob La Londe
      Professional Hack, Hobbyist, Wannabe, Shade Tree, Button Pushing, Not a "Real" machinist​
      I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.


      • #18
        you can also do a spark test on a bench grinder. Sometimes that can get you in the right ball park.


        • #19
          Originally posted by dmartin View Post
          I will go ahead and degrease one,sand it, wet it and check it in a few days. Thanks
          Testing with cold blue as mentioned above is a much faster and more reliable test. Looking for a little bit of surface rust on a wetted part doesn't tell you for sure, some "stainless" gun barrels rust more than you'd expect. With cold blue, you'll know for sure in less than a minute. If you work on guns, you should have some anyway.


          • #20
            I think a magnetic test would be unlikely to show the difference.
            A rifle barrel would most likely be of a martensitic stainless steel which has been hardened and back tempered.
            The crystal structure of martensite is ferro-magnetic.

            An austenitic stainless has a crystal structure which is non ferro-magnetic.
            Austenitic stainless is tough, and softer with lower fatigue endurance compared to low-alloy carbon steels.

            A complication is that austenitic stainless can become slightly magnetic with work hardening,
            for example I have seen roll-formed threaded fasteners of austenitic stainless which attacted a magnet ( weakly).