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Thread: Monel or Stainless?

  1. #1
    Join Date
    Apr 1999
    Location
    Rock Hall, MD
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    I've got some hunks of metel that I picked up at a scrape yard that specializes in the more exotic metals. The guy at the scrapyard told me that the pile I grabbed them from contained some stainless steel and some monel. They all look like stainless to me, but I just looked at some metal in our shop here at work that I know is monel and it looks just like stainless steel. Does anyone know an easy way to tell stainless from monel?

  2. #2
    Join Date
    Jan 2001
    Location
    Stuart, Florida
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    The following is derived from ASTM STP 550 “Nondestructive Rapid Identification of Metals and Alloys by Spot Test”. Langley Research Center originally documented these procedures.

    Start with a magnet test:

    Magnetic: 400 series SS, 17-4 PH, Monel
    Slightly magnetic: Cold worked 301, 17-7 PH
    Nonmagnetic: 300 series SS, 17-7 PH, Nonmagnetic Monel

    If Magnetic:
    1 drop 1:1 nitric acid and water, observe after 5 minutes
    No reaction indicates 400 series SS or 17-4 PH
    If bright green, add 1 drop concentrated ammonium hydroxide
    Blue color indicates Monel

    If Nonmagnetic:
    1 drop concentrated nitric acid
    Reaction indicates nonmagnetic Monel
    No reaction indicates 300 series SS or 17-7 PH

  3. #3
    Join Date
    Oct 2002
    Location
    westbrook, ct, usa
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    70

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    Monel has a high copper content along with the nickel and chromium. In my finishing shop when we electropolish monel to achieve a bright finish we can only process it for approx 1/4 the time of any 300 series s/s or else the monel begins to get duller in relation to the lentgh of time it is electropolished. What occurs is that the copper comes to the surface under reverse current in electropolishing. Visually, monel and 300 series look identical before any surface finishing.

  4. #4
    Join Date
    Dec 1999
    Location
    Brooksville, Florida, USA
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    Ross

    are there any tests to determine copper alloy in ASTM? I specifically would like to know tests for brass, tin-bronze, silicon-bronze and manganese-bronze.

    /// Frank ///

  5. #5
    Join Date
    Jan 2001
    Location
    Stuart, Florida
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    It does, in fact…

    First separate by color:

    Reddish or red brown color: Coppers, Berylco 50, Berylco 10
    Dark yellow color: Bronzes, beryllium copper, red brass
    Light yellow: Brasses, silver solder, manganese bronze

    For Dark Yellow Colors:

    2 Drops concentrated Nitric Acid (sp gr 1.42, by the way)
    After 2 minutes add 2 drops watebr /> White precipitate: Tin bronze, high leaded tin bronze, phosphor bronze;
    Oily drop with white precipitate: Silicon bronze, oil impregnated bronze
    No precipitate: Beryllium copper, aluminum bronze, red brass

    If white precipitate:
    1 drop ferric chloride, observe after 1 minute
    Black spot: Phosphor bronze
    No black spot: Tin bronze, high leaded tin bronze

    For Light Yellow Colors:

    3 drops concentrated nitric acid on surface, after 2 minutes transfer 1 drop to porcelain spot plate and add 1 drop sodium bismuthate solution (3.5 grams sodium bismuthate mixed with 60 milliliters of water)
    Purple color: Manganese bronze
    Black color: Silver solder (requires further confirmation tests)
    Brown color: Brasses - QQ-B-626B, QQ-B-613B, yellow, admiralty, naval or aluminum

    Hope you find this helpful!

    Ross

    [ 02-22-2003, 02:15 PM: Message edited by: Ross McDonough ]

  6. #6
    Join Date
    Dec 1999
    Location
    Brooksville, Florida, USA
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    Ross

    Thanks! Now I will have to find a source for reagents.

    /// Frank ///

  7. #7
    Join Date
    May 1999
    Location
    Lake City, MN
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    Spark test, monel will give you an orange spark more so than stainless. If you know you have both it will be easy to see the difference when touched to a grinder. So says an old machinist, me.

    Gary
    "The hand feeds the mind."
    Weston Farmer

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