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Thread: Problems with rolling 9ct gold

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  1. #1
    Join Date
    Jun 2017
    Posts
    34

    Default Problems with rolling 9ct gold

    hi, I've been sandcasting gold rings for a while but thought I'd try making some bangles then maybe have a go at making a curb chain.
    I've recently picked up a new rolling mill and Researched the hell out of which way to go about making 9ct yellow gold wire.
    The problem I'm getting is the gold starts to get small cracks after rolling for a while (whilst annealing in between). And I can even snap the gold like a matchstick.
    I've seen so many different ways online of the full process. Which is the best way? Or where am I going wrong?
    I'll list equipment I'm using then process...
    Small kiln with 4oz graphite crusible
    Wire reversable ingot
    Basic rolling mill (unknown make/cost 180)
    9ct scrap yellow gold. (Already melted down 2 times)

    Melt in crusible adding a small amount of borax toward the end
    Heat ingot slightly
    Pour
    Run through the mill as I've read everyone does, closing down slightly each time
    After around anneal until red, leave till red goes away then quench
    Then mill again.

    I have read that hammering down after pour can help but I haven't tried this yet.
    Will try this today.

  2. #2
    Join Date
    Mar 2016
    Location
    Vancouver, Canada
    Posts
    19

    Default

    I'm definitely no expert, but do you need to quench?

    When knife making, quenching hardens the metal and makes it more brittle and prone to snapping. And only done just before finishing stages, after shaping has been completed. It's prior to quench and post-heating that the metal is soft and best for reworking. I don't know if this all translates over to jewelry though, as the properties of gold are much different than steel.

    I hope this helps but maybe best leave this to someone more experienced than me!

  3. #3
    Join Date
    Jun 2017
    Posts
    34

    Default

    Thanks for the reply, just about every video I've watched it's quenched but I'll try still that.
    It's a long process of trial and error but I'll get there

  4. #4
    Join Date
    Dec 2009
    Location
    Central London
    Posts
    8,327

    Default

    And while the wire is fat, reduce the gap more slowly and anneal after two passes.

    One of the problems with annealing wire is that if the flame is too fierce and not moved around a lot some sections will become overheated and too brittle to work. Anneal in a darkened corner and never heat more than dull red, as evenly as possible.

    If your annealing is successful, the wire will feel soft to slight manipulation by hand. Obviously making wire in a mill is not entirely successful and you next need to think about draw plates for the final passes.

    Unfortunately, the heat treatment of ferrous metals is completely different and almost the direct opposite. Dennis.
    Last edited by Dennis; 15-04-2018 at 12:37 PM.

  5. #5
    Join Date
    Jun 2017
    Posts
    34

    Default

    Thanks Dennis. Yes I do have a draw plate set up in a vice ready.
    Maybe it's down to the annealling then.
    I'll try annealling it more often.
    Just to check the way I'm doing it is right...
    I heat the metal with the tip of the flame at one end until red then move along it making the rest red as I go. So not moving the flame side to side.
    Then leave it till the red has gone then 5 seconds or so then quench and roll

  6. #6
    Join Date
    Dec 2009
    Location
    Central London
    Posts
    8,327

    Default

    As said above, the wire is easily overheated in patches and will then break. The point of the flame outside the blue cone is the hottest part, so pull the flame back a little and move it from side to side, to avoid lingering in one place.

    A darkened area allows you to check that the metal only ever goes to dull red and that you have done the whole length evenly. Dennis.

  7. #7
    Join Date
    Jul 2010
    Location
    The Netherlands
    Posts
    415

    Default

    Not an expert here but from my limited metallurgy knowledge here are my thoughts:
    Melting metal too hot will make an unstable brittle ingot that no amount of annealing will solve. Oxygen contamination will produce a brittle ingot. Hammering before rolling is important. Annealing temperture, length of time and type of flame.

    Sent from my SM-T520 using Tapatalk
    Poor old Les

  8. #8
    Join Date
    Jun 2017
    Posts
    34

    Default

    I get most of my gold from eBay. I've seen quite a few people disagree with getting it from there but I test everything before I use it and I've made items before and had them hallmarked in the uk just fine.
    I haven't tried hammering the ingot so I may try this.
    Over melting may be a cause too as I only check the kiln every 20 minutes to see if it's melted enough.
    Oxygen contamination...I know nothing about.

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