[Jewelry making - Article 00537] - Re: [Orchid] Casting Steel?

[Sebastien Bailard]

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Allen,

    I had crossposted the initial question to the hobbicast  AT 
    yahoogroups forum. Here is Doug Allen's reply of how he does it,
    which I found quite informative: 

          As a knifemaker, blacksmith, and, yes, hobbycaster, I have
          fiddled a bit with steel casting. It is quite possible to do,
          even on a small scale, but you'll have a few more isues to deal
          with compared with the more usual aluminum and brass casting. 

          First off, you'll need to figure out what kind of steel to
          use. There are literally thousands, ranging from sible low
          carbon plain steels, almost purely iron with only a few trace
          elements to high-speed complex alloys, where iron plays second
          fiddle to vanadium, chromium, cobolt, and other exotics. 

          I cast a simple stainless steel, 304 I believe, for a guard,
          but I have also done a bit of wootz experementation (wootz is a
          high-carbon semi-cast steel that has pronounced carbon
          dentricles which make a wonderfu "watered silk" pattern in the
          final pie) and have studied enough ferrous metalurgy that I
          feel comfortable expanding beyond what I've actually done. 

          Iron has a great afinity for carbon, and the more carbon there
          in in a steel, vice other alloying agents, the lower the
          melting temperature. Hence, cast iron is easier to ast than
          pure iron, as it is several hundred degrees lower in
          temperature when poured -- hence the popularity to this day for
          cast iron of around 3-4% carbon. Most high carbon steel, such
          as used for knives, is around 1%, and most low carbon is
          around .1% (think car bodies and other sheet steels that will
          be deeply deformed during fabrication). 

          One aspect of this carbon affinity is that the longer it sits
          in contact with carbon, such as a clay-graphite crucible, the
          more carbon it will dissolve out, both changing the carbon
          content and lowering the temperature of the melt. But carbon
          can also be burned out, so if you leave it exposed while molten
          to an oxidizing atmosphere, you'll end up with carbon loss. 

          So, first you'll need a setup that can get your melt
          relatively quickly to the pour temperature, while keeping the
          steel away from atmosphere. For this, I used a small silicon
          carbide crucible with my steel stacked inside, along with some
          borax as a flux, and the whole thing sealed with a bit of
          kaowool and furnace cement, with a small hole (about 1 mm) left
          to prevent gas build up. To get it hot, I used a propane
          forge, blown, which I sealed up except for a small exit vent.
          This is similar to what I used for my wootz experements, and
          which I've seen other smiths use for various steel castings and
          wootz ingot melts. 

          To cast, I used an oil-bonded sand mold (commercial petrobond
          from our Sponsor) with plenty of sprue, venting, and so on --
          molten steel is incandescantly ho, and the oil bonded sand does
          produce a bit of smoke and outgassing. In fact, if I were to do
          steel casting in any quantity, I'd go with ceramic shell or
          greensand (bentonite based)to avoid the whole smoke and stink
          issue. 

          Even in thermonuclear toaster such as my forge it takes a
          while to melt. I had about a pound of steel, and iirc it took a
          good couple of hours before it just sloshed when shook -- for
          quite a while I could hear/feel a lump of something floating in
          the melt. 

          When you open the crucible, be prepared for sparks. Even with
          the low-carbon there was quite the sparkler effect when
          pouring, and at a demo where we had a crucible break during a
          wootz smelt it looked like quite the fireworks display. Use a
          fqaceshield, heat-resistant clothing, and all other precautions
          when dealing with molten, buring, hot stuff. 

          Also keep in mind, if you're going to be casting high carbon
          steel, that if it cools too fast, it may shatter under the
          stresses. OTOH, if you cool steel down too slow you'll get a
          lot of grain growth, which can only be removed by forging or
          really painstaiking heat treatment.

    Casting steel seems to be a lot more challenging than bronze or
    silver; I've decided to put the idea on hold for a while until I have
    more experience. (Unreleated but cool aside: casting a pewter stool
    at the beach: 

    http://www.pingmag.jp/2006/11/10/tokyo-design-week-2006-report 

    Regarding finding someone to cast your design, I don't know. I would
    check your local dental labs and blacksmiths. There may be forums or
    websites where you could put the job up for a bid; I would ask for
    leads to such job boards heRe: http://www.anvilfire.com/slacktub/ and
    maybe ask the moderator of the internetdentalforum.net Tim Lane,
    although I'm not sure if that's a particularly good way of looking
    into it. 

    You'll probably have more success asking the swordsmith Rick Barrett,
    who did the legwork for this when he found someone to cast the steel
    pommel for his sword LongClaw:

    http://www.barrettcustomknives.com/contemp_1 

I'll forward your email to him.

Regards,
Sebastien Bailard
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