Skip to main content Skip to navigation
Hydrogen Properties for Energy Research (HYPER) Lab nathaniel.j.jones

Extruding Indium Wire

We use indium wire for creating cryogenic seals in the HYPER lab. We buy most of our wire from Indium Wire Extrusion (IWE). Indium is expensive however, quoted by IWE at $180/oz. Rather than selling the wire back for half its original price, we like to recycle our indium by melting it down and re-extruding it into usable indium wire. Indium’s low melting point of 156.6 °C (313.9 °F) and softness (Mohs hardness 1.2) make this process cheap and easy. We have the capability of extruding 0.0625 inch (1.5875 mm) and 0.1 inch (2.54 mm) diameter indium wire with the equipment we have in the lab.

20160707_123729_HDR
A 13.6 oz. block of indium worth $2,450.

The following article provides an easy-to-follow guide to the HYPER lab’s indium extrusion process. The hope is that this guide will serve as training for those working in the HYPER lab, as well as a good starting point for others who would wish to extrude indium for cryogenic applications.

 

20160708_103308_HDR
HYPER’s extruder setup.

 

MATERIALS:

  • Hydraulic extruder
  • Hot plate capable of at least 200 °C (the higher the better)
  • Flat copper plate
  • Puck cast mold sized for extrusion chamber
  • Indium scrap
  • Empty spool
  • Metal bin with 2-3 inches water for quenching
  • 3/8″ Hex key
  • Hammer
  • Metal shaft with diameter smaller than puck diameter
  • Slip-joint adjustable pliers
  • Retractable blade knife
  • Large pipe wrench
  • 2 wood or metal blocks of the same size

 

STEPS:

  1. Gather indium scrap. Make sure scrap pieces are small enough to fit into puck mold.

    Indium scraps in a cup and in the puck mold. Notice the puck mold is placed on top of a copper plate.
    Indium scraps in a cup and in the puck mold. Notice the puck mold is placed on top of a copper plate.
  2. Place copper plate onto hot plate. Place puck mold onto copper plate.
  3. Heat the hot plate to around 250 °C (or higher for faster melt).
  4. Put indium scrap into mold and wait for indium to melt. For faster melting, push indium down into the mold.
  5. While waiting for indium to melt, extruder can be assembled. The assembly consists of three parts: die, die holder, and extrusion chamber. Begin by placing the die into the die holder.

    20160706_152637_HDR
    From left to right: Extrusion chamber, die, die holder.
  6. Screw the extrusion chamber into the die holder.
  7. Bolt the assembly onto the end block of the hydraulic extruder.

    20160706_153825_HDR
    The completed assembly attached to the end block.
  8. Once indium has begun to melt, it will fill the mold cavity. At this point, add more indium scrap until the mold is full.

    20160706_161106_HDR
    Melted indium.
  9. Using the adjustable pliers, grab the hot copper plate (with mold on top) and dip plate, mold, and indium into the water to quickly cool the assembly. You may now turn off the hot plate.

    20160706_161142_HDR
    Quenching.
  10. Once water has stopped boiling and making sure all parts of the assembly have been cooled, take the assembly back out of the water.
  11. Placing the mold with indium stuck inside it onto two wood or metal blocks, use a hammer and shaft to knock the indium out of the mold.

    Here’s one way to get the indium out…
  12. Cut off impurities using the retractable blade knife.
    20160706_161741_HDR20160706_161901_HDR (2)
  13. Place indium puck into extruding chamber of extruder. Place the metal spacer behind it.

    20160706_161935_HDR
    Indium puck inserted in the extrusion chamber (without metal spacer).
  14. Turn on the hydraulic extruder by opening the compressed air valve and set it to ‘EXTEND.’ Then get ready on the output end of the extruder with the empty spool. It is best to have two people for this task: one controlling the extruder, one spooling.
    20160708_103330_HDR (2)
  15. Wait until the plunger reaches the indium and indium wire begins to emanate from the output end of the extruder. Be prepared, since wire will come out at high speed.
    20160706_162201_HDR (2)20160706_162326_HDR (2)20160706_162357_HDR (2)
  16. As wire emanates from the output end, wrap it around the spool while keeping a small amount of tension on the extruding indium.
  17. When you hear the hydraulics begin working harder than they were initially, set the extruder to ‘RETRACT.’ When you hear this sound, the plunger is trying to extrude the metal spacer.
  18. Break the end of the indium wire away from the extrusion outlet. You should now have a nice spool of indium wire.

    20160706_162415_HDR
    The final product.
  19. Disassemble the extrusion assembly in order to remove the metal plunger. At this point a large pipe wrench will likely be necessary to unscrew the extrusion chamber from the end block. The remaining indium can be left in the extrusion die until the next extrusion.
Washington State University