Heat-welding of Wire Rings

Thanks to new metallographic research, such as that presented by leading researchers in the field of arms and armour, Dr. Alan Williams and Mr. David Edge at the annual Arms and Armour Study Days at the Wallace Collection Museum in London, there is little doubt now that at least some of the solid rings found in "European" maille garments were heat-welded, and not punched from sheet metal.

While the evidence seems quite clear now, the practicalities of actually welding wire may still seem daunting.

I set out to attempt to weld wire rings together, using heat and pressure.  I do not have access to a forge, therefore I used a standard propane torch.  Propane can burns as high as 3600 degrees Fahrenheit, and as it turns out burns plenty hot enough to weld mild steel wire.  Though my torch is certainly a modern heat source, I do not see any problems with using a forge to supply the heat.  The ring could either be thrust directly into the forge fire with tongs, or the heat from a furnace could be directed into chimney into which the ring could be thrust.

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Standard propane torch.  Click to enlarge.

Up until this experiment, I had never tried to forge weld metal.  I had seen it done, however, and it was done using heat from a forge and a hammer.  The heat excites the atoms of the iron and the hammer supplies the pressure to get the atoms from each piece of iron close enough together to permanently weld together.

I first attempted to use a hammer to forge weld the wire rings as well.  Unfortunately, even moving as quickly as I could, I could not get the ring onto a flat steady surface and strike it with a hammer before the ring became too cool to weld.  This was compounded by the fact that the steady flat surface, being a nice cool anvil, readily sucked the heat out of the ring.

Rather than use a hammer to supply the welding pressure, I decided to try tongs.  It worked perfectly.

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Pliers and overlapped rings.  Click to enlarge.

I used a small set of pliers to hold the ring in the fire.  I grasped the ring on the opposite site of the area to be welded - the overlap:

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Ring gripped opposite from overlap.  Click to enlarge.

My pliers are quite short and stubby.  There is no reason why they could not be long, like long needle-nose pliers.  Such long pliers would no doubt be useful for inserting rings into a hot furnace fire, keeping ones hands away from the intense heat.  Because the flame from my propane torch is nicely localized, such long pliers were not necessary for me.

The next step is to heat the ring a bit so that the fluxing agent will stick to it:

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Pre-heating the ring before fluxing.  Click to enlarge.

The fluxing agent is simply "Mule Team 20" Borax.  It can be found at any grocery store in the laundry detergent section.  Here you can see the box of borax and the small container I have ready for running the ring through:

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Mule Team 20 Borax.  Click to enlarge.

Now that the ring has been warmed up, insert it into the borax.  The borax will stick to the hot ring:

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Fluxing the ring.  Click to enlarge.

Flux is important during forge welding, because it helps to exclude oxygen from the surfaces you are trying to weld together.  If the iron surfaces are exposed to oxygen they will prefer to bond with those oxygen atoms rather than the iron atoms of each other.  This is why when you heat iron in fire a black, scaly oxide forms.  This oxide can make welding difficult or impossible.  

Medieval wrought iron contained large amounts of impurities known as "slag".  Slag was made up of, among other things, silicates.  These silicates melt at a temperature below the welding temperature of iron.  This is helpful because as you heat a wrought iron object up to welding temperature the molten slag acts as a built-in fluxing agent.  

However, my low-carbon steel wire, with the aid of the borax flux, welded just fine, even though modern steel lacks the slag impurities of medieval steel.

After the ring has been fluxed, it is thrust back into the flame and brought to a welding temperature.  I simply allowed it to get as hot as it could in the propane flame:

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Heating to welding temperature.  Click to enlarge.

I was holding the ring with the small pliers in my left hand.  In my right hand I had a larger set of tongs at the ready to squeeze the ring overlap as soon as I removed it from the flame.  The picture below shows how this is done, though the ring is not hot at this point as I could not hold both pliers with both hands, play with fire, and take the picture at the same time.  To perform the actual weld, obviously, the ring overlap is squeezed while the ring is still at welding temperature:

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Squeezing the overlap to weld.  Click to enlarge.

For this experiment, I welded 4 rings:

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Welded rings.  Notice flux residue.  Click to enlarge.

Notice in the above picture the black shiny residue left around the weld area.  This is what is left of the flux.  Once the molten borax solidifies it turns into a shiny black glass-like substance.  This can be chipped off or dissolved in water.  I used the same tongs I used for forming the weld and gently crushed the solidified borax under running water.  This caused it to shatter and rinse off easily, revealing clean gray metal around the weld area:

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Welded rings.  Notice clean metal after removal of flux.  10X magnification.  Click to enlarge.

To ensure that the ring had actually welded, I twisted the ring with two pairs of pliers.  The weld held and seems quite strong:

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Twisting the ring to test strength (left); close-up (10X) of weld (right).  Click to enlarge.

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60X view of the weld.  Click to enlarge.

So, as this experiment shows, it is quite possible to heat-weld steel wire rings.

 

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