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Firefly :: Welding Titanium

A wise man once told me (about welding), if it looks good, it is good. He was mostly right. If you assume the things you can’t see, such as: the metal is cleaned and prepped properly, the correct filler rod is used, there is adequate penetration and the weld is properly purged; then yes, if it looks good, it is good…

T.I.G (Tungsten Inert Gas) welding is more than just melting tubes together with an electrical arc, it straddles the line between art, science and dexterity. It requires a steady hand, excellent hand-eye coordination and an intimate understanding of metal in it’s liquid state and how it responds to the world around it, so in other words: experience. When I say “liquid in it’s metal state” you have to take a step back and look the world a little differently. Titanium is solid (essentially a frozen liquid) at room temperature. It becomes liquid above a little over 2000 degrees and quickly re-freezes when the heat is taken away. In it’s liquid state titanium is susceptible to absorbing many of the elements in the air around us and it must be protected. If it is exposed to any of these elements the extremely strong titanium becomes an oxide and becomes brittle, like a combination of chalk and glass. This is not good.

To protect the the titanium in its liquid state we use an inert gas (argon) to surround the weld puddle. The argon gas does not bond with the titanium molecules effectively shielding it from the potentially dangerous atmosphere that surrounds it. The torch, pictured above, has a steady stream of argon slowly blowing out of it, surrounding the weld and the tungsten electrode (the sharpened piece of metal protruding out of the cup). This protects the weld on the outside. To protect it on the inside we fill the frame itself with argon. The argon flows through the frame via a system of purge holes that are drilled in it before assembly. We get the argon into the frame through our heatsinks (all bout our heatsinks here). The tungsten electrode must also be clean and sharp. Any contamination on the electrode can cause the electrical arc to wander and results in a loss of control over the weld bead.

The tubing that we use for our titanium bikes is an aerospace grade alloy called 3al/2.5v. That translates to 94% titanium, 3% aluminum and 2.5% vanadium. This is one of the strongest alloys of titanium available in a seamless tube form and is available in a wide array of diameters and wall thicknesses, making it an ideal alloy for building bicycle frames. The filler rod we use to make the weld bead is actually an even stronger alloy called 6al/4v (6% aluminum and 4% vanadium). We use a stronger alloy for the filler metal because when you heat up the titanium to its liquid state and it cools down to room temperature the grain structure changes and it loses some of its strength.

We built-in purging fixtures into all of the jigs we use to tack weld the cut tubes together. Every time a tube is welded it must be purged. Inside and out.

There are a few ways to weld the tubes together. We employ the “double pass” method. There are two stages to this type of welding. The first stage is laying a root pass. The root pass essentially melts the joint together, sometimes with a little bit of the filler rod and sometimes without any rod at all. Pictured above is a root pass.The root pass serves a couple of functions. First, it guarantees that the tubes are fully welded together with the proper penetration. Secondly, it allows more material to be put in the joints that are deeper so that the proper fillet can be achieved in the second pass, essentially laying the foundation for the final dress bead.

If you look closely at a weld bead you will notice that it is composed of little crescent shapes. Each one of those crescent shapes is where a little bit of the filler rod is dabbed into the liquid puddle. The goal is to dab the rod into the weld at even intervals creating a uniform distance between each bead. Another thing to look for is consistency in the width of the weld beads. the edges of the bead should be parallel to each other throughout the length of the weld.

The color should also be shiny, not just because shiny bikes rule, but because the color represents the metals level of exposure to contaminants. The shinier the better. A little bit of yellowing on the finished bead is also acceptable and is just on the surface.

This post is actually a precursor to the release and unveiling of our first titanium bike. The bike that we built is for a very special event, very far away from Boston and should garner a lot of attention. Per customer request, we are not posting any pictures of the complete frame until the unveiling. We should be able to show pictures of the completed frame sometime next week. We are working on a few more frames right now that we will be posting in our gallery soon, so keep an eye out there.

On a side note, I just want to thank everyone that follows our blog. I am an avid tracker of our analytics and notice all of the attention that it has garnered. So if you like posts like these and want more…

…for up to the minute info on what we are up to be sure to follow us on twitter, for more detailed daily info on the goings-on around Firefly like us on facebook, and continue to be visually aroused by our purely visual tumblr.

13 Responses to Firefly :: Welding Titanium

  1. Joseph Hoffert

    THANK YOU for a great TIG post.

  2. Glenn

    Great job on the blog Tyler and the Ti Weld tech 101
    Looking forward to some Ti goodness soon…

  3. Niall Gengler

    I miss working next to you and watching you flawlessly sharpen 10 electrodes at the same time, lay down the worlds best weld beads and finish TIGing a frame in 15min to perfection!! You are truly ze best. So great to keep tuning in here and see you doin your thing! You rock—- Niall

  4. Michael Murray

    These blogs make my bike that much better. I love the passion and enthusiasm that you have for bike building.

  5. Ryan Coover

    For a guy that has a custom bike addiction, these pictures don’t help with my rehab program…but the good news is that if you do have an addiction – THIS IS THE PLACE TO BE!

  6. Joe

    Amazing! It gets me excited about bikes again. It is funny, i know all this and have witnessed the design and fabrication greatness of Tyler, Jamie and Kev for years but your blogs are artwork too. Well shot, well written…..making us want more. Thanks for making me love bikes, riding, fabrication again.

  7. Jonathan Cooper

    Thanks for the explanantion ….. I am on my second titanium bike – Merlin Extralight – which is an awesome ride and knowing the background to quality Ti is v important…..the Merlin Cielo I had previously was not as stable due to the mix of Carbon and Ti .. beautiful though ..

    Thanks Jon

  8. so nice, so strong, so real.

    I love it. stay on fire.

    Todd.

  9. Yeah, what they said. The bikes are amazing, the blog is amazing. I feel like a fly on the alignment table. Your documentation is superb, not sure I could see the welds better if I was holding the frame in my hands. Truly inspiational! Thank you.

  10. velowood

    Great stuff for us laypeople. Keep it comin…

  11. nice…great write-up! like the chainstay fixture, is that one of jeff B’s rigs?
    doug

  12. The welds at the down tube / bottom bracket shell are just beautiful

  13. Its good to see some one explain the process of root passes, double and triple passes, think this is one of the first times I have seen this post/article out there.

    It seems like a lot of the big Titanium frame builders some times don’t want people to know secrets of titanium welding beauty.

    Good post and from one welder to another the work looks good, keep it going.

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