This weekend I was at the shop hanging some new parts on the show bike.  Yes it’s back, no you can’t see pictures yet .  I figured since I didn’t have any tubes, I would just practice weld instead.  There’s always a good assortment of steel tubes to weld because 99% of seat tubes are trimmed to length.  For the last few months I’ve been hording  decent length titanium cutoffs like gold.  I hope to build a ti road bike for myself once the dust settles from the NAHBS rodeo.  I only had enough tubing for three joints, but I think there’s a few more around the shop. 

I was truly shocked at how different titanium behaves in all facets of construction.  It machines differently, cleans up differently, and welds differently than steel.  All things I’ve heard time and time again, but sometimes you’ve got to experience it. 

The other day, Carl was explaining why he liked to weld titanium because it’s not as hot.  I didn’t really have a frame of reference at the time, but I did know that steel can get pretty hot.  When welding a frame, you rest your hand on one of the tubes to steady the torch.  Ideally you want to make fairly long passes to avoid starts and stops, which cosmetically don’t look so hot.  At the same time, the torch must move at a rate of speed which allows the metal to cool before advancing too far out of the argon coverage zone.  When making a really long pass it’s more of a pain threshold test because your palm is heating up.  However on ti, you can bring a sack lunch and camp out because it doesn’t conduct as much heat.  I’ve only done a few titanium joints, but I’m already hooked.

Below is a  picture of the fusion pass.  This pass uses little to no filler rod.

This is the dress pass.  Filler rod is used here to alleviate any undercut and ensure a strong joint.  In short, two passes are chosen because titanium doesn’t weaken from multiple heating/cooling cycles.

Why say it again, when you’ve got this explianaiton of double pass welding http://www.strongframes.com/blog/?p=3391