How do I deal with this?

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I was building a small aluminum rack for a customer today. Simple design, thin wall 1x1 square tubing for most of it. I tigged it together and each time I tried to finish the last weld on a piece of tubing, it would blow out from the hot air pressure being trapped inside these short (6") sections of tubing, leaving a pinhole that was impossible to close up. I finally drilled some relief holes that would be hidden so I could finish the beads. Is there an easy way to deal with the pressurization? I'm not sure what I would have done if I wasn't able to have the relief holes...Miller Dynasty 200DXMiller 252 Miller 250xMiller Syncrowave 250Miller AEAD200 LegendMiller 375 Xtreme plasmaLincoln WeldPak 100Victor O/A
Reply:Let everything cool a little bit then just quickly close off the last bit of hole and let the puddle quickly solidify. No need to waste time drilling holes usually.Welding/Fab Pics: www.UtahWeld.com
Reply:I tried that, but the small amount of air in the 6" pieces of 1" tubing heated up too quickly. I was thinking of trying to figure out a way to chill part of the tubing somehow while finishing up but I haven't played with it yet.  Originally Posted by MikeGyverLet everything cool a little bit then just quickly close off the last bit of hole and let the puddle quickly solidify. No need to waste time drilling holes usually.
Reply:I've noticed that welding the part with a good amount of heat lets you add heat at the end ,while overall the part is cooling at that moment. Or just drill a hole, I bet Zank doesn't finesse the internal pressure to finish weld his bikes.SqWave 200Millermatic 190Airco 200 ACHypertherm PM45Boice-Crane Band SawVictor O/A
Reply:Yea, I'd drill a hole (just a tiny one will do) or you fight that push of air at the very end...
Reply:If possible then vent the tubes prior to welding.If that isn't an option I've found it easier to seal tubes while the job is nice and hot because at this point the air inside is so hot it has expanded as much as it is ever going to and it doesn't build up much pressure as the final weld is done.Regards Andrew from Oz.We are Tig welders, gravity doesn't worry us.Miller Dynasty 350. 350 amps of awesomeness.OTC AVP 300 hybrid wave AC/DC inverter tig. (now retired)Kemppi MLS 230 amp for home, a sweet little AC/DC Tig