Weld is vomiting at the end of the process.

admin

Millermatic 175 Mig.Hello all, What would cause my weld to puke a little shaft of metal at the end of the bead.  I was installin some new mufflers on my truck and this was happening.  It took me about 2 hours to weld them on. Before welding,  I grinded down  the spots on the exhaust pipe the best I could thinking that it was clean enough.   Would rust cause this to happen?  I also heard the dirty wire will cause the same thing.  Is their something that I can use to  clean the wire off as it is coming off of the reel.Millermatic 175Miller Sychrowave 180sd
Reply:Without more info, I'm going to guess this was a little volcano like cone that appeared just as you let off the trigger and as the weldment was migrating from molten to solid stage. If you watched real close you could see it magically appear as you watched. I'm also going to guess that you were using solid wire with shielding gas?If so, this is caused by the gases from the weld process trying to escape the weld and getting trapped while the metal solidifies. That can be caused by a couple of things or both.  One would be dirty base metal as you mentioned. Solid wire with shielding gas likes pretty clean metal. The other would by insufficient shielding gas to the weld area. I doubt you have dirty wire. That's generally pretty darn obvious if it is and seldom the case. Think about and check for the two things mentioned above, dirty base metal and insufficient shielding gas."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Yes I was using .035 wire with straight argon.I have my gas turned up to 30.  You described it perfectly.  Maybe I need some new nozzles.  Would the straight argon be causing this?  Is their any more info that you need? ThanksMillermatic 175Miller Sychrowave 180sd
Reply:The argon won't be an issue in this case, other than the cost of straight argon. A flow of 30 cfm is way more than you need and could be turned down a little unless there is a flow problem. That would be something easy to verify. Do a little test welding on some nice clean material with the flow at around 18 to 22 and see if this doesn't go away. If it doesn't then you may have a flow issue, either restriction or leak. Turn the wire speed and voltage down to zip, pull the trigger and you should here the solenoid klick, and hear and feel a slight breeze out of the nozzle.  Normally a flow problem manifests itself throughout the whole bead. Probably just the base metal. Old exhaust is coated on the inside with carbon, rust and crudes. This produces huge amounts of burning smoking gasses from out of the pipe that has to come out somewhere. In this case just grind out and weld over those small end spots. The interior will be sealed off then. Do a quick pass over if you think it needs it. Probably not though. Another thought and most likely contributor is the new muffler. It was likely zinc coated or rust protected in some way. That coating should have been ground off too.  Zinc actually burns and smokes pretty badly which can really pollute a weld. I'll cast my vote on the mufflers coating  if you didn't remove that combined with the smoke from the inside of the exhaust.Try some clean metal. That'll really help prove it out."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Thanks Sandy.  I will give those suggestions a try.Millermatic 175Miller Sychrowave 180sd
Reply:#1 switch to co2 for the mig..... trust me ! and 30cfm your just blowing the sheilding gas away from the weld pool............go to 15cfm b-