Should it be this hard?

Date 07-30-2003 20:04

Hi,
What size wire are you using? I've worked on quite a few exhaust systems (usually old and rusty) - I use .035 wire, 75/25 Ar/Co2, Millermatic 200 - almost always "trigger" the weld right on the center of the joint until I have enough build-up to actually run a weaved bead on the joint. If you are triggering the gun correctly you can walk it right around the joint. Haven't ever had a problem with this on thin gauge material as far as soundness - in fact it is an accepted practice where there are gaps to big to run a bead on 16 to 20 gauge where I was employed for 23 years. Takes a little practice though - I have seen it done where it looks very nice and is structural on our product. Is the machine as low as you can set it and still get the base metal / filler to melt?
Brian

By jwright650 (*****)

Date 07-30-2003 20:47

I've also used .030"FCAW-S on exhaust pipes and usually do fairly well. Hardly burn through at all even with flux core that digs deep. Gotta move, can't hang around in one spot very long, weaving helps if the joint is not fit up tight. Key is to move along and keep your current / wire speed set low, but use enough to still melt the base metal.
John Wright

By bzzzzzzzzzz (**)

Date 07-30-2003 21:38

Mine was old and rusty no doubt. The tacks go down ok, but when I run the bead it just wants to burn through. When you mention "triggering" the gun are you talking about laying a series of overlapping fish scales at a right angle to the seam or is movement parallel to the joint. Do you stop often to allow it to cool or just one continuous movement. I'm using .030 wire. I really haven't used a stop/go motion to deal with heat build-up, except for filling holes. The holes always fill in ok, but to do it I wind up with a huge tit of metal where the burn through occurred.

By flashburner1 (*)

Date 07-30-2003 23:00

Triggering would be like placing many tacks - instead of moving a distance from the previous tack you only move about 1/8" from the previous tack and lay a new tack overlapping the previous tack. You have to watch the color of the metal so you don't blow through, but do it fast enough so that you are able to get the base metal hot enough to get penetration, so it is not really one continuous movement, rather a series of small movements. Squeeze your trigger for a second or two, move a little bit and do it again. Travel is the same as it would be if you were able to run a bead, but you might have to build up on one or both side(s) of the joint a little before you get enough thickness to actually sustain an arc for more than a second or two. You will probably not get rid of the huge blob on rusty exhaust pipe, but after you have triggered enough filler metal in so that you have some actual metal there, you can run another pass on top of it to smooth it out.

By RonG

Date 07-30-2003 23:02

I believe by triggering he means rapid on and off almost to the point you are make a chain of tack welds. You can do that from side to side or straight down the seam.

This may sound off the wall but when I have a similar situation I try to do it down hill.

By flashburner1 (*)

Date 07-30-2003 23:05

Yes Ron,
Downhill as much as possible.

By bzzzzzzzzzz (**)

Date 07-30-2003 23:13

I'll give some of these techiques a try as I have some more exhaust pipe to weld. Thanks.

By DavidP66 (*)

Date 07-31-2003 19:24

When i used to weld on thin metals. Sometimes in cases like yours where it wants to burn through all too often. I get a separate filler rod and use it to add some metal if it starts to want to blow through. It helps on building up metal, and will act as a coolant at the same time. It takes some practice. Its like TIG'ing and MIG'ing at the same time. I think some people refer to this as "Japanese Arc Welding" :)

David

By RonG

Date 07-31-2003 20:57

BZZZZZZZ,
Keep in mind rust dose not weld. By that I mean rust will not melt and most of the time it will not even conduct electricty.

Most of the time thats where your holes come from. You are better off to get rid of it befor you attempt to weld (a SS wire buffing wheel will work very well). Take time to patch bad areas befor you try to close the zipper.