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Tips for mig welding exhaust tubing by zkhennings
Started on: 07-26-2013 11:01 AM
Replies: 8 (6776 views)
Last post by: fieroguru on 07-26-2013 06:02 PM
zkhennings
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Report this Post07-26-2013 11:01 AM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
So I am mig welding some exhaust tubing and I was wondering if anyone has any tips or tricks.

At the moment this is my process / equipment:

I have a 170 amp 220 volt mig with C25 gas and .023" wire. I am welding mild steel 16ga tubing, butt joining the sections.

I currently bevel the edges of the tube and make sure I have a nice fitment and there are no gaps. I tack weld the tubing at 4 locations.

I can put down a pretty nice bead, but after around 1.5 inches I have to stop and reposition the tubing and when I start up again, all the areas I overlap my old weld look really ugly. Also I am having trouble keeping the torch at the same angle to the tube as I move along it. I am currently sitting down while I weld and welding on a table with the piece sitting on the table. I don't have sealing problems or anything, I just want it to look really nice and not have to grind down the ugly sections where the welds overlap.

I am open to any tips or advice, I know it is recommended to stitch weld but I hate stitch welding I like putting down a nice flat bead I use a little looping motion as I weld.
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Arns85GT
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Report this Post07-26-2013 11:57 AM Click Here to See the Profile for Arns85GTClick Here to Email Arns85GTSend a Private Message to Arns85GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I can relate. I trained myself to weld, while fabricating headers. (yeah I do things the hard way)

I have found, ultimately, that stitch welding is superior. You don't want the pipe to heat up as you go, and you can get good penetration using stitches.

The drawback is that you don't get a nice even flow initially and you will likely want to grind the joints smooth.

In my case, I didn't, but, I was coating the work with black ceramic so looks didn't matter so much.

Hope this helps

Arn

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fieroguru
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Report this Post07-26-2013 12:22 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have a 220V Lincoln welder. For 16ga exhaust, I use .030 wire, with the heat 1 range hotter than normal. The pipes need to be tight, but I do not bevel the edges. I spot weld the entire joint with a slight overlap between spot welds. So pull the trigger, count 1-2 seconds, release, move about 3/16 to 1/4 inch and do it again... all the way around.

The hotter heat provides quick penetration and a flatter/wider weld bead, but you have to stop quickly or you will blow through.

Using this method you can make your welds look similar to a row of dimes... just takes practice and patience.
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tesmith66
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Report this Post07-26-2013 12:28 PM Click Here to See the Profile for tesmith66Send a Private Message to tesmith66Edit/Delete MessageReply w/QuoteDirect Link to This Post
That's how I do it, too.
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zkhennings
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Report this Post07-26-2013 02:38 PM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yea I guess I will try it... it just looks reeeaaalllllyyy nice when you get a good bead going and I love that look. I will take some pics soon.
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fastblack
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Report this Post07-26-2013 05:20 PM Click Here to See the Profile for fastblackSend a Private Message to fastblackEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:

I have a 220V Lincoln welder. For 16ga exhaust, I use .030 wire, with the heat 1 range hotter than normal. The pipes need to be tight, but I do not bevel the edges. I spot weld the entire joint with a slight overlap between spot welds. So pull the trigger, count 1-2 seconds, release, move about 3/16 to 1/4 inch and do it again... all the way around.

The hotter heat provides quick penetration and a flatter/wider weld bead, but you have to stop quickly or you will blow through.

Using this method you can make your welds look similar to a row of dimes... just takes practice and patience.


^^ This.

Done right it can look just like you laid down a continuous bead.
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rourke_87_T-Top
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Report this Post07-26-2013 05:40 PM Click Here to See the Profile for rourke_87_T-TopClick Here to Email rourke_87_T-TopSend a Private Message to rourke_87_T-TopEdit/Delete MessageReply w/QuoteDirect Link to This Post
Anyone used a MIG to do thin wall T-304 ?

The reason I'm asking is I bought a Lincoln 140 last year, I know an experienced welder that told me it is possible to do it with a MIG so I did some research, I just bought a spot timer kit, allows the gas to come sooner, high heat and short duration I bought a small bottle of tri-mix and a spool of .025" 308 SLI wire, I'm going to stitch it together.

I'm not doing headers, just from my downpipe, V-Band, 90*, Cat and a Borla system.
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fieroguru
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Report this Post07-26-2013 05:43 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
The weld bead at the Y section of the pipe was done with a series of hot tack welds (I will see if I have some other pictures, I grind most welds smooth on the visible sections of the exhaust):
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fieroguru
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Report this Post07-26-2013 06:02 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by rourke_87_T-Top:

Anyone used a MIG to do thin wall T-304 ?


The exhaust on my LS4/F40 swap was 16ga 409 stainless and I mig'd all of it. The stainless wire flows a little different than mild steel, but you get used to it pretty quick. Its best to back purge (tape the ends and fill with shielding gas) stainless as well.
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