Technical Welding Help

I'm welding up a bunch of old header pipes to make a header that will fit. I cut the pieces, tack them with MiG, and then do the final welding with gas. Some of the welds (most of them) look like crap - I only weld stuff about once every eight to ten years. Can I "dress" these welds by brass brazing over them?
Dick J

 

Dick, are the header pipes just plain mild steel? Can you post some pictures?

 

You'd be better off spending some time practicing welding spare scrap tube segments together, till you get the hang of it. It's not that hard, I just made my first set of headers, doing the same thing--fit the tubes well, tacked them with the mig in 3 places. ground down the tack welds, then welded them with the torch. Fit is important. Clean bare metal welds better than rusty dirty metal, too. Sand the crap off the ends first.

 

Agreed with above. If they are a bit crappy you might want to clean the welding areas with a satainless brush and MIG them using a string of "tacks". This may work a bit better using straight Argon but the Argon/CO2 mix will be fine. Sandy Belond, the original header builder used to dress his headers with brass and they looked and survived great. There are a bunch of threads on here that show it done and here's some I built a while back, MIG and gas.

http://s861.photobucket.com/user/larrykoz1/media/NEED TO BE SORTED/100_0476.jpg.html

 

Also agree with the above. Tack them with about 1/16" space so you get good penetration.(assuming your are MIG welding) Then do stitch welds...hit the trigger about 5 times or about a quarter of the circumference of the tube. Finish the welds with an angle die grinder and about a 40 grit disc just before you hit the parent metal, then finish with about an 80 grit. If you want to get crazy, you can file them as the last step. Good luck!

 

If you add the brass it might work but that will interfere with future welding with MIG or TIG or stick.
The brass must be removed to use other forms of welding.

 

I try to get a gap about half the thickness of the metal, when welding with a torch. This is what my first header looked like. I brazed the tubes to the flange, and gas welded the tube segments, and the collector.

 

I would not braze over the gas welds. Its not very strong, and will most likely crack and prevent any future weld repairs. Practice on some scrap tubing, using good welding rod. Clean the joint well and get a good neutral flame. Use a small tip, like a 0, shouldn't need more than that with exhaust tubing.

 

Practice, practice,practice , 00 tip neutral flame clean material , no gap and no filler(maybe a touch but not much) !

 

Im with Snaptwo. No gap and little to no filler. Working on a set of headers for my S2D. I tacked with the torch in 2-3 spots then welded it, no mig at all. Clean Clean Clean on the metal
metal

and I brazed a fillet on the flanges too, this should prevent any cracking and remove the need to repair.

 

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If you have rusty metal, run it across a wire brush on the bench grnder. If you have new metal with a galvanized coating, do the same hard enough to remove the galvanizing in th elast 1/2 inch. Fit th etwo together and tack in two or three places, then gas weld with no filler. Contrary to what one guy above said about brass, a good braze is about a 60,000 pound connection, or the same as a fair gas weld. For filling little holes, and adding stregth, brazing is good. Hard to paint over though. Furnace brazing looks glorious on headers.

 

And don't forget to pinch and weld the tube ends before welding on the collectors.

 

Butt welding with a torch with no gap doesn't guarantee that you'll get full penetration with the weld. I guess it's ok on headers, there's not much load on the tubes. Just something to consider.

 

Question for those that are re-enforcing the weld on the flange with braze on the outside --- How do you avoid any warpage to the flange?

Have Sanderson headers that are welded on the inside leaving a gap all around the outside, but they use a machined weld bead on the inside for sealing.

Canuck

 

I clamped mine to the 1/4" steel plate topped work bench before brazing. There is a slight amount of warpage in the flange that pulls flat when bolted to the head. Less than .030"

 

Also, since you are using old header tubes, make sure to clean the inside as well as the outside around the weld areas. Wire brush is good way to clean, and ensure no contamination.

 

because brazing is done at a much lower heat, you are not getting into the parent metal as much as juts useing extreem heat to get the brass to stick---hard soldering

 

what does brazing over a weld do? never heard of that.

 

I think it fills in the holes so it doesn't leak.

 

I like to go over my Mig welds with just the torch creating a puddle that I can control. You might be surprised at how you can clean up a weld after it is made. Mig welding is a function of wire feed and heat. Once it is welded together you can control the heat and the speed with a torch getting a consistent puddle which gives you a consistent pretty weld. Is that cheating?

We had a few artisans that could make art out of a weld. One local guy was famous. I don't like brass. It's just my personal preference. It's quick and easy but I'm an elitist I guess.

 

that must be why I've never heard of it.

 

If you've got a hole, you just need more weld.

Seriously, I think lack of cleanliness is the cause of 99% of welding problems.

 

So poor fitment is only 1%? I'd give it more than that

 

I don't leave a gap as if you do put a bit of scrap to space it ,it will most likely get clamped in there. Instead just chamfer the ends to get the weld to penetrate. As for the brazing.. DONT ! as every time it gets very hot the brass penetrates more and cuts through the steel, cracks and falls apart. JW

 

I'm left wondering after this what percentage can we give to just plain lack of skill

 

Forget all that brazing, just stick with parent metals, & use fusion on the tubes.

 

Lots of different ideas here... My take... We're talking tube here, not pipe, so I'd go for a closed butt (no root gap), and wouldn't bother with any bevelling, and if you know what you're doing 100% penetration is obtainable. I'd also be using filler wire as I feel a little weld reinforcement is a good thing. At the flange joint, I'd weld the inside with mild steel wire, and braze the outside, once again for reinforcement. This is how I've just done my headers (which are the last entry on my build thread), except I tigged them instead of gas welding. No real difference though with the process for headers in my opinion.

 

On hi-end headers and custom ones I have seen and done the flanges are silicone bronze welded. This keeps the tubes from cracking at the flange.
A little tip thought to me by George kook sr. Of kooks headers