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Anybody know about TIG Brazing?

33K views 40 replies 10 participants last post by  Smoker 
#1 ·
Been thinking alot about tube frames, their designs, materials, and the welds alot here lately, and how I can apply it to a frame I want to build. I have had this idea in my mind to TIG weld a frame and clear coat it, leaving the HAZ still colored ( the blueing ). Just a raw look. Last night I remembered a there was a thread on here where TIG Brazing was breifly mentioned. Found it this morning but nobody went into detail about doing it. Searching the net isnt coming up with specifics for doing so on tubing, just alot of topics in recards to cast.

Here is 2 pictures of what I'm talking about on a Harris frame. Stole these pics from the thread I found




If I can figure out a few things and practice a few times, I'm sure I could duplicate that look. Plus clear coating a bare steel frame leaving those joints seen would be bitchin

So my questions are-

What is the right choice filler metal that is applicable in a structural application like this?

Is it DCEN just like steel welding?

Is the parent metal melted any like in welding or is it not like in brazing?

And are these joints a full TIG braze joint or is there some fusion welding done under the braze joint?
 
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#2 ·
ever since I saw that picture a while back, I've been dreaming about tig bronzing a frame also. That frame is dead sexy. I've done some research but I haven't given it a try yet so this is all second-hand info.

There are two filler rods: Aluminum-bronze and Silicone-bronze. Silicone being more common.

Apparently you can run it on DCEN or AC and it comes down to preference.

I think you need to heat up a small puddle in the parent metal but not much. The whole point of using bronze is on thin stuff or stuff like 4130 where you don't want a lot of heat in it. So if done right you shouldn't see much blueing in the HAZ.

Give it a shot and post pics. Good luck.
 
#3 ·
I think I will pick up a pound or so of the silicone bronze filler next week and start playing. I have been trying to research it but everything I'm reading mainly is in regards to cast repairs and stuff like that. Haven't found a single thing having to do with making the welds look like pictured. I have read that ac seems to have an erratic arc and most like it set on DCEN.

Another thing I do keep reading about is that its not good in a structural application. Something about the tensile strength being about 60% of mild steel. So that has me wondering if the frame pictured above has some fusion welding ( with or without filler ) done prior to the TIG braze for full strength
 
#4 ·
On motorcycle frames almost all of it is rigidity rather than strength. Other than in a crash you're never anywhere near the strength of the frame.
 
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#5 ·
Went and picked up a pound of Radnor 3/32 Silicon Bronze filler today at lunch break. Didn't have much lunch break left after chatting with the guy at the supply store. But I did manage to get a bead layed in. Took some scrap 1/8" plate that was laying on the floor, gave it a quick buff, and lit up.

This is the result



DCEN, 3/32 red tungsten sharpened to a point, gas lense with 15-20 cfh, and machine set to 120 AMPs ( never even came close to full pedal though), and a tight arc. I let the sides wet before adding filler. The bead welded alot like aluminum, very soft. About half way thru the bead I picked up some contamination and a couple more spots after that also. Its hard to see it good in the picture but the contaminents wont come off after the bead cools. So first lesson is the metal needs to be extremely clean.

I then spun the piece around and switched over to AC. Basically the same setup as before. Right off the bat it was a bit*h as the arc was all over the place. I made about 1" of weld and decided that wasn't the right choice. Next lesson, NO AC

I cut the weld in half, etched the sides, and you can clearly see that no fusion actually happens. Took one half of the T joint and put it in the vise. Was able to bend the piece almost all the way over before the weld tore from the sides. Didn't get any pictures though.

Tomorrow, I'm going play around with bead ripple spacing, tungsten points, and arc length to see if I can get the bead to resemble anything like the ones on that bike above. I think a blunt nosed tungsten and a slightly longer arc should give the results I'm after. I'll try and take an actual camera to get some better pictures. My phone isnt the best
 
#37 ·
Pics!
Went and picked up a pound of Radnor 3/32 Silicon Bronze filler today at lunch break. Didn't have much lunch break left after chatting with the guy at the supply store. But I did manage to get a bead layed in. Took some scrap 1/8" plate that was laying on the floor, gave it a quick buff, and lit up.

This is the result



DCEN, 3/32 red tungsten sharpened to a point, gas lense with 15-20 cfh, and machine set to 120 AMPs ( never even came close to full pedal though), and a tight arc. I let the sides wet before adding filler. The bead welded alot like aluminum, very soft. About half way thru the bead I picked up some contamination and a couple more spots after that also. Its hard to see it good in the picture but the contaminents wont come off after the bead cools. So first lesson is the metal needs to be extremely clean.

I then spun the piece around and switched over to AC. Basically the same setup as before. Right off the bat it was a bit*h as the arc was all over the place. I made about 1" of weld and decided that wasn't the right choice. Next lesson, NO AC

I cut the weld in half, etched the sides, and you can clearly see that no fusion actually happens. Took one half of the T joint and put it in the vise. Was able to bend the piece almost all the way over before the weld tore from the sides. Didn't get any pictures though.

Tomorrow, I'm going play around with bead ripple spacing, tungsten points, and arc length to see if I can get the bead to resemble anything like the ones on that bike above. I think a blunt nosed tungsten and a slightly longer arc should give the results I'm after. I'll try and take an actual camera to get some better pictures. My phone isnt the best
 
#6 ·
I'm a fan of silibraze... From Tony Foal's book on chasis design; brazing a frame together, the right way, is a much better practice as it doesn't weaken the parent metals.


I'm not totally sure what the "right way" actually is... That's old school secret... You can mig silicone bronze as well, but from my readings on the stuff, it's always stressed as a non-structural medium...


God damn shit looks so pretty... Avid fucking fan right here...
 
#7 ·
From what I've read the bronze filler technically isn't as "strong" as the steel, but because it is somewhat softer and not prone to cracking it actually produces a very structurally sound joint. Our late Minneapolis cafe racer had a very high opinion of this technique. The guy on weldingtipsandtricks.com who was a fan of AC I think was using the aluminum bronze rods (which makes a little sense).

I'm loving the pics, keep em coming.
 
#8 ·
I have done quite a bit of it myself....we use silicon bronze (or we call it everdur....brand name?)
I havent welded anything that required alot of strength...I work for a custom stainless shop, we do mostly countertops, cabinets, etc... and we make the underbracing, and framework from black iron or galvanized, and the everdur just welds faster for us, so I am not sure of the structural integrity (motorcycle frames....?) but it sure looks purty!
 
#9 ·
Here is the piece I had cut in half a week or so ago



I havn't had all that much time here lately to practice very much. I did try a heavy blunt nosed tungsten, but I found that I was in the weld far too long. One thing I have found was if you hang around to long the weld looses it bright color. Wire brushing does bring back the lost color some but its a dull color instead.

I also tried increasing to bead spacing more. What I found there was that with the 3/32 filler, I was having a concave bead. Tried pushing more filler per ripple but then I was back to being in the weld to long. Going to have to get some 1/8 filler for that

In this next picture I was pushing alot of filler per ripple. In the begining of the bead its clear thats what I was doing. But the interesting part is towards the end of the bead once the metal warmed up a little. Notice how the weld sags?



The contamination problem has been solved. Most of the problem seemed to be in the filler metal. A quick cleaning with some scotch brite and I havn't had an issue since. Other than those prior times when I got the puddle to hot, because it was in those beads also.

Decent bead pic



All in all, I'm very happy I decided to try this stuff out. I have found quite a few good applications where this stuff will come in handy and work has already picked up a few pounds to have on hand. As for if I feel confident enough using this stuff, solely as the filler holding a bike frame together that I plan to beat the living hell out of. I'm still not 100% sold. I'm sure it would work and be fine as long as proper attention was placed on good fitup and your beveling. But like I said, I'm not 100% and wont be fully confident, which will limit how I ride. So what I'm currently thinking is that I will lay a small root pass using typical ER70s filler and cap that with the silicon bronze. Where the silicon bronze acts more like a gusset
 
#38 ·
More pics!
Here is the piece I had cut in half a week or so ago



I havn't had all that much time here lately to practice very much. I did try a heavy blunt nosed tungsten, but I found that I was in the weld far too long. One thing I have found was if you hang around to long the weld looses it bright color. Wire brushing does bring back the lost color some but its a dull color instead.

I also tried increasing to bead spacing more. What I found there was that with the 3/32 filler, I was having a concave bead. Tried pushing more filler per ripple but then I was back to being in the weld to long. Going to have to get some 1/8 filler for that

In this next picture I was pushing alot of filler per ripple. In the begining of the bead its clear thats what I was doing. But the interesting part is towards the end of the bead once the metal warmed up a little. Notice how the weld sags?



The contamination problem has been solved. Most of the problem seemed to be in the filler metal. A quick cleaning with some scotch brite and I havn't had an issue since. Other than those prior times when I got the puddle to hot, because it was in those beads also.

Decent bead pic



All in all, I'm very happy I decided to try this stuff out. I have found quite a few good applications where this stuff will come in handy and work has already picked up a few pounds to have on hand. As for if I feel confident enough using this stuff, solely as the filler holding a bike frame together that I plan to beat the living hell out of. I'm still not 100% sold. I'm sure it would work and be fine as long as proper attention was placed on good fitup and your beveling. But like I said, I'm not 100% and wont be fully confident, which will limit how I ride. So what I'm currently thinking is that I will lay a small root pass using typical ER70s filler and cap that with the silicon bronze. Where the silicon bronze acts more like a gusset
 
#10 ·
I was actually thinking of asking a similar question - I'm looking at doing some work on a fuel tank and was considering doing a weld and then capping it off with braze of some sort. Didn't manage to find much searching but that may be me.

What's wrong with a somewhat concave fillet? A convex filler puts much more of a stress riser at it's edge than a concave fillet.
 
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#14 ·
Been having trouble with surface contamination, wondering if it has to do with argon flow, my shop has a fixed argon pipeline, the only way to fook with the flow is putting a bored out connector on the end of the pipeline, gonna have to try this with the silibraze to see if it helps my cause... More info soon
 
#16 ·
You need an increased argon flow to push contaminents. And yes, DCEP always.

The biggest advantage here is flexibility in race chassis form. Many of the trellis frames benefit from the torsional give inherent and allow the filler to calm some of the buzz from triangular construction.
 
#21 ·
DCEP is going to melt your tungsten in no time flat. I have read plenty of stuff about people running it DCEN, some people prefer AC.

I'm trying some carbon arc brazing and it's being a PITA to get at all pretty, but even some very ugly brazes are ending up stronger than the base metal.
 
#28 ·
just found some interesting stuff... it appears you may be correct about the size of your electrode...



"As a consequence of heat distribution, for the same current one has to select in DCEP a larger electrode size than what is proper for DCEN.

Due to the electrode limited current carrying capacity (about 1/10 of DCEN), DCEP is used only for welding thin sheet metal where low current is sufficient. For most other applications welded with higher currents, DCEN is selected if welding other materials than aluminum or magnesium (see below)"

found on
http://www.welding-advisers.com/Tig-welding-tips.html

Here is another quote i found real interesting on another forum

"Since you are referring to GTA, I can tell you that back in the 80's I had heard of using DCEP with a 1/4" electrode to make spot repairs on bronze castings, apparently extreme arc cleaning action was benificial, and a huge electrode was needed to carry barely enough current to get a melt. Never actually seen it, but there may be some logic behind it. That may have been the only way to attack the issue back when transformer power supplies did not have adjustable "cleaning action". And now the programmable DCEP/DCEN wave form of a Miller Dynasty would probably be the best GTA weapon casting repair since the peak current and % time at + and - can be set."

found on
http://weldingweb.com/archive/index.php/t-52275.html
 
#26 ·
quote; Me too. Didn't even think of it.
And of course, gas braising needs flux, why wouldn't TIG also benefit from flux shield in addition to argon?
Now we're getting somewhere..


i believe that because tig's heat is so much more concentrated that negates the need for flux... not exactly positive. i remember seeing something on it, ill look for it!
 
#30 ·
I gave a friend of mine who's pretty good at TIG a couple rods of silicon bronze to try out.
my first attempt at tig brazing silicon bronze, base metal is 16ga mild steel with scale removed. machine set on DC-

no porosity as far as i can tell, went on really clean as long as scale was removed. the broze stayed shiny as long as you stayed right above the base metal melting temp, you can see on the braze where it mixed in with the base metal a little
 
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#33 ·
Alright, so I started playing around with tiging bronze this weekend. I was experimenting with all sorts of settings and stuff. I definitely don't have it dialed in yet. Here's some of what I'm working with, some observations, and some questions.

Miller syncro 250, 3/32 electrode, 3/32 sili braze filler rods, 15 cfm argon, welding on 4130 tubes.

AC: The arc was jumping all around for me, but when it got in line the puddle flowed nicely

DCEN: this is where I practiced most. I'm probably still running too hot, but I had a hard time welding if I wasn't melting the parent material a little. After re-reading this thread, I'll probably turn up the argon flow, turn down the amps, and maybe try "laying the wire" more to get the puddle going.

DCEP: this gave me problems. I'm not sure if something is wrong with my machine, if the settings were off, or if it's just operator error. I turned the amps down so I didn't fry my tungsten. The arc was kinda pop n crackn start n stoppn. I'll go back and try turning the AC balance all the way to clean, see if that helps.

Any ideas about the settings? Where should the AC balance be at? what is the arc control dial for?

I noticed a lot of different color from the beads while I was practicing. On the beads where I was too hot the bead was more silver like the steel. I would brush the welds with a stainless wire brush (which may have been contaminated) while the bead was still hot and it would turn different colors depending on how hot. Should I wait until weld is completely cooled before brushing?

Back to the drawing board.
 
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