Interesting Oxy/Fuel Brazing Video

[tapwelder]

This is 1 inch and .25 inch. Done 10 plus years ago. It is brazed on both sides. I think closer to a tubing coupon since it is welded all the way around. Notice a tear beginning. I did cut it yesterday, the bronze did not flow into the joint. I guess this answers my question about TIG braze with silicon bronze and reinforcement.
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Ironically, the day before this thread began, my son and i added a hydraulic cylinder to my JD2 bender. Totally brazed. Using silver and bronze on different parts. Did not shatter bending 1.25 x 14g square tube.

My first metalworking project was a lugged track bike. I raced in 1996 olympic trials. I survived and it still lives.

[tapwelder]

As i recall Reynolds Technology who makes bicycle tubing required test coupons before one could buy their higher level tubing. Thus, the brazing might be the approved tested method?

[William McCormick]

Brazing has its place, to me, it is not in the tubular racing industry. I use Everdure rather often and it is great, it is just not the equivalent of 70S-2. As I have said I have seen the braze joint destroyed and it looked like fractured chunks of brazed material, some of it held to the base metal and broke the braze, in other cases, it let go of the base material. It just did not look right to me. If you have ever seen copper tubing brazed with silicon bronze you know that lightning and or high pressure can blow those joints, and it is the bond of the silicon bronze that lets loose. I have re-brazed a few in my day.

When I use it for something like dolly wheels or a lap joint I still melt the base metals and I get a very gnarly braze-weld. But still not the same as 70S-2 on steel. But it lowers the amount of heat you have to apply a lot, but that is just for expedience, or on parts that have plastic, paint, or grease, or to make do with the size of the equipment you have to weld with, or in cases where it does not matter. It is used a lot in the sheet metal industry, it is usually applied with MIG, but it is not really for a structural frame type of weld.

Sincerely,

William McCormick

[Welder Dave]

We don't enough about the material or the reason(s) brazing is used. It could also have something to do with proper flexing of the frame. In 1997 Honda were the first with an aluminum frame MX bike. It was the wave of the future but not without serious problems. The frame was too stiff and didn't flex enough. I figured it was just a matter of figuring out the right aluminum alloy to use since aluminum has been used for eons on aircraft. Now all the Japanese bikes have aluminum frames but the first one was a disaster. These are custom frames they're making and I would bet they have evaluated and tested every possible method of joining the tubes on them. They aren't brazing them without very good reasons to be brazing them.

[William McCormick]

We don't enough about the material or the reason(s) brazing is used. It could also have something to do with proper flexing of the frame. In 1997 Honda were the first with an aluminum frame MX bike. It was the wave of the future but not without serious problems. The frame was too stiff and didn't flex enough. I figured it was just a matter of figuring out the right aluminum alloy to use since aluminum has been used for eons on aircraft. Now all the Japanese bikes have aluminum frames but the first one was a disaster. These are custom frames they're making and I would bet they have evaluated and tested every possible method of joining the tubes on them. They aren't brazing them without very good reasons to be brazing them.

Never leave it up to the race people to decide what is right. I was in the business, and much of the business was oriented around planned obsolescence. I have no idea why but that is what a lot of it was about. More so on non-critical parts but by no means only non-critical parts. If money was no object what they would do is Kenmill parts down so that the centers of the tube that do not have much force on them would be etched down to a paper-thin wall, while the joint areas would be rather thick. So I am sure their technology is not all that or all that advanced, as that is 60 plus-year-old Aero Space tech. In the defense of the few race teams that are figuring out how to mill down their titanium pipe, and get back up or shielding gas behind every weld as they TIG weld it, I apologize. But to the others, they are just getting it done so they can sell it or race it with what they have. I am not putting them down I am just keeping the bar where it should be. I jumped waves in a boat I just re-fiberglassed, that took myself and two friends above the top second deck of a fishing boat so that we waved down to the people on that deck. So I get it but the technology is the technology.

Sincerely,

William McCormick

[William McCormick]

Doubt I would have been so kind. I, probably, would have made sure he stayed unconscious, until a cop arrived at the scene.

The next day when I had pain in my right lung and shoulder, a strange bruise on my arm from slapping the ground to break my fall, and my friend said that what the guy had said "that's what you get" was aimed at me, I agree with you totally. But at the time I was fine he was really out of it, I wouldn't want him to die, I just cannot imagine how he could be going that fast on wet pavers, crossing a city sidewalk without looking to see if anyone was there. Since then I wear an orange or yellow hat for that reason. Anyone else would have started a billion-dollar law suit.

Sincerely,

William McCormick

[Welder Dave]

You have no idea what material they are using for the frames, the brazing material or the reasons they are using a brazing technique. Overheating the tube can cause a loss of tensile strength is one reason. Below are some advantages of brazing. You can't categorially disregard a process without knowing all the pertinent details. Bronze welding as they call it was used extensively in the UK for high performance motorcycle frames and even on Jaguar E types.

"Producing joints with minimal thermal distortion and residual stresses when compared to welding. Not needing a post-processing heat treatment."

[Mike_L]

It is used a lot in the sheet metal industry, it is usually applied with MIG, but it is not really for a structural frame type of weld.

Sincerely,

William McCormick

We mentioned it earlier, but strangely enough MIG brazing is currently the only approved welding process for structural repairs on many vehicles.

In the days of body-on-frame vehicle construction Oxy-Fuel brazing was the norm. As automakers shifted more to uni-body and HS and UHS steels became the norm brazing was not an approved process and became verboten. MIG became the norm. Then within the last 10 years, beginning with Honda, some automakers have switched back to brazing, and it’s the only approved structural welding repair process on many vehicles. Honda Fit is one off the top of my head, there are more, both from Honda and other manufacturers. The process is MIG brazing instead of Oxy-Fuel brazing but it’s brazing none the less.

I remarked earlier in the thread how strange it is that the collision repair industry seems to have come full circle in that regard.

[William McCormick]

We mentioned it earlier, but strangely enough MIG brazing is currently the only approved welding process for structural repairs on many vehicles.

In the days of body-on-frame vehicle construction Oxy-Fuel brazing was the norm. As automakers shifted more to uni-body and HS and UHS steels became the norm brazing was not an approved process and became verboten. MIG became the norm. Then within the last 10 years, beginning with Honda, some automakers have switched back to brazing, and it’s the only approved structural welding repair process on many vehicles. Honda Fit is one off the top of my head, there are more, both from Honda and other manufacturers. The process is MIG brazing instead of Oxy-Fuel brazing but it’s brazing none the less.

I remarked earlier in the thread how strange it is that the collision repair industry seems to have come full circle in that regard.

Sheetmetal is not structural, it is sheet metal. And I am well aware of the strength you can achieve from sheet metal shapes, structures. However, it is not structural welding when implying a frame or structure that supports the sheet metal. To me, tubing is not sheet metal it is structural.

Sincerely,

William McCormick

[Mike_L]

Sheetmetal is not structural, it is sheet metal. And I am well aware of the strength you can achieve from sheet metal shapes, structures. However, it is not structural welding when implying a frame or structure that supports the sheet metal. To me, tubing is not sheet metal it is structural.

Sincerely,

William McCormick

They weldments that are being brazed in the auto repair process are just that though, structural. It’s not simply a fender or quarter panel, the latter of which would also be considered part of the uni-body construction, it’s actually the main sections of the skeletal backbone of the vehicle, B-pillars and lower frame rails for a couple of examples, both very much structural members of the automobile. Some of it is also thicker than the tubing being brazed in the video.

I’m not saying the guy in the vid is right or wrong, I simply don’t have enough information about his choice of process and material selection to make a judgment either way, and I’m not trying to call you out or start a pissing contest about whether it’s acceptable or not as I’m not even sure I understand your objection, I’m simply stating that brazing is currently being used for structural weldments in certain applications, no more, no less.

If removing a component of an assembly seriously compromises the structural integrity of the whole assembly, then it’s a structural component, regardless of the construction material selected, wouldn’t you agree?

[farmersammm]

https://www.bodyshopbusiness.com/mig-brazing-its-here/

https://rts.i-car.com/collision-repa...g-brazing.html

All this being said, and me being no expert on the matter, I still find brazing to be suspect for structural use. It might be very strong when applied to a capillary joint, but a fillet made of the stuff is not as strong as a real weld. Bronze is about as brittle as ice. Ask any Bronze Age soldier that watched his sword shatter, leaving him defenseless.

I get the HAZ thing, but it still seems to be an inferior way to do things. But, like I say, I'm no damn engineer.

[Welder Dave]

Totally depends on the material being brazed and the type of brazing rod used.

[Mike_L]

https://www.bodyshopbusiness.com/mig-brazing-its-here/

https://rts.i-car.com/collision-repa...g-brazing.html

All this being said, and me being no expert on the matter, I still find brazing to be suspect for structural use. It might be very strong when applied to a capillary joint, but a fillet made of the stuff is not as strong as a real weld. Bronze is about as brittle as ice. Ask any Bronze Age soldier that watched his sword shatter, leaving him defenseless.

I get the HAZ thing, but it still seems to be an inferior way to do things. But, like I say, I'm no damn engineer.

I had some of the same reservations, but at the end of the day I’m not going to open myself up to a liability issue when a vehicle is involved in a second (or 3rd or 4th) collision and something goes awry that can be laid upon the repairer for not using the recommended procedure. I also agree with Dave though, a lot of it depends on the material, both filler and parent, and I have to assume that the major manufacturers have taken those things into consideration. I will say a lot of time is spent now training techs how to properly do a repair without compromising the structure to corrosion down the road, that may have been one of the considerations.

I will tell you something about the collision industry. Every passing year it seems to become less about Collision Repair and more Collision Replace. They’re building vehicles now that are more like LEGO composites, where you repair or straighten less and replace sub-sections more, if that makes sense. There’s also a lot more training now too, seems you’re sending folks every other week to learn about some new vehicle specific process.

[Frenetic]

Probly a dumb newbie question but: where's the flux? Silver brazing uses black flux. Bronze brazing uses white flux coated on the rod. TIG brazing uses the argon as shielding gas. Oxy-fuel welding uses co2 from the burning gases as shielding gas. I'm think i'm answering my own question: use flux when capillarity is needed to fill the joint, otherwise flux not needed?

[Welder Dave]

A lot of "bronze welding" type of brazing uses a fluxer with liquid flux.

[Kelvin]

Probly a dumb newbie question but: where's the flux? Silver brazing uses black flux. Bronze brazing uses white flux coated on the rod. TIG brazing uses the argon as shielding gas. Oxy-fuel welding uses co2 from the burning gases as shielding gas. I'm think i'm answering my own question: use flux when capillarity is needed to fill the joint, otherwise flux not needed?

The purpose of flux is both to shield the molten metal from the air, and to lift trash/impurities out of the joint. If the metals you're joining are super clean, you shouldn't need flux if using the tig process.

When you tig braze, you don't use flux, which is one reason I prefer brazing with O/A, since I'm often brazing things like cast iron which (in my experience) need flux to remove the trash. I once tried to use borax flux when tig brazing and it made a mess.