New Aluminum Brazing Rod.
 

HTS-2000.

Have you guys heard of this stuiff?

If you had the latest in alloy brazing rod technology available to repair that old 7005 aluminum bike frame, a brazing rod that is actually stronger that the original tig welding, would you use it? It's not Alumaweld, or any of the other commonly known rods. From what understand, it's relatively new. I couldn't help but scratch my head at the properties of this stuff.

Now, I'm no welding expert, so I thought I would post this here to see what the welders on here had to say or comment on this.

PHYSICAL PROPERTIES

Tensile: 45,900 PSI
Therm. Exp.: 15.2 x 10- 6in./in./F°
Elongation: 10% in 2 inches
Elec. Cond: 26 (% of copper std.)
Impact: 43 Ft. lbs (charpy)
S.P. Grav.: 6.6
Shear: 31,000 PSI
Weight: 0.24 lbs/cu. in.
Melting Point: 717°- 737°
Rockwell: 48

Here's the video they show.

http://aluminumrepair.com/login/Vide.../newflash.html

I have an old aluminum frame I'd like to repair, and when I saw this online demo video, I couldn't help but ask a friend of mine who welds aluminum. He heard of it too, but never saw it use dbefore, as it hasn't been out for long. If this stuff is no B.S., then alloy repairs will become an everyday acceptance.

That look pretty promising! I've actually had good luck with the Alumaweld rods. But only on 6061 alloys. The zinc content of 7005 makes it difficult to stick. You should ask them if this HTS stuff actually works on 7005. I also suspect like steel-brazing that it doesn't like big gaps to be bridged. The parts should fit as precisely as possible.

I have an old Rockhopper I am rebuilding, and I found a crack that goes about halfway around the tubing on one of the chainstays, about 2" behind the BB shell. It look slike the chain came off and jammed in there and damaged the tube, causing it to crack. It's just a hairline crack that goes about 50% around the tube.

Well, I do know that when repairing aluminum with this brazing rod, they show a butt weld as the process. They show how a crack is basically "V'd" out so the braze can fill it in. They also said that with Aluminum, the "tinning" is really a necessary part. I would think the more you really scrub the surface with the molten rod and a SS brush, it will penetrate and stick better. Not sure though.

If I can't find someone to do a really good TIG weld to fix it, then I may just give it a shot, as I have nothing to lose at that point.

Be very careful with the torch! Aluminium doesn't glow when heated and you might get it hotter than the melting-temp of the underlying alloy. Best to keep the torch and the rod moving quickly like they have on the the video; just enough heat to flow the brazing-rod. I've actually successfully replaced a dropout on a Cannondale with the Alumaweld brazing rods. :)

^^^ That's exactly what the manufacturer told me. Keep the torch moving. When it melts, keep it on for just a couple seconds more, because it takes a few more degrees for the rod to penetrate and stick to the aluminum. We went trhough the tinning process and so forth, so I'm gonna give it a shot. Apparently, the tinning is the key to getting it to work on aluminum for best results. It needs a good scrubbing when the rod is wet.

I have an air-acetylene "turbo torch" at work which I will be using. It has a good wide flame to cover a good area to prevent concentrated heat from burning a hole. I also have a bunch of scrap aluminum flat stock to practice with.

I don't think anybody has actually tried to braze an entire aluminum frame.

Why have you formed this opinion?

I have heard that there is no point to any of this if you can't heat treat the whole thing after you are done. Annealed aluminum has the mechanical properties of a warm chocolate bar.

That's what I was wondering about, too. If the frame in question was heat-treated after welding, then you'd lose a lot of the strength if you welded or brazed it without heat treating it again. But I don't know how common that actually is on bikes. Some research into the alloys should show you if they're heat treatable.

If the frame was originally 6061-T6, then it has a tensile of about 42,000 psi. After welding you can expect to lose over half, or about 18,000 psi in the HAZ. It's risky business to repair thin aluminum tubes then bypass proper post heat treatment. I would not use HTS-2000 for anything structural. However it's fine for patching holes in aluminum boat hulls or sprinkler pipes.

I'm curious now. Is there really an HAZ to treat if you are brazing and not melting (welding) the base aluminum metal, similar to brazing steel. Is there an HAZ with the brass in the case of steel that needs to be heat treated? I don't think so in most cases.

I'm just an old welder and not a metallurgist but doesn't 6061 T6 regain it's strength through aging and not heat treatment? (maybe not including an HAZ as in the case of TIG)

Enlighten me. :)

Bruce

"Is there an HAZ with the brass in the case of steel that needs to be heat treated? I don't think so in most cases."

Not if the metal wasn't heat treated for hardness in the first place, or unless the welding caused the metal to harden. If you are just welding normal structural steel, or chromo aircraft tubing then you don't need to heat treat. If you are brazing a metal that was heat treated, then you may, it would depend on whether the extra properties are actually required where you brazed, for instance if you brazed a butt, and didn't affect the thin waleld section of the tube. Same goes for inducing hardness in metal, if it isn't to a negative degree as it won't tend to be in low carbon steel, then localized differences may not mater.

Aluminum is not something I really understand where heat treating is concerned. I have heard other stories of a readjustment over time, but if it was that simple why would they bother heat treating frames. I thinkt he big issue is with 7075-t6

Of course there is a HAZ. Annealed 6061 is not something you would want to use on a bike in a part that carries stress.

HAZ (or Heat Affected Zone) is determined by temperature, not jointing method. Partial annealing (reduction in tensile) begins when temperature of almost any tempered aluminum alloy reaches between 350f and 400f. Full annealing occurs at 500f to 700f. Liquidus (welding) is about 1200f.

Generally speaking, steel has a much higher tensile than most aluminum alloys to begin with, so any tensile loss due to annealing is largely insignificant.

Yes, usually. But you'll only achieve T4 - and will not happen overnight.

Well... I heard that Roger Durham (of Bullseye pulley fame) built several oversize aluminum bike frames in the '70's. They lasted thousands of miles without incident, even though they weren't heat-treated post-welding. This came up in the Cannondale-Klein patent fight.

I'd be interested in your references.

IIRC Roger was mechanical engineer and prone to careful structural analysis prior to melting tubes. His forte (among bolt-on bits'n pieces), was short and compact BMX and folders.

I don't remember the details of the Bullseye bikes. Just because they lasted does not mean that a bike that was designed with the strength properties offered by heat treating will last after local annealing. And the frame in the OP has already demonstrated that it is marginal strength-wise. I'm sure the heat treating is a large expense that would be eagerly skipped if that was possible.

Two more tid-bits to ponder:

While HTS-2000 claims 45,900 PSI tensile, they are referring to bead strength... which is not to be confused with overall joint integrity after you've annealed it with heat. Use a flame, i.e. O/A, propane, Mapp, and you expand the HAZ, annealing even more tubing. Use TIG (GTAW), and the HAZ will be greatly reduced.

Most aluminum fractures I've seen occurred in the HAZ... just like this one