Welding Tips and Tricks

Here's the story.
Yamaha crotch rocket exhaust pipe looked like it might be 18ga. the new $400 dollar muffler inlet end looked like .035 with a butt joint not a slip joint. The exhaust pipe is a double wall setup. Imagine 2" ID w/ 1-7/8 OD . The muffler inlet is single wall .035. (The inside pipe then a space then the exhaust pipe). We fit the 2 parts with a butt joint, then I tacked them. When I let off bit to place another tack, the first tack pulled apart as though it wasn't even there. I tacked it again in the same spot, then re-position to place another tack and the first tack just pulled apart again. On the 4th attempt after the first tack I got a second tack. When we let off to place another tack, the 2 tacks pulled apart. I have never had an experience like this before.

stainless steel exhaust (18ga) and muffler inlet (.035) with a butt joint.
308L filler rod
2% thoriated tungsten
about 14cfh on the flometer
I have enough time in to know that I should not have had this happen, yet I have no idea what was wrong.
Any suggestions?


Jim

Hey,
Welcome to the forum. We welcome a comers here.

Now, first of all, forgive my forwardness, but is there any possibility that one of the parts could be titanium? Jody, the head hog around here, has spoken about how, if you weld ti with anything except ti filler, it just drops apart like you are saying. Im not sure you can weld it to Anyother metal with normal process.

Hope this helps
Mick

That's a very good question Mick. The owner of the bike swears that the exhaust pipe is SS as well as the 400 dollar muffler. The tacks did just FALL apart as you stated so I was doing some internet research to try to find out the composition of the parts. The muffler is SS. I don't know as of yet about the exhaust pipe. I do know that first of all, I shouldn't even have attempted to weld the BUTT joint. It should have been a slip joint. The vibration will surely cause a failure. Secondly, can you weld ti to ss even with ti filler rod?

Thanks for the "WELDcome" (get it - - - weld come) sorry, I couldn't resist.
Jim

Get some Royal 220t filler from Crown alloys. I use it extensively at our shop. It is billed as a general purpose repair rod that works well on a variety of stainless and tool steel.

just found this filler on their site as well: ER 409Nb Used primarily for welding catalytic converters and exhaust system components

Also try backing off the heat slower and keep some post flow gas on the tack after welding

Hey,

If it is high end enough to be Ti, it should have a model number, or at least a brand, that you should be able to contact, to get more info on. However , they may not like you welding on their products. Maybe do a google search on Identifying titanium.

Your weldcome for the tip..lol


Mick

I don't think its likely to be titanium useless it very highend race bike. Titanium cost a ton and welding it is not cheap. If if is titanium you can't weld it to stainless. You m ight be able to braze them if its titanium to SS not sure. My guess is you are probly dealing with either two different kinds of stainless like 409 to 304 or 321 would be my guess, both are common in exhaust, 321 is very popular on racing applications because of is designed to handle the heat and not break down. There is a possibilty that one part might also be a nickel alloy like iconel some of the NASCAR guys run iconel. Iconel to SS or two different kinds of stainless will crack if you don't choose the right filler. For two different kinds of stainless 312 stainless filler works awesome and is very crack resident. For iconel to SS this way can be more difficult but nickel 99, iconel 82 work well. Most of your maintenance filler rods like the one listed above are 312 stainless just with a fancy name. Also a fully penetrated butt would be better than a slip joint, make sure to purge the backside to avoid getting sugaring on the backside. O one last thing make sure you add filler when tacking dissimilar metals if you fuse tack they will crack.

I suppose it's possible the exhaust pipe is 4140 or some other high-alloy steel. This may lead to that kind of tack fail with 308 filler. IF (big IF) that's the case, preheat is in order, and 309 is worth a try for the tacks, to see if they hold better (to rule out Ti).

If it's a high-alloy steel, it's likely a chrome-moly, like 4140, or maybe even more exotic, like a Cr-Mo-Nb alloy, to get the lightest weight for the strength, and finding a reliable filler may be a challenge. There are fillers for high-chrome, chrome-moly, and the "exotics", but finding a best fit to tie to 18/8 (304) may take some research.

Okay, that wasn't much help. I'll have to dig a bit deeper.

Steve S

Hey, Do a spark test with a grinder on an inconspicuous part of both parts. If it is Ti it will spark Bright white.

Mick

Let's remember, it's a tube inside a tube. The outer tube acts like a heat shield. The bike is a Yamaha R6. I found some of the exhaust systems that are ti. I can't say definitively that the pipe in question is ti though. I do know that when I tacked it and let go to reposition the piece simply fell apart. The outer tube is the tell tale grey color. It's not magnetic. Other than that, I don't know what NDT to perform to identify the part. I suppose I could do the spark test on the pipe. The piece of exhaust pipe was only about 16" long so it doesn't seem to far out of line that a piece that short "could" be ti. It would sure explain what happened. The owner of the bike just got it so he really didn't know that much about it.
Let's try the link below. the pipe before the muffler is the culprit.

https://encrypted-tbn3.gstatic.com/imag ... ORO2dNdlyw


Thanks,
Jim

I can't tell from the pic because I am on my phone and quality sucks but one way to tell titantium is it will discolor like stainless but a lot worse. You could try heating up a spot with a standard cup and see how bad of discolors. Stainless should be silver or gold if you hold the post flow on it, titanium will discolor badly with a standard cup. This is not the best way if it titantium and you use a standard cup you will likely form porosity because it is a reactive metal and reacts with oxygen when hot. That's about the only way I can think of cause a lot of stainless, titanium and nickel will have a dull grey loo.

I have no concern for the "outer" pipe. It's heat-shielding... There's no other purpose for jacketed pipe but insulation, heat, sound, or both. It's the inner pipe you should be concerned with.

I'll review the link you provided shortly. If Ti is a possibility, you may be best off cutting the outer jacket back far enough to make a slip-fit (expand the muffler inlet) and clamp the new muffler.

Steve S

I found this on ebay.
http://www.ebay.com/itm/Akrapovic-Slip- ... 0692242401

200 bucks really isn't that much money, so I would call that affordable performance that many would take advantage of.


Jim

Jim, not only is that a great solution, it might be the definition of the original problem, since it's described as titanium.

Good find.

Steve S

Ya that is a really good solution.

The fact that it's described as titanium is the point that I meant to get across. Not to buy another part. That does nothing for the reason I ask for your input. Back to point. Is there a ti alloy that is compatible with SS?


Thanks

Otto Nobedder wrote:I have no concern for the "outer" pipe. It's heat-shielding... There's no other purpose for jacketed pipe but insulation, heat, sound, or both. It's the inner pipe you should be concerned with.

I'll review the link you provided shortly. If Ti is a possibility, you may be best off cutting the outer jacket back far enough to make a slip-fit (expand the muffler inlet) and clamp the new muffler.

Steve S

I called the guy this morning and suggested the expansion over the outer pipe and clamping it. This seems to be an accepted method. No where did I find anyone who welded the after market muffler on.

FlyBoy12,

If that solution is acceptible to the customer, what research I've done (to be honest, not that much...) suggests it may be the best option. I've not found anything yet that suggests a 308 to Ti weld will be reliable in a high-vibration/high-thermal shock environment. What little I've found I'd describe as "anecdotal" and unreliable. It seems mechanical connections are preferred due to the dissimilar properties.

I saw an article that suggested a silicon-bronze "brazing" was possible, but it still required an expansion for a slip-fit, and there was no follow-up on durability. I should have kept and shared that article, but I was looking for "welding".

Let me see if I can get Jody's attention on this question. If there's an answer I'm not seeing, he knows these metals as well as anyone can without an advanced degree.

Steve S

Hey,

Just asked my mate about this, he is a welder/welding inspector and also a yamaha aficionado. He reckons that the bike would have come out with an ss or chrome steel exhaust, most likely ss. It was probably swapped for a ti header, (some people have too much money) to do a spark test on the rear end of the pipe would be ok as it doent matter if its a little shorter. There is a huge hi tech merket for "slip on 'cans'so that people can up grade their bikes easily with out the need to take it to a specialist welder. Thats the path I would take as Otto said, it solves any issues here.

Best of luck , Mick

Otto Nobedder wrote:FlyBoy12,

If that solution is acceptible to the customer, what research I've done (to be honest, not that much...) suggests it may be the best option. I've not found anything yet that suggests a 308 to Ti weld will be reliable in a high-vibration/high-thermal shock environment. What little I've found I'd describe as "anecdotal" and unreliable. It seems mechanical connections are preferred due to the dissimilar properties.

I saw an article that suggested a silicon-bronze "brazing" was possible, but it still required an expansion for a slip-fit, and there was no follow-up on durability. I should have kept and shared that article, but I was looking for "welding".

Let me see if I can get Jody's attention on this question. If there's an answer I'm not seeing, he knows these metals as well as anyone can without an advanced degree.

Steve S

It surely sounds like we are dealing with a titanium part.
When Titanium is fusion welded to metals like stainless, inconel, or steel, brittle inter-metallic compounds are formed.
that's a fancy way of saying that it becomes brittle as glass....and usually you can hear it cracking as it cools.
there is no rod that will work to weld titanium to other stuff. the closest I have come is with Aluminum bronze but it still wont hold up to stress and vibration.

jody

Thanks, Jody,

That backs up what I found, and relieves me from digging deeper.

The OP's options, then, are a clamped slip-fit, or revert to the factory style header in a weldable steel. I appreciate the share, as much for my own knowledge as for help on the original question.

Steve S