Welding Tips and Tricks

Hey all.

I'm about to embark on my first stainless job. Bike stuff again. This is a used muffler that I will need to cut open, gut, then weld back together again.



You can see where I'll be slicing both ends off in the photo - blue marker arrows point to the weld seams I'll be cutting along. I'm aware that being a used part, cleaning it up (especially the inside) will be a challenge. Another little concern is that while the tail cap and the main body of the muffler are stainless, the rear of the thing is magnetic (dull looking section in pic below:



So, overall my thoughts are to do careful cutting for good fit up, lots of cleaning, and then do lots of short stitches to control heat and distortion, giving the piece some time to cool in between welds.



I suppose I'll use ER309L filler as I understand this is a good bet for areas such as where the stainless body meets the non-stainless rear zone of this part.

This is a pretty big job for a noob like me. Happy to hear any tips you wise ones might have before I start chopping this baby up.

Cheers,


Kym

I've got to do a similar job on my Land Rover exhaust ( adapt a Range Rover v8 exhaust to fit a Landrover 90)
Let me know how you get on.

Many exhaust systems are made of 409 stainless steel. Most 400 series stainless is magnetic. I work with a lot of 410 and 440 stainless and the exhaust pipes on my Mustangs are made of 409. The 309 might work fine for this. I use 410 on most of the stuff at work.

Looks like your muffler was MIG welded. Probably done by a robot. Try to purge inside when welding.

big gear head wrote:Many exhaust systems are made of 409 stainless steel. Most 400 series stainless is magnetic. I work with a lot of 410 and 440 stainless and the exhaust pipes on my Mustangs are made of 409. The 309 might work fine for this. I use 410 on most of the stuff at work.

Looks like your muffler was MIG welded. Probably done by a robot. Try to purge inside when welding.

Thanks for the advice BGH.

Okay, didn't realise some stainless is magnetic. Also find it very odd that while the end cap and main body of the exhaust are not magnetic, the back of the unit towards the link pipe is magnetic.

Purging? Good point. Heck, I can barely afford just the one bottle of argon...might have to see if I can borrow my brother's bottle on the day. (I don't have multiple outlets on my reg, or a tee connector, either).

Tell me, how would I go if I simply fitted up nice and tight, ran a gas line into the muffler for awhile, then capped the ends with aluminium tape and started welding? I assume I'd simply lose all my argon fast...it's a gas, after all. I doubt there's such a thing as a tight enough fit up to contain gas! My apologies for knowing so little about purging...just about everything in welding is still new to me.


Kym

I keep forgetting how expensive argon is for you. We treat argon like air where I work. There is no telling how much we use in one day with the huge furnaces that we run. I don't think anything about the amount that I use most of the time. If I were you I would try to keep a little bit of argon flowing inside and weld it as quickly as possible. Try to keep leaks as small as possible.

Hey, argon might be pricey here but if it takes an argon purge to get the weld right then trust me, I'll purge!

I see too much welding on bike exhausts that just looks like arse. I want to learn to do better than than. So I'll happily do whatever it takes to make a strong weld that goes the distance and looks neat.

Part of the reason I started out with TIG is hoping to create welds that are not only string but also look professional. This job is going to be a pretty significant test for me.


Kym

Kym,
See if Solar B paste (Harris I believe) is available down under and you can use it instead if back purging. On stainless we've had more than one discussion here on using Nitrogen for your back purge also, much cheaper than Argon.

I've personally never knowingly welded 400 series so I'm not going to offer any advise on the welding end of it.

Len

yeah the back purge is critical, i did my first stainless project recently and had to rent a second smaller tank hooked up to some rubber engine block freeze plug expansion plugs that i rigged up with some plumbing fittings to do the back purge... you have to have a back purge with SS or else it'll come out like crap in the back of the weld, a nasty sugaring that will be weak and rust through especially on an exhaust... comes out real sweet with a good back purge though... I was using new SS tubing though, not sure what your results will be with existing old exhaust with a lot of rust and carbon contamination inside, guess you're gonna have to go to town cleaning it up

Good tips already. Is that from CBR btw?

To sum up.

- Use purge gas. This will prevent any future problems like cracking. After all that oxide is very brittle so its not ideal to have it on a bike that revs like a hell and also the exhaust goes trough lot of heating and cooling. Flux will do, but flowing purge gas will cool down the weld? So basicly welding is a bit easier.

- I believe Nitrogen can be used as a purge gas in this case as long as it won't get in the arc. So keep gaps closed.

- Use back step welding. This reduces distortion




How magnetic the rear is?
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Markus -

Well spotted. The exhaust is from a 2006 model CBR600RR.

Okay, all the advice I see says purge, so I will definitely purge. I'll use my brother's argon bottle and set up some sort of rig that no doubt will look like a mad professor's science experiment. But I'll make it work.

Is 'back step welding' the same as simply short stitches? I'd better do some Googling.

Oh,and Markus, the rear is very magnetic. My workshop inspection magnet clings to it very strongly.

Thanks again, wise ones.


Kym

Braehill wrote:Kym,
See if Solar B paste (Harris I believe) is available down under and you can use it instead if back purging. On stainless we've had more than one discussion here on using Nitrogen for your back purge also, much cheaper than Argon.

I've personally never knowingly welded 400 series so I'm not going to offer any advise on the welding end of it.

Len

Hey Len.

Thanks for the tip. I found some of this online...some guy in Perth has literally 4 cans of it, NOS, for sale. $50 a can but possibly worth a shot. I will try it on some test pieces before the real thing. Still leaning towards argon purge as it seems to be accepted by all as 'the right way' but I'm not going to ignore this flux option, either.

Cheers,


Kym

Hey Kym,
FWIW, back when my 06 CBR1K was new (w/ stock exh) it had this annoying "tick" coming from the exhaust after shut down. Figuring it was a joint somewhere contracting back from cooling, I found suspect joint and buzzed it up solid....no more tick . Anyway point being, I believe it was 308L I used and no problems at all for the year or so it stayed on the bike. Granted, it was a slip joint in the header that was welded and not the can itself. As far as purging goes, if it were me and especially given your argon costs, I wouldn't even think about it. Sure you'll get a sounder joint out of it but given it's a non-life dependent weld and you'll never see inside the can, I personally wouldn't waste the gas...just my penny.

Thanks for your thoughts, dunkster.

While I respect what you have to say, here's the thing; with the number of bikes and parts that move through my garage, this part could wind up anywhere. If I could say for sure that it was always going to be on my bike, I'd possibly risk no purge or other treatment, but seeing as one day it might find its way onto someone else's bike, I'll try to be as thorough as I can. It's not a critical part but I'd hate a fellow rider coming back to me one day and saying "Hey, my exhaust fell apart, what's up with that?"

Have been surfing YouTube regarding the Solar B flux. It seems to be getting some pretty solid endorsements. But for now will probably set up back purge when I do the weld.

Thanks again for your input. Good to hear from fellow bikers!


Kym

No harm Kym...definitely not trying to steer you into taking short cuts, just sharing thoughts and options.

After thinking about those cans, I'd tend to believe the main chunk of it would be 304, given it started life out as a sheet...but who knows.

Good luck with it and post up result pics.

No problems at all, dunkster.

Will post up pics...unless I ruin it so badly it just winds up in the bin!



Kym