Welding Tips and Tricks

Hi
I'm from Sydney Australia, country born, did some stick welding as a teenager before heading off to Uni for an electrical engineering degree. Been working in the utility industry ever since.
Family is important and my hobbies are simple. I spent 5 years with my brother restoring an old 30' timber cruiser, all wood work, fibre glass resin and stainless screws. With that done I'm aiming now to upgrade my old '86 Rx7 FX3S. It's a journey of love, relaxation and challenges. The aim is to do as much as I can myself, even if it takes 10 times longer. That's the journey.

Wow, the internet is a great community. When I first learnt to weld it was back in the early 80's (last century) at night at a technical college - stick welding. You only had word of mouth, books and tech. At uni, I didn't get a dial up modem until 5th year: 9600 bits per second - awesome. My class mates bought earlier and only had 2400baud.

Today, 100 MBits and streaming videos to teach you or entertain you. Many forums and articles where everyone has advice and experiences to share. I'm teaching my son to gather the information but be aware that some of it will be teaching you "not what to do". The art being to pick the good and the bad.

The internet is a great resource for welding and it hasn't been too polluted by profit driven internet content.

I have a budget priced TIG welder 250A AC/DC and a reasonable setup. The online information has helped me successfully weld my intercooler piping and weld a custom exhaust manifold flange for the turbo that you just couldn't afford to pay someone to make never loan weld. Having family contacts with a shaper and lathe certainly helps.

I'm pleased with the start I've made, particularly the exhaust flange (photos below). The intercooler piping is also all but done.

If you want to see snippets of my journey you can do so at:
http://www.ausrotary.com/viewtopic.php?f=21&t=252447
https://www.rx7club.com/build-threads-2 ... s-1148220/

I'm working on the design for the exhaust system (4" down pipe into dual 3") and that is where I'm hoping for some advice, information from this forum. I'm not sure how I can contribute other than experience on how not to do things , or back yard solutions.

The topic I'd like to explore is about back purging, flux, 308L versus 309L, so an indication on where I should post the topic would be handy, if not here.

Happy welding
Shawky

Use 308l when welding 304. Use 309 when welding stainless to carbon steel.

If at all possible, PURGE. you don't need a fancy rig to setup a purge. Either a dual flow regulator or a separate tank and regulator, whichever you prefer. You mentioned family with a lathe... you can have them turn some ally plug (think tapered slugs) with a press fit piece of tubing to attach some simple hose to for your purge source. Mostly block the other end with stuffed tin-foil or tape. Your welds will be infinitely better and last longer. IF the fit-up is good enough, you can autogenous weld the joint.

Definitely backpurge stainless. Makes it all so much nicer. Dual flowmeter works great and usually not too expensive as it's still on a single regulator and bottle.

Also, check out the plumbing section in your local DIY store for your welding back-purge supllies

Expanding plumbing plugs like these work great:

https://www.newmantools.com/cob/nylon.htm

In AUS:

https://www.drainchem.com.au/plugs-mech.html

Hollow center, so you can feed a tube through for an argon supply. Stick a sintered brass 'filter' on the end (usually used on compressors) as a diffuser and to stop the hose pulling out.

Work great for areas where you can put the back purge feed source further down a pipe so it's not exposed to as much heat. These things are cheap too, so even if you melt/damage one it's no biggie

'Real' back-purge kits with inflatable plugs and such are wonderful, but quite pricey..

Bye, Arno.

Thanks Weldmonger and Ace much appreciated for the comprehensive feedback.

Yes, pretty obvious for the best way forward as you say.

I got a number of interesting responses from a local reputable exhaust system shop and a supplier of exhaust piping who worked on performance vehicles for years. Basically, they gave me the impression that a lot of shops don't back purge at all. Quote "you're over thinking it". I don't mind over thinking it as it is the journey and the learning that makes it more fun.

Ah the DIY solution - love it: I was thinking of the poor man's purge kit as explained well on The Fabrication Series:https://www.youtube.com/watch?v=d8vN4vwX4ag cheap and easy to add to my existing rig.
I'm also trying to find out if my Weldclass Platinum series regulator will support two flow meters (two low pressure outlets) but the regulator plugged outlets are not labelled. https://www.weldclass.com.au/product-gr ... regulators. No luck from the retailer or other outlets, so I am now waiting on the manufacturer for a response. That would be a neater solution though more expensive. I'm probably over thinking this bit

Initially I thought the solar B flux would be a more manageable solution but I got turned off when the documentation said it shouldn't be used on 309 (not sure if that also meant with 309 filler rod), and the application of the flux tricky and messy and might not be worth the extra effort compared to the DIY purge solution - gas cost aside. I confirmed the 309 constraint with the manufacturer, though I think the response was more generic and best practice. Its great how so many companies are willing to respond promptly to individuals. The poor man's purge kit might result in a better result and work for the remainder of aluminium welding I need to do. Plus your suggestions above combined should do the trick.

My main interest is nutting out the importance of using 308L over 309L for welding 304 stainless exhaust for a turbo vehicle:
- I have 2kg of 309LSI that will last me a life time and I found it great to work with on my first task. So why not use it for the exhaust?
- I could buy some 308L and have two life times of filler rod in stock and I'd be using what is recommended by just about everybody (one welder said, just keep 316 and use it, which is what my very first supplier gave me for the 304 flange welding - it was problematic with the mixed metals - of course).
- the 309L would support 304 to 409 welds (e.g. cat converter might be 409) and 304 to mild steel (e.g. welding up to my old mild steel rear section exhaust as an interim solution - which has not rusted after 26 years)
- my first few welds on the vehicle were actually done with 316L filler rod. I successfully welded a few nuts (mild steel, 304 and 316) to junk panel metal, and other mystery plated metal (yellowish coating). I tested the same with the 309 and it was like chalk and cheese.

This is from https://www.lincolnelectric.com/en-gb/s ... etail.aspx

When should I use 308L, 309L or 316L filler metal?
308L (including ER308LSi) is predominately used on austenitic stainless steels, such as types 301, 302, 304, 305 and cast alloys CF-8 and CF-3. For high temperature applications such as in the electrical power industry, the high carbon 308H electrode provides better creep resistance than does 308L.

316L (including ER316LSi) filler metal should be used with 316L and 316 base metals. CF-8M and CF-3M are the cast equivalents of 316 and 316L, respectively.

Use 309L (including ER309LSi) when joining mild steel or low alloy steel to stainless steels, for joining dissimilar stainless steels such as 409 to itself or to 304L stainless, as well as for joining 309 base metal. CG-12 is the cast equivalent of 309. Some 308L applications may be substituted with 309L filler metal, but 316L or 316 applications generally require molybdenum and 309L contains no molybdenum.

Now this might stir the pot or incite a laugh but the great information that caught my eye on the AWS forum titled "308 vs 309" got me to thinking that 309L would actually be better to use in my case as the 309 provided marginally better high temperature strength, ductility, and less chance of hot cracking:

The 2 main advantages of using a 309 instead of a 308 when joining a stainless steel to another steel is 1) the higher chemistry, Cr=22.0-25.0 and Ni=12.0-14.0 for the 309, as opposed to Cr=18.0-21.0 and Ni=9.0-11.0 for the 308. And 2) the 309 has a higher ferrite percentage than the 308. A typical 309 can have a FN of approximately 12-18 FN, while the 308 is usually approximately 4-9 FN. Ferrite is beneficial in counteracting the possibility of hot cracking, or solidification cracking. Both the 308 and the 309 have an All-Weld-Metal Tensile requirement of 80ksi minimum"

and additional clarification

...the higher chromium content in 309 promotes the formation of ferrite and increases resistance to oxidation and corrosion. The higher nickel content in 309 promotes the formation of austenite, and increases high temperature strength, corrosion resistance, and ductility.

So with all that info above, it begs the question: can 309 be used instead of 308 for producing a good strong weld of 304 stainless exhaust pipe? or what important piece of chemistry or mechanical disadvantages/advantages have I missed?

shawky wrote: So with all that info above, it begs the question: can 309 be used instead of 308 for producing a good strong weld of 304 stainless exhaust pipe? or what important piece of chemistry or mechanical disadvantages/advantages have I missed?

Can you use 309, sure. Will it hold, yes. Will it outperform a 304-304 weld that was done with 308, no.

Lots of shops don't purge because it takes more time, and does cost a bit more for the dual flow setup and extra gas. But... you said, "Do it right even if its more expensive because the journey is the point...". That says 308.

Personally, for 304->409 I use Silicon Bronze. (Stirring up the pot)

LOL can't argue with my own statements.

That's a pretty firm NO for 309 over 308. So $40 worth of 308L it will have to be. Why the no for outperform?

Is it simply because 308 is a closer chemistry to 304 or that 309 has specific weaknesses due to its chemistry?

Interesting comment about the use of silicon bronze for 304 - 409. I did buy some of that for body work. Don't put too much chili in your pot! Too much stirring results in hot spit back when it boils

I tend to rely on 308 for 304 to 304 and even 304 to 316. But I keep 312 around as well as 309. I know 310 is an option in this case as well, but I have no experience with that. I currently have a project on the bench that’s for a turbo dump regulator. The pipes are getting welded into steel on one side and SS on the other. I used 312 to tack it. Plan to weld it out with 312. But there’s some stress cracking on a steel bolted flange to SS pipe, that I will fix with 309.

No reason why 309 wouldn't do a good job on 304 exhaust. If you don't want to buy in filler that you are not going to use up, go with 309.

A suitable T or Y-piece and a second floating-ball flowmeter can turn any normal regulator into twin for a backpurge setup.

Something like:



Doesn't need to be expensive

Most hih-to-low pressure regulators can flow plenty to feed the combined flow of two outlets and the adjusters on the floating ball flowmeters make sure you can set up each outlet with it's individual desired flowrate.

Bye, Arno.

Yep
I ordered a Y piece with valves and another flow meter last night. Less fiddly than the fabrication series budget solution.
Thanks for all comments

Also, my apologies, I wrote this blurb up yesterday and didn't post, as some quotes may be of interest here it is:

I found a different source of flux other than Solar B the other week on the net https://www.tinmantech.com/products/wel ... g-flux.php still perplexed by the constraint with Solar B flux so I asked tinmantech a similar question. I this is the response I got:

Me:
I am after backing flux for TIG welding 304 stainless exhaust pipe. I want to use my existing 309LSI filler rod as it was quite expensive, worked extremely well on my previous job (stainless to mixed metal flange weld). Your TIG stainless backing flux has no details and I am concerned it may not be suitable. Is it suitable for my task: Weld 304 stainless exhaust pipe (turbo down pipe) with 309LSI filler rod as alternative to backing gas on the inside of the pipe?
Feedback:
Yes.
I just finished building a stainless exhaust of 304, using 309 filler and our backup flux.
I also ran it 1000 miles and cut it apart to see how the welds were healing up.
All is 100%.... as expected.
I would use this flux on 310, 312, 316 and 321, too.

That is really keen for testing, if for real. But IMO, based on all the research I've done to date, I reckon it will be fine.

I also pulled another quote from Google from one of the many engineering sites for 309, 310:

Grade 309 Stainless Steel is used often for higher temperature applications. While its oxidation resistance surpasses that of alloy 310, its resistance to corrosion is equivalent to that of alloy 310. Alloy 309 is highly weldable and cold formable, although it does require stronger forming machines and continuously increasing pressure. Typical machining methods are used for stainless steel grade 309, but it is tougher and does tend to harden more quickly. Like 310 Stainless Steel, Grade 309 Stainless Steel has a high chromium and nickel content which grants excellent resistance to aqueous corrosion

and

Also, 304, 309, 310, 321, or 316 are all austenitic being alloys of chromium, iron and nickel which I'm sure is why we are successful at welding them together.

Reading up about 312, it is more appropriate for steels that are difficult to weld (machine components, tools and austenitic-manganese steels), joining dissimilar steels especially if one is fully austenitic. i.e. also fine with 304, 309 etc

With all that said, using backing gas and 309, the clincher will be the quality of my welds.

Thanks

BTW, this is what I selected to run the two flow meters:

BTW.. Solarflux-B should be OK with 309 as it's allowed to be used with up to 25% Cr content and thats the max for 309 too.

I don't use it often, but when I do I use it on big-volume or open sections (eg. silencers) so I don't need to back-purge as much and conserve my Argon. Works well in my opinion and results in a kinda glass-like inside slag/cover layer that protects the weld on the inside. Not suitable for food grade welds, but fine for exhausts. I mix it with methanol (caution.. toxic!) and apply it to the back of the weld-joint.

I have used 309 filler on various exhausts and never had issues. Normally I actually use 316 welding rod as, a bit like you, I once got a bunch of that given to me from soneone and 'free' is always good

It works fine as well to join 304/316 and 409 too in my experience.

Would love to get my paws on some 321 or even inconel to re-do the manifold on my car, but that's a bit too pricey at the moment when I add up all the lengths and bends I need.. Oh well.. The 304 does OK at the moment.

Bye, Arno.

Thanks Ace. I am pleased the information has come together nicely.
My exhaust pipe supplier actually commented that he just uses 316 rod with 304 and 316, if any at all.
IN a perfect world where supplies are unlimited we would use the ideal tools and parts.
Exhaust piping order Thursday night arrived today (Monday). How quick is that, good price, top quality AND made in Australia to boot.

The cost of the car build is going through the roof, especially when it comes to the fuel solution and electrics.