Welding 304

[Balders]

Evening people

I've ordered myself a 304 header for my Subaru engined camper. I know it's not going to fit straight out of the box but it's cheaper than buying the bends.

What's the correct filler to use when I cut and shut it? I have some 316L rods & hoping this will be suitable.

Cheers

 

[hotrodder]

308L is the ideal stuff, 316l will be fine. TechnicAl did a nice simple stainless wire/electrode selection chart for the forum, it'll be in the 'welding other steels' section

 

[Balders]

Thanks Hotrodder
I can't find the "welding other steels" section :-/

It turned up today, however the flanges do not appear to be 304 as they're magnetic and 304's meant to be austenitic (SP?) They're not very flat either, however I might chop them off to change the angle of the pipes

 

[hotrodder]

http://www.mig-welding.co.uk/mig.htm (also appears in the TIG and and Arc sections) my bad, it's 'welding different steels' not other

How magnetic? Cold working and welding can both result in austenitic stainless becoming weakly magnetic. Cold working/bending the stuff transforms some of the austenite to martensite and you can often detect an attraction if you wave a magnet at welds too... as i understand it it's due to a slight increase in ferrite from the wire/electrodes which is done for added resistance to hot cracking.
If a magnet will stick to it 'properly' then something else is going on- you've been lied to/whoever made it is as sloppy with material specs as they were when making the thing (wonky gasket surfaces) but then if it cost less than the materials alone would it's maybe not that suprising

 

[Balders]

Thanks again HR.

The flanges are magnetic enough that they'll hold a dead cheap, plastic fridge magnet - the ones that just about stick to a fridge.
Cost of the header including separate "up pipe" was £149. Bends bought separately IRO £20 each and it'd require a minimum of 12 (flat 4, boxer engine)

I think I want to reposition the header in the flanges to:
1/ Give more ground clearance
2/ Raise the position of the silencer

I think my easiest option would be to cut the pipes flush at the orig flanges and weld into new flanges.

Spoke to a local laser cutter today and he said it would be IRO £20, 8mm SS for the pair with me supplying the DXF files

 

[Paul G]

Assuming the flanges are not mild steel;

it is very likely they are 409.

It's used a lot in exhausts, especially the cheap ones, and is steel with 11% chrome added. (ish)

When welding flanges to pipe I always bolt them down to a thick flat piece of steel and unbolt after the weld has cooled.
Your flanges were probably OK until they were welded.

HTH
Cheers,
Paul G

 

[hotrodder]

For future reference bends are a LOT cheaper from the right supplier... that includes most stainless stockholders (hygienic fittings for thin wall stuff, nominal bore fittings for thicker wall). One example... http://www.allstainlessltd.co.uk/ Note that hygienic stuff tends to only be available in 1/2" increments though. Langy (member here or google Langy's rod shop) sells a wider range of sizes at very good prices. OJZengineering do an even wider range but are spendier although still generally a lot cheaper (for raw components) than many other exhaust suppliers/ebay.

 

[Balders]

Thanks chaps

After offering up the headers it looks like it's going to be easier than I thought.
Although I'll have to merge two pipes into a 2.5" collector.
I only have normal tools eg vice, hammer etc maybe ask Paul_f If I can use his hydro press.

Would 316 and 314 mix of bends & straights present a problem? (I know you can use 316 filler)
I'm thinking of this:
http://www.ebay.co.uk/itm/2-1-2-90-...arts_Vehicles_CarParts_SM&hash=item1c28d45998

and this
http://www.ebay.co.uk/itm/2-1-2-63-...arts_Vehicles_CarParts_SM&hash=item19d36a0c39

Plus a centre & back box from Jetex or similar

I will contact Langy shortly too

 

[hotrodder]

Mixing 304 and 316 will be fine. Strictly speaking you can get problems with some applications but it's not something to worry about with an exhaust. Vice, hammer etc work fine, press will obviously be faster with something suitable to ram up the pipe. This is 2.5" into 2 x 2.25" via a V-band connector, tools used were an angle grinder and belt sander to cut and fit the 2.25 bends. Once they were welded together the end was reshaped using nothing more than hammers, a sandbag and dollies. Once it was close it was tacked 'where it touched' to the V band collar (in your case a bit of tube) and finished off with another round of hammering and tacking...





I've not got any progress or detail pics of the collector, just these that the owner sent me. His pipe fitting and tacking, my hammer wielding and welding. Dunno what size your primaries are but if they're relatively small compared to the above example then a concentric reducer can sometimes make life easier, for a 2 - 1 just ovalise one end in a vice and then tweak to suit

 

[Balders]

Many thanks once again Mr Hotrodder.

I've just Googled V-bands - they look a great idea.
Thanks for the concentric reducer idea, looks like I'm gonna need one & a bigger hammer

Been playing with some 304 tube. Autogenious (sp) welds are a nice straw/gold but using 316 I get grey (Wasn't backpurging on either)

 

[hotrodder]

Have a read of this thread... http://www.mig-welding.co.uk/forum/showthread.php?t=23592&highlight=arc+length
Heat input will be higher when using wire (as you're melting more metal*) which makes it easier to overheat things. No purge compounds things in that while autogenous comes out nice if you get things too hot with wire (or if you're aiming for full pen) the back of the joint will oxidise LOTS (aka coking/sugaring) and those oxides can be drawn through into the weldpool. Another thing that can happen with wire is that if it's not kept close enough to the pool to remain within the gas shield the hot end will oxidise and then next dip of the wire you dunk those oxides into the weld. Newcomers often subconciously increase their arc length with wire too... gave a mate of mine a few lessons the other week and he was soon producing some lovely autogenous welds with consistant pen and profile. When i got him using wire it all fell to pieces- initially constantly tagging the tungsten and then tripling his arc length out of frustration at the constant trips to the grinder

* as the weldpool melts the wire it cools some i.e. you either need to up the amps or slow the travel speed in order to avoid the weldpool freezing each time you dip the wire. Diameter of filler wire used makes a difference here... If the fit up is spot on then 1.6mm can be overkill on something like this. Smaller dia wire = less heat needed to melt it. There's 2 butt welds in that Beetle exhaust that haven't been sanded out, made with 1mm wire they're just about visible in the full size pics. IIRC Langy prefers 0.8mm for this sort of thing

If you want to try some thinner wire (assuming you're currently using 1.6) then stainless MIG wire can be used if there's any to hand. Failing that 1.0mm 316L is available in small 'maintenance' packs from Weldequip and R-tech do 1kg packs in both 308 and 316 fairly cheaply

 

[Balders]

Thanks for all the help guys. Most of my bits have now arrived.
A local welding supplies shop sold me 40x 316 1mm rods for £10

Where abouts in the SE are you HR? How much for a lesson or 2? <cheeky grin>

 

[hotrodder]

I'm in Bexley, and am usually around Shorne a few times a week so can probably swing by yours sometime one evening. How does a donation to Help for Heroes and/or The dogs trust sound?

 

[Windy Miller]

I'm in Bexley, and am usually around Shorne a few times a week so can probably swing by yours sometime one evening. How does a donation to Help for Heroes and/or The dogs trust sound?

And on your way back home, you're welcome to stop off in Strood for a cuppa!

Edit:

On second thoughts I'd quite like a lesson myself, so if there's any room for an observer let me know!