Welding Schedule 10 & 40s 304L butt weld els:-

[carlos420uk]

Ok after a few months of regular Tig practise I now feel confident enough to start a little project.

I am going to have a go at making a 4 cylinder turbo manifold. I intend to use 1.5" schedule 10s or 40s butt weld fittings and straight pipe in 304L (got a few pieces on the way to have a play with before I decide which to go for) and am looking for a bit of input on the best way to go about butt welding these pieces together.

I know that I will need to back purge all joints, but what about just tacking up? Do I still need to be purging then or should I be trying to avoid full penetration when tacking?

As for the actual welding procedure, what is the best method for maximum penetration / strength, as in how many amps, number of pasess, tungsten and filler size? I have read that you can just fuse a root in and then use filler for a cover pass. Others are saying use filler for both, and some say that a single pass with enough filler will be fine

I was thinking 2.4 Thor. Tungsten, 1.6 filler, no.8 gas lens and around 120amps adjusted on the pedal? Would pulse be of any use also?

Lastly I have been told that 308L filler is fine to use for joining the 304L, is that correct?

Any advise on this would be great,

Cheers

 

[Thebuttrussler]

Hi Carlos

For 1" 1/2 sch 10 best way is 37 deg angle knife edge prep i.e no land, bout a 1mm gap about 70-80 amps and push the wire through, then cap off. Use bridge tacks and as you approach them cut them out with a thin cutting disc. Bridge tacking is basicly putting a tack on your bevels with out burning the root gap/land about 6 lpm will do you on the back purge.
2.4mm tungsten and 1.6 wire
308 or 316 filler wire
Sch 40 will be over kill.
Post some pics of your practise runs and i will give you some guidance.
ATB

 

[chrismac]

As above, but personally I hate bridge tacks, if you are getting a hand to tack up I would prefere to purge and tack but it's not me doing it, if you just put on a small tack you won't burn through, a bit of experience needed here though and you can get away with out purging when tacking, the fit up has to be spot on though.

Just my opinion Chris.

 

[carlos420uk]

Thanks for the advice lads, just what I needed

Right got the parts yesterday and late last night had an hour at the table practising a few welds. The main problem I had was like Chris said about holding the pieces together with a 1mm gap and getting a tack on. I used a piece of 1mm filler folded into a U but obviously whilst i'm holding the piece in one hand I have no hand free to add filler for bridge tacks. It was getting late and I just wanted to weld one up, so decided to just butt up the pieces and do really small fusion tacks, which worked very well with no sugaring on the inside.

After tacking up I contemplated fusing a root in 1st and then doing a filler pass, but instead thought I'd use filler and see how I go.
Well after the first bead I quickly realised that I wouldn't be getting a second pass on the top, as I had filled the V in completely in one go. Anyway I continued on and welded it all the way round trying to use as much heat as I dared. The finished weld looks very nice for a 1st attempt, pretty flat and uniform, however I failed to get full penetration miserably, and the after removing the purge line could still see the seam line inside the pipe

That little learning curve made me realise that the gap is important to get the penetration and also I was being a too timid with the heat. I'm going to have another go tonight but get the missis to hold the pieces whilst I tack up with a 1mm gap. Then I'm going to go hot enough to just keyhole and try to keep pushing the filler in like you say, should I just leave it in the puddle? Only thing that worries me is that I won't have enough space left to add a second pass?

Lastly the pieces I'm using are already bevelled with a land, do I have to grind a 37* knife edge or can I get away with it as is?

I'll post some pictures of my setup and welds from last night once I work out how to get them off of my phone.

Thanks again for the tips

 

[Thebuttrussler]

Hi Carlos
A good tip you could use some Alu foil tape to hod the pipes together with your filler wire as a spacer although it is a pain to get off and can leave a sticky mess!
I use these at work brilliant for setting up pipes on your own
http://www.sumner.com/sumner/sub/productb/main.85.7.11.120.85.0.html
Although very expensive
Another way is to weld two pieces of angle iron to a G clamp or vice grip.

I wouldn't worry too much about penetration, as its not hygienic or pressurised liquids, obviously it will be under strain from heating and cooling but it should suffice.
You could always but your pieces up and just fuse the root, just turn your amps up and watch for "the dancing ladies" you will see your weld pool start to twirl and you know you are fusing to the inside.
Sch 10 should give you enough for two passes but if your filling up in one its no biggy.
Regarding your bevel its always best to grind your fittings down you know everything is even, remember to keep it clean too, post weld pre weld and inbetween runs bit of scotch brite on the inside and out prior to welding all helps

 

[chrismac]

Hi, common in welding procedures would be fuse the pipe, prep to a knife edge purge and with more amps the root could be done with ease, I would fine it more difficult to weld with gap, not impossible just not as straight forward, for the closed butt you should point the tungsten upwards and get the weld pool sloping upwards before moving round the pipe then the weld will flow and you will see it, it takes practice, but easier on thin stuff,

Chris

 

[carlos420uk]

Those clamps look good! I know what you mean about not worrying about penetration as even though the weld hasn't flowed right the way through it still looks and seems plenty strong enough to me.

Managed to get another one welded up tonight but used a different technique this time as per the advise above. Using about 100amps I just fused a root in as hot as I dared go, the puddle wetted out a bit wider than what I'd have liked and after I was done that pass had penetrated but was badly undercut. So I then went back over and did a second pass with the Tungsten "sloping" and just left the wire in the edge of the puddle weaving the arc left and right to fill in all of the undercut.

The resulting weld although not as clean and pretty as the night before penetrated properly with no sugaring on the inside Forgot to take pics after the filler pass, but will post them later.

What I'd really like to know is how can I achieve the same good root penetration without the bead width getting too big and wetting out too wide? Should I try less amps and slower travel speed maybe?
I can't help thinking that if I could get the pulse set right it would do a good job of fusing in a root with a nice uniform bead - after all this is for a performance car so it needs to look pretty too

Here's some pics of the 1st and 2nd attempts:-

 

[chrismac]

The problem is that doing a closed butt is that you need a good deal of heat to get the metal flowing' once you do a few you wil be able to move quicker this giving you a narrower weld, if when you start the root and get both sides into a pool roll the tungesten round till it points upwards the weld pool wil then start making its way up the prep to form a point in the pool, its not easy to explain, hopefuly I have given you a bit of an idea of what I mean, once, you see this you can move quite quick as this is when the weld is giving full pen, once you get a few it will come, nothing much wrong with what you have done,
Chris


Ps if you make the preps more like 45 deg there will be less metal being pulled in from the sides making penetration easier.

 

[carlos420uk]

Hi Chris, thanks again

Yep spot on I was finding that too much of the material from the bevel was washing down into the fused root cooling the weld and making it harder to get the penetration I wanted, hence I had to run hotter. I think like you say, and as said at the start of the thread a gap is the best way to go for best results.

By rolling the tungsten till it points upwards I assume you mean that as you come up vertical on one side of the pipe heading towards the top tilt the torch backwards so the tungsten is pointing up in the direction of travel with the arc coming off the tip and downwards to make the puddle longer sort of?
If so then that is what I found myself doing after I had done the first 2 passes for the root and I know what you mean about the puddle being thinner at the end and sinking down a bit.

Going back to using a gap. The thing is when it comes to mocking up the finished part I dare say I will have some of the fit up butted, where as some of it may very well end up with a bit of a gap as I don't expect to get everything to line up mm perfect. So in that case I better have a technique that works for each really.

At the end of the day going back to the first weld I did with one pass and filler, in the real world would a Turbo header welded like that be strong enough for it's intended purpose? If so then I'd be happy enough to weld it all up like that and be done with.

Will have another go tonight with a 45* prep and no land, see how we get on

 

[langy]

I use a 1mm tungsten and 1mm 316 filler rod on my 316 bends, cant help with amps as using a pedal.
to hold the joints together i use a wide hose clamp with 3 holes drilled in it at equal points around the clip, just tack through the holes.