Tig welding stainless manifold help

[Phataz1]

Sorry to hi-jack the thread, but I also have a few questions about TIGging stainless

I want to weld this inlet manifold up, but I'm scared of it bowing massively having heard lots of stories about stainless distorting.

I've done dozens of these in mild steel (MIG) and I can minimise the distortion to about 1mm from flat, what can I do to prevent this stainless one distorting? I have two G-clamps which I will use to clamp down each end of the flange, but is there anything else I can do?

Thanks,

Arun

 

[Mad Mick]

Hi Arun,
Suggest a long sprag well tacked across all four inlets would be a good starting point,making sure the tubes are well tacked to the flange in the first place,regards,Mick

 

[Paul.]

I've moved this into its own thread,

Its tricky to predict distortion, I know what would work for my welding style, but it will depend on your welding speed, size of fillet weld, joint fit up etc, I would try to improve the joint fit up to minimise the gaps, make the pipes up as sub assembly's, tack it all together, then clamp the ends of the bar to a decent flat bench with a packing under the middle to pre set it, you probably only need 1.5 or 2mm in the middle,
If you dont get it quite right, its a simple structure and will straighten easy enough with a clamp and some blocks, or a gentle nudge with a flypress if you have one.

 

[Phataz1]

I just gave this a go this afternoon. I'm fairly happy with the results seing as it was my first time actually joining two peices together...

I realise it needs back purging though and I'm working towards making up some sort of system. I was mainly happy about the fact that when I un-clamped it it was flat as a washboard! I was expecting it to be like a banana lol!

I know there's a lot of improvement needed, if there's any advice anyone can offer me I'd appreciate it!

Thanks,

Arun

 

[langy]

If its clamped down to something chunky it shouldn't bend unless your putting in huge heat which you shouldn't need, don't unclamp till its cold.
Welds are a bit on the big side, what amps & tungsten did you use ???
Is the plate 8 or 10mm ??? I presume the tube is 1.6 - 2mm ???

Could you not have welded the tubes on the inside ???

 

[Steve182]

Clamping it down to a similar size piece is a good idea, it acts as a heat sink drawing the heat down and out of the parent metal, the ideal material for this would be copper but the cost of a 10 or 12mm thick piece of copper would be astronomical, alluminium would be my second choice as a heat sink.
The welds look fine but i would say maybe a little too much heat and not enough filler rod if anything, this shows up on the visible undercut on the pipe and the concave look to the weld, certainly not bad though considering the fiddly nature of what you were welding.

 

[Phataz1]

Cheers for the replies :-)

I'm using 2.4 thoriated tungsten and 2.4 308L filler on 304 tube and flange. The flange is 10mm thick and the tube is 2.5mm. Was using a foot pedal set at about 130 amps max.

The reason I was worrying about the bowing was because I have migged up a couple of similar manifolds in mild steel and no matter how well it's fixed down or how long you let it cool for it always bows slightly. And with all the things I've read about stainless having heat distortion problems I thought it would be much worse! I'll take on board the heat sink material, I have a peice of aluminium I can use.


Cheers for the advice

Arun

 

[johnny99]

Sorry to inform you after all your work, you should never make an inlet manifold from SS, it should be aluminium

John

 

[Phataz1]

Why is that? Does petrol degrade it or something?

 

[hotrodder]

Sorry to inform you after all your work, you should never make an inlet manifold from SS, it should be aluminium

John

Why, will it make the world end or something

Phataz, biggest thing to work on is your arc length by the looks of things. Sort that and the undercut will partially fix itself in the process and overall heat input will go down some too.
Other things to watch for are crater defects when ending a weld- several very obvious pinholes in those welds

 

[langy]

Hotrodder thats a good little exercise for people to look at, good job.

Why, will it make the world end or something

Phataz, biggest thing to work on is your arc length by the looks of things. Sort that and the undercut will partially fix itself in the process and overall heat input will go down some too.
Other things to watch for are crater defects when ending a weld- several very obvious pinholes in those welds

 

[Phataz1]

Thanks for that Hotrodder, that is exactly what happens so I'll try and use a closer arc length.

Cheers,

Arun

 

[Delgado]

If you had lots to do, could maybe get some channel and drill and bolt the flange to it. Without trying to be funny, are you sure you're welding with DCEN, looks a bit like an AC weld to me, although a little hard to tell from the fotos.

 

[Phataz1]

Well there's only AC or DC options on my R-tech, and the AC switch is turned off...

I've accidently tried to weld stainless before after forgetting to switch AC off and the tungsten just burned away in seconds lol, so I know when I've got that wrong!

I have the head which it will be fitted to which I could bolt it to, but in past experience with the MIGged manifolds this has allowed it to bow. I think the 'pre-loading' that TIG Paul suggested on the previous page would work to stop that.

Cheers

Arun

 

[julieanncharters]

Sorry to inform you after all your work, you should never make an inlet manifold from SS, it should be aluminium

John

you gonna give a good reason why or just leave it open ended as i'm curious.

 

[Phataz1]

I did a little bit of googling on the subject and I think its just due to heat absorption and the possibility of water vapour in the air rusting it.

Apparantly stainless can get verrry cold and frosts up very easily which might cause the fuel and water vapour to freeze...


These were my second attempts yesterdayafternoon before I ran out of gas, they're a little better than the first attempts on the other side, but now I realise that the arc length is too long I can work towards getting that right.

These were done with a little home-made back purging system I bodged together, I think it made a slight difference...

 

[Paul.]

I would go down to a 1.6 tungsten, and keep a tight arc, although the plate is heavy, the tube is thin and the undercut has now reduced the effective tube thickness, practice and perfect your arc length using off cuts before you move on to the manifold, and as I said earlier try to improve the joint fit up, it will be easier to establish and control a small pool if you're not trying to bridge a gap

 

[langy]

Thats why i asked what size tungsten Paul, I prefer a 1.6 for that type of job also.

I would go down to a 1.6 tungsten, and keep a tight arc, although the plate is heavy, the tube is thin and the undercut has now reduced the effective tube thickness, practice and perfect your arc length using off cuts before you move on to the manifold, and as I said earlier try to improve the joint fit up, it will be easier to establish and control a small pool if you're not trying to bridge a gap

 

[Phataz1]

I would go down to a 1.6 tungsten, and keep a tight arc, although the plate is heavy, the tube is thin and the undercut has now reduced the effective tube thickness, practice and perfect your arc length using off cuts before you move on to the manifold, and as I said earlier try to improve the joint fit up, it will be easier to establish and control a small pool if you're not trying to bridge a gap

Advice noted. What sort of amps would you recommend I go for with the 1.6 tungsten?

Thanks

 

[Paul.]

Advice noted. What sort of amps would you recommend I go for with the 1.6 tungsten?

Thanks

I reckon I would get round that at about 100 -115 amps or so, use a 1mm filler rod as well, and certainly no bigger than 1.6mm, it will melt into the pool easier without chilling it, grind a decent point on the electrode, like the picture at the bottom of the page here, set a bit of slope down, say 2 or 3 seconds, and about 5 or 6 seconds post gas.
When you reach the end of the run, add a small touch of filler rod to fill the crater, then hold still while the arc slopes out and until the gas stops, depending on your welding syle you may want to add a second or 2 to those values, but try it and see.