s/s pipe suitability for welding

[galeus]

I am in the process of fitting a new s/s exhaust elbow with water injection to replace a rusted through mild steel one.
On the new elbow there is a spigot for connecting the cooling water for the exhaust, but it is at the wrong angle for it to work for me.
I have found a local welder who will do this for me, but (on this tiny job ) he does not have any 22mm s/s tube to weld to the existing elbow.
I have some 22mm s/s pipe left over from me making some hand rails, which I'm pretty sure is 316 grade.
What I'm uncertain of is the suitability of my pipe ie the wall thickness; it does'nt feel especially light or unsubstantial and I don't know where I would go for anything better.
Any thoughts out there.

 

[Ian_Rob]

316L rather 316 is the preferred choice when stainless steel is welded.

 

[John the kiwi]

What Ian said!
the "L" means that the stainless is low carbon and OK for welding. Standard stainless when welded can suffer from Carbide precipitation in the heat affected zone. That is usually just adjacent to the weld and forms an area of weakness that i understand is also more susceptible to corrosion as well.
Tubing would normally be welded so the expectation would be that it is Low Carbon, but i wouldn't use it without confirmation from the original supplier as consequences of failure in your case could be a bit nasty.
All of which begs the question as to the grade of the elbow itself?

 

[vyv_cox]

What Ian said!
the "L" means that the stainless is low carbon and OK for welding. Standard stainless when welded can suffer from Carbide precipitation in the heat affected zone. That is usually just adjacent to the weld and forms an area of weakness that i understand is also more susceptible to corrosion as well.
Tubing would normally be welded so the expectation would be that it is Low Carbon, but i wouldn't use it without confirmation from the original supplier as consequences of failure in your case could be a bit nasty.
All of which begs the question as to the grade of the elbow itself?

Yes, here is a little more information. The carbides that form in the HAZ are chromium carbides, which therefore reduce the chromium content of the surrounding stainless steel to a level that cannot resist corrosion. This failure mode is known as sensitisation. The best alloys for welding have low carbon and preferential carbide formers such as niobium and titanium.

 

[vyv_cox]

Use of AISI 347 filler rods will help, as this alloy contains niobium.