In article ,
"fred bruce" wrote:

Can 300 series stainless be welded with a gas welder?

Yes.
However you will have a higher probability of chromium carbide formation
in the cooling weld.
This is due to how long the metal is kept hot.

TIG welding is faster and cleaner and reduces the instance of chromium
carbide formation.

To gas weld stainless steel you have to use a very carburizing flame.
With a carbon feather at least 3 - 4 times as long as the inner cone.

SS melts at a lower temp than steel, and will tend to have a very liquid
weld pool.

Also you will get substantial oxidation of the heat affected zone around
the weld.
This can be removed with abrasives.
If the welded piece is to be used near food or salt water you will have
to passivate it after welding.
Passivation removes iron particles from the weld surface that will rust
and restores the stainless properties.

This is always performed on SS TIG or MIG welds before exposure to food
or salt water, and gas welding needs it even more.

Any strong acid will work, the simplest being Naval Jelly (phosphoric
acid gel).

Citric, nitric, sulphuric, and hydroflouric acids are all used for this
in industry.

I use citric acid and electricity.

--
Welding Instructor - South Seattle Comm. Coll.
- Divers Institute of Technology
CWI/CWE
WABO Examiner