Subject: stainless welding

From: [email-masked] (Richard L Wagner)
Date: 19 Oct 1994 16:31:15 GMT

I am having trouble with some stainless steel welding. I use a mig welder 
with argon flow. The parts are 0.1 304 ss wire to 0.1 wall 304 square tube.
The problem is a lot of sputter and black carbonlike discoloration, and 
welds that seem brittle. That is, they break after flexing much more 
readily than the wire. 

Thanks in advance for any suggestions

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From: [email-masked] (KLM)
Date: 19 Oct 1994 19:51:24 GMT

In article <[email-masked]>,
>welds that seem brittle. That is, they break after flexing much more 

1)The carbon discoloration: I've seen this on the back side of stainless,
  where there isn't any shielding gas, but not on the front where there is
  shielding gas. I turn my flowmeter all the way up for stainless. A 
  different, more inert, gas might help, too - I just use normal 75 Ar/25 CO2.

2)Spatter: AFAIK, the cause would be the same as for normal steel. Try
  a different diameter wire, different voltage or wire feed speed. Keep
  the wire aimed at the puddle, ... FWIW, I recently saw an ad for
  stainless-safe anti-spatter spray. Sorry, can't remember details.

3)Brittleness: I have heard rumors of extreme brittleness in SS following
  long heating, e.g. torch welding. I haven't had problems. I understand
  that the solution (besides minimizing heat input) is to quench the weld.
  I do that anyway (with a sopping wet rag, right after welding) but to
  maintain the full corrosion resistance. Any metallurgists out there
  with the real scoop?

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From: [email-masked] (Steve Hampson)
Date: Thu, 20 Oct 1994 21:27:45 GMT

>welds that seem brittle. That is, they break after flexing much more 

Assuming that current and wire speed are set correctly for that size material,
the problem could be that too little shielding gas is surrounding the weld
puddle.  Are you welding in a breeze?  Argon is not very dense and is
easily blown away.  Try turning the flow way up to see if that helps.
-- 
Steve Hampson                       [email-masked]
17624 Schalit Way                   home (503) 636-6966
Lake Oswego, OR  97035              work (503) 222-9571
USA

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From: [email-masked] (Howard Anders)
Date: 21 Oct 1994 07:28:51 GMT

> >welds that seem brittle. That is, they break after flexing much more 

****** I'm  not an expert, but as I understand it you shouldn't use the 
same shielding gas that you use for regular steel. It needs to be 
specifically designed for stainless. I think there is a percentage
of oxygen in the Argon mix. Maybe someone who IS an expert could 
enlighten us??

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From: [email-masked] (Dion Hollenbeck)
Date: Fri, 21 Oct 1994 16:08:51 GMT

>>>>> "Richard" == Richard L Wagner <[email-masked]> writes:

Richard> I am having trouble with some stainless steel welding. I use
Richard> a mig welder with argon flow. The parts are 0.1 304 ss wire
Richard> to 0.1 wall 304 square tube.  The problem is a lot of sputter
Richard> and black carbonlike discoloration, and welds that seem
Richard> brittle. That is, they break after flexing much more readily
Richard> than the wire.

I use 25% argon 75% CO2 for welding SS and only get black stuff on the
back side if I am not filling the back side with shielding gas.  If
you do not have a sufficient gas flow for the distance your torch is
>from  the work, this will occur also.  I use about 25 psi inside my
garage in still air and about 30-35 psi outside when there is any
breeze at all.

Sputter can also come from not having current, wire feed speed and
stickout matched properly for the size of wire and the metal you are
welding to.

Brittleness will come if you do not cool the SS immediately after
welding it.  Leaving SS above 800 degrees for several minutes will
cause incredible brittleness.  You can literally tap it with a hammer
and it will shatter.

One other thing to note, you say you are using 304 wire to weld 304
SS.  It was recommended to me that you always go up one level with
your wire, so you should be welding with 316 wire.  And if you can,
fill the tubing with CO2 so you do not get oxidation on the backside
of your welds.

dion

-- 
Dion Hollenbeck (619)675-4000x2814     Email: [email-masked]
Staff Software Engineer     Megatek Corporation, San Diego, California

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From: [email-masked] (Scott Cannoy)
Date: 21 Oct 1994 20:33:24 -0700

>>welds that seem brittle. That is, they break after flexing much more 

FWIW,

For "short arc" MIG welding of 304 Stainless Steels you should be
using a Helium/Argon/Carbon Dioxide. The most common mixture is
90% He-7.5% Ar-2.5% CO2.  75% Argon-25% CO2 mixtures that you normaly
use for carbon steel welding can be used, but you might (probably
will) affect the mechanical properties of the deposit. (what we usually
see is that the weld area will get rusty).

Using pure Argon on stainless will give you welds that a lot of "sputter
and black carbonlike discoloration, and welds that seem brittle" :-)

Save your Argon for MIG welding Aluminum.  But that's another chapter. :-O

BTW, if I read your note correctly, you say your using 304 MIG wire?
Are you sure that it's not ER308? This would be the better selection
for 304 base metal, and easier to get. (I would spec ER308lsi type) 

-- 
Scott Cannoy               //    Also to be found at:
Albany, Oregon            //  Industrial Welding Supply Inc.
[email-masked]    //       Corvallis, Oregon