Stud welding stainless

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Can you safely stud weld mild steel studs to stainless?  ( 316)
  I am highly suspicious of this because welding mild steel to SS can have
problems if the incorrect filler is used.  In the case of a stud weld no
filler is used.  Is there a problem?
Randy



Re: Stud welding stainless

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IIRC, we used a device called a Cad Weld.  You pressed the stud where you
wanted it, and it sent a quick pulse of electricity through there that fused
the filler metal in a spark producing pop.  You had to try several to get
the setting right, but they worked pretty good.

Steve



Re: Stud welding stainless
   That's that we regularly do but the question can you shoot mild steel
studs onto stainless?


IIRC, we used a device called a Cad Weld.  You pressed the stud where you
wanted it, and it sent a quick pulse of electricity through there that fused
the filler metal in a spark producing pop.  You had to try several to get
the setting right, but they worked pretty good.

Steve





Re: Stud welding stainless

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And the answer was YES, with a CadWeld.

Steve



Re: Stud welding stainless
This is really a guess, but I think it would work.  The problem with
welding mild steel to stainless is that the carbon from the mild steel
mixes with the stainless and forms chrome carbides.  So you generally
need to use filler rod with a higher chrome percentage than the
original stainless.

My guess with stud welding in that there is much less mixing, and
therefore less of a problem.  316 has higher chrome and nickel so would
be less of a problem than say 304. You might get a better answer here,
but the best thing would be to try it.

                                                                    Dan

R. Zimmerman wrote:
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Re: Stud welding stainless
    How would you know just how much carbide precipitation has taken place
and if there is a possibility of future cracking?  Will a 30 degree standard
proof test be adequate?
  There is close to 6000 pounds of plate taking multiple studs.  I worry
about litigation and due diligence if something fails months or years from
now.
Randy

This is really a guess, but I think it would work.  The problem with
welding mild steel to stainless is that the carbon from the mild steel
mixes with the stainless and forms chrome carbides.  So you generally
need to use filler rod with a higher chrome percentage than the
original stainless.

My guess with stud welding in that there is much less mixing, and
therefore less of a problem.  316 has higher chrome and nickel so would
be less of a problem than say 304. You might get a better answer here,
but the best thing would be to try it.

                                                                    Dan

R. Zimmerman wrote:
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Re: Stud welding stainless

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You welding on a highway tunnel in Boston, by any chance? :-)

GWE

Re: Stud welding stainless
No tunnel Grant :'))
  I once was involved in a massive run of stainless imbeds for a pulp and
paper plant.  All the reinforcing bar and imbedded plates were 316
stainless.  The corrosive liquids in the mill would seep into the concrete
and eat away regular rebar.  That was some very expensive concrete work.
    This stud question was asked by me when I was told to start studding
huge stainless plates.  No one has come back with an answer.  I often find
that planners and engineers are not asking the right questions when they
design something.  I just don't want to see my employer take a big hit.  We
haven't started studding so hopefully a welding engineer is being consulted.
  It also doesn't make sense to have a stainless plate against concrete with
carbon steel anchors in the concrete.  This is a marine environment.
  I am sure that Boston business will thread its way through multiple
lawyers each taking his cut and ending in some multi-million dollar
settlement quietly signed off on ten years from now.  It will of course have
a non-disclosure clause.
  A store roof collapsed on opening day in my area many years ago.  The roof
served as a parking lot.  The steel erectors were alarmed at the roof and
questioned the strength.  An engineer looked at it and had a few more cross
braces put in.  No one double checked the math with an unfortunate result.
At least the iron workers asked.  In that case however it wasn't enough to
avert disaster.  There were many serious injuries to customers as they
evacuated the  building.
  Randy




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You welding on a highway tunnel in Boston, by any chance? :-)

GWE





Re: Stud welding stainless
You need even more caution in a marine envireonment.  Stainless
corrodes in stale saltwater.  Here in Washington State some of the
state ferries were fitted with stainless steel pipe for the saltwater
fire sprinkler system.  The saltwater in the pipes lost its disolved
oxygen which in necessary to keep the surface coated with chrome oxide.
 The chlorine corroded the pipes and they all had to be replaced with
regular pipe.

I would think the studs and back side of the plate would be a similar
situation.   So mild steel may be better than stainless in this case.
I hope you have smarter engineers than our state ferry engineers.


Dan
R. Zimmerman wrote:
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Re: Stud welding stainless
On 30 Aug 2006 09:10:03 -0700, dcaster@krl.org wrote:

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Caution is required when using SST in an environment where chlorides
are present, primarily because of the risk of "intergranular stress
corrosion cracking" (Google search on that term recommended for anyone
interested).  IIRC primary risk factors are stress levels, which can
be controlled by design, and intergranular carbide precipitation,
which can be introduced by welding and eliminated by solution
annealing.  Since post-weld solution annealing is not always practical
alloys with very low carbon like 316L or with carbon grabbing
additives like titanium or niobium ? (321 or 346 ?) are available to
reduce risk of stress corrosion cracking in the as-welded condition.

Intergranular stress corrosion cracking selectively attacks the grain
boundaries while leaving the bulk of the metal untouched.  I have
heard of cases where intact looking SST parts would crumble apart into
individual grains on touch, although usually failure occurs long
before that degree of grain boundary corrosion.

Welding carbon steel studs onto SST in a marine environment is not
something I would risk unless the design had already been proven to
have long term reliability in the application, as there will almost
certainly be some carbide precipitation at the grain boundaries.  316L
studs on 316L plate would be much better, or perhaps even 321 studs.

YMMV, the above is my hazy recollections on the subject from decades
ago presented solely as a suggestion of subjects for you to
investigate further.

Glen

Re: Stud welding stainless
Just to let you know Glen and others,
  Stainless steel studs are on order and will be installed on the stainless
plates rather than carbon steel studs.  I found this out today. ;'))
Randy


On 30 Aug 2006 09:10:03 -0700, dcaster@krl.org wrote:

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Welding carbon steel studs onto SST in a marine environment is not
something I would risk unless the design had already been proven to
have long term reliability in the application, as there will almost
certainly be some carbide precipitation at the grain boundaries.  316L
studs on 316L plate would be much better, or perhaps even 321 studs.

YMMV, the above is my hazy recollections on the subject from decades
ago presented solely as a suggestion of subjects for you to
investigate further.

Glen



Re: Stud welding stainless
Sorry, some one else will have to answer you on that.  I am not a
welding engineer and my opinion is likely to be worth less than you
paid for it.   I no longer get the AWS journal, but there was a column
in on welding stainless.  You might be able to get that expert to
answer your question.


Dan
R. Zimmerman wrote:
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Re: Stud welding stainless
This is a good example of a thread confused by top posting.

I am not a weld engineer and this thought is worth what you paid, but here
it is

The studs could be surfaced with stainless before stud welding them?
Perhaps they are available from the mfg already prepared?
Perhaps stainless studs are available from the mfg?

If this is a critical fabrication and you have liability concerns then IMHO
you should get a weld engineer's certification stamp on all non standard
welding. procedures  I would expect the customer/owner or the design
engineers to require this or to specify the correct procedures to be used.
The mfg of the studs or the stud welder may be able to help with approved
procedures.

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