I run a sub arc welding tanks of 3/16 to 1/4 thick steel. We have had
a lot of problems with porosity but things are getting better. I had
started to run a torch on the seams to be welded which I have been
told and read that this is to drive out moisture.
One of the guys told me today that while I was off last week he put
the torch to the seam and saw what he claims is flux that is left from
when the real welders back weld the seams and heads of our tanks. He
says he could burn this out by slowly running the torch on the seams.
I have not seen anything about this in any of the articles I've read
on sub arc or from the people who sold us the machine who spent
several days with me. He came over today and kept telling me about his
theory and tellling me to slow down when I run the torch to get it
hotter to burn off this "flux" he thinks he sees. I think what he is
seeing is thin slivers of metal that are getting much hotter than the
metal since they are just thin slivers.
I did slow down on one tank since I'm willing to try anything. It
didn't make any difference but that was only one trail.
I think this guy is wrong and wondering what y'all think.
They are backwelding with Makay wire, flux core. What temp would flux
melt at anyway? It seems that if it were somehow getting trapped in
there that my running a torch isn't going to get it hot enough anyway
I do see there is a lot of moisture that has condensed on the tanks.

When you say you are back welding the seam does that mean the inside weld is
being done with flux core??

Flux core is not intended for open root welds. If you are seeing part of
the weld from the outside before you run your sub arc my guess that is your
problem. For some reason flux core tacks don't like sub arc. Don't ask me
why because I do not know the answer. That bit of weld you see will have
flux attached to it.

The better way to tack or back weld is with hard wire. Even hard wire
tacks will give problems. I had an experience with periodic porosity on
truck wheels. The reasons given to me ranged from cheap Chinese steel to
trace amounts of machining coolant. I traced it to big bad tack welds done
with hard wire.

The way I confirmed it was to mark on the steel before sub arcing the
location of all tacks. Sure enough the porosity was at the tack weld
locations. Once I badgered the assemblers to run a proper little bead in
the root rather than holding the gun on the steel and pulling the trigger
while wiggling the problem went away.
I would try running a narrow grinding disc along the seam grinding clean
any bits of weld metal you see. My guess is that will work as well as
"cooking" it out.

I have found out that sub arc is very forgiving in most cases.
Re: "driving out moisture" On such thin material you do not need to
preheat. If the metal came in from the rain then it is a good idea to dry
it off. The moisture you see when you heat your material is the hydrogen in
the heating fuel joining with oxygen in the air forming steam that condenses
on the colder metal surrounding the flame. When you "Drive" the moisture
out all you are doing is heating the metal above 212 F.

Randy

"Butter" <clann...@yahoo.com> wrote in message

news:1170109300.514840.57170@m58g2000cwm.googlegroups.com...
I run a sub arc welding tanks of 3/16 to 1/4 thick steel. We have had
a lot of problems with porosity but things are getting better. I had
started to run a torch on the seams to be welded which I have been
told and read that this is to drive out moisture.
snip
I think this guy is wrong and wondering what y'all think.
They are backwelding with Makay wire, flux core. What temp would flux
melt at anyway? It seems that if it were somehow getting trapped in
there that my running a torch isn't going to get it hot enough anyway
I do see there is a lot of moisture that has condensed on the tanks.

Try grinding the weld seam as I suggested before you sub arc. Also inspect
before welding and mark questionable areas with soapstone before you weld to
see if your suspicions are correct.

Many years ago I was at an AWS meeting where there was a presentation on
the construction of a certain bridge. The presenter showed slides of their
operation. They were having all kinds of porosity issues at the tack welds.
They ended up having to aggressively grind all tacks.
An older and highly respected person at the back of the room interjected
and asked why they even entertained the thought of using dual shield rather
than hard wire. Most of the old hands in the room nodded in support.
Flux core welding is excellent when you are welding against a backing bar
in a groove weld or the groove weld is done is an absolutely tight butt
joint. If there is a gap some of the flux will end up on the bottom of the
gap as it is sealed up and there is risk of porosity of the weld because
there is little or no shielding on the back side of that root.
I was in a shop where they used air tools and had prepped their joints
with the air grinder. The lube oil in the exhaust of the grinders was
contaminating the joint. Once they went to electric grinders for cleaning
the problem disappeared.

The big ugly tacks and oil on the surface are the only problems I have
seen with repeated porosity.in front of the nozzle. I stopped and checked the flux thinking there was something contaninating it and catching fire. I found nothing and started it up again. No more fire. I guessed there was oil or something in the seam that boiled out after i temperarily stopped. Now I have an idea what happened.

Don't discount your skill level on sub arc. A lot of "real welders" run
from the units. Even though it is automatic there is still a lot to learn.
Good operators know everything by sound and colour. I have seen guys run
way outside the recommended parameters and still produce excellent welds.
They know how to tweak the speed, stickout, heat and voltage to get the
result they want.

I love the "cheap foreign steel line". I have seen just as many flaws in
plate made in North America. One CFS situation I was shown was a 2.5 inch
plate that the operator had started to roll when it snapped apart. Close
examination showed that someone had used the plate as a work bench and there
were short tack welds on the surface ground flush. Those tacks on such a
heavy plate created stress sites that caused failure during rolling. The
company had already call the steel representative ready to hit him with both
barrels about his defective plate. I would have liked to be a fly on the
wall when he arrived later that day.
Breaking at the bottom of the range of Ultimate Tensile Strength is a
good thing. I would bet dollars to donuts the steels ductility was high.
He didn't mention the elongation percentage before failure did he?? I'll
bet not.

Your question about condensation from the flame on the plate? The amount
of condensation you see on the plate is determined by the temperature of the
plate to start with and the relative humidity in the shop.

Randy

On Feb 1, 8:01 am, "R. Zimmerman" <m-zimmer...@shaw.ca> wrote:
Try grinding the weld seam as I suggested before you sub arc. Also
inspect
before welding and mark questionable areas with soapstone before you
weld to
see if your suspicions are correct.

I started doing this today.I'm marking where they are tacking it,
where there is a gap also. I've also started grinding the seams. Of
the 11 tanks I've done this week the one that was by far the worst had
the worst fit up, and preparation. I'm real hesitant to try and tell
these guys what to do. My background is in the machineshop and not
welding. I'm not exagerating when I say they just picked someone off
the street, pointed at the sub arc and said go figure it out. But I am
getting experience and I at least know more about the sub arc than any
of them. I'm trying to be diplomatic. Even the Lincoln factory rep
didn't know anything. He would come out and read the book to me.

Many years ago I was at an AWS meeting where there was a
presentation on
the construction of a certain bridge. The presenter showed slides
of their
operation. They were having all kinds of porosity issues at the
tack welds.
They ended up having to aggressively grind all tacks.
An older and highly respected person at the back of the room
interjected
and asked why they even entertained the thought of using dual shield
rather
than hard wire. Most of the old hands in the room nodded in support.
Flux core welding is excellent when you are welding against a
backing bar
in a groove weld or the groove weld is done is an absolutely tight
butt
joint. If there is a gap some of the flux will end up on the bottom
of the
gap as it is sealed up and there is risk of porosity of the weld
because
there is little or no shielding on the back side of that root.
I was in a shop where they used air tools and had prepped their
joints
with the air grinder. The lube oil in the exhaust of the grinders
was
contaminating the joint. Once they went to electric grinders for
cleaning
the problem disappeared.

I'm going to tell them this tommorrow. A few weeks ago I noticed
something catching fire occasionaly
The big ugly tacks and oil on the surface are the only problems I
have
seen with repeated porosity.in front of the nozzle. I stopped and
checked the flux thinking there was something contaninating it and
catching fire. I found nothing and started it up again. No more
fire. I guessed there was oil or something in the seam that boiled
out after i temperarily stopped. Now I have an idea what happened.


Don't discount your skill level on sub arc. A lot of "real
welders" run
from the units. Even though it is automatic there is still a lot to
learn.
Good operators know everything by sound and colour. I have seen
guys run
way outside the recommended parameters and still produce excellent
welds.
They know how to tweak the speed, stickout, heat and voltage to get
the
result they want.

I was amazed when we had three experts come out and they said I had
set the thing up fine and they didn't need to change anything. I may
not know what I'm doing but I work at it, read what I can find and ?
everything.

I love the "cheap foreign steel line". I have seen just as many
flaws in
plate made in North America. One CFS situation I was shown was a
2.5 inch
plate that the operator had started to roll when it snapped apart.
Close
examination showed that someone had used the plate as a work bench
and there
were short tack welds on the surface ground flush. Those tacks on
such a
heavy plate created stress sites that caused failure during rolling.
The
company had already call the steel representative ready to hit him
with both
barrels about his defective plate. I would have liked to be a fly
on the
wall when he arrived later that day.
Breaking at the bottom of the range of Ultimate Tensile Strength
is a
good thing. I would bet dollars to donuts the steels ductility was
high.
He didn't mention the elongation percentage before failure did he??
I'll
bet not.

No


Your question about condensation from the flame on the plate? The
amount
of condensation you see on the plate is determined by the
temperature of the
plate to start with and the relative humidity in the shop.

I'm in the Ozarks in Arkansas and we get lots of rain here
sometimes.

Randy

Thanks again. Your really being big help. I got an email today from
the Lincoln guy saying they have several of these units in service
now. Apparently we were the first and that might explain why he didn't
know anything. He was telling me about problems at the other shops
that might help me.
Rosco

One more thing about sub arc:
Lincoln Electric has several information sheets/booklets dealing with sub
arc settings and troubleshooting. It was years ago when I downloaded them
but I am sure they are hidden away in the information section. They are in
adobe format so that you can download and read or print out for yourself if
anyone is interested.
Submerged arc welding is a very old process. It is not cutting edge yet
it is quiet, relatively smoke free and produces quality welds once set up
properly.
Randy