True. I find 7018-AC runs just fine on a little AC buzz box. My only
problem with 7018 is vertical up. And I think I'm just moving too
darn slow. I'm working on it and starting to get it.
I don't find it any harder to start than any other rod.
rvb
--
As Iron Sharpens Iron,
So One Man Sharpens Another.
Proverbs 27:17
On Wed, 07 May 2008 23:42:32 -0400, "Rick Barter (rvb)"
Here's another question I've always wondered about. Why run 7018
anyway? The parent metal is probably mild steel and tests about 60,000
Lbs. 6010/11 and 6012/13 are easily obtainable and will make beads
about as strong as the parent metal - why bother with 7018?
Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)
The one thing that 7018 does that other rods don't do is lay unlimited
thickness multi-pass welds without infusing damaging amounts of
hydrogen into the weld.
That is the only reason to use Lo-Hi rods in the first place.
Which is why they need to be kept dry.
Water + electricity = hydrogen and oxygen.
The hydrogen problem only really applies to metal 1/2" or thicker as
hydrogen can eventually escape from 1/4" of steel.
Some people just apparently have a problem with it sticking on the start.
Burn enough of them, and that reduces.
Strong welds. You get to add a lot of filler metal without making multiple
passes. You can wash the puddle up from thick to join thinner metal. You
get a molten puddle that allows you to boil out impurities left by previous
passes or on the metal to start with. A pass with 7018 that is laid down at
the right amperage and buffed up with a wire wheel is a thing of beauty that
makes one at least look like they can weld. Anyone can do the "stack of
dimes" trick that is essentially a very weak weld, yet so many neophytes
think is the pinnacle of weldinghood.
Steve
Bruce, everyone
Given only so-so experience - I know from sledge-hammering to break
sample fillet-welds seeking approval to stock 7016's/7018's that quite
a small 7016 bead strength-matches the plate it's welding. Nice.
Given the rods run really nicely (7016 sweet on AC), there seems every
reason to want this outcome - UNLESS you want to weld to break first -
which can be the case with things designed knowing they will always
suffer agr(o|avation) - typically car-park height-restriction barriers
(which you design to fold gracefully to the floor with progressive
tear of the weld), in which case 6013 is the rod for you.
Rich Smith
Mild steel, as I specified, has a tensile strength of about 60,000
psi. The 60 series rods have a tensile strength of about 60,000 psi. A
properly made weld is thicker then the parent metal and thus is
actually stronger then the parent metal. Which prompted my question,
why use a 70,000 psi rod if it is hard to start or run, as the
original poster mentioned.
Now, if you want to specify that the lo-hi rods can run thicker beads
without hydrogen embitterment that is a good reason, but how many
people are running beads on 1/2" plate, or thicker - and I suggest
that those who are, are probably welding to the owner's welding specs
and have to run the rod specified anyway, which again is a good
reason.
But a semi-skilled guy out in the dooryard with the 110 VAC buzzbox -
why bother?
Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)
Good point. Any weld that holds is a good weld, gorilla welds included. If
it HAS to look good for one reason or another, then it goes from there. If
technical stuff enters in to it, then rod selection goes from there. It all
depends on the results and appearance you desire.
Steve
Don;t know about the "gorilla welding" but I've seen a bunch that
looked more like a bird flew over..... :-)
Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)
>>>>
Bruce
Given that you have way-out-there experience, I'll try to tread
respectfully...
Seeing is believing doing a simple destructive "sledgehammer" test on
7016/7018 welds - especially compared to Rutile (6013)
Quoting "60ksi plate, 60ksi weld" as the basis of an argument tells
far from the complete story.
For a start, to blur the picture, isn't there a marketing issue and
naming of rods "according" to AWS. In the UK for instance, you never
see a rod labelled "6012" (suspect all non-iron-powder Rutiles are all
labelled "6013" regardless). Iron powder Rutiles - I don't believe
you come across "6014" rods (all are called "7014").
Speaking now as a metallurgist who has sectioned some welds and looked
at microstructures...
The
- xx10/xx11 "Cellulosic" family
- (xx12 and) xx13 "Rutile" family
- xx15/xx16/xx18 "Basic" family
are three way different animals.
Comparing the "60" and "70" would tend to distract from the big
metallurgical differences giving big property differences.
Important point - this is only about *"stick"/SMA welding* (FCW MIG
welding is a different thing, for reasons I now can't remember - you
can weld an oil-rig with Rutile FCW, as their weld metal deposits are
excellent)
Seen under an light-optical microscope, Rutile SMA weld beads have
"huge" inclusions which look the size of dinner-plates at higher
optical magnification - 500X to 1000X.
Consequently, you have to make the matrix weld metal soft in order to
have the weld metal plastically deform around the inclusions, rather
than the inclusions act as a crack-initiating stress-raiser sites. But
this has a doubly very sad consequence on properties. Yes it's softer
which is synonymous with strength is reduced. But the really really
"sad" thing is that the "acicular ferrite" microstructure which gives
good strength is also tough. Normally strength and toughness work in
different directions, but the fine "intra-granular nucleated"
acicular-ferrite weld microstructure has both. So with Rutile stick,
in deliberately degrading the transformations so you don't get
hard/strong acicular ferrite, you end up with coarse blocky "normal
transformation" ferrites - which are way down on toughness compared to
the very desirable acicular-ferrite microstructure. So there you have
it - a low-strength rod which is also brittle as a carrot (cue various
sobbing sounds, etc.)
"Basic" 7015/7016/7018 rods form tough microstructures so there is no
call for a 60ksi strength rod. You have way adequate inherent
toughness that no purpose would be served by dropping strength below
70ksi. The weld-metal is notch-tough at 70ksi strength level anyway.
That "Basics" if treated in a particular specific way can give a
Low-Hydrogen stick welding rod is irrelevant for welding mild steel.
They are "Basic" rods giving "Basic" mechanical properties.
Incidentally and irrevantly (?) - the hydrogen level they give in the
weld can climb about as high as for a Rutile (?). When I say "Basics"
I usually get the riposte "You mean Low Hydrogens.". Sucking up a lot
of water from the atmosphere, I wouldn't say so myself...
(???)
So back to the "sledgehammer test" and the evident superiority of the
Basic fillet.
When you do the sledgehammer attack on the piece of metal Basic test
welded to an immovable steel object, even a small single-side fillet
bead causes the deformation to initiate and remain in the structural
steel, not the weld metal. So deformation is spread over say 30
millimetres of the structural steel - not 0.25mm at the fillet corner
of the weld metal - and you are going to sweat a lot before you've
broken the single welded piece into two broken bits. Then - even if
there were a welding defect in the 7015/7016/7018 fillet bead - it's
tough - so it still isn't going to give - you'll still be bending the
structural steel backwards and forwards trying to get it to break.
With a Rutile bead - to compensate with increased fillet size, the
fillet leg-length increases linearly as the fillet-bead area goes up
as a square relationship - so to double the fillet leg-length, you
need to quadruple (4X) the amount of metal deposited. Doing a
double-sided fillet is more economical of metal. If you can get
access to the back of the weld. And if so, if you fancy walking
around there. Lugging your welding machine if it's some sort of
dividing wall...
Then the weld metal is inherently brittle, so you better put down a
good bead... 'cos if it starts to deform at the fillet corner where
the plate edge aims like a sharp crack right into the weld root, it'll
"go" quickly - won't take much energy (sledgehammer blows!).
Cellulosic rods are somewhere in the middle between Rutiles and
Basics. Where a Rutile weld will be wiped away by one sledgehammer
blow, a Cellulosic would typically take three blows...
Well Bruce - appreciate your help before and hope this is interesting
and worth-while for you...
Regards
Rich Smith
Good comments.
While the 'sledgehammer test is better than nothing, it does have
limitations. Since most welds are stronger than the base metal, IMHE it is
the base metal (most commonly <45k tensile) that is most likely to fail
first. This is particularly true of fillet welds, IMHO, a 'Charpy notch
test' performed by notching (with a saw) a butt weld in plate then breaking
with a sledge will be more revealing and, IMHO a 'guided, sidebend test is
much more demanding and revealing of weldor performance. The same press
used for a guided sidebend test can also be used for a root or cap test of a
butt weld in 1/4 - 1/2" plate but IMHO the side bend is a much tougher test.
Just my .02, YMMV
>>>>
Either your description of testing is not sufficiently clear or the
test method is faulty.
Yesterday I cut some 4 inch coupons and welded them . I then
mechanically cut a 2 inch wide section from the center of each coupon
and "bashed it with a hammer as you describe.
All welds were 100% penetration and both butt and fillet welds were
made.
I used 6010, 6012 and 7018 rod for the tests.
After the bashing none of the welds had failed. In all cases the
parent metal bent. In no case did a weld, regardless of the rod used,
fail.
Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)
On Sat, 10 May 2008 04:58:55 -0700 (PDT), Jim Wilkins
Well, that is certainly a valid reason.
My comments were aimed at the original remarks about 7018 being hard
to start or run. Not to disparage anyone but the guy seemed like a
beginner that either had a small welding machine or limited skill. I
was pointing out that if you have trouble running one particular rod
then switch to a different easier rod. It doesn't make any difference
in the type of welding that average door yard welder does as the 60
series rods (that are usually easier to weld with) are plenty strong
enough.
Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)
To get your travel speed just remember that an 1/8" electrode 14" long
should yield 5 - 6 inches of weld bead in any position, any direction.
Hold to that and your flux will just fall off.
.
On Wed, 07 May 2008 23:04:15 -0700, Ernie Leimkuhler
Thanks, Ernie. I'll keep that in mind and try it out. I'm heading
out to the barn later and to the welding school today or tomorrow.
I'll have plenty of time to practice.
rvb
--
As Iron Sharpens Iron,
So One Man Sharpens Another.
Proverbs 27:17
In the flat position, if you got everything right, as it cools, it starts to
bend up on one end, and continues until it comes off in one piece looking
like a curved banana peel. Most of your spatter will have been kept in by
the molten slag, and the outsides of the weld metal will have very little
spatter on them. You can just rake the unfluxed end of a rod along the
sides of the finished weld, and knock off 99% of the flux that doesn't come
off in one piece. It sure is pretty when it does that.
Steve
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