7018 rods question

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)

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. .

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.

7018 restarts easily if you pinch off the flux ball on the end.

It does, unfortunately, like to stick to the metal on first contact, at least for me.

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

Yup. I just take it out of the electrode holder and bump it on the metal table or just bump it to get the flux off and then scratch start as normal.

rvb

-- As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17

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

If your machine is so equipped, turn on the HF

Makes stickwelding 7018 a joy all the way down to the stub

DO pay attention to where that stick IS however, at all times

Or use your pedal and set Start Current to 100%

Gunner

Yes... I think that HF with pedal is the ticket... thanks...

I use a high temperature firebrick to brake off the flux myself.

I sometimes weld atop of one.

Martin

Mart> >

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I just tap it on a piece of steel not in the welding circuit, often the side of my slag hammer. Ernie welds 7018 holding a chunk of steel in his left hand.

Grant

Mart> I use a high temperature firebrick to brake off the flux myself. >

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)

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)

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

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

It's the ones where you'd guess that the pidgeon ate a Vindaloo curry the night before that really make you worry :-)

Why? I like the way 7018 runs and I want to get past the 'semi'.

Jim Wilkins