using 7018 - advice in 7018-free-zone

I have used E 7010 for root passes and tack welding in one pressure vessel shop for one customer contract. My guess is that the customer wanted a slightly stronger weld alloy. From my understanding successive passes allow several reheats to allow any hydrogen in the root and hot pass to disperse out. There are a few methods to restart a weld to avoid porosity. One way is to strike up ahead of the old weld by about an inch. Hold a long arc and track back to the old crater then plant the rod over the crater, fill and continue on. The second or so tracking back allows the rod end to heat up. Any small bit of metal droplets that are sticking to the forward area are melted into the puddle as you carry on. Another way is to strike up on the previous bead, hold a long arc, track forward to the crater and carry on. This leave an arc track on the previous bead. This is not good if it is your final cap. The last is to do a tap strike right on the crater, fill and carry on. If you have a electrode and welding machine you know personally this is doable and the most efficient. Use run off tabs if possible. The only low hydrogen electrodes that have frustrated me with porosity at the start are the AC versions. In one structural shop I was in they used several big old AC machines for the fabricators tack welding. It took great care to get a tack without porosity at the start of the tack. It was not a great concern because it was structural rather than pressure work. The welding over the tacks was 1/16 inch flux core wire so most things would burn right out if the tack was small. This shop eventually changed over to tacking with 6011 on those AC machines then finally chucked the machines, bought MIG machines and ran solid wire for tacking. I would stick to 1/8th rod for learning.

Randy

"Richard Smith" wrote in message news: snipped-for-privacy@Richard-Smiths-Computer.local... Hello everyone

At college, I want to experience commercially useful welds. Want to try 7018's for the first time.

Technical question:

Does using 7018 as "hot pass" capping runs dilute-down and disperse the hydrogen and make the procedure OK even on slightly quench-hardenable steels (eg. up to 0.25%C) - so you can get reliable pen. and fast procedure without concerns over cracking?

Productivity question:

How fast should a 7018 weld be?

Technique:

I read from past SEJW postings that you use a very short arc with xx18. The suggestion is that you are so close as to lightly drag to flux edge on the job. So if you have the rod slope angle at

Where do you start your run, given that the start is prone to porosity? Do you start on top of the previous run so far, say about

What other things I should be watching / doing?

Rod recommendation and size:

I read that Lincoln Excalibur 7018 recommended. Any knowledge Bohler / Boehler "Fox EV 55"?

Have DC welders at home and at college.

What sizes, thinking of productivity? Is 3.2mm large enough for good productivity on 6mm (1/4") plate? Should I try to blag 4mm (5/32") rods? Is 4mm 6010/6011 root, 4mm 7018 cap good?

Thanks in advance.

Richard Smith

Practice your travel speed until you get about 6" of weld bead from a 1/8" 7018 rod.

GWE

Really? About half the run-out that the rod is long? That's going to be a big bead in a single pass. Just on run-speed alone. And then there is the iron powder mixed in the flux, increasing the amount of bead per length of rod burned by another few percent, isn't there?

That implies a different technique to 6013 where we were told to have a run-out of about the same length as the rod length.

What are typical run techniques. Root run, capping pass(es)... How would you do a T-joint on 1/4" / 6mm plate, for example? Or where do I go see recommendations?

Thanks - please do give me more detail.

Regards

Richard Smith

Really. I just spent the whole summer running 7018 at South Seattle Community College in Ernie's class, and every single instructor there says the same thing

- 1/8" 7018 should yield a 6" bead, whether horizontal, vertical, or overhead. If you're having great luck getting 10" beads, fine. Mine passed the severe WABO certification test (slicing, polishing, U-bending) so I'll stick with how I was taught. I don't know anything about recommended bead length for 6013 or indeed any other rod. I run a small amount of 6010 for tacking but mostly all 7018. It's the only welding process I really know anything about.

GWE

Grant

I'm here to learn. By "really?" I meant surprise and great interest. I do want to know what it is you have been taught.

Your bead is bigger so your pass sequence must be different, to get the same sized & strength weld.

For example - I found that for a 1/4" (6mm) plate h-v (horizontal-vertical) T-joint when you have rutiles, the fastest and best I could find which passes test (visual, nick-break and macro-etch) is: all 1/8" (3.2mm) at 125A - 1xcellulosic fillet-corner and 2xrutile stringer-bead cap (r2 follow root-bead-to-lower-plate with around 45deg tilt; r3 follow root/r2 bead to upright plate with around45deg tilt), the rutiles running-out at about a rod-length. I won't describe what is "official", as this involves significantly violating the maximum current recommendation of a welding rod in one pass.

Your bead cross-sections must be bigger at around twice the cross-sectional-area when run-out is half the rod length. So what run sequence do you do? With what diameter 7018 rods? What current(s)? Could you give this for a 1/4" plate T-fillet or lap joint so I can compare with what is familiar?

Please describe it - choices, settings and techniques. I have never seen a 7018 run being done!

Thanks again.

Richard Smith

Grant Erw> Richard Smith wrote:

Hi everyone

Ernie Leimkuhler said I am welcome to share with you the advice he gave me...

"Well the most common procedure we use is:

This setup is used for unlimited thickness of steel, with multiple passes.

Maybe 9 passes to fill a 1 inch plate weld.

The rod is run flat and overhead with a backhand technique, rod at around a 60 degree angle, with a slight weave side to side.

Vertical up is run with a 10 -15 degree uphill angle.

The same narrow slow weave side to side as you proceed slowly up the joint.

The weave is never wider than 2 rod thicknesses, and the weave is extremely s...l...o...w.

Never move quickly with 7018 in any position, it almost guarantees a slag inclusion.

If you move slowly the molten flux has a chance to flow out.

If you don't do a slight weave, the weld will have too high of a profile with sharp inside corners on the sides.

The weave wets out the weld on the sides so the next bead can flow right into it.

If you move too fast you will get undercutting on the sides. If you pull too long of an arc, the center of the bead will be to high. If you weave too fast you will get slag inclusions.

When you get the travel just right your beads should end up 5" - 6" long and the flux should just fall off."