7018 root pass

[apprentice welder]

Hello everyone,
I have been welding for a few years now at home and have decided to start my welding apprentiship. I have already passed my F3 plate ticket, and am now starting my F4. I'm using 3/32 BOC 7018 rods kept in rod oven, and am welding with a Miller Syncrowave 250. The only trouble im having is laying down a good root pass. I grind the bevel on the plates to have a flat 3/32 landing and tac them together with a uniform 3/32 gap. Currently I am using a step motion with the rod, and it seems to work ok but i usually end up with to much or to little penetration. Any advice would be appretiated. Thanks

[Sberry]

Normally this electrode wouldn't be used on an open butt root, it has been done but most often its done with a backing strip of if its open a 6010 type electrode is used.

[Craig in Denver]

The size of the keyhole defines penetration. Bigger KH = more penetration; smaller KH = less. If your KH is inconsistant, so is your penetration.
Good Luck.

Edit: I agree with Sberry about the 6010. I quessed inst. called for the 7018.

[apprentice welder]

Thanks guys, my instuctors also said that I most likley won't use 7018 for a root pass again. I forgot to mention that I have to weld these coupons (like I already did with my F3 ticket) in all postions. Any tips on out of position? Is it simular to 6010?

[fabricator]

Thanks guys, my instuctors also said that I most likley won't use 7018 for a root pass again. I forgot to mention that I have to weld these coupons (like I already did with my F3 ticket) in all postions. Any tips on out of position? Is it simular to 6010?

Isnt this is what an instructor is for?
6010 is what you need to use.

[apprentice welder]

Isnt this is what an instructor is for?
6010 is what you need to use.

I know that its alot easier to use 6010 when welding a root pass, but to pass the F4 you cant use 6010, you need to weld the entire joint with 7018.

[enlpck]

I've worked on it a bit, but am by no means an expert, though I have worked with a couple.

A common application: marine work, where you may be welding plates that will see temps of -40 or below routinely. The typical filler here would be 7018-1 (charpy at -50 deg F is specified, as opposed to -20 for regular 7018), open root weld. Plenty of other apps, but they tend to be special to particular industries.

Technique I was taught and have seen (not the only way, by a long shot): Try thinking of the weld as being done in a different position. Easiest to describe for vert-up: Instead of pointing the rod into the groove, level or slightly pointing up, the rod is closer to up-and-down (maybe 45 degrees drag), and a slight in-out walk can be used, as if running a ton of real short flat beads in the direction of the groove depth. One end of each is in the grove near the bottom, the other is through the keyhole. A slightly wider gap helps, and you need to reform the keyhole on every motion.

The guy that tried to teach me (my open root '18 is not what I would call good) can lay in a weld where the root looks like a cap, and is dead pretty once the slag is knocked off. Then again, his caps look like one of those 'artists renditions' of what it should look like.

[lynx_welding]

if you are able to take more land i would go as far as 1/8 to 5/32 if possible. other than that it's all minipulation of the rod

[Sberry]

Certainly makes sense for extreme service. Look how strong and tough a 7018 tack weld can be. I used a 7018 for the root on a fillet back bend test once, they were breaking the ones that had 6010 roots.

[lynx_welding]

thats because 6010 only has a 60000 tensile strength. and i know every pass over another aneils it and makes it srronger but only to a point. but having a 70000 tensille the whole weldment there should be no question the 6010 root breaks before the 7018 root the tensile strength just isn't there