Dual shield rookie

[Willie B]

I've only run two 33 LB reels of .045" Dual Shield. First roll I had a miserable time with porosity & / or worm tracks. I was crying the blues at Maine Oxy & the manager explained that part of the number on the box includes the gas needed. I had wire for 85% gas, but was using 75% gas. He sold me a different roll & cured that problem.

Another problem plaguing me was bird nesting. I could run as much as I wanted without striking an arc. Strike an arc, within an inch of weld it'd bird nest! My gun is a big Bernard 300 amp gun I bought when I melted my Miller M25 gun. Down side of Bernard is no two guns are alike, & part numbers are hard to find. Eventually I found a "JUMP LINER" It replaces the last 18" of the liner & is much smaller in internal diameter. This, along with some little felt pads & lubricant cured the birdnesting problem.

 

[Old Doug]

Bird nesting was a nightmare were i worked . One big deal was never trigger it. If you started to weld and stopped for a second then strated agin it was all over . Dual Shield was a big learning deal . If there would have been someone that could have come in and schooled us on it he would have saved the company several thousands of dollars in lost time and scraped wire. It was a new shop and a new way to weld for everyone there.

 

[Vetech63]

OK, I'll admit I didn't know wtf dual shield meant here. Last time I heard that I was asked about the possibility from a chick I picked up in a bar. I was much younger then.

 

[Jonas302]

Don't forget duel shield calls for knurled feed rollers and proper feed wheel pressure I have run either way but knurled rollers are better

 

[Welder Dave]

Dual-shield is flux-core wire that uses an external shielding gas. It needs knurled drive rolls but you have you to be very careful you don't have too much tension on the drive rolls. Too much can make birds nesting more of a problem. The wire is hollow so it will squish easier and deform from too much drive roll pressure. Too much drive roll pressure will also shave tiny bits of wire off the spool as the wire is fed. Birds nesting is the wire piling up right after the drive rolls. Birds nesting can be caused by a few factors or a combination of factors. Wrong size liner or a plugged liner from dirt or metal shaved off the roll, too tight of curve in the gun, wrong size or deformed contact tip (worn out or built up with spatter) (deformed wire can jam in the contact tip as well). Flux-core wire doesn't normally use a wiper before the drive rolls because it is coated with graphite. The graphite acts as a lubricant and also prevents rust. Using a dry wiper would actually make feeding worse. A lubricated wiper may or may not help. There are some that believe a lubricated wiper makes the wire attract more dust and dirt. Flux-core also uses a little more stick out than solid wire. Self-shielded flux-core can have up to 3 3/4" stick out but is uses with a long insulator. On wire without an insulator using too short of stick out could also contribute to birds nesting because the wire would expand from the heat and get jammed in the contact tip. That's likely what happens if the wire birds nests after striking an arc and stopping and starting again.

 

[oceanobob]

I've found:
1) a careful exact investigation of the welding voltage and amperage by way of a good DVM will give the answer as to the 'random' defects .... this has solved the problem more occasions than blaming the subtle breeze.
2) A 'no brush' gound clamp (w sealed Hg) is advised when using a rotator; the one we tried and bought is from meridian lab and is called rotocon IIRC.

 

[Welder Dave]

Random defects sometimes just happen with flux-core even when everything is set up perfect. I worked in a shop where another welder threw the gun across the shop because the flux-core went wonky. I had the exact same thing happen. Welding 4 gussets on the base of flare stacks, 3 went perfect, roll the pipe to put the 4th one in flat position just like the other 3 and would get worm tracks and porosity. Didn't happen very often but did happen a few times. Real pain to have to grind out with a die grinder. Usually had to grind it out as best as possible and reweld it with stick. If you tried to run flux-core again the porosity would just come back. Welds in the open without corners rarely had any problems.

 

[Stick-man]

I use hard wire for 5/16 and under. Over, I love Lincoln 71A85. It is stupid easy to run in any position. I have only used 75/25.

 

[Toddgarage]

Something very crusty and rusty got to the yard this weekend. Guess it’s time to try this outer-shield or dual shield welding process.
It might be a few weeks. But I’ll try to remember to reply here with an update

 

[Welder Dave]

I'm not sure how dual-shield works on rusty dirty steel. That's 6010 territory.

 

[Willie B]

I have had a long learning curve with Dual Shield. First try I burned up my stock MIG gun, it is a HOT process!

I had occasional trouble with porosity, & worm tracks, & the last time I used that 33 LB reel it would bird nest immediately! I tried everything, even these little felt gizmos you put a special oil on. Nothing solved my problem until I was poking through my ftuff that came with the big Bernard gun. Found a Jump liner. It is about 16" long, you cut off the main liner, this fits over it & necks down to a smaller diameter, wire pushes easier.

When I was ready to give up on Dual Shield entirely, the manager at Maine OXY asked what gas I was using. I was using wire meant for 85% argon, I was using 75% argon. He sold me a new roll of wire worked much better.

 

[Willie B]

I'm not sure how dual-shield works on rusty dirty steel. That's 6010 territory.

Dual Shield is supposed to be better than short circuit MIG on rust, but it isn't 6010 by any means. I believe you still need to grind away rust or mill scale. Any weld you want strong, grind first.

 

[Old Doug]

Something very crusty and rusty got to the yard this weekend. Guess it’s time to try this outer-shield or dual shield welding process.
It might be a few weeks. But I’ll try to remember to reply here with an update

I passed several weld test with dual shield it needs to be very very clean . It will not weld over any paint or rust.

 

[Welder Dave]

I would think dirty or rusty steel would wreak havoc with dual-shield. I recall there was a Lincoln Innershield (self-shielded flux-core) wire that was good for galvanized and dirtier steel. Can't remember if it was NR211 or a different wire. There are a lot of different Innershield wires but you never hear much about them. Some are straight polarity and some are reverse polarity. I always shake my head a little when I read comments that (self shielded) flux-core always has to be run on straight polarity. It depends entirely on what wire you're using. I've never seen a dual-shield wire that runs on straight polarity though. Another interesting tidbit is that sub-arc, which is a wire feed process can run on AC current. A tandem sub-arc set up can run on DC and AC at the same time. Sub-arc can also have 2 wires feeding each puddle for max. deposition rates. I worked in 1 shop that had a tandem sub-arc but they never used it. It was older but there was a huge 1200 amp Lincoln AC power source sitting there. I did a quick look and they still sell the Idealarc AC1200 for over $40,000us! Being AC it runs on single phase power. I wouldn't want to have to pay the electric bill for that welder.