Dual Shield Flux Core Welding Class at Hobart

[Don52]

For the past two weeks I attended a dual shield flux core welding class at the Hobart Institute of Welding Technology in Troy Ohio. It was the sixth Hobart class that I attended. Hobart has two basic welding class series: Structural, which is five months long and Pipe, which includes structural and is ten months long. Most of the students take the pipe class. The first shift class, which I attended was from 8 till 4, with one hour off for lunch. The first week we welded 3/8” plate and the second week we welded 1” plate. There was one written test each week and every different position of weld was tested. In my case all of my welds were tested with a bend test. If I had been enrolled in the entire series, they would have tested my 1” horizontal and overhead welds by a CWI and an Xray test. The students that passed the CWI and Xray tests (which was most of the class) received a AWS certification. I could have paid extra for the additional testing, but for $350 I chose not to. To pass the course you have to pass all of the written and weld tests. Every few weeks they start another group of students, so at any time they are actually conducting most if not all of the classes. This means that a student like me can take any class at pretty much any time. I took my first class in 2008 and every few years I took another class. I actually scheduled this class two years ago, while I was still working, but it was canceled due to Covid. The two-year delay was due to my stent and hernia operations. I really enjoyed the class, but I should point out that I was the slowest student in the class in terms of getting welds done. I was also the oldest student in the class.

I just did a very slight weave for the root pass

1. Horizontal root


As directed, I did all stringer beads for all of the horizontal welds.

2. Horizontal cover


3. Cutting test samples


4. Horizontal weld tested


I did a single weave pass for the first vertical fill pass. Some people did two beads instead.

5. Vertical first fill pass

[Don52]

I did a single weave pass for the cover. They told us that keep weave passes below one inch.

6. Vertical cover


7. Vertical test samples


8. Overhead cover


The sample passed even with the cracks, because the cracks didn’t occur on the weld. The fact that I quenched the sample before I ran the cover pass, might have contributed to the cracks. It is ok to quench practice welds, but it is a bad practice to quench test welds. My bad.

9. Overhead test samples


10. Overhead root

[Don52]

I chose to use multiple weave passes for each fill level.

11. Overhead fill pass


12. Overhead cover


For the one-inch-thick plates we cut 3/8” strips and side bent them. If you look closely, you can see the weld profile in the test sample.

13. Overhead test samples


14. First fill pass


15. Fill pass

[Don52]

16. cover pass


If I had run straight stringer beads it would have taken ~21 passes. I used narrow weave beads instead.

17. Run on tab


18. Vertical test samples

[smithdoor]

I used dual shield flux core for over 20 years. Great welding wire.

Dave

For the past two weeks I attended a dual shield flux core welding class at the Hobart Institute of Welding Technology in Troy Ohio. It was the sixth Hobart class that I attended. Hobart has two basic welding class series: Structural, which is five months long and Pipe, which includes structural and is ten months long. Most of the students take the pipe class. The first shift class, which I attended was from 8 till 4, with one hour off for lunch. The first week we welded 3/8” plate and the second week we welded 1” plate. There was one written test each week and every different position of weld was tested. In my case all of my welds were tested with a bend test. If I had been enrolled in the entire series, they would have tested my 1” horizontal and overhead welds by a CWI and an Xray test. The students that passed the CWI and Xray tests (which was most of the class) received a AWS certification. I could have paid extra for the additional testing, but for $350 I chose not to. To pass the course you have to pass all of the written and weld tests. Every few weeks they start another group of students, so at any time they are actually conducting most if not all of the classes. This means that a student like me can take any class at pretty much any time. I took my first class in 2008 and every few years I took another class. I actually scheduled this class two years ago, while I was still working, but it was canceled due to Covid. The two-year delay was due to my stent and hernia operations. I really enjoyed the class, but I should point out that I was the slowest student in the class in terms of getting welds done. I was also the oldest student in the class.

I just did a very slight weave for the root pass

1. Horizontal root


As directed, I did all stringer beads for all of the horizontal welds.

2. Horizontal cover


3. Cutting test samples


4. Horizontal weld tested


I did a single weave pass for the first vertical fill pass. Some people did two beads instead.

5. Vertical first fill pass

[tapwelder]

What did you grind with?

[psacustomcreations]

Don,
Nice work and great pics as usual.

I will also recommend the Hobart school or the Lincoln Electric Weld School to anyone interested in specific classes.
I attended the two week Oxy-Acetylene course at the Hobart school. This is one of the first classes in their comprehensive courses. The instructors were very knowledgeable and it is a clean and well run school.

I also attended the GMAW, Flux core GMAW, and GTAW classes at the Lincoln Weld School.

[Willie B]

On my own, no instructor, I have NOT mastered Dual Shield. Sometimes it works, other times I get worm tracks, or even porosity. Can't figure out if it's gas coverage, or bad wire. Oscar had some promising suggestions as to nozzles & techniques. I have a TERRIBLE time with bird nests.

[Don52]

I used dual shield flux core for over 20 years. Great welding wire.

Dave

I have used it for several projects already. Here are a few dual shield flux core welds that I have done in the past.

21. Dual shield fillet weld


22. Leveling foot welded


23. Slag chipped from leveling foot

[Don52]

What did you grind with?

I really like the Metabo grinders. I own a bunch of them. My favorite is the 6" grinder. I use it with the Metabo long life grinding wheels. This grinder draws 14.5 amps and is as powerful as my large and heavy 7" Ingersoll grinder, which I hardly ever use. I especially like the s-clutch which will allow cut off wheels to slip if you accidently bind them. I also like the fast brake, which stops the wheel rotation in 2 seconds. I bring this up because not all models have these options. I also prefer the non-locking paddle type switch.

19. Metabo grinder


20. Grinding wheel


-Don

[Don52]

Don,
Nice work and great pics as usual.

I will also recommend the Hobart school or the Lincoln Electric Weld School to anyone interested in specific classes.
I attended the two week Oxy-Acetylene course at the Hobart school. This is one of the first classes in their comprehensive courses. The instructors were very knowledgeable and it is a clean and well run school.

I also attended the GMAW, Flux core GMAW, and GTAW classes at the Lincoln Weld School.

Thanks, good point. I considered both the Lincoln school and the Hobart school for the first class that I took, which was the TIG class. I chose the Hobart school because it was two weeks (The Lincoln school was only one week). I felt that longer class would give me more practice and I could use all of the help that I could get. If unlike me you are a fast learner, the Lincoln school will save you some money. I did take a design of weldments class at Lincoln and got to tour their welding school lab. I understand that since I was at Lincoln, they built a brand new welding school lab, which is much nicer than the old lab.

-Don

[albrightree]

I ran some Blue Demon gas shielded .035 mild steel wire yesterday on a new machine I picked (180 amp mig). Used straight CO2 with 23-24volts @ 375-400 inches/min. Used on 1/4" plate and 1-1/2"x 11ga. sq. tube , not much power to spare, but it did it.






What wire/size did you use ? I'm guessing it was a Hobart Product Excel Arc is the only one I've seen in .035", .045 seems more common.


What did you use to cut the 1" thick coupon ?

Thanks for sharing, those pictures are nice.

Best regards

[Don52]

I ran some Blue Demon gas shielded .035 mild steel wire yesterday on a new machine I picked (180 amp mig). Used straight CO2 with 23-24volts @ 375-400 inches/min. Used on 1/4" plate and 1-1/2"x 11ga. sq. tube , not much power to spare, but it did it.

What wire/size did you use ? I'm guessing it was a Hobart Product Excel Arc is the only one I've seen in .035", .045 seems more common.

At home I am using .035" Lincoln Outer shield 71M wire 24 volts 330 wfs

At class we used .045" wire 24 volts 286 wfs for vertical up

At class we used .045" wire 25 volts 305 wfs for overhead

What did you use to cut the 1" thick coupon ?

We used a Oxy-Propylene track torch. it made a nice clean cut. Here is another cut that I made on the one inch plate.

28. one inch cut

Thanks for sharing, those pictures are nice.

Thanks,
-Don

[Don52]

On my own, no instructor, I have NOT mastered Dual Shield. Sometimes it works, other times I get worm tracks, or even porosity. Can't figure out if it's gas coverage, or bad wire. Oscar had some promising suggestions as to nozzles & techniques. I have a TERRIBLE time with bird nests.

I had a similar problem with worm hole porosity that you described. I put a fresh roll of dual shield flux core wire in my welder and it worked fine. At the time I did my welding on weekends, so I left the wire in the welder in between sessions. It was summer so it was very humid here in Michigan. After about two weeks the worm holes appeared.

The theory is that the current passing through the electrode extension, (which is the length of wire extending from the contact tip to the arc) causes the wire to heat up, which drives out the moisture from the wire. The following two things can increase the electrode extension and therefore help to eliminate worm hole porosity:

1. Lower Voltage results in a shorter arc, so more wire sticks out.

2. Keeping the nozzle further from the work piece, again so more wire sticks out.

I tried both of these things and they didn’t stop the worm hole porosity. Plus, the voltage and wire feed speed settings that worked fine one week , now resulted in worm hole porosity.

The spool was plastic so I was limited in the temperature that I could heat the wire, so I but it in a brisker at 120 °F, for one week. This didn’t solve the problem, so I put it back in the brisker of a second week. This solved the problem. Now I remove the wire from the welder when I am done using it and I put it in a large zip lock bag with a desiccant. The type of desiccant that I use can be recharged by plugging it in. below is a picture of the wire in a Ziplock bag with the desiccant and a picture of the desiccant plugged in.

24. Zip lock bag


25. Desiccant


If you maintain too long of an electrode extension it can result in conventional porosity. To solve this problem, I cut down the contact tip so that it was recessed into the nozzle instead of protruding, to give me better shielding gas coverage at the same electrode extension.

26. Recessed contact tip


27. Protruded contact tip


Here is an example of what happens when you loose shielding because of too long of a contact tip to work distance.
29. Porosity due to inadequate shielding gas


I am hoping that my experiences might help you.
I have never experienced bird nesting, so I can't help you on that one.

-Don

[motolife313]

Never birds nested the core machine either. Birds nest is when you're tip is messed up and gets stuck and the rollers keep feeding and can get ugly after that. Bad cup can give all kinds of funny problems. Make sure you're gas lines aren't kinked either. Just takes experience like everything else in life

[Willie B]

Thanks. I have not yet replaced the roll of wire, it ain't cheap, I'll be annoyed if new wire doesn't help. Oscar suggested different nozzles, One day it welds fine, another day problems. I do find long stick out is essential.


The bird nest issue is consistent with all wires .023 through .045, three guns, Miller 252, all variables of alignment have been adjusted & checked including a retired Miller authorized service man. Nothing helps.

Friday I was running .035" hard wire on 3/8 steel to 1", it worked OK.
Switched to 1/4 to 1/4, turned down a bit, bird nest became unbearable. I could run as long as I wanted until I struck an arc, then, instant birdnest. I could see rust puffing out of both ends of the liner with each pull of the trigger. The .035 had a copper coating but visible rust on the first layer. I spun off 200 feet, it didn't help.
Finished my project with the TIG welder.

[old miner called Pop]

[QUOTE=Willie B;8830434]Thanks. I have not yet replaced the roll of wire, it ain't cheap, I'll be annoyed if new wire doesn't help. Oscar suggested different nozzles, One day it welds fine, another day problems. I do find long stick out is essential.


The bird nest issue is consistent with all wires .023 through .045, three guns, Miller 252, all variables of alignment have been adjusted & checked including a retired Miller authorized service man. Nothing helps.

Friday I was running .035" hard wire on 3/8 steel to 1", it worked OK.
Switched to 1/4 to 1/4, turned down a bit, bird nest became unbearable. I could run as long as I wanted until I struck an arc, then, instant birdnest. I could see rust puffing out of both ends of the liner with each pull of the trigger. The .035 had a copper coating but visible rust on the first layer. I spun off 200 feet, it didn't help.
Finished my project with the TIG welder.[/QUOT

Willie try wrappin apiece of an old t shirt with just wee bit of WD40 on it that should clean the rusty dust off your wire, dont go crazy with the WD40 just a wee little bit. Take your gun off sometime before you do that though and blow the dirt, dust and rust out of the liner...take your gooseneck off first though. That might help a bit

[tapwelder]

Why does wire birdnest in the machine? Usually from lack of tension or over feeding/too much tension/ no slip/no brake. Are there other reasons? Does not seem the gun end should cause bird nest, if the machine is adjusted?

[old miner called Pop]

Why does wire birdnest in the machine? Usually from lack of tension or over feeding/too much tension/ no slip/no brake. Are there other reasons? Does not seem the gun end should cause bird nest, if the machine is adjusted?

If the drive rolls are too tight it squashes the the wire and wont go thru the liner and tip smooth, then it gets a bit of resistance goin thru and and the drive rolls keep pulling wire off the reel, it has nowhere to go except around a ring inside the feeder, this is specially true with flux core wire because its actually a hollow tube filled with dirt (the flux) if they are set proper the drive rolls will just spin on the wire but wont pull wire off the reel to go thru. This is why I blow my liner out evry roll of wire and use a tip cleaner to clean my tips. Keep in mind I work in crummy conditions not a clean shop

[Don52]

I could see rust puffing out of both ends of the liner with each pull of the trigger. The .035 had a copper coating but visible rust on the first layer. I spun off 200 feet, it didn't help.
Finished my project with the TIG welder.

I purchased knurled rollers for my Lincoln SP-250 MIG welder and tried some .045" Dual Shield Flux Core wire in it. I released the feed rollers and the brake on the wire spool and attempted to pull wire through the liner. It took a lot of force to pull the wire through. I never had any problems feeding .035" solid wire through the liner. I replaced the liner and now the .045" wire pulls right through. If you haven't replaced your liner recently, you might consider doing so.

-Don

[tapwelder]

If the drive rolls are too tight it squashes the the wire and wont go thru the liner and tip smooth, then it gets a bit of resistance goin thru and and the drive rolls keep pulling wire off the reel, it has nowhere to go except around a ring inside the feeder, this is specially true with flux core wire because its actually a hollow tube filled with dirt (the flux) if they are set proper the drive rolls will just spin on the wire but wont pull wire off the reel to go thru. This is why I blow my liner out evry roll of wire and use a tip cleaner to clean my tips. Keep in mind I work in crummy conditions not a clean shop

It that is the case the the issue is still inside the machine. I guess l knurled rollers do not slip readily and the wire roll keeps rotating/not braking in his machine. Assuming knurled rollers are installed

Prehaps, mix the rollers?

Seems frustrating

[Willie B]

I purchased knurled rollers for my Lincoln SP-250 MIG welder and tried some .045" Dual Shield Flux Core wire in it. I released the feed rollers and the brake on the wire spool and attempted to pull wire through the liner. It took a lot of force to pull the wire through. I never had any problems feeding .035" solid wire through the liner. I replaced the liner and now the .045" wire pulls right through. If you haven't replaced your liner recently, you might consider doing so.

-Don

Three guns, four sizes of wire, correct rollers (per manufacturers specifications) for each wire.
It's been a problem for several years. I swore off .023 & .030 a long while ago, now .035 & dual shield .045 won't run either. .035 solid core wire I run with original equipment M25 gun.
Dual Shield I use a Bernard 400 amp monster gun. I do not believe it is roll alignment. or liner length, proximity to the rolls.

These days I favor stick or TIG to avoid MIG.

[M J D]

MM252 is the best feeding machine I've ever used. No issues with hard wire or dual shield. I did have minor issues with stainless .030 hard wire once, put on new drive rolls along with minor adjustment to align rollers and all was good. I use the wipers and the " lubricant" on my wire as I believe it catches a lot of crap before entering the liner.

[Willie B]

[QUOTE=old miner called Pop;8830467]

Thanks. I have not yet replaced the roll of wire, it ain't cheap, I'll be annoyed if new wire doesn't help. Oscar suggested different nozzles, One day it welds fine, another day problems. I do find long stick out is essential.


The bird nest issue is consistent with all wires .023 through .045, three guns, Miller 252, all variables of alignment have been adjusted & checked including a retired Miller authorized service man. Nothing helps.

Friday I was running .035" hard wire on 3/8 steel to 1", it worked OK.
Switched to 1/4 to 1/4, turned down a bit, bird nest became unbearable. I could run as long as I wanted until I struck an arc, then, instant birdnest. I could see rust puffing out of both ends of the liner with each pull of the trigger. The .035 had a copper coating but visible rust on the first layer. I spun off 200 feet, it didn't help.
Finished my project with the TIG welder.[/QUOT

Willie try wrappin apiece of an old t shirt with just wee bit of WD40 on it that should clean the rusty dust off your wire, dont go crazy with the WD40 just a wee little bit. Take your gun off sometime before you do that though and blow the dirt, dust and rust out of the liner...take your gooseneck off first though. That might help a bit

I've asked the question of lubricant a number of times. Until now everybody has said avoid lubricant. I have used an earplug as a duster in past, no different.

[12V71]

Three guns, four sizes of wire, correct rollers (per manufacturers specifications) for each wire.
It's been a problem for several years. I swore off .023 & .030 a long while ago, now .035 & dual shield .045 won't run either. .035 solid core wire I run with original equipment M25 gun.
Dual Shield I use a Bernard 400 amp monster gun. I do not believe it is roll alignment. or liner length, proximity to the rolls.

These days I favor stick or TIG to avoid MIG.

Ok, I have mentioned this before... When you birdnest pull the wire out of the gun and clamp the rear end of the wire in a vise, stretch it out and VERY closely inspect ALL the wire for anything "snaggy". I had a 250 Esab with the Euro block gun connector that wasn't making good contact at the block and would weld the wire in the liner because the gun cable wasn't carrying the weld current. The wire showed little burnt spots about every 12".