Welding thin tubing with a HF 125 flux core welder

[mickri]

My HF 125 has been modified with a bridge rectifier and a capacitor so it is a DCEN welder. I am using 030 wire that came with the machine. Spent most of the afternoon watching videos on flux core welding and practicing welding electrical conduit thin wall steel tubing. It's what I have on hand. Cleaned the conduit to bright and shiny before welding. Tried all kinds of different settings. Min and Max power and wire speeds from 1 to 5. Except when the wire speed was set to 1 I didn't really notice much difference in the welding.

Out of all of the videos I watched only one gave the settings being used. Power on max and wire speed on 5 welding exhaust tubing. He was doing overlapping tack welds. All the rest mentioned adjusting the settings to suit the material. Yet no demonstration on how different settings impacted the weld or the settings being used.

I found that it was real easy to blow a hole in the tubing no matter what the settings were.

First question is power setting. Intuition suggests that you should be using the min power setting when welding thin tubing. But what about penetration? Should I see the weld on the inside of the tubing. Only about half of my tacks looked like they had penetrated all the way through. If you are tack welding would max power be better to get quick penetration without blowing a hole?

How does wire speed effect the weld? Is it dependent on how thick the material is? Or how fast you are welding? Or some combination of the two.

Some of my tacks would be a small flat circle. I think this is what I am striving for. Others would have a dent in the center. What causes this? Others would have a bulge in the center or a bulge around the edges with a deeper dent in the center. What causes this?

Sorry no pictures. They were too blurry to show anything. I'll try again tomorrow.

Thanks for any advice you can share.

 

[4ssss]

The HF welder works well, but the wire they sell or comes with the welder is supposedly junk, and all of the guys I've talked to have said the same thing. If you're new to welding, I would think that's where you should start first.

 

[Dudemanrod]

For thin material use gas and .025 wire and get good wire. The setting you have to adjust for the material and the machine your using. Fluxcore is better on thicker 1/8 and up. Watch welding tips and tricks on you tube he has the best tutorials. Practice is key if something is not working change what your doing if it looks bad it usually is bad. Good luck

 

[mickri]

The HF welder is what I have and there is no money in the budget for a mig or tig welder.

I will be getting some more wire in the next week or so. I am almost out of the HF junk. Will probably get some Lincoln NR211 MP. That is what I see most of the people using in the videos and has been recommended by people on this site.

 

[C-Bag]

i don't even try to mig thin wall tubing anymore. I oxy/acetylene and use steel rod or braze it. Either one is stronger than the tubing and I get a much nicer weld and way easier to control.

 

[Old junk]

Thin steel is hard with flux core for a beginner.flux burns hot no matter what setting,solid wire with gas is way to go or oac

 

[MontanaLon]

Conduit is galvanized so be careful with exhausting fumes out of the area. If you are actually grinding off the zinc on the outside you still have the zinc on the inside to off gas. This will make you feel like you have the flu. It won't make you chronically ill, like getting cancer or silicosis but you will feel like crap afterwards.

Not sure what effect the zinc will have on the welds themselves but it seems like the zinc would be vaporized anywhere the steel is melted so likely not be creating the issues you are seeing.

 

[savarin]

Having mig welded a lot of thin wall steel tubing when building recumbent bicycles. I would suggest the best method is to weld vertically downwards.
Get the tubes to butt nicely, start the bead on the join and travel downwards.
It will probably burn through but dont worry thats what you want, just keep the arc in the middle of the bead weld and do not go side to side (weaving)
The bead should just keep forming and traveling downwards filling / fusing in as it goes.
Stay too long in one spot and the weight of the weld/bead will collapse and form a bigger hole.
Keep moving vertically downwards.
If after the run is finished just go back and do the hole, still vertically.
I expect when you look inside the tube there will be heaps of wires inside, I used a small grinding wheel on a long shaft to remove them.
I used the thinnest solid wire (0.6mm) with mig gas, the zinc will leave a white fluffy powdery residue and as previously mentioned do not breathe in the fumes.
By vertically downwards I really do mean vertically, once it starts getting towards the horizontal the hole will collapse.
I would not attempt this with flux core.

 

[Aaron_W]

I'm just a welding student and haven't done any flux core, but conduit is usually coated with a galvanized like coating and that is probably causing some of your issues. Assuming it isn't aluminum instead of steel which would be a whole different issue (wrong welding method).

I've MIG welded galvanized a couple times when not thinking about the fact that they are galvanized (nuts, bolts etc) and it definitely causes issues. I get black sooty deposits and a lot of porosity (pinholes) similar to forgetting to turn on the gas.

The gasses produced by welding on galvanized metal are also really bad for you, so you really want to remove any coating from the weld area, and some distance up inside and out both for the weld quality and your health.

 

[mickri]

This is what the inside looks like. Is this sufficient penetration?