slag ending up along the middle of the weld, inside (diagram included)

[decoir]

Hey guys. I have a fairly cheap arc welder that I got second-hand. It ranges from 20-90 amps and that's more than enough to destroy the metal I'm working with, if I let it (very mild steel, mostly, plus some stronger stuff from bike frames). Some of my welds are pretty good, I think. Others are terrible. I'm using non-descript 2mm rods.

Now, a common problem with my welds is that instead of getting metal along the weld line, I end up with a line of slag with the metal piled up along the edges. I illustrate this below, with two rectangles of metal as examples. In reality I'm working entirely with tubing, roughly 12mm OD and 1-3mm wall thickness.

It's not always quite that bad - usually there will be a fair bit of metal-metal bonding, but with significant lengths of the weld being these "holes" filled only with very porous slag.

It was especially difficult just now - I was trying to weld two tubes together, end-to end, one being very mild steel and the other being from a bike frame. Over several attempts, I threw 18" of rod at this little 40mm weld line, and nothing has stuck

(It's especially tricky because the bike frame metal needs a whole lot more energy to take the weld than the mild steel, which blows out if I so much as look at it.)

I guess this is a "common" problem - can anyone suggest how I can avoid this situation of having mostly just slag joining my work pieces?

Thanks a lot

 

[Bsmith]

If you're a beginner and welding vertically down the slag will run in front of the weld and go in the join. Try welding on the flat or slightly up turning the tube as you go, until you get used with controlling the slag

 

[Arsonista]

You'll notice a difference if you use 'name brand' rods too.

 

[runnach]

Arc welding 12mm OD pipe/tube is a tall order for a hand with some degree of arc welding experience, for a new learner not an easy task, as you now know. can you use another process?

Cheers.........

 

[R BEADLE]

slag

Hey guys. I have a fairly cheap arc welder that I got second-hand. It ranges from 20-90 amps and that's more than enough to destroy the metal I'm working with, if I let it (very mild steel, mostly, plus some stronger stuff from bike frames). Some of my welds are pretty good, I think. Others are terrible. I'm using non-descript 2mm rods.

Now, a common problem with my welds is that instead of getting metal along the weld line, I end up with a line of slag with the metal piled up along the edges. I illustrate this below, with two rectangles of metal as examples. In reality I'm working entirely with tubing, roughly 12mm OD and 1-3mm wall thickness.

It's not always quite that bad - usually there will be a fair bit of metal-metal bonding, but with significant lengths of the weld being these "holes" filled only with very porous slag.

It was especially difficult just now - I was trying to weld two tubes together, end-to end, one being very mild steel and the other being from a bike frame. Over several attempts, I threw 18" of rod at this little 40mm weld line, and nothing has stuck

(It's especially tricky because the bike frame metal needs a whole lot more energy to take the weld than the mild steel, which blows out if I so much as look at it.)

I guess this is a "common" problem - can anyone suggest how I can avoid this situation of having mostly just slag joining my work pieces?

Thanks a lot

i think i'll start by saying welding that size tube isnt easy for the more experienced welder . try welding a bead right round the joint without weaving first then when thats done chip the slag off and go around the bottom half and then the top half like a multi run . they should be info on the box of rods stateing the amp range for that paticular rod example 90 - 140 amp etc. try practicing on scrap first and experiment to get your tecneque right ( a bit like a woman before we find the right one to settle down with ) also arc welders dont like gaps at all in the join good fitting joins are a must and well worth time in getting right , need good personal disaplin . another must is never make your more than twice the thickness off inner core of the filler rod ( the metal part covered in flux ) as if you go over it will as sure as eggs lead to slagy hole in the centre of your joint . basic rules are nice clean matal , good tight joint , and keep the weaving action to just under twice the inside rod diamiter . it would also be easier to weld in a flat position . when going over welds again its absalutly imperrative that all slag is removed or your wasting your time . helps if your rods are warmed up aswell for striking arc . keep rods in an aring cupboard , iv herd of people keeping them in old fridges .

 

[Welderpaul]

With 1mm to 3mm wall thickness, your at the bottom of the range for stick welding. 2mm and up, no problem for stick welding, 1mm thick, should be migged.
As your laying the bead, it sounds as if you are not allowing sufficient time for the weld metal to fuse to both pieces of parent metal, or the gap is too great for it to jump the gap.
Once slag is stuck in the weld, every last trace must be removed by grinder/chipping hammer/wire brush, otherwise evry time you weld over it, it will foul the new weld. Not such a problem with high amps, or with cellulosics, but small rods are 'orrible to use.
So, keep the joint tight, keep the amps as high as you can manage and keep practicing!

 

[cookie munsta]

some rods not so good v.down. try E7014 great multi purpose stick, or E6013 designed for quicker freezing of slag perfect for v downs, especially thin stuff.

 

[Weldingartisan]

i think i'll start by saying welding that size tube isnt easy for the more experienced welder . try welding a bead right round the joint without weaving first then when thats done chip the slag off and go around the bottom half and then the top half like a multi run . they should be info on the box of rods stateing the amp range for that paticular rod example 90 - 140 amp etc. try practicing on scrap first and experiment to get your tecneque right ( a bit like a woman before we find the right one to settle down with ) also arc welders dont like gaps at all in the join good fitting joins are a must and well worth time in getting right , need good personal disaplin . another must is never make your more than twice the thickness off inner core of the filler rod ( the metal part covered in flux ) as if you go over it will as sure as eggs lead to slagy hole in the centre of your joint . basic rules are nice clean matal , good tight joint , and keep the weaving action to just under twice the inside rod diamiter . it would also be easier to weld in a flat position . when going over welds again its absalutly imperrative that all slag is removed or your wasting your time . helps if your rods are warmed up aswell for striking arc . keep rods in an aring cupboard , iv herd of people keeping them in old fridges .

What? weaving/multi-run on 12 dia 1-2mm wall tube. Throw the buzz box under the bench and get the TIG out! W/A

 

[decoir]

Thanks for the all the replies, everyone. I have almost completed this project already, and made dozens of welds joining the tubing together, but these last two welds (actually repairs, haha) are different in that they're two very different types of metal, and they don't fit quite so well.

I'll see if I can figure out a way to make them more compatable in terms of shape and position, to get a neater surface.

Thanks for all the tips, I'll report back when I've tried again.

 

[cookie munsta]

if they are two different types try to find a filler rod that is compatible with both and matchs the position you require, low hyd's pretty compatible to most steels,

 

[Delgado]

You could also try using an E318 stainless rod. If they only have E316 stainless rods in the shop you could use them, it should weld fine, but it's not strictly kosher for anything structural.