What would cause this?

[stevemon15]

Started using the MMA function of my machine a few weeks ago. After a lot of frustration, I'm at the stage where I can lay some okay looking runs and the slag comes off easy. My first attempt to join 2 bits of metal together, resulted in a fair looking bead, but very brittle, one whack of the hammer, and the weld itself snapped cleanly in half, leaving two bits of metal with weld fused to it.

Inside the weld looked a bit like the inside of an aero, lots of tiny 'bubbles'.

The metal was cleaned to a shine with a flap disk, the rods are a decent make I think (BOC), and I think I had the volts right as the arc was easy to start and the rods burning nicely if the tutorial vids on here are any indicator. Which leaves user error. Any ideas where I went wrong guys?

Always grateful for advice or suggestions. Thanks.

 

[cumbriasteve]

My first question would be what sort of metal is it?

Was not cast by any chance was it?

 

[sardine]

Picture.

 

[stevemon15]

Hello guys, thanks for your reply. It was mild steel. Unfortunately, I can't take a pic as I've cut out the welded segment to reuse the metal later on.

 

[sardine]

What electrode EXACTLY was it ?

Was it defo mild steel ?

What machine on what settings ?

Was it switched on ?

 

[Bill Edwards]

Can you tell us what numbers are on the rod packet (e.g 6013) and what the metal is that you're welding (I don't simply mean 'steel', but new flat bar, machine, vehicle part etc).

I ask for these because, generally speaking, it's hard to get this kind of problem with stick welding.
The 'bubbles' you speak of is porosity, and the fact it breaks so easily makes me wonder if the rods are the wrong type, or more likely that the steel isn't simply mild steel.

There are some combinations that simply can't work, no matter how skilled the welder is.
For example, I once welded a machine part, the weld seemed to run fine, the slag was lovely to remove, and the weld bead looked lovely (as seen by my then boss who was watching). Except it had a crack right through the length of the weld! Wrong rod for the steel being welded!

 

[Kent]

Nope, I seriously doubt you were welding regular mild steel! That sounds exactly like some form of casting. Take some Box section or similar and I bet it don't happen

 

[Kent]

Nope, I seriously doubt you were welding regular mild steel! That sounds exactly like some form of casting. Take some Box section or similar and I bet it don't happen

Unless is got some serious galv or other plating finish on it perhaps?

 

[Richard.]

The weld shouldn't break down the middle. Something ain't right there at all and my suspicions would be as above material/rod compatibility.
Without knowing the rod type for sure it's a guessing game.

 

[109party]

Sounds a lot like slag not weld that was holding it together, picture needed

 

[stevemon15]

Sorry for my late reply guys, I tried last night and the board was playing up. And thank you everyone who has taken time to comment.

Rods are 3.2mm 6013's (boc brand). The welder only has one control on the mma side (1-10) and I had it set at around 8.

Yes, welding in the flat position dragging the rod at around 20 degrees from vertical (I bent it in the holder at the appropriate angle).

Thinking on it, I think you may have a point regarding the steel. It was a bit of 5mm plate I'd cannibalised from an old office chair, it had some sort of black paint / coating on it, which I cleaned off. I used it because I didn't have anything thick enough for stick. I assumed it was mild steel, but now you've made me wonder...

I've now visited a local fabricator and got, amongst other things, some 5mm box offcuts, definitely mild steel. I'll give them a go and get back to you.

Thanks again for your comments and suggestions.

 

[Kent]

Sorry for my late reply guys, I tried last night and the board was playing up. And thank you everyone who has taken time to comment.

Rods are 3.2mm 6013's (boc brand). The welder only has one control on the mma side (1-10) and I had it set at around 8.

Yes, welding in the flat position dragging the rod at around 20 degrees from vertical (I bent it in the holder at the appropriate angle).

Thinking on it, I think you may have a point regarding the steel. It was a bit of 5mm plate I'd cannibalised from an old office chair, it had some sort of black paint / coating on it, which I cleaned off. I used it because I didn't have anything thick enough for stick. I assumed it was mild steel, but now you've made me wonder...

I've now visited a local fabricator and got, amongst other things, some 5mm box offcuts, definitely mild steel. I'll give them a go and get back to you.

Thanks again for your comments and suggestions.

Office chair painted / coloured black? My bet is your trying to weld Ali. take a file to it and see

 

[PTvor]

Thinking on it, I think you may have a point regarding the steel. It was a bit of 5mm plate I'd cannibalised from an old office chair, it had some sort of black paint / coating on it, which I cleaned off. I used it because I didn't have anything thick enough for stick. I assumed it was mild steel, but now you've made me wonder...

Metal off an office chair might well not be steel, but some type of aluminium alloy. Does it attract a magnet?

You should get on with the mild steel offcuts from the fabricator.

 

[stevemon15]

Well, I gave it another go today with some of the bits I got from the local fabricator. Same rods, same machine, same settings, and though the join was far from perfect (I need much more practice), the metal bent every which way in the vice but the joint held.

It must have been something to do with the metal.

Cheers for all the help and suggestions, next time I'll make sure that I'm actually using the right metal.

 

[Kent]

If you are ever in the slightest doubt again give it a go with a file it can tell you a lot, next to that watch the colour and shape of sparks from the piece when put it to a bench grinder

 

[Bill Edwards]

^^^^^^
This.

Take a piece of the steel you've just got (which you know to be mild steel) and grind it, making a mental note of the color, shape and quantity of the sparks.
Then next time you are struggling to weld something touch it with a grinder, if the sparks are different from the metal you know to be good you can expect difficulties.

 

[stevemon15]

Thanks again for the suggestions above gents. It just goes to show I have a long, long way to go.

Still, I'm enjoying my new hobby so far, even if it has been frustrating at times.

 

[Bill Edwards]

I've been welding for many years, and to this day still get frustrating times on occasion!