tig advice please?

[barry w]

Hi
im having trouble welding some 1" cds tube. I have sanded up the areas prior to welding and they look very clean.
The weld pool starts okay but soon fizzes up and touches the tungsten? Its dificult to see exactly what happens but its leaving a hole in the steel and a tungsten in need of resharpening?
Gas flow is spot on tig rods are good.
When Im welding flat steel it welds perfect.
As I am welding two pieces of tube together is it possable that it is drawing any dirt from the inside of the tube?
Many thanks Barry

 

[wyn]

If the tube was coated with some sort of oil protection it could still be on the inside. Or whatever you are cutting the tube with may be leaving something on the cut edge.

 

[hotrodder]

The other suspect could be expansion of the air inside the tube blowing the puddle out but you'd need to be welding smallish pieces and it typically happens as you get close to finishing the weld i.e. tube is about completely closed off cutting off other routes for the air to escape

 

[barry w]

hi
if i wipe the inside with a rag there are no traces of oil but its not as clean as the outside i have prepared.
I didnt use and cutting oil just incase.
Has anyone else had this problem?
many thanks Barry

 

[pedrobedro]

How close fitting are your joints ? It sounds like too much power or not moving fast enough and burning the edge away.

 

[tufty113]

sounds like too many amps also...try as lower amps as you can on a few bits of spare and just raise till you get the fault again(then just back it off a tad)...if your joint isnt a perfect butt then even a few amps high will blow a hole in a split sec....how thick is the material....

 

[barry w]

hi
ive spent a lot of time getting joints to fit well and have been using the calculator on the miller website for amp settings.
Its 2mm cds.
Is a clean up with emery cloth and wipe over enough? The steel is in very good condition, and kept in a dry worshop?

 

[weldequip]

The weld pool starts okay but soon fizzes up and touches the tungsten?

You sure it's not you touching the Tungsten in the weldpool? It's easy on the flat, not so easy welding around tube etc. Also, is it a scratch start machine or HF push button start?

 

[Shox Dr]

Pictures paint a thousand words, as they say

Post some up and we will have a better idea of the problem

 

[toddy]

as well where abouts are you feeding in the wire, as if you are feeding it on from the outside of the pipe i used to get that problem on the bigger pipes, so the knack was to feed the wire through the pipe from the other side, so it melts into the root of the weld.

as well i would run a flapper wheel i have a few boxes of these some where.

 

[Turbo Gav]

Might sound odd im still learning..... are you DCEN ? you can get away with DCEP at low amps but when you crank it up a touch ive found that sometimes iv plugged the leads in wrong way round Just a thought as it frys the tungsten

 

[Delgado]

Sounds to me like what happens when you try to weld galvanized or coated steel without grinding it off properly, also try using a die grinder/dremmel or a drill with a flap wheel on the inside of the tube. The same thing also happens if you try to weld wet steel with Tig, probably not your problem, but worth a mention.

 

[hotrodder]

As said pics are worth a thousand words, especially when pretty much all the suspects have covered. If you've never had this issue welding plate/sheet, only with tube that eliminates filler wire and (should) eliminate polarity cock ups. Leaves us with material issues (coated material) or user issues

What is the gas flow set at? Tube to tube welds means lots of changes to torch angle which (along with the shape of tubing) can result in the shielding gas being 'deflected' away from the weldpool or some air being drawn in if the angles are lost (torch laid back too far etc)

Is a clean up with emery cloth and wipe over enough? The steel is in very good condition, and kept in a dry worshop?

Should be. Not that it's recommended but you should be able to weld over light to medium mill scale without the puddle spitting and wrecking the tungsten.

 

[Dave Richards]

solution to your problem

The problem that you are suffering from is caused by oxygen being drawn into the weld pool from the inside of the tube, the solutions are either backing rings or gas purge tubes. Hope this helps Dave

Hi
im having trouble welding some 1" cds tube. I have sanded up the areas prior to welding and they look very clean.
The weld pool starts okay but soon fizzes up and touches the tungsten? Its dificult to see exactly what happens but its leaving a hole in the steel and a tungsten in need of resharpening?
Gas flow is spot on tig rods are good.
When Im welding flat steel it welds perfect.
As I am welding two pieces of tube together is it possable that it is drawing any dirt from the inside of the tube?
Many thanks Barry

 

[barry w]

hi
thanks for the replys. I can see your point.
Would the same problem happen on thin steel if the weld was penetrating through and picking up the oxygen on the other side?
thanks barry

 

[Andyb]

Hi
Sounds like air is getting in from the inside of the tube and contaminating the pool, we rig up an extra pipe to pass argon through the tube but its tricky to set up.

 

[astro_al]

My vote is for dirt from the inside of the tube being drawn in. I run a die grinder round the inside of the tube first - get it all shiny, and maybe some acetone or whatever degreasant too. Al.

 

[Dave Richards]

Hi Barry, yes the problem is even greater with thin wall thicknesses, as some of the other guys are saying you must shroud the back of the joint by purging with argon this is done in tube and thin sheet in industry. If aesthetics are not a primary concern go to mag welding possibly.