First non filler tig weld.....

[Bristolbulldog]

I'm still useless at tig welding. I tried doing it no filler on flat plate and struggled to undertsand what I was learning as it seemed very easy (I'm pretty good at mig, but struggle like mad with tig)

I knocked up a snorkel cover, and rather than mig decided to tig it for practice. 6mm steel.

The inside weld.

This is how I set it up. 99% certain The end joint had to have filler to make it good, but I'm not there yet with the filler ;(

 

[Welderpaul]

The reason you are getting bad porosity is the plate is covered in millscale and rubbish. It needs to be perfectly clean. Clean as in the photo below.
Other than that, not too bad.

 

[Lawnmowerboy]

Have you got the weld porn group on Facebook Paul? Literally just seen that pic

 

[Welderpaul]

I have mate, have you seen last weeks photos

 

[Lawnmowerboy]

Indeed I have. Avid follower!

 

[justmental]

the thing with tig it has to be clean

 

[Lawnmowerboy]

It has gotta be spotless as said. More so with ally.

 

[backpurge]

You need to use TIG specific filler wire on carbon steel to avoid porosity, keep at it you look to be getting the basics right

 

[Bristolbulldog]

Thanks chaps. To clean it up I used a heavy duty wire cup brush, and didn't get any spitting or anything, but the end as you can see welded very differently. And I know it wasn't as clean as it could be, as the wire wheel on the grinder had been used on all sorts and near the end of its life!

What's the best (and simplest) cleanup method? Flap discs?

 

[chevy2]

I try to use bright mild steel mostly but when i need to remove the millscale i use the 4.5" poly discs that fit your angle grinder,
Millscale can be very difficult to remove sometimes, i recently had some 3mm flat plate that the poly disc barely took the top layer off and had to resort to a regular grinding disc not through choice.

 

[Lawnmowerboy]

Flap discs are the best thing for it I've found. Go straight through it.

 

[hotrodder]

While you can't get things too clean for TIG it all gets a bit overstated a lot of the time IMO and, as Backpurge said, when it comes to carbon steels autogenous (no filler) welds typically don't work properly no matter how long is spent cleaning things. The filler wire contains specific deoxidising elements to prevent porosity that can and usually does occur on the most lovingly cleaned piece of mild steel. This is typically easy to demonstrate by trying to use oxy fuel filler with TIG... result is usually porosity because the O/A flame creates a very different atmosphere around the weld pool compared to the argon used with TIG which is inert.

The above is pretty much specific to carbon steels. With austenitic (non magnetic) stainless steels the chemistry is different and IIRC the nasties that cause porosity on carbon steels are soluble in austenite which is why 1) autogenous welds work and 2) there's no differences in the wires used with TIG and O/A
Aluminium's slightly different in that autogenous welds don't typically work so well with TIG due to solidification cracking but with oxy fuel this is less of a deal because it's a less efficient heat source i.e. weldpool doesn't freeze so quickly and less of a temp gradient across the weld. Again no differences in the wires used as hydrogen porosity is the enemy with ally and is a moisture/hydrocarbons deal which is dealt with by cleaning and preheat where necessary

Millscale varies a lot but wire brushes tend to only remove the loose bits while polishing the underlying/heavier stuff. As Chevy i tend to use a poly (clean 'n strip) disc which is usually painless and quick but not always. If you're not in a hurry and want/need the entire piece clean and have a big enough container for it then soaking for a while in citric acid will deal with it.