Root Run on a V butt weld

[graann]

I have a problem when I am welding 6mm flat plate.
I am using two pieces approx 150 mm long x 40 mm wide to practice v butt welds.
I put a 30 degree chamfer on both pieces to form the V.
I leave a gap of about 2mm between the two pieces and the root face is also about 2mm.
I am practising to put in a root run , followed by a cap run.
I get penetration but fill the V in one run.

Can anybody advise me how to get a root run ?
Do I need to move the torch faster and keep the same volts ?
Or do I need to decrease the wire feed and move the torch at the same speed ?
I am having inconsistent runs with whatever I try.
Any advice will be gratefully appreciated .

 

[Tigman]

what size rods are you using , what amps ?

 

[graann]

0.8mm mig wire , 180 amp mig welder on 4th setting of 6, fixed , not infinitely variable.

Thanks

 

[F.J.]

Are you weaving your root run? I did my stainless testing on 6mm plate overhead with similar prep work as you. I can't remember what amps as it was two years ago but I kaput my wire in a straight line and moved quite quickly.

 

[Rrunnach]

When I am demonstrating joint you mention, slow, stringer run for root, give root time to burn through, so SOT is very important, I do cap at same setting, as your only interest now is to achieve a decent profile, re-enforcement run. As for m/c setting, difficult to say, as each are different, but certainly dip transfer......

You practicing at home?

 

[graann]

Thanks for your replies.
Yes practising at home but also at college in the evening , one day a week.
Some people on the course are ok with it , others need more practice.
75 mins to share between 15 people is a lot to ask.

 

[graann]

Are you weaving your root run? I did my stainless testing on 6mm plate overhead with similar prep work as you. I can't remember what amps as it was two years ago but I kaput my wire in a straight line and moved quite quickly.

Yes weaving from side to side because the gap is larger than the mig wire diameter.

 

[Lawnmowerboy]

Is 6mm really thick enough to require multiple passes?

 

[Rrunnach]

Thanks for your replies.
Yes practising at home but also at college in the evening , one day a week.
Some people on the course are ok with it , others need more practice.
75 mins to share between 15 people is a lot to ask.

Have your tutor demonstrate and, then watch you perform welding joint, if he/she is worth their salt, they should be able to correct you. Speed of Travel (SOT) and length are important factors, along with tilt angles too........

 

[Rrunnach]

Yes weaving from side to side because the gap is larger than the mig wire diameter.

I use exactly same setup you described and, .8 dia wire, I do not weave, slow down give weld time to burn through to produce root, there is no need to weave on root.................

 

[F.J.]

Weaving will be the reason your root is to big, just let the puddle form and push it in a straight line

 

[Rrunnach]

Is 6mm really thick enough to require multiple passes?

Root & Cap should be suffice...............

 

[graann]

Weaving will be the reason your root is to big, just let the puddle form and push it in a straight line

Thank you for your imformative reply.
Something to work on.
Will keep you informed.

 

[graann]

Root

Thanks very much for your advice.
Will let you know how I get on