Lap joint problems

[tab]

Just having a bit of practice on 3mm steel, getting a nice puddle flowing, adding filler in from the top and every now and then the puddle seems to stop in the middle and starts to form a "U" shape and doesnt seem to want to carry on.

I'm using a foot pedal so not sure what amps are coming out, tried backing off a bit but that didnt help, if i put my foot down more i can get over it but the puddle becomes too wide and the weld doesn't look neat.

Tom

 

[gavuk]

Sounds like the plate is lifting and separating,are your tacks close enough together?,I normally dress the join with a hammer to ensure they are touching,whilst tacking and after tacking..
I would stop and get the plates touching rather than carry on
Try and keep a constant travel speed,as well...

 

[Shox Dr]

As Gav Says you need a lot of tacks so the top sheet doesn't lift, washing the top sheet down on to the bottom sheet. However this can only be done with SS, as you are welding Steel you must add filler, as you are burning off properties while welding that need to be added back through the use of filer

 

[langy]

What size tungsten and rod you using ???

 

[tab]

What size tungsten and rod you using ???

i'm using 1.6mm tungsten and rod

i was using 15cm long strips and just tacking the ends to start with but after your replys i tried another tack in the middle and also hit it with a hammer (not really needed that time but was fun to make some noise )

welds came out alot neater, may have over done it with the heat on the tack though as you could tell where it was, but i guess thats why they call it practice

 

[Shox Dr]

Even 3 tacks is not enough. You need them at least every 30mm, dependant on material thickness, and the ability of clamping a long the seam

 

[gavuk]

I'm with the Doc,little tacks and close together,and dress down while they are cooling ,ensures plates are touching when welding up

 

[tab]

Tried with more tacks today and got betters results again! Thanks for the info