Preheating shouldn't be needed unless working with thicker sections and/or the metal is properly cold i.e. below room temp where taking the chill off is a good idea for porosity reasons. Ally is a much better conductor of heat than steel which is why it's typically welded at higher amperage despite it's relatively low melting point. When you're working (especially learning) with smallish offcuts/parts this conductivity makes it seem harder than it is in some ways... Turn the amps up and hit it the way an experienced welder would and the (small) offcut quickly becomes heat soaked requiring largish changes to amperage or travel speed to avoid blowing holes. Trying to build the heat slowly to avoid this doesn't work out so well, especially with thin fillets where the cut edge will try and burn back before you get a proper weldpool. Once the part becomes heatsoaked from the first few attempts though it'll appear easier as the amp requirements are lowered if that makes sense.Interesting discussion fella's
I have trawled the net looking for what the different settings such as AC balance and AC frequency do and I think I have a bit of a handle on it now
What would be good to know is how much one setting affects the other ie: if you change one should you change the other to suit? As well as the amps etc
One thing i noticed today while practicing fillet tack welds on a piece of ally angle was that the hotter the metal got the easier it was to start the tack and hence the weld so I was wondering how much preheating should be brought into the equation?
So much to learn about this TIG stuff but it is fun and rewarding when it all works
Balance, frequency & amperage do have an effect on each other but not to the extent where it's important or even noticable a lot of the time...
Balance biases the arc time to either EN (electrode negative) or EP. Around 2/3 of the arcs heat occurs at the -ve electrode i.e. biasing the arc towards EN puts more heat into the work and less into the tungsten. EP is what provides the 'cleaning' so go too far and you end up with a manky weldpool full of oxide inclusions.
Higher AC frequencies mean it's changing between EN and EP more quickly. The most noticable effect is that the arc gets more constricted/stiffer/better focused. Lower AC frequencies do a better job of transfering energy (larger, deeper weldpool) i.e. if you're welding thicker ally the narrow weldpool is of less use as 1) you want a larger weld and 2) thicker ally = higher amperage = more stable arc anyway
If (for whatever reason) you've got the balance pushed as far as it'll go while maintaining a clean, fluid weldpool @ say 60Hz then increasing the frequency may call for a reduction (less EN) in balance to maintain puddle cleanliness. On the other hand if the balance is set at a 'happy' medium it can pretty much be forgotten about while using frequency to fine tune weld size
Best way to get to grips with things is to play... run welds playing with one parameter at a time noting the effects and then do it again after altering something else... say for example run through balance settings at 60Hz and then do it again at 100Hz, 120Hz etc etc. The catch 22 is that you need to be pretty consistant and reasonably experienced to work out exactly what's going on which is pretty much what started the debate about bells and whistles...
Thanks for all this! Whilst it isn't my thread, I need much the same help as Malcolm. I am having trouble with 1.6 mm vertical up fillet welds in particular, using 1.6 mm tungsten and filler with a Kemppi MasterTIG (plenty bells and whistles here). I am sort of OK with the other types of welds but that particular one has me beat. Lots of great advice I intend to try out.
Vertical up makes life harder in that the heat wants to rise anyway making it more difficult to control the weldpool and get the wire to it without it melting. If it's just vertical up then it's probably more a case of there being less margin for error with the angles of attack etc