View Full Version : 316 stainless sheet 0.3 to 0.5mm blowing holes
11-17-2006, 12:40 PM
following on from my previous emails
got the short straw to learn to tig 0.3mm & 0.5mm 316 stainless sheet
how do i stop blowing holes in it( or cooling the sheet down) , i can resonably manage small runs(no filler ) , then once a hole starts theirs no stopping it , ( also any tips in filling the holes too)
i am using about 30A dc with 1.0mm thorated 2% tungstens
and argon in running at about 4.5Lt a min
i have 1.0mm 316L filler rods too
with my invertor ( wolf 75 ) any lower current and i dont seem to get HF from my tig add on or the DC don't start ,
i may did later into the electronics and see if i can lower the amps
any tips appriciated
11-17-2006, 01:11 PM
1- make sure you are not pre-heating the material
2- make sure your amps are on the lowest setting
3- do not hold the TIG tip on the material ( i know from teaching others they tend to hold the tungsten on the material because they think it's welding, so they must hold the tip on it)
4- make sure your tip is the proper length out of the collet - 1/8 to 1/4 is fine.
5- only hold the tip over the area until you just barely see a puddle form
6- once puddle forms, add filler and push it forward...again, holding the tip AWAY from the material
Hope that helps...give it a shot.
11-17-2006, 01:39 PM
What are you making, are these butt welds/fillets/corners, how long, straight flat pieces, tubes?
As I think you realize, since you imply that you tried lower current, 30 A is simply to hot for combination of thickness/travel speed/arc length/gas type you are running. The "rule of thumb" is about 1 amp per every 0.001" thickness, so that would be about 12 and 20 amps for your 0.3 and 0.5 mm sheets. So try to tweak the arc started/inverter so you can run a lower current, or try scratch starting the low current arc, possibly on a bit of scrap sheet laid next to the actual joint.
Some other ideas.
Since the arc gets broader/less concentrated at greater arc lengths, its important to keep the arc length as short as possible. For a machine weld, I would run this at a 0.030" gap (sorry you'll have to convert now), don't know how tight you can hold this by hand.
Joint fit-up has to absolutely perfect, no gaps, no chamfers on the edges.
Maybe you can clamp a chill bar (copper) on the backside? This would help in filling holes.
Argon-5% hydrogen shield gas produces a more constricted arc, and promotes wetting by reducing oxides, but it also is hotter. It's quite commonly used for very small precise SS fusion welded products.
Put tack welds along the joint to prevent warpage and opening of the joint while welding.
Re-design the joint so instead of a difficult butt weld it is a lap or edge weld.
Get a better low current power supply and pulse it.
11-17-2006, 02:09 PM
Note: I don't know nothing about TIG, so this advice is worth what you paid for it. :waving:
What kind of weld joint are you doing? Lap welds would be easier from the standpoint that you have doubled the thickness of the metal in the welding zone, butt joints would be harder to do because you only have a single thickness of metal and possible gaps as well in the welding zone.
Start the weld, and then drop the amps down lower, that 0.5 mm sheet is pretty thin (26 gauge approximately). That's what the pedal or knob is for, to fine-tune the current as you go.
Weld a bit, then stop and let the sheet cool.
Use a chill bar on the back side of the welding area.
Weld a section, then move to a different section and weld some, then move to another section and weld some there, then maybe move back to the starting section and do some more welding.
Use your filler rod to dip into the welding pool more and cool it down.
Move faster to minimize heat build-up in any area.
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