[bobthe]

Howdy all. New poster and new TIG welder here....

Before I get to my question I just wanted to say thanks for having such a big pool of information on the web for all to use... I imagine I'll spend a good bit of time browsing old threads.


Now for my question. I have been butt welding .125 304 stainless. I have been able to put down some nice beads with little difficulty but every once in a while when the geometry of a part I am working with is a bit of a pickle I'll have an area that just does not want to bead. Normally if i turn up the heat a bit or if the spot is really difficult add a bit of filler, I can get past the problem area. But every once in a while I'll spend a fair bit of time in a certain trouble spot and the weld just does not want to behave. The arc keeps wandering away from the bit I want to form the bead, the way I hold the torch or the settings seem to make no difference. Are there any tricks to FORCE the weld to do what you want it in problem areas?

TIA

[TRACKRANGER]

How much of a point do you have on your tungsten?

Has the tungsten been sharpened 'axially' to the grinding wheel (the grinding lines follow along the length of the electrode, not across it)?

Can you increase frequency on the welder? That sometimes will help to focus the arc.

What size electrode? Too big can cause arc flutter.

Trevor

[bobthe]

Trevor,
Thanks for the reply.

I have had a tip that was anywhere from a fairly rounded, blunt tip to a virtual spear point that hurts if you press your fingertip against.

I have tried multiple techniques for making a tip and spinning the tip against a cutoff wheel on the angle grinder seems to give me the best results.

I'm using a miller maxstar. it offers pulsing but it's fixed frequency.

[Rick_H]

Can you post a picture? Once you have a nice fluid puddle with stainless it usually runs pretty good. Maybe as your geometry changes your moving farther away with your arc length.
How many amps? What's the joint prep, bevel, gap, etc? What's your flowmeter set at? What's the cup size and tungsten?

FWIW- I don't see a huge difference when sharpened with or across the grain unless I am welding some very thin material at low amps.

[bobthe]

the miller site says 11 scfh for argon and 80-120 amps, so I have the welder set for a max od 120 amps and I would guess the fine current control on the torch is right about the 80amp mark when I get a good bead, although even current higher than 120 amps doesnt seem to do the trick.

the parts are cnc milled plates where one plate has a recess and the other plate is cut to match. the fit is tight with only the edged broken to deburr as opposed to any real bevel.

Not sure on the cup and tungsten - I'll have to check.

While i dont know this to be a fact it seems to me that for whatever reason when I have a problem spot where i goof the bead up for whatever reason, say a tight geometry to work with, the metal at the bead doesnt want to flow together properly so any voids stay even after trying to continue on with the bead. I can back up and run a bead over existing weld no problem, but when I get to the problem area the weld just stops and doesnt go on (for lack of a better way of explaining it)

I'll try and post a pic later.

thanks again

[Rick_H]

How are you cleaning the parts? Pictures will be great!

[MinnesotaDave]

Any chance that where you have trouble, a magnet is holding the parts for you?

One of my friends did that and forgot about the arc blow it would cause.

[bobthe]

cleaning prior to welding? the parts are as machined, but deburred. All surfaces are brights and shiny and clean.

no magnets. I use a deep throat vicegrips to clamp the workpiece to the table.

[bobthe]

my tungsten is .090
forgot to measure the cup.

see two attached images.

the first shows a good weld. please ignore the obviously not perfectly steady hand.

what is important is that the bead from both sides of the weld quickly and easily ran together and i got a nice smooth surface with no voids.

i took a grinder to the problem area i talked about in the other image. i assume what is happening is slag is keeping the bead on each side of the weld from wetting together, but like I said earlier, I'm having trouble controlling the arc and making it heat locally in the problem area.

ideas?

[AKmud]

Are you not using any filler? That should close up easily with a bit of filler rod. The gap in the crack will keep you from doing a fusion weld.

[DSM8]

Is it just me or does it appear as though you have occlusions within the base material that you are welding?

Regardless I would try wiping it all down with acetone prior to welding just in case you might be getting some sort of hydrocarbon contaminant that is unseen to the naked eye.

[Artie F. Emm]

but every once in a while when the geometry of a part I am working with is a bit of a pickle...The arc keeps wandering away from the bit I want to form the bead, the way I hold the torch or the settings seem to make no difference.

Is it possible the odd geometry of the workpiece is causing your arc length to get too long? Too long an arc can cause arc wandering.

[bobthe]

the gap in the crack is a result of the bead going haywire on me. the arts are machined so that they fit within a few thousandths. I initially didnt use any filler. After I had the problem I tried using filler and it just was sucked up by every surface BUT where I wanted it to go.

everything was cleaned with acetone after milling to remove cutting fluid

it's entirely possible that the bad bead started because i didnt control the arc length properly in that spot. but while trying to correct the flaw I did spend quite a bit of time in that area while carefully working the torch. there was nothing I could seem to do to get the arc to heat the spot I wanted it to along the crack...

thanks again for the comments guys!

[kiwi2wheels]

Are you sure it's not a free machining grade ( with sulphur ) of stainless ?

[AKmud]

Is this sealing up a container of sorts? I've had issues with the air trapped inside blowing the puddle out when I try to seal things up.

[Superiorwelding]

I will comment further when I get home but it seems your underlying problem is actually not enough amps. While that top plate might be 1/8", the bottom looks like a nice size chunk. Try to light up usin more amps or at least more than when you were doing it before and when you get that puddle, move. It also appears that you are very inconsistent with the amps as you move along. If you can find a "sweet" spot, set the machine at this amperage and hol the pedal down.
Some thoughts for now.
-Jonathan

[bobthe]

the part is spec'ed as 304

this is a container but it is not closed, there is plenty of room for trapped gasses or moisture to escape

there have been times where I have varied the current but these problem areas arent associated with messing with the torch settings, at least not initially. FWIW when I had the fine control set at 100% meaning I was running at 120a, the top of the range miller recommended - the bead didnt behave any better and the workpiece got very hot very quick. I was much more comfortable using a lower current. And your guess is correct, one piece is .125 but the other piece is MUCH thicker. The one piece is a cover sitting in a recess milled into a thick block of stainless. In case this is what you suspect, there is no problem working the pool of melt from the side thats thicker. it forms just as nicely for me as does the pool on the thin side.

[Superiorwelding]

Ok I believe I am confused and would like to sort a few things out. First, that appears to be a lap joint, not a butt weld. No big deal just want to make sure that is the case. Second, the .090 tungsten will not carry 120 amps very well. I would switch to 1/16" or 3/32". Again not that big of a deal. Third, you keep referring to "problem spot" this leads me to assume a few things. Is it possible that this area is near a hole that was drilled and became magnetized. Is it possible that it is magnetized somehow? The only reason I ask it you also refer to the arc wandering at these trouble spots.

I am still guessing that the arc wander also could simply be that you are backing off the pedal and when you reach lower amps the arc is not stable enough to stay at the point. Know that the are will naturally wander between the two pieces on a lap joint.

Here is where I ask others to weigh in.
-Jonathan

[MinnesotaDave]

Second, the .090 tungsten will not carry 120 amps very well. I would switch to 1/16" or 3/32".

-Jonathan

I'm assuming .090"

1/16" = .0625"
3/32" = .09375"

[Superiorwelding]

Second, the .090 tungsten will not carry 120 amps very well. I would switch to 1/16" or 3/32".

-Jonathan

I'm assuming .090"

1/16" = .0625"
3/32" = .09375"

Man that's embarrassing, I was using .040" today and mistakenly had that on my mind. Sorry there.
-Jonathan

[bobthe]

i guess it's a hybrid between a lap joint and a butt joint.

there is one plate of stainless .125 thick that sits in a machined recess in a thicker block of stainless. the top surface of the .125 plate and the thicker block at the weld is level.

in the one photo the problem spot was near a drilled hole, but this is 304 were talking about, not magnetic stainless. the problem occurred in other areas as well that were not near a drilled hole.

I'm not using a pedal, but a thumbscrew on the torch so once i set the current it's constant.

[Superiorwelding]

I am going to re-visit this tomorrow with a clear head. For some reason I am not getting it, sorry.
-Jonathan

[GreinTime]

I have a clear head and I still don't get it. Is that whole area you posted in the first picture a problem spot? Aside from obvious edge control inconsistencies, I don't see any cracks or anything. I am also very confused on the second picture. I have no idea what I am even looking at there, as to me, it looks like your crack is not in a weld joint, but the material itself.

Also, the hybrid joint thing confuses me as well. If it sits in a machined pocket, and you are welding the vertical edge of the .125 piece to the horizontal edge of the 'pocket' then it is in essence a fillet weld, no? I ran into a similar situation on AL today, where the thickness difference was quite large, making for a difficult (for me at least) weldment. You almost have to choose which edge you are going to try and maintain.

A few more questions.

Gas lens or straight collet?

What size cup?

How much stick out are you running?

Have you tried starting the bead on the thick piece and washing it onto the thinner piece to get started?

Can we get a top down drawing/picture showing where your problem areas are, because I'm still very confused by where the second picture is in relation to the first.

Sorry for the novel, but Jonathan asked me take a look and these are some of the questions that came to mind.

[Rick_H]

Yeah if I understand correctly the piece with the hole is the thinner piece, and where they butt together the surfaces are machined.

This would be more like a fillet weld, but it doesn't look like your adding filler? I'd use some thin filler .035" might wire would work try to keep the heat on the thicker portion and wash it down onto the thinner section adding a little filler along the way. I would think 80-100amps would be fine depending on your travel speed. If you get the stainless too hot you will start to see the sugaring, grayness and oxidizing. I'd have the flow down to 10-15cfm, with a 7 cup if you have one.

If you get the stainless over heated you'll have to grind it out or you'll be pulling contaminates into your puddle. I'd also try a 45 degree sharpened angle with a blunt tip to try to keep the arc tight.

Is this a Maxstar 150sth? Pulsing will be 50% peak an 50% background, pulsing would help at the edges.

[bobthe]

sorry for my poor artistic skills, but hopefully this will clarify the question of what the weld is. this is a cross section mind you.

the two different colors are the two different pieces, with black the weld bead.

it will be monday before I can look at the cup.

this is a maxstar sth

I did notice the weld went eaiser at lower powers. 80 amps is probably right about spot on.

int he first photo i posted this as a 'good' weld on the same sort of material.

the second photo shows a problem spot that had been ground down. the two edges of the pieces had beaded up independently instead of flowing together, and thats what caused the gap. once this happened it was more or less impossible to get a bead to flow together. if i added filler it would just pool up on one side or the other, not in the crack.

I didnt give any preference to heating the thicker part or the thin bit. in areas where i didnt have a problem the bead from each edge flowed into one another like a charm.

I should actually measure the tungsten int he torch before I answer but I'd guess maybe 3/8" or so....

thanks for the time, guys!