[martinr]

Following tweake's suggestion, I had a look at some arc shots where I varied the tip angle on a 2.4mm 2% lanthanated tungsten on aluminium.

130 Amps, 70%EN, 100Hz

The Lincoln Foundation TIG book recommends a hemispherical ball for 2.4mm lanthanated electrode, so I balled one up to that shape:

2.4mm hemi.JPG (761.14 KiB) Viewed 1648 times

Then I tried one with a 55 degree tip:

2.4mm 55 deg.JPG (621.31 KiB) Viewed 1648 times

Next is a 90 degree tip

2.4mm 90deg.JPG (730.56 KiB) Viewed 1648 times

and then a 115 degree tip:

2.4mm 115deg.JPG (606.75 KiB) Viewed 1648 times

and finally, I thought I'd see what a 3.2mm 2% lantanated electrode looked like at 115 degrees with the same settings:

3.2mm 115 deg.JPG (414.26 KiB) Viewed 1648 times

And the conclusion I've come to is that I can't come to any conclusion based on the photos, except possibly that the shape of the intense central arc seems to possibly reflect the tip angle to some degree - maybe. I think the next step would be to forget the pretty photos and try laying beads in Jody's aluminium drill and see what difference the tip angle makes in practice, or which, if any, works better Unless, that is, you can draw some other conclusions from these photos.

[tweake]

wow thats some really nice pics

[martinr]

wow thats some really nice pics

Thanks, tweake, but it was your idea. There is one more thing I do want to try: take one particular tip angle, and look at the effect on the arc of changing the frequency, say, 50Hz, 120Hz and 200Hz. Ideally, I need to refine my setup so it’s more consistent (the tripod is wonky) and perhaps see the effect of frequency on all the different tips. Leave it with me.

[martinr]

Today, I had a look at the effect of ac frequency. I first tried with a hemispherical ball on the 2% lanth. 2.4mm electrode but I had a devil of a job trying to maintain the arc: the arc would start then sputter and pop. I checked and changed everything I could think of, and it was only when I tried a different tip angle that the problem went away.

Again, I can't see any obvious effect on the arc shots of changing the frequency.


135 Amps, 70% EN


50 Hz

50Hz.JPG (596.98 KiB) Viewed 1607 times

120Hz

120Hz.JPG (555.41 KiB) Viewed 1607 times

200Hz

200Hz.JPG (563.86 KiB) Viewed 1607 times

some shots of the workpiece: Again, I can't draw any definite conclusions.

P9140275.JPG (982.57 KiB) Viewed 1607 times

P9140279.JPG (831.18 KiB) Viewed 1607 times

P9140280.JPG (810.37 KiB) Viewed 1607 times

[BillE.Dee]

it seems to me that the higher the frequency, the more distinguished the feathers (secondary arcs) became. Jody had a video of that happening and he couldn't explain it.

[martinr]

it seems to me that the higher the frequency, the more distinguished the feathers (secondary arcs) became. Jody had a video of that happening and he couldn't explain it.

Well spotted. I think you are dead right. That’s why I included those shots of the aluminium strip; as the frequency increases, there is a very slight cleaning effect on the outer regions from those secondary arcs usually accompanied by a ring of pepper as those secondary arcs stray out of the shielding-gas zone. (I was laying beads a couple of days ago at a high frequency and noticed that previous beads were getting “peppered” as well as the area ahead of the weld; as soon as I dropped the frequency to 50Hz, the problem went.)

Jody has a video where, using a welding lathe, and taking great care to keep everything but ac frequency constant, he shows the effect of ac frequency on penetration. He runs an arc only - no filler metal - and at 50 Hz the arc penetrates through to the reverse side. But as the frequency increases the penetration falls off. At the higher frequencies, there is no penetration at all. So, even though the photos above don’t show anything obvious (other than those feathers), in practice there are some quite obvious effects. ( Jody has other videos where he will use a higher frequency when welding on an edge.)

Thanks very much for your comment.

[martinr]

Here’s a link to that video I was referring to - I misremembered: he did use filler wire, sorry.

https://youtu.be/XzsfBV6_vNY

[tweake]

jody must be watching
todays weldingtipsandtricks video

https://youtu.be/5HsZZmVXYgw

[BillE.Dee]

I just now watched that video, tweake. There is another video by Jody where he is doing some testing and I believe he is using a rotator and no filler. Kind of thinking he was testing various tungstens. I'll admit that I'm far from smart enough to drive this electronic stuff to "find" that video...sorry.

[martinr]

I just now watched that video, tweake. There is another video by Jody where he is doing some testing and I believe he is using a rotator and no filler. Kind of thinking he was testing various tungstens. I'll admit that I'm far from smart enough to drive this electronic stuff to "find" that video...sorry.

That must be the one I was mixing up with this one

https://youtu.be/XzsfBV6_vNY

I also seem to remember the rotator and no filler. I’ll do some digging.

[martinr]

I just now watched that video, tweake. There is another video by Jody where he is doing some testing and I believe he is using a rotator and no filler. Kind of thinking he was testing various tungstens. I'll admit that I'm far from smart enough to drive this electronic stuff to "find" that video...sorry.

Here it is, BillE.Dee

https://youtu.be/ZI3SyGjjbfw

Another great video from Jody. Has he ever produced one that isn’t? When I think of the trouble I’ve gone to just to get a couple of static arc shots, it makes Jody’s video photography even more impressive and stunning. And what superb shots of those secondary arcs on the very fine tapered electrode!

Thanks, BillE.Dee; this video was well worth the 20 minutes search to find it.