TIG welding T joints

Quote:

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Originally Posted by spudboy

...I was holding all of this together at 90 degrees with a dirty big welding magnet, so that may be contributing to my problems.

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[Mick Dundee voice on]That's not a magnet! [voice off]:D

Over the years I've done a lot of work for aluminium smelters. The magnetic field in a potline is huge.

From memory, even the molten aluminium in the pot has a degree of magnetism. The surface level of the molten aluminium varies slightly across the pot because of the magnetic fields.

Ferrous tools are difficult to use and welding steel is hopeless without using what they call Nelson's Eye - a piece of thick plate with a hole in it.

The plate is positioned with the hole over where you want to weld and the welding arc is kept inside the hole.

Sorry to hijack - back to the topic now.

Yes, the magnet can affect the arc while you are tig welding.

Well I spent about 3 hours ruining a lot of 1mm steel plate this afternoon. I STILL can't do Fillet (T) welds :(

I have tried:
- Very sharp point. Much better than the flat nose point.
- No magnet. Again much better.
- Cleaning/sanding the metal. Can't tell much difference with or without.
- 3-4mm gap between the tip and the joint.
- Poking the tungsten tip further out from the shroud.
- Angling the head more toward the base than the T piece, to put more heat into the plate and less into the base of the T
- Tried smaller 1.6mm tungstens (down from 2.4mm).

All to no avail.

If I use 30-40A there doesn't seem to be enough heat to flow the molten metal from the bottom of the T to the base plate. If I use 50-60A it melts a lot better but I always end up burning holes in the steel. I am using a filler rod to try and bridge the "gap" between the 2 molten pools of metal (one vertical/one horizontal).

I've rung TAFE to see if they are running any courses but nothing at the moment........

Anything else you guys can think of that's worth trying?

I am running in DC Negative mode BTW. Should I be trying to pulse this?

try the pulsing technique if you havent... even when migging I sometimes have to start the fillet weld by making 2 spot welds at the start one on the base and one on the upright then put a 3rd spot weld that links the 2 inital spots.

This makes a small bridge of molten metal that I then work back and forth in a C kind of shape from the upright down to the base and back.

when the metals too thin to support that I do them using the same technique but I manually turn the current on and off as i position the tip where I want the next deposit to go.

use about 40 amps.

make a little molten pool in the continuous tube close to the end of the end of the other tube

The end of that tube will melt much quicker because there is less material for the heat to run to, so it will hit melting temp quickly. so you heat the continuous tube directly and run the heat across the joint as you add a little filler to the pool.

Is you torch connected to the +ve or -ve?

Don't do the tafe course, do the WEA course - I did it earlier in the year and they let you bring in your own welding gear and teach you to use it, great for working out how your gear works so you are comfy with it and don't have to work out why yours at home doesn't behave the way the one at the course did.

WEA course - http://www.wea-sa.com.au I did it at Prince Alfred College,

INTRODUCTION TO METAL WELDING

Learn the theory and procedures to weld metal. Processes covered in theory include Oxy-Acetylene, Oxy-Propane, Manual Metal Arc, Gas Metal Arc (MIG) and Tungsten Inert Gas (TIG). You will have practical experience with most methods, be shown safety procedures and have the chance to make a small item using your new found skills. Gas and consumables levy of $25 per student, payable on the first night. TIG covered in theory but no hands on.

I got to try some TIG so it was a tad hands on, and the plasma cutter is a cool tool. In the end all I needed for what I wanted was a small MAP gas setup and the fellow teaching was great and got me doing stuff with it very fast.

BlkNight - I will read the manual and see how to set the pulsed setting. I'm not sure if pulsed is only for AC Alumininium welding or it also workes in DC.

Procastination - I'm not sure what you mean by "continuous tubes" or the "other tube"! I am running DC negative. The unit does also DC positive but you have to do something special to get it there so I presume this is not a normal setting.

jsp - I took a look at that course, but it is booked out. I might ring them tomorrow and see when the next one is being run. I love plasma cutting too. Beats the hell out of hacksawing/grinding things.

Damn - I want to be able to to this NOW!! Will give it all another go tomorrow after a sleep as I have another day off. Hopefully more luck tomorrow.

Spud, a few guys there had big cigweld jobbies they wanted to learn to use, both mig and arc. A few of them commented they had done the same course at christies beach school and they didn't get much 1 on 1 and didn't get help on their own gear when they brought it in.

They start of really basic, on oxy and work up. But you can just jump straight on the mig first night if you want and just do that all the course. For someone like me who didn't know the difference between mig and tig etc it was great but there was guys there making all sorts of stuff like bench grinder stands andd ute tray boxes the first night.

Hi spudboy,
I hope the following may help, when welding mild or stainless steel with tig you need to run a +ve earth not your conventional -ve earth. Also run the welder on DC. You can run a -ve earth with mild steel but it will not give you as much arc control. AC is only used for tig on aluminium and it needs to be a high frequency AC welder. The electrodes for tig are as follows; Red= thoriated ideal for mild + stainless. Grey= ceriated a general purpose electrode for mild or stainless but usually thinner material as it starts easier. White= Zirconated and only used for aluminium. Grind thoriated and ceriated to a needle sharp point for accurate arc control. Zirconated electrodes get ground to a ball radius for a spray arc for aluminium. A 1.6mm electrode should be o.k at 50Amps, but you may need to use a 2.4 @ approx 70Amps for corner fillet welding due to the greater surface area. The first setting would be fine for tube welding. Good luck.
Brian.:cool:

Thanks Brian,

Can I just clarify the negative/positive earth thing with you? The front panel has a setting for DC- (which is what I am using) for mild steel.

I am assuming that setting it to DC- is for the handset, so.... the clamp must be positive. Is this what you are recommending for mild steel?

I might just set it to DC+ mode and see what happens, as maybe I have it back to front.

G'day spudboy,

On most portable units (240v) the handpiece and earth leads can be disconnected and swapped over so that you can make your earth lead either +ve or -ve depending on the welding application. If yours is a bigger 415v unit it may have internal switching as it sounds like yours does. so any reference to +ve or -ve should refer to your earth feed. So i am guessing (without seeing the unit) that DC +ve would give you a +ve earth on DC current supply, which should be what you are after. Good luck and happy welding. There is a certain satisfaction that comes with mastering the finesse of the tig welder!
Regards
Brian. :D