Introduction of doped tungsten TIG electrodes

[Jack Ryan]

I'm curious (sorry) about when doped tungsten TIG electrodes were introduced. What oxides were used first and what was the claimed benefit at the time.

Old sales pamphlets would be useful as would recollections of the time.

Thanks

Jack

 

[Misterg]

Patent US2798808A by Westinghouse Electric Corp covers zirconia doped electrodes dates to 1953.

US2798808A - Method of introducing zirconia into tungsten powder preliminary to forming electrodes - Google Patents

I wouldn't be surprised if thorium doped electrodes were used from the start of their use in welding.

 

[fizzy]

Patent US2798808A by Westinghouse Electric Corp covers zirconia doped electrodes dates to 1953.

US2798808A - Method of introducing zirconia into tungsten powder preliminary to forming electrodes - Google Patents

I wouldn't be surprised if thorium doped electrodes were used from the start of their use in welding.

Thorium was first used in gas mantles back in the 1800s so yes quite probably!

 

[Jack Ryan]

Patent US2798808A by Westinghouse Electric Corp covers zirconia doped electrodes dates to 1953.

US2798808A - Method of introducing zirconia into tungsten powder preliminary to forming electrodes - Google Patents

I wouldn't be surprised if thorium doped electrodes were used from the start of their use in welding.

Thorium was first used in gas mantles back in the 1800s so yes quite probably!

Thanks Misterg, I hadn't seen that patent.

Yes, doping of tungsten has been used for a very long time - for example, in producing "non-sagging" lamp filaments. Patent US2798808A (and the patents it references) also seems to be aimed at the material properties related to the production of electrodes, rather than the properties that affect the arc.

I assume that green tungsten is not doped at all and that seems to have been used up until fairly recently. Perhaps it was only used for AC - but why not use a doped electrode if the doping improved arc stability?

I was initially wondering if there was a correlation between the introduction of square wave machines and then balance control and the doped electrodes that claim to improve arc stability. I haven't seen any evidence of that though.

In older references I have checked, there is no mention of doping. The only mechanisms used to improve AC arc stability are HF and the addition of a battery or other DC supply to overcome self rectification.

I'll check in more detail the patents referenced by US2798808A and see where it leads me.

Thanks again.

Jack

 

[Brad93]

A lot of tungsten development had already been done by the likes of Wolfram Alpha and Plansee for lighting and scientific use of tungsten electrodes.

I imagine it filtered down to welding.

 

[Jack Ryan]

A lot of tungsten development had already been done by the likes of Wolfram Alpha and Plansee for lighting and scientific use of tungsten electrodes.

I imagine it filtered down to welding.

Yes, I would imagine so too, but it is hard to see any evidence of it.

As I mentioned, many of the patents relate to the mechanical properties. There are very few claims about reduced work function and (welding) arc stability generally.

A selection of old catalogues might be interesting.

Jack

 

[Munkul]

Thanks Misterg, I hadn't seen that patent.

Yes, doping of tungsten has been used for a very long time - for example, in producing "non-sagging" lamp filaments. Patent US2798808A (and the patents it references) also seems to be aimed at the material properties related to the production of electrodes, rather than the properties that affect the arc.

I assume that green tungsten is not doped at all and that seems to have been used up until fairly recently. Perhaps it was only used for AC - but why not use a doped electrode if the doping improved arc stability?

I was initially wondering if there was a correlation between the introduction of square wave machines and then balance control and the doped electrodes that claim to improve arc stability. I haven't seen any evidence of that though.

In older references I have checked, there is no mention of doping. The only mechanisms used to improve AC arc stability are HF and the addition of a battery or other DC supply to overcome self rectification.

I'll check in more detail the patents referenced by US2798808A and see where it leads me.

Thanks again.

Jack

Doped electrodes have been around for a long long time, but prior to square wave and adjustable balance AC, the only practical choice for AC was pure tungsten. The sine wave at 50% EP was very hard on tungsten, and doped tungstens go into strange melty shapes when overheated. Pure tungsten just balls up then offers a good stable arc, albeit not a very focused arc.

Obviously with modern inverters with wave shaping technology, it makes no sense at all to use pure tungstens, as you can use doped ones and wave shaping to keep a pretty sharp point on the tungsten and a very precise focused arc.

 

[Jack Ryan]

Doped electrodes have been around for a long long time, but prior to square wave and adjustable balance AC, the only practical choice for AC was pure tungsten. The sine wave at 50% EP was very hard on tungsten, and doped tungstens go into strange melty shapes when overheated. Pure tungsten just balls up then offers a good stable arc, albeit not a very focused arc.

Obviously with modern inverters with wave shaping technology, it makes no sense at all to use pure tungstens, as you can use doped ones and wave shaping to keep a pretty sharp point on the tungsten and a very precise focused arc.

Thanks for that.

The doping that is used now, in addition to reducing the work function of the electrode, increases the melting point (current carrying capacity). With the introduction of balance control, those doped electrodes are, obviously, more suitable for AC.

Doped tungsten has been around for a long time, but doped tungsten to address arc stability, arc starting and current carrying capacity in welding may coincide with the introduction of square wave machines with balance control - or perhaps sine wave machines with balance control.

I'll keep an eye out for more patents and sales literature but your, and others' observations have been very helpful and are much appreciated. Thank you.

Regards
Jack

 

[Erie Fred]

I'm thinking I had seen some old boxes of thoriated tungsten's from here, used to be Sylvania:

History - GTP | Global Tungsten & Powders

www.globaltungsten.com

Towanda PA 1956 History of Sylvania Tungsten & Chemical Division -- Lots Names | #3881296096

Towanda PA 1956 History of Sylvania Tungsten & Chemical Division -- Lots NamesOffered here is the vintage booklet shown, a newsletter of Sylvania Inc.'s Tungsten and Chemical Division at Towanda, Pa.,

www.worthpoint.com

IIRC Linde (in their Indianapolis lab) was one of the first with TIG.

Westinghouse had a light bulb factory in New Jersey and was experimenting with all manner of
materials for filaments, including uranium.

Westinghouse Lamp Plant - Wikipedia

en.wikipedia.org

"Westinghouse continued its manufacturing and research at the plant after the war. In 1964, Westinghouse was issued a permit from United States Atomic Energy Commission to conduct research using thorium and uranium to produce thorium-tungsten wire. "

 

[Jack Ryan]

I'm thinking I had seen some old boxes of thoriated tungsten's from here, used to be Sylvania:

History - GTP | Global Tungsten & Powders

www.globaltungsten.com

Towanda PA 1956 History of Sylvania Tungsten & Chemical Division -- Lots Names | #3881296096

Towanda PA 1956 History of Sylvania Tungsten & Chemical Division -- Lots NamesOffered here is the vintage booklet shown, a newsletter of Sylvania Inc.'s Tungsten and Chemical Division at Towanda, Pa.,

www.worthpoint.com

IIRC Linde (in their Indianapolis lab) was one of the first with TIG.

Westinghouse had a light bulb factory in New Jersey and was experimenting with all manner of
materials for filaments, including uranium.

Westinghouse Lamp Plant - Wikipedia

en.wikipedia.org

"Westinghouse continued its manufacturing and research at the plant after the war. In 1964, Westinghouse was issued a permit from United States Atomic Energy Commission to conduct research using thorium and uranium to produce thorium-tungsten wire. "

Lots of rabbit holes there to follow, thanks.

From an initial scan, yes, people have been doping tungsten for many years but again, mostly for properties not really related to TIG. There was mention if the reduction in work function for filaments (cathodes) used in valves (tubes) but not applied the TIG electrodes.

The first mention of the reduction in work function for TIG electrodes and arc stability was from the 1990s - but that just means I missed something. That has to be at least a decade late.

I'll keep looking.

Regards
Jack

 

[Misterg]

I'll keep looking.

Try US Patent 2695945 (1952): Refractory metal electrode for inert gas-shielded arc welding

It says this about the (then) existing technology (my emphasis):

"Although additives have been used in the past with consumable, and non-consumable electrodes, sintered tungsten electrodes containing thoria or thorium oxide have only recently been used commercially for such welding. Electrodes containing 1% to 2% thorium oxide are generally preferred.
The advantages obtained by adding small amounts of thorium oxide to tungsten are (1) increased resistance to contamination by molten metal, (2) more stable arc operation at low welding current, (3) easier arc starting at relatively low voltage, (4) electrode operation at lower temperature, and (5) less Work contamination by small particles of electrode. The major advantage is claimed to be an increase in electrode life by a factor of approximately 10, and is believed to result chiefly from the increased resistance to contamination by molten metal. A disadvantage may lie in the health hazard accompanying the presence of thorium or its oxide in the welding zone. "

It goes on to describe yttrium doped electrodes:

"The main object of this invention is to provide a refractory metal electrode containing an additive that greatly improves the welding performance with respect to contamination losses, open circuit starting voltage, and arc starting losses even over thoria. This is accomplished by the use of yttrium oxide as the additive."

 

[Erie Fred]

Lots of rabbit holes there to follow, thanks.

From an initial scan, yes, people have been doping tungsten for many years but again, mostly for properties not really related to TIG. There was mention if the reduction in work function for filaments (cathodes) used in valves (tubes) but not applied the TIG electrodes.

The first mention of the reduction in work function for TIG electrodes and arc stability was from the 1990s - but that just means I missed something. That has to be at least a decade late.

I'll keep looking.

Regards
Jack

Yes,I agree.
My point was, if anyone was doing it, probably sylvania made them.

 

[Jack Ryan]

Try US Patent 2695945 (1952): Refractory metal electrode for inert gas-shielded arc welding

It says this about the (then) existing technology (my emphasis):

"Although additives have been used in the past with consumable, and non-consumable electrodes, sintered tungsten electrodes containing thoria or thorium oxide have only recently been used commercially for such welding. Electrodes containing 1% to 2% thorium oxide are generally preferred.
The advantages obtained by adding small amounts of thorium oxide to tungsten are (1) increased resistance to contamination by molten metal, (2) more stable arc operation at low welding current, (3) easier arc starting at relatively low voltage, (4) electrode operation at lower temperature, and (5) less Work contamination by small particles of electrode. The major advantage is claimed to be an increase in electrode life by a factor of approximately 10, and is believed to result chiefly from the increased resistance to contamination by molten metal. A disadvantage may lie in the health hazard accompanying the presence of thorium or its oxide in the welding zone. "

It goes on to describe yttrium doped electrodes:

"The main object of this invention is to provide a refractory metal electrode containing an additive that greatly improves the welding performance with respect to contamination losses, open circuit starting voltage, and arc starting losses even over thoria. This is accomplished by the use of yttrium oxide as the additive."

That's a nice find.

So, in 1952, arc stability, work function and current carrying capacity were all being considered. No mention of AC welding but the ground work had been done.

I don't remember hearing of Yttrium doped electrodes but there has been a lot of talk about it. For example:

Y2O3 is extensively used to fabricate oxide-dispersion-strengthened tungsten to refine grain size, improve thermal stability, and increase high-temperature strength. However, excessive Y2O3 addition weakens the grain-boundary strength, which increases the ductile-to-brittle transition temperature.

From: Journal of Alloys and Compounds, Volume 953, 25 August 2023, 169961

And they are available, claiming:

High compression strength, high and medium current welding high penetration. With good corrosion resistance and current carrying capacity. The yttrium tungsten electrode has a long arc beam and large compression degree during welding, especially in middle and large current. Excellent welding performance under high load current. Mainly used in military industry and aviation, aerospace industry.

(Sales blurb)

It's a bit like arc stability and reduced work function are a side effect of the improved material properties they were looking for. Never-the-less, those properties are known and ready for AC welding.

Thanks!

Jack

 

[Erie Fred]

Try US Patent 2695945 (1952): Refractory metal electrode for inert gas-shielded arc welding

It says this about the (then) existing technology (my emphasis):

"Although additives have been used in the past with consumable, and non-consumable electrodes, sintered tungsten electrodes containing thoria or thorium oxide have only recently been used commercially for such welding. Electrodes containing 1% to 2% thorium oxide are generally preferred.
The advantages obtained by adding small amounts of thorium oxide to tungsten are (1) increased resistance to contamination by molten metal, (2) more stable arc operation at low welding current, (3) easier arc starting at relatively low voltage, (4) electrode operation at lower temperature, and (5) less Work contamination by small particles of electrode. The major advantage is claimed to be an increase in electrode life by a factor of approximately 10, and is believed to result chiefly from the increased resistance to contamination by molten metal. A disadvantage may lie in the health hazard accompanying the presence of thorium or its oxide in the welding zone. "

It goes on to describe yttrium doped electrodes:

"The main object of this invention is to provide a refractory metal electrode containing an additive that greatly improves the welding performance with respect to contamination losses, open circuit starting voltage, and arc starting losses even over thoria. This is accomplished by the use of yttrium oxide as the additive."

I see the patent was assigned to union carbide, IIRC the predecessor of Linde. (Linde bought them)

 

[Munkul]

I see the patent was assigned to union carbide, IIRC the predecessor of Linde. (Linde bought them)

Linde then span off the welding division as a seperate company called L-tec which was then bought by ESAB.

 

[Erie Fred]

Linde then span off the welding division as a seperate company called L-tec which was then bought by ESAB.

Yes, this ^^^^ will add to the paper trail for the OP.
IIRC allot of the pioneering research was done in Indianapolis.
I recall the CNC cutters & power supplies were made in South Carolina, where they still exist as ESAB.