Soldering or brazing to Tungsten

Soldering or brazing to Tungsten

Post by Jo » Thu, 28 Oct 1999 04:00:00



I need to attach some other metals to tungsten TIG welding rod I am
using as electrodes in glass-envelope tubes I make myself.

The TIG rod I am using is 1/16 and larger, 2% thoriated.

I want to be able to solder or braze to it: copper wire, other shapes
of tungsten, and/or stainless steel wire or other stainless steel
shapes. If other metal types are easier to solder or braze to
tungsten, I would certainly consider them. (The advantage to using
tungsten is its excellent match of thermal expansion coefficient to
glasses, and its high temperature strength.)

Tungsten sure is weird stuff. Any suggestions for soldering/brazing
methods?

I found one reference in Strong's "Procedures in Experimental Physics"
(Lindsay Publications, from the 1930's) to something called "Advance"
metal that could be soldered on to tungsten. Anyone know what that is,
how or where to get some, or what fluxes to use with it?

Thanks in advance.

Jon F_o_x

directly)

 
 
 

Soldering or brazing to Tungsten

Post by Robert Basto » Thu, 28 Oct 1999 04:00:00


I can't help with brazing..but I sure know how to WELD 2% thoriated electrodes
to everything I try to tig weld!!  8^)

Electron beam or even spot welding may be a route to investigate.

Try a web search on tungsten..there is a ton of information out there.

SOP..Find a company that makes the equipment to do it and ask for
literature/tech help.

If you can duplicate the technology, great.  If not BUY it or find a different
product to make and save yourself a bunch of time and heartache!

BTDT too many times.

***ut

Quote:

> I need to attach some other metals to tungsten TIG welding rod I am
> using as electrodes in glass-envelope tubes I make myself.


 
 
 

Soldering or brazing to Tungsten

Post by tomw.. » Thu, 28 Oct 1999 04:00:00


The ASM handbook covers this pretty well.

Tom


Quote:
> I can't help with brazing..but I sure know how to WELD 2% thoriated
electrodes
> to everything I try to tig weld!!  8^)

> Electron beam or even spot welding may be a route to investigate.

> Try a web search on tungsten..there is a ton of information out there.

> SOP..Find a company that makes the equipment to do it and ask for
> literature/tech help.

> If you can duplicate the technology, great.  If not BUY it or find a
different
> product to make and save yourself a bunch of time and heartache!

> BTDT too many times.

> ***ut


> > I need to attach some other metals to tungsten TIG welding rod I am
> > using as electrodes in glass-envelope tubes I make myself.

Sent via Deja.com http://www.FoundCollection.com/
Before you buy.
 
 
 

Soldering or brazing to Tungsten

Post by Randy Zimmerma » Thu, 28 Oct 1999 04:00:00


I  suggest that you silver solder the tungstens.  Technically you are
brazing with silver alloy.
    I regularly use old tungsten ends as scribers.  I silver solder them to
mild steel of stainless rod.
    In fact I helped an apprentice make up his own scribers this way last
month.
    Try this site for selection of flux and alloy.  I just use regular
easyflo 45
    http://www.handyharmancanada.com./
Quote:

>I need to attach some other metals to tungsten TIG welding rod I am
>using as electrodes in glass-envelope tubes I make myself.

 
 
 

Soldering or brazing to Tungsten

Post by brian whatco » Fri, 29 Oct 1999 04:00:00



says...

Quote:

>I need to attach some other metals to tungsten TIG welding rod I am
>using as electrodes in glass-envelope tubes I make myself.
>The TIG rod I am using is 1/16 and larger, 2% thoriated.
>I want to be able to solder or braze to it...
>Jon F_o_x

To solder, copper plate - could use electroless solution,
 then soft or hard solder.    This is a weak joint.

Try brazing - most all metals can be brazed. (but cast iron is difficult!)
 I seem to recall that tungsten was the favored brazed contact tip for
'breakers' and  'points' due to its high melting point.
Brazing alloys include copper silver zinc:    copper zinc;
 copper, nickel, zinc.

Ref: Materials & Processes in Manufacturing,
 DeGarmo, Black, Kohser,
Macmillan.

Brian Whatcott    Altus Ok

 
 
 

Soldering or brazing to Tungsten

Post by Don Wilki » Fri, 29 Oct 1999 04:00:00


Quote:

>I need to attach some other metals to tungsten TIG welding rod I am
>using as electrodes in glass-envelope tubes I make myself.

>The TIG rod I am using is 1/16 and larger, 2% thoriated.

>I want to be able to solder or braze to it: copper wire, other shapes
>of tungsten, and/or stainless steel wire or other stainless steel
>shapes. If other metal types are easier to solder or braze to
>tungsten, I would certainly consider them. (The advantage to using
>tungsten is its excellent match of thermal expansion coefficient to
>glasses, and its high temperature strength.)

My recollection is that our glass shop used molybdenum and/or Kovar
for glass-metal seals instead of tungsten. Kovar was developed as an
alloy having thermal expansion characteristics matching those of hard
glass. Kovar is a Fe-Ni-Co alloy (Westinghouse trademark).

Many of the *** structures they made inside vacuum apparatus was
spot welded or silver soldered.

<balance snipped>

 
 
 

Soldering or brazing to Tungsten

Post by Rich Osma » Fri, 29 Oct 1999 04:00:00


Most of the vacuum tubes I've seen spot weld the tungsten elements.  I'm
not sure how practical this will be in your case, 1/16 is pretty big
stuff.

Quote:


> >I need to attach some other metals to tungsten TIG welding rod I am
> >using as electrodes in glass-envelope tubes I make myself.

> >The TIG rod I am using is 1/16 and larger, 2% thoriated.

> >I want to be able to solder or braze to it: copper wire, other shapes
> >of tungsten, and/or stainless steel wire or other stainless steel
> >shapes. If other metal types are easier to solder or braze to
> >tungsten, I would certainly consider them. (The advantage to using
> >tungsten is its excellent match of thermal expansion coefficient to
> >glasses, and its high temperature strength.)

> My recollection is that our glass shop used molybdenum and/or Kovar
> for glass-metal seals instead of tungsten. Kovar was developed as an
> alloy having thermal expansion characteristics matching those of hard
> glass. Kovar is a Fe-Ni-Co alloy (Westinghouse trademark).

> Many of the *** structures they made inside vacuum apparatus was
> spot welded or silver soldered.

> <balance snipped>

--

Rich Osman   +1 972-879-2301 (Pager)
POB 93167; Southlake, TX 76092 (Near DFW Airport) ARS: WB0HUQ
 
 
 

Soldering or brazing to Tungsten

Post by Gordon Coug » Fri, 29 Oct 1999 04:00:00


Quote:



>> >I need to attach some other metals to tungsten TIG welding rod I am
>> >using as electrodes in glass-envelope tubes I make myself.

Make sure you are using the right kind of glass to match the expansion
of tungsten.  I think it is borosilicate glass but I am not sure.
Different types of glass have very different amounts of expansion when
heated.

You can make a spot welder out of a big capacitor, a power supply, a
block of carbon and a pair of pliers. You connect the pliers to one
terminal of the capacitor the block of carbon to the other, charge the
capacitor, twist the two wires togeather grip them with the pliers and
touch them to the carbon block. If you are real careful you can do it
with out much of a twist.

It takes a little expermenting but I have welded a lot of
thermocouples that way.

Gordon
Gordon Couger
Stillwater OK.
www.couger.com/gcouger

 
 
 

Soldering or brazing to Tungsten

Post by mulli.. » Fri, 29 Oct 1999 04:00:00




Quote:
> My recollection is that our glass shop used molybdenum and/or Kovar
> for glass-metal seals instead of tungsten. Kovar was developed as an
> alloy having thermal expansion characteristics matching those of hard
> glass. Kovar is a Fe-Ni-Co alloy (Westinghouse trademark).

Kovar wire is indeed used in the presses of vacuum tubes - and is
spot welded to the elctrodes.  The older tubes (pre kovar alloy)
frequently used platinum as the wire inside the press.  These
tubes often have small sections of platinum wire ***welded
inline with inexpensive wire - with the platinum sections embedded
inside the press.

Jim (is the original poster making deforest audions?)

Sent via Deja.com http://www.FoundCollection.com/
Before you buy.

 
 
 

Soldering or brazing to Tungsten

Post by Lou Boy » Fri, 29 Oct 1999 04:00:00


Quote:


> says...

> >I need to attach some other metals to tungsten TIG welding rod I am
> >using as electrodes in glass-envelope tubes I make myself.
> >The TIG rod I am using is 1/16 and larger, 2% thoriated.
> >I want to be able to solder or braze to it...

> >Jon F_o_x

> To solder, copper plate - could use electroless solution,
>  then soft or hard solder.    This is a weak joint.

> Try brazing - most all metals can be brazed. (but cast iron is difficult!)
>  I seem to recall that tungsten was the favored brazed contact tip for
> 'breakers' and  'points' due to its high melting point.
> Brazing alloys include copper silver zinc:    copper zinc;
>  copper, nickel, zinc.

> Ref: Materials & Processes in Manufacturing,
>  DeGarmo, Black, Kohser,
> Macmillan.

> Brian Whatcott    Altus Ok

Does anyone know of a source for "off the shelf" 1/4" dia tungsten rod?
--
Lou Boyd
Fairborn Observatory