Sciencemadness Discussion Board
Not logged in [Login - Register]
Go To Bottom

Printable Version  
Author: Subject: Welding Nichrome wire
angelhair
Hazard to Self
**




Posts: 81
Registered: 14-4-2008
Member Is Offline


[*] posted on 26-10-2009 at 16:26
Welding Nichrome wire


I wish to join some o.8mm nichrome end to end using an oxy torch. before anyone says it's too small, you can't do it, let me say that I have done it very well with thinner copper wire.

What I wan't to now is, is a neutral flame the right one to use?
View user's profile View All Posts By User
kilowatt
National Hazard
****




Posts: 311
Registered: 11-10-2007
Location: Montana
Member Is Offline

Mood: nitric

[*] posted on 26-10-2009 at 17:12


Nichrome has quite a tenacious oxide coating, and so is much more difficult to join than copper. It may be possible with a neutral or reducing flame, or it may require a TIG torch with it's inert shielding gas. I have accidentally welded nichrome wire by electrolysis in a molten salt bath before, so this may be a good simple way to join it intentionally as well. All that is needed is the nichrome joint to be the cathode, and another piece of nichrome wire to be the anode.
http://chrisf.4hv.org/projects/chem/HPIM1495.JPG




The mind cannot decide the truth; it can only find the truth.
View user's profile View All Posts By User
garage chemist
chemical wizard
*****




Posts: 1805
Registered: 16-8-2004
Location: Germany
Member Is Offline


[*] posted on 26-10-2009 at 17:34


I make my own type K thermocouples from the wires (one is nichrome, the other mostly nickel) with, incidentally, also 0,8mm diameter.
I do this by twisting the wires together on a length of about 3cm, briefly holding the twisted section into the flame to heat it, and then dipping it in borax powder so that it sticks to the wire.
I then carefully heat the wire with the borax so that the borax loses its crystal water (foaming, steaming) and flows onto and between both wires and covers them.
Then I melt the tip of the wires (0,5cm) together into a small sphere, using a small sharp flame (it's either neutral or oxidising, don't know for sure). The molten borax dissolves the oxides- without borax or another flux, nichrome couldn't be welded because of its tough oxide layer.
The connection is very reliable and strong.




www.versuchschemie.de
Das aktivste deutsche Chemieforum!
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 3946
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: pumped

[*] posted on 26-10-2009 at 17:37


Although my experience may not be relevant to your situation, I will relate it just in case it is.

It was just the other day when I needed to weld two ends of a nichrome wire for a heater element. So, I searched on the internet and some said that the secret was using an acid flux (zinc chloride, HCl). So I tried it. Didn't work. Then I called the one man in my community that I thought might have the answer: an AOOF owner of an antiquated electrical repair store - a dying breed - very rare. His crusty response was "you can't weld it." I replied that I'd heard (on the internet, of course) that it could be silver soldered. He says "what good will that do if the melting point of silver is below the operating temperature of the wire?" Duh. He said you have to use a SS crimp. So that's what I did. Works great.

[Edited on 27-10-2009 by Magpie]




Knowing that I can buy good quality NaOH, HCl, and H2SO4 locally gives me great peace of mind.
View user's profile View All Posts By User
kilowatt
National Hazard
****




Posts: 311
Registered: 11-10-2007
Location: Montana
Member Is Offline

Mood: nitric

[*] posted on 26-10-2009 at 18:55


You should send him some welded nichrome wires. I wonder what he'd think. ;)



The mind cannot decide the truth; it can only find the truth.
View user's profile View All Posts By User
densest
National Hazard
****




Posts: 333
Registered: 1-10-2005
Location: in the lehr
Member Is Offline

Mood: slowly warming to strain point

[*] posted on 26-10-2009 at 20:36


I've welded nichrome wire two ways: oxy/gas and pulsed electrical spot welding.

For gas welding, carbon embrittles nichrome, so use a lot of flux (fluoride based flux is what I use) and prefer hydrogen before methane (natural gas) before propane before acetylene. Use a somewhat oxidizing flame. It should hiss a little. There's a very nice little torch sold under the name "little torch" which is very useful for that sort of work.

For spot welding, I use a homebrew capacitor/IGBT setup which delivers about 500A peak and tungsten electrodes. For that, you need to have a lot of pressure and make sure the wires being joined have been cleaned until shiny. One zap and it's done.
View user's profile View All Posts By User
merrlin
Hazard to Others
***




Posts: 110
Registered: 3-4-2009
Member Is Offline


[*] posted on 26-10-2009 at 22:35


Quote: Originally posted by densest  


For spot welding, I use a homebrew capacitor/IGBT setup which delivers about 500A peak and tungsten electrodes. For that, you need to have a lot of pressure and make sure the wires being joined have been cleaned until shiny. One zap and it's done.



A similar but somewhat cruder method for a butt weld is to connect each of two wires to a charged capacitor and shove them into opposite ends of a short piece of glass tubing (e.g., capillary tubing) of slightly larger diameter. The arc melts the ends of the wires just before impact.
View user's profile View All Posts By User
Eclectic
International Hazard
*****




Posts: 899
Registered: 14-11-2004
Member Is Offline

Mood: Obsessive

[*] posted on 26-10-2009 at 23:55


Yep, Oxy-gas with fluoride flux seems to work just fine.:)
View user's profile View All Posts By User

  Go To Top