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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Apr 03, 2012 7:29 pm Post subject: |
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| Tim in Phoenix wrote: | I found this
Kovar (trademark of Carpenter Technology Corporation) is a nickel-cobalt ferrous alloy designed to be compatible with the thermal expansion characteristics of borosilicate glass (~5×10-6 /K between 30 and 200°C, to ~10×10-6 /K at 800°C) in order to allow direct mechanical connections over a range of temperatures. It finds application in electroplated conductors entering glass envelopes of electronic parts such as vacuum tubes (valves), X-ray and microwave tubes and some lightbulbs.
The name Kovar is often used as a general term for Fe-Ni alloys with these particular thermal expansion properties. Note the related particular Fe-Ni alloy Invar which exhibits minimum thermal expansion.
My guess is that this is the alloy for tube pins.
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We already looked at that Tim. Kovar is magnetic and apparently the pins are not. Did you check your pins to see if they were magnetic?
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Tue Apr 03, 2012 8:14 pm Post subject: |
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| macgyver655 wrote: |
We already looked at that Tim. Kovar is magnetic and apparently the pins are not. Did you check your pins to see if they were magnetic? |
The pins on a Marquee CRT do respond to a magnet, as if they are made of steel.
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Tim in Phoenix
Joined: 21 Oct 2006
Posts: 4409
Location: Phoenix
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| Posted: Tue Apr 03, 2012 9:22 pm Post subject: |
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Guys
I would not automatically expect substances that contain iron to be magnetic. Stainless steel is not, and I bet rust is not.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Apr 03, 2012 10:32 pm Post subject: |
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| Tim in Phoenix wrote: | Guys
I would not automatically expect substances that contain iron to be magnetic. Stainless steel is not, and I bet rust is not.
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Tim. From the link I posted on Kovar:
"Magnetic Properties
Kovar alloy is magnetic at all temperatures below the Curie point".
Of course if the pins are magnetic like Mike says then it could be. Nash said they were not and Mike says they are. I have no idea. Maybe I'll check the tubes I have here later to see.
I know Scott posted a spec sheet on a tube a while back but I have no ides where it is or if it stated what the pins are made of.
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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Tim in Phoenix
Joined: 21 Oct 2006
Posts: 4409
Location: Phoenix
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| Posted: Wed Apr 04, 2012 9:02 am Post subject: |
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Hmmm
I had believed that only iron was magnetic, not alloys.
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Wed Apr 04, 2012 10:19 am Post subject: |
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Hi,
If You look at the specifications for the lead-through wires on Page 37 of the brochure it becomes apparent that those alloys contain up to 50% of iron...
You may also look for the term "Dumet wire" over here: http://www.dumet.net/
Regards,
barclay66
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Wed Apr 04, 2012 11:18 am Post subject: |
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I double checked using a magnet touched to the pins on my Marquee 8500LC, which has both Rebuilt and Stock Tubes in it.
Both rebuilt and stock tubes were magnetic.
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