On Monday, November 30, 2015 at 8:29:40 AM UTC-5, Ed Huntress wrote:
On Mon, 30 Nov 2015 05:02:48 -0800 (PST), "
wrote:

On Sunday, November 29, 2015 at 8:12:23 PM UTC-5, Ned Simmons wrote:


The low CTE of Invar only applies near room temperature. At 500F its
CTE is in the range carbon steel's, and continues to increase with
increasing temperature. At 1000F Invar's CTE is close to that of other
nickel alloys like Inconel.

--
Ned Simmons


The invar with lot expansion at room temperature is 36% nickel.

Invar 42 with a slightly higher percentage of nickel has less CTE at higher temperatures. I kind of assume that the CTE at 1000F is not a problem as the yield strength ought to be low at that temperature.

Obviously Nickel 55% rod must be better or they would not make it for welding cast iron. But the Invar 42 was cheap at Boeing Surplus.

Dan

I'm curious about why one would want to weld with Invar. The iron
you're welding with it has a very different thermal coefficient of
expansion. It seems likely that a gray-iron/Invar joint is going to be
under stress from differential expansion at ALL temperatures except
for one.

Or what?

--
Ed Huntress

Why would you want to weld with nickel 55? Invar 42 is kind of close to Nickel 55. It is 42 % nickel, while the nickel 55 is 55 %. The Invar is not as high in nickel as Nickel 55 but it is relatively close.

One definition of an engineer is somebody that can make what any fool can make, but the engineer can make it cheaper. In this case the Invar 42 came from Boeing Surplus and was as I remember a dollar a lb. I would have picked up a bunch of Nickel 55 and Nickel 99 , but I never saw any at Boeing Surplus.

Looking on line , I found a place that sells Nickel 55 for $22 per half lb.
So if the Invar 42 will work, it will save Terry relatively a bunch of money.

You are better at finding information on the internet than I am. If you can find anything that explains why Nickel 55 is good for welding cast iron ( as opposed to 50 % nickel or 60 % nickel ) let me know about it. I have looked but not found anything that explains why everyone sells nickel 55 for welding cast iron and not some other percentage. There must be a reason, but I have not found it.

Dan