Stress, yes relatively speaking. The
Here's a general pic of the machine, just something I got off the internet, but the vintage of the whole machine is very close (1920's in the pic, the one my MIL has is 1918 by the serial #).
It's hard to see, but the curved piece that supports the foot pedal (aka treadle) is broken on both sides. The left one is an old break, the right one is fresh.
I surfed a bit today, and came across this:
http://www.bocworldofwelding.com.au/media/pdf/WELDING CONSUMABLES-Cast Iron.pdf
"Grey Cast Iron
As grey cast iron contains graphite in flake form, carbon can readily
be introduced into the weld pool, causing weld metal embrittlement.
Consequently, techniques that minimise base metal dilution are
recommended. Care must be taken to compensate for shrinkage
stresses, and the use of low strength filler metals helps reduce
cracking without sacrificing overall joint strength.
Grey cast iron welds are susceptible to the formation of porosity.
This can be controlled by lowering the amount of dilution with the
base metal, or by slowing the cooling rate so that gas has time to
escape. Preheat helps reduce porosity and reduces the cracking
tendency. A minimum preheat of 200°C is recommended, but 315°C
is generally used.
The most common arc welding electrodes for grey cast iron are
nickel and nickel-iron types. These electrodes have been used with
or without preheating and / or postweld heat treatment. Cast iron
and steel electrodes must be used with high preheats (550°C) to
prevent cracking and the formation of hard deposits."
So.... high nickel rod, let it cool slowly.. I have heard of guys using stainless filler rod in a pinch too, but not sure if there is enough nickel in stainless to control the contraction.
