[Farmall] Welding cast iron

[olmstead at ridgenet.net]

Hi, Chris!  Haven't heard from you for a while.  30" lathe, huh?  I'm
"making do" with a 1944 12" Monarch CK.  I could turn the old ears off the
casting, but it is going to require welding two 3/8" or 1/2" inch ears
back on; the surface where the ears bolt to the tractor frame runs right
through the centerline of the tubular crank support, so a single plate
won't fit.  Welding new ears on the casting would certainly be the
cleanest approach.  Most of the dozen or so damaged brackets I've checked
out only have the mounting ears broken; the central tube is fine.  Two or
three of them also have broken tubes.  Regardless of whether I make new
tubes or not, I will have to fabricate new mounting ears.  I just figured
that if I made steel tubes, the whole cast iron welding problem would be
eliminated.  I have several friends who can do a fine job on mild steel; I
just don't think they'd do well on 70 year old cast iron.  I appreciate
your discussion of the metallurgy involved.  I knew that nickel rod was
recommended; I just didn't know why.

-Karl
---------------------
>
>    The problem I have found with mig welding cast iron most of the time
> they use an iron based wire. Cast iron contains large amounts of carbon
> in the form of graphite.  When melted by the welding process this mixes
> with the weld pool. With iron filler you end up with high carbon steel
> which is very hard and brittle.  This is why most cast iron rods are
> nickel or stainless steel which will not absorb the carbon. Nickel makes
> for a more forgiving weld when it comes to pre and post heating.
> Stainless generally makes for a stronger weld but heating is more
> critical.  I  recently ran across this with a cast iron clutch pilot off
> of a large stationary engine.  They had built up the wear surface with a
> mig welder and then tried to turn it down and had no luck. Actually
> damaged their lathe trying to force it. They thought my 30" lathe would
> have better luck but all that did was eat carbide. I ended up turning it
> down on the crankshaft grinder.  It  was a slow process I doubt it will
> ever wear out.
>
>    The plus side of mig welding is generally less heat is generated than
> with stick welding.  This helps with the preheat and post heat  problem.
> I think this is how most are able to get away with it in non structural
> applications.
>
>    I do not know what the crank bracket looks like on an O-12 but on
> 10-20's and 15-30's they are not too bad to fix.  I turn off the part
> where the mounting  bolts go till it is round. Then cut out a steel
> plate to match the old mounting bracket  drill to match the turned crank
> bearing and weld it together.  For that I usually use a bronze stick
> electrode it seems to work well for joining cast to steel.
>
>   Chris Klossner
>  http://home.att.net/~klossner/