View Full Version : SG IRON

04-21-2005, 09:26 AM
I'm working with a friend who is developing a special kind of hitch for quickly coupling farm implaments.
he has had quotes for a number of castings.
all of them are steel castings .
except this one.
the hitch drives the farm implament thru a drive shaft with flanges that enguage into each other.
this means the farmer will back up to the trailer and hit the other flange quite hard sometimes.(thats if he makes mistakes and leaves the coupling sticking out) depending what sort of mood he is in.
and the flanges will be abused......and used for god knows what.
here is the patent ...look at the drive shaft part of it

I dont know the properties of sg iron.....I would have thought harder cast steel was more suitable .......the rest of the components will be cast out of steel.
plese tell me guys .....what i should do.
all the best..mark

ps the castings will be blanks that get machined after.

from the net

Definition: An abbreviation for Spheroidal Graphite Cast Iron. As the name implies, graphite is present in spheroidal form instead of flakes and compared with Grey Cast Iron it has higher mechanical strength, ductility and increased shock resistance.

is it upto abuse by farmers though.

[This message has been edited by aboard_epsilon (edited 04-21-2005).]

Dave Opincarne
04-21-2005, 09:58 AM
Sounds like ductile. I'd see if manganise steel is an option.

04-21-2005, 10:37 AM
SGCI has excellent toughness and is used widely in crankshafts, housings & casings.

Here's a link that compares Grey CI to SGCI: http://www.wear-management.ch/?path=root+castiron&lang=en

Barry Milton

04-21-2005, 10:41 AM
yes ...but will it shatter ..if its hit hard.

all the best.mark

J Tiers
04-21-2005, 04:15 PM

The stress strain diagram shows a material which will NOT "shatter". Shatterable material has very little or no elongation before fracture.

The whole point of malleable iron is that it is, well, malleable....it "gives" somewhat before it fractures.

04-21-2005, 04:25 PM
well thanks guys
yup it gives 16 percent before it fractures.
which suposidly means that it can take a good clout before it fractures.
it looks like a go then .so far so good.
i'll tell him to go ahead and get the first lot of castings done.
then it's onto testing.
All the best.mark

[This message has been edited by aboard_epsilon (edited 04-21-2005).]

04-21-2005, 08:39 PM
Is this the same stuff that's called 'nodular iron'? If it is, its probably some really good stuff. I remember back in my hot rodding days they always said to run a forged steel crankshaft, not a cast nodular one, but every small block Chevy crank I ever saw broken was forged steel.

04-22-2005, 12:00 AM
..........I'm sure other auto manufacturers were the same. I'd read that Ford used high nodularity cast iron in most all their crankshafts, the exception being the few forged steel units. On the high performance engines the CI crankshaft had a mark where the unit was tested. The only reason for the test was to guarantee the correct high nodularity structure, rather then to assume it was up to snuff.


Norman Atkinson
04-22-2005, 03:06 AM

SGCI is probably what your lathe chucks are made of.

At least, you now know what you are looking at.

Good Luck