As I said some suppliers do certain parts in Ductile, the ones marked in the Gade photo were the Ductile iron ones. Other makers such as Nick Rowland of RMC and also Dennis at Historic Reproductions both do all there iron parts in ductile iron. So yes Typical models are using ductile iron. Moving on to things like model traction engines then again axles and crankshafts are SG or Ductile.
Even Stuarts when they were supplying their crankshafts as castings did not us egrey iron for those, early ones were described as cast steel and I think later were SG Iron so yes "Typical" models use ductile iron.
You missed my point about using ductile iron for small section parts, would not need to use a sledge hammer to break a delicate part like this if it were in grade 40, but it was cast in ductile iron so will tend to bend rather than snap.
When I first started trying to melt gray iron, lots of folks (pretty much everyone perhaps with a rare exception) said to use a cupola/cupolet with coke as a fuel.
I set about to find coke (coal heated in the absence of oxygen), and came up empty handed, except for a semi-truckload, which was readily available for about $12k.
I finally settled on a diesel burner, and that worked well once I figured out how to tune it correctly.
Finding nicklemag4 has proven even more difficult than finding coke.
Even when I find a supplier, they won't sell it.
I don't have time to drive all over the country to ask foundries if they would share, but I think that is what it is going to take.
No time for that now.
I can purchase a ton of it from asia, but it actually has a shelf like, and I would only use a few pounds.
I do have the materials to make lead-free bearing bronze, and am interested in casting that.
There are not that many pieces in an engine casting kit that need to be ductile iron.
Perhaps the crankshaft and connecting rod; beyond that I think it would be just a wasted process, other than perhaps some thin parts that JasonB mentions.
My philosophy is don't fix things that are not broken; if the part will work well in Class 40 gray iron, don't upgrade to ductile iron for no gained benefit, because ductile iron cost more money to make.
Those mini-Wilton vices were cast in steel, and that is the ultimate achievement in my opinion, although many commercial foundries would find it routine.
The casting magazines point out that ductile iron is a less expensive alternative than casting the same part in steel in most cases, and they publish a lot of successful case studies of folks converting from both weldments and steel castings to ductile iron castings, with great success.
Ductile iron castings rival steel castings, and sometimes exceed the qualities of steel in strength-to-weight ratio.
Steel casting as I understand it is a much more complex process than ductile iron casting.
Steel castings basically force you into induction melting, whereas ductile iron can be made using a diesel burner.
Rome was not built in a day, and so hopefully one day I will find a source for additive that will make ductile iron.
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