Relative cost of casting superduplex steel versus ductile iron

I know this is not an easy question to answer, but am looking for a rough order of magnitude of the cost to make large castings (a few hundred pounds max.) in superduplex and/or superaustenitic stainless steels, as opposed to ductile iron.

Background - we manufacture a line of HVAC control valves for chilled water (fresh water) that have certain advantages for large installations. We have been approached by one of our reps who thinks our technologies might have advantages for large desalination works. But, that means replacing all of our mild steel, cast ductile iron, and even generic austenitic stainless steel parts with something more corrosion resistant in salt water and brine. The boss saw a lot of $$ in sales, but I’m seeing $$$ in material costs alone, much less machining. Any help?

Can you use the same tooling? I assume the raw material is more expensive. Will it be more difficult to machine?

Talk to your vendors, and work out the extra cost. Maybe the users of stainless steel components are used to paying extra. Crunch the numbers and pass them on to your boss.

Yeah, I know that approach Rev, but am trying to avoid excersizing our vendors for quotes on stuff that has about .01% chance of coming to fruition. Just want ballpark figures, which I can double or triple, to show that the cost of the new parts would be horribly expensive. The production volumes being discussed are also ludicrous, roughly 10 each.

According to some database pricing on per pound costs we have, superaustenitic steel is about 3.75x higher than ductile iron on a unit rate basis. I don’t have any data points readily available on how castings may compare to forgings. We have some data on super duplex but it’s too far out of date to be useful at this point.

I hope that helps.

Thanks Koach, that is useful info, and is around my own ballpark guesstimates based on limited info. We have a sister company that does subsea work, but they generally use wrought forms, not castings, as well.

Ductile iron to super duplex stainless steel must be in range of 4-5X, for 304 grades it will be 2.75-3X.

Hope it helps.

Ok, thanks Arun.