hlare, the nickel pig iron argument was used to rebase nickel at US$25,000/t when it was US$50,000/t. Realistically, the lower the price of nickel the less impetus to mine these rather crappy pig iron resources.
If you're looking at austenitic stainless with 18/10 or 10/8 you have at most 18% nickel. To achieve this blend from a 50% Fe, 1% Ni feedstock you have to add around 14% nickel w/w to bring it up to 18% Ni content; the pig iron is hardly a substitute.
Similarly, for a 10/8 austenitic stainless you'd still have to add a significant amount of nickel.
Nickeliferous pig irons from ni laterites can substitute in for 400-series martensitic steels, you can probably get away with chucking your laterite into the furnace and tweaking it by either adding plain Fe ore to drop the 2% resultant Ni content (but you have to dilute over 4:1 to drop to the usual 0.5% Ni content of most 400 series steels) or in some cases, adding a little bit more nickel.
Note that you have to still add chromium, by the bucketload; balancing your manganese is also a problem for some grades of stainless steel where you don't want manganese, which can often be a sizeable component of nickel laterites. Eg, martensitic steels have 1% Mn,
I would suggest that these so-called nickel pig irons are useful for crappy-quality chinese steels where alloy properties aren't adhered to strictly, but in any case, the economics mean they can't do more than cheapen your 100 and 200 series steels, and become volumentrically insignificant in most 400 series steels where you may need 1 tonne per 16 or less.
For example; making a 446 stainless with a 50% Fe, 1 % Ni pig iron (goes to a 97% Fe, 2% Ni steel) you'd need to dilute the nickel out with 16 times the amount of Ni-free Fe ore. So to make a million tonnes of the stuff you'd need only 62Kt of nickel laterite.
On the other end of the spectrum, to make a million tonnes of 18/10 stainless you'd need 1.8Mt Chrome, and if you used laterites, you'd consume 2Mt to get the required Fe but still need to buy an additional 160Kt of nickel from sulphide (the pig iron would only give you 20Kt of contained Ni).
So, realistically, nickel laterites can only substitute for about 10-20% of the nickel used in the stainless steel industry.
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