Austenitic stainless is the 300 series: 18-20% chromium, 8-10% nickel and carbon at or below 0.08%, non-magnetic and the most corrosion-resistant of the three families, used for medical, food-processing and chemical equipment. For a village the limiting input is nickel, so the realistic route is to salvage and remelt existing austenitic scrap, not to build the alloy from ore.
Part of Stainless Steel Production
The nickel-bearing stainless family: composition, why it is the best and hardest to make, and how to work what you salvage.
Nickel Buys Corrosion Resistance And Toughness, At A Price
The 300 series is the nickel-bearing stainless family.
The carrier gives the austenitic (304 type) range as 18-20% chromium and 8-10% nickel, with carbon at or below 0.08%, non-magnetic, excellent corrosion resistance, and uses in medical, food and chemical work. The cost is the extra metal: see Nickel Sources for why a village depends on salvage, and why copper-nickel coins are not a substitute.
The carrier also treats it as the grade you move to “when you have reliable nickel supply and better furnace control”. That is the honest summary: it needs everything ferritic needs, plus nickel.
What You Need
- Sorted austenitic scrap: sinks, saucepans, milk cans, non-magnetic or only weakly magnetic (Metal Identification).
- A furnace for remelting, or for building the alloy from base steel plus ferrochrome plus nickel.
- A solution-annealing furnace for finished or welded parts (Solution Annealing).
Method: Working With It
Step 1: Sort and clean the scrap. Strip any steel parts, plating or coatings.
Step 2: Remelt or forge. Forge at 1,100-1,250 °C per Hot Forging; never work it cold below 900 °C, the carrier’s limit.
Step 3: Weld with a stainless filler and keep heat input low (Welding Stainless).
Step 4: Solution anneal and passivate after welding or forging (Passivation Treatment).
Worked Example
To build a 100 kg heat from base steel at 18% chromium and 8% nickel: ferrochrome 18 / 0.65 = 27.7 kg and nickel 8 kg, leaving 64.3 kg of base steel (see Alloy Addition Sequence). The same heat from sorted 304-type scrap needs no ferrochrome at all and no nickel, because the scrap already carries about 18-20% and 8-10%.
Cooling Is Where The Carrier Is Inconsistent
The carrier’s forging section says not to quench austenitic stainless; its annealing section says to quench it rapidly from 1,050-1,100 °C. Both appear in the same article and I could not reconcile them as written. Rapid cooling through the carbide-forming range is the logic of solution annealing (Solution Annealing); my recollection is that austenitic steel does not harden by quenching, so the quench is for corrosion resistance and not for strength. Treat “do not quench” as meaning “do not expect a quench to harden it”.
Common Mistakes
- Treating non-magnetic as proof of austenitic. Weakly magnetic pieces exist, and non-magnetic is not a chromium or nickel assay.
- Adding nickel without carbon control. Carbon still limits the grade.
- Slow-cooling a weld or forging. Sensitization follows.
Safety
Hot work and acids
Forging, casting and welding involve metal over 1,000 °C and chromium-bearing fume. Passivation uses nitric acid; see Passivation Treatment for its danger block.
What’s Next
- Learn next: Solution Annealing - restoring corrosion resistance after heat
- Combine with: Martensitic - the family that does harden