Three stainless families are within reach of a village that has chromium, in rising order of difficulty: martensitic (12-14% chromium, hardenable, moderate corrosion resistance), ferritic (16-18% chromium, magnetic, good corrosion resistance), and austenitic (18-20% chromium plus 8-10% nickel, non-magnetic, best corrosion resistance). Which one is practical depends less on chromium than on whether you can hold carbon down and whether you have nickel.
Part of Stainless Steel Production
Choosing between ferritic, austenitic and martensitic stainless on what a village can actually make and what each is for.
The Carrier’s Grade Table
| Grade type | Cr% | Ni% | C% max | Properties | Applications |
|---|---|---|---|---|---|
| Ferritic (430 type) | 16-18 | 0 | 0.08 | Magnetic, good corrosion resistance | Kitchen equipment, water tanks |
| Austenitic (304 type) | 18-20 | 8-10 | 0.08 | Non-magnetic, excellent corrosion resistance | Medical, food processing, chemical |
| Martensitic (410 type) | 12-14 | 0 | 0.15 | Hardenable, moderate corrosion resistance | Knives, surgical tools, valves |
The 430, 304 and 410 labels are the carrier’s. I recall the standard 430 specification allowing a slightly higher carbon maximum than 0.08%, but cannot source it, and use the carrier’s figure here.
The Carrier’s “Start With Ferritic” Advice Needs A Qualifier
The carrier recommends starting with ferritic because it needs only chromium and “tolerates less precise carbon control”. The arithmetic in Carbon Control shows the opposite risk: a ferritic melt at 16-18% chromium made from carbon-reduced ferrochrome carries more than 1% carbon, against a 0.08% limit, and that is the same problem as for austenitic. The carrier’s own table makes ferritic’s carbon limit just as strict as austenitic’s. What is true is that ferritic skips the nickel.
Which Family For Which Situation
| Your situation | Realistic target | Why |
|---|---|---|
| Salvaged stainless, no ore | Remelt and recast the same family | Carbon and chromium already right |
| Ferrochrome route, no nickel | Martensitic at high carbon, or ferritic only with a low-carbon chromium source | Carbon-rich ferrochrome fits the hardenable family best |
| Ferrochrome route with nickel and carbon control | Austenitic | Best corrosion resistance, hardest to do |
None of these is a village-scale routine. They are listed so that a plan names the family and not just “stainless”.
What The Family Decides Downstream
- Forging: Hot Forging works for all three, but cooling and heat treatment differ.
- Heat treatment: only martensitic hardens by quenching (Martensitic); austenitic is quenched for corrosion resistance, not hardness (Solution Annealing).
- Welding: each family has its own failure mode (Welding Stainless).
- Sorting scrap: a magnet separates the magnetic families from the non-magnetic one (Metal Identification), though some stainless is only weakly magnetic.
The metallurgical reasons for these differences belong to the materials-science treatment of each family and are not covered here.
Common Mistakes
- Choosing a family from the applications column alone. Match it to the carbon and nickel you can control.
- Calling every non-rusting steel “304”. The label is a family reference in this tree, not a guarantee of composition.
What’s Next
- Learn next: Ferritic (400 Series) - chromium-only stainless
- Combine with: Alloy Addition Sequence - how to hit the composition