Last verified 19 August 2026.
The comparison
| Property | 410 | 420 | Evidence |
|---|---|---|---|
| Proof strength Rp0.2, typical | 340 MPa | 500 MPa | E3 E3 |
| Proof strength Rp0.2, typical (bar) | 500 MPa | 550 MPa | E3 E3 |
| Tensile strength Rm, typical | 580 MPa | 650 MPa | E3 E3 |
| Elongation A, typical | 30 % | 20 % | E3 E3 |
| Density | 7.7 g/cm³ | 7.7 g/cm³ | E3 E3 |
| Modulus of elasticity | 215 GPa | 215 GPa | E3 E3 |
| Thermal conductivity | 30 W/(m·K) | 30 W/(m·K) | E3 E3 |
All shared rows compare like for like.
Where each side’s numbers come from
See 410 and 420 — each page lists every source, every demotion and every gap. Nothing on this page is derived from anything not on those two, and our coverage limits are stated separately.
Where a PREN appears above, read it as a ranking number rather than a qualification: what PREN can and cannot tell you.
When to choose which
410. Parts that must be hard and are not asked to resist much. Valve components, pump shafts, fasteners, turbine blades, cutlery and wear surfaces. At 12% chromium it is the cheapest thing that can be called stainless and then hardened, and hardenability is the entire proposition — no austenitic can be heat treated to a useful hardness at all.
420. Cutting edges and wear surfaces. Knives, scissors, surgical instruments, moulds for plastics, valve seats and pump parts. Quenched and tempered it holds an edge and resists abrasion, and in mild environments it stays presentable, which is the combination cutlery needs and no austenitic offers.
Against 410: Corrosion and welding. Twelve percent chromium with no molybdenum is the minimum that counts as stainless, and it rusts in chlorides and in anything acidic; the hardened condition makes it worse, not better. It also hardens in the weld heat-affected zone and cracks unless preheated and post-weld tempered, so welded construction in it is specialist work.
Against 420: Anything wet, anything welded, anything that has to be tough. Higher carbon means lower effective chromium in solution once carbides form, so its corrosion resistance is below 410 and far below 304. Welding it reliably requires preheat and post-weld temper, and hardened martensite is notch sensitive.
What this comparison does not cover
- No heat treatment condition on any row, which for a hardenable steel means the numbers describe delivery, not service.
- No hardness values, which is what this grade is usually bought against.
- No specified minima. Everything here is a mill typical value and cannot be used as a design allowable.
- No corrosion data at all, and this is the least corrosion resistant family on the site.
- Welding, preheat and tempering practice.
- No hardness values, which is the property this grade is specified on.
- No corrosion data, and the higher carbon makes this worse than 410, not better.
- Impact toughness, which for hardened martensite is the property that surprises people.
Generated from data/materials/410.yaml and 420.yaml.