Data completeness: partial. Last verified 19 August 2026.
Designations
| Common name | 420 |
| UNS | S42000 |
| EN number | 1.4021 |
| Class | Martensitic stainless steel |
| Specified by | EN 10088-2 |
420 is 410 with more carbon — around 0.2% against 0.12% — and carbon is what a martensitic steel hardens on, so the whole difference between the two grades is how hard they can be made and how much corrosion resistance is given up to get there. Every figure below is an Outokumpu typical value rather than a specified minimum, and none of the rows names a heat treatment condition.
Properties, with what each one rests on
| Property | Value | Unit | Condition | Evidence | Source | Retrieved |
|---|---|---|---|---|---|---|
| Proof strength Rp0.2, typical | 500 | MPa | wire rod; heat treatment condition not stated by the source | E3 | Outokumpu Dura range datasheet — martensitic and precipitation hardening stainless steels | 2026-08-20 |
| Proof strength Rp0.2, typical (bar) | 550 | MPa | bar; heat treatment condition not stated by the source | E3 | Outokumpu Dura range datasheet — martensitic and precipitation hardening stainless steels | 2026-08-20 |
| Tensile strength Rm, typical | 650 | MPa | wire rod; heat treatment condition not stated by the source | E3 | Outokumpu Dura range datasheet — martensitic and precipitation hardening stainless steels | 2026-08-20 |
| Elongation A, typical | 20 | % | wire rod; heat treatment condition not stated by the source | E3 | Outokumpu Dura range datasheet — martensitic and precipitation hardening stainless steels | 2026-08-20 |
| Density | 7.7 | g/cm³ | 20 °C | E3 | Outokumpu Dura range datasheet — martensitic and precipitation hardening stainless steels | 2026-08-20 |
| Modulus of elasticity | 215 | GPa | 20 °C | E3 | Outokumpu Dura range datasheet — martensitic and precipitation hardening stainless steels | 2026-08-20 |
| Thermal conductivity | 30 | W/(m·K) | 20 °C | E3 | Outokumpu Dura range datasheet — martensitic and precipitation hardening stainless steels | 2026-08-20 |
| Heat treatment condition for every mechanical row | not established | — | — | — | the datasheet prints product form but no condition, and for a hardenable steel the condition is the property | — |
| Hardness | not established | — | — | — | the hardness column is empty for every grade in the datasheet consulted; for a cutlery and wear grade this is the specification | — |
| Specified minima | not established | — | — | — | the datasheet states its figures are typical values; no standard was opened for this grade | — |
| PREN | not established | — | — | — | the Dura datasheet prints no PRE column, and importing the formula from a different datasheet would import a method this document does not apply | — |
7 sourced values, 4 gaps named. Publishing the gaps is more useful than filling them from an aggregator that does not say where its numbers came from. The routes to filling them are the standard itself, a mill datasheet, or a mill certificate for your actual heat — which supersedes both at E5.
Where the numbers come from
Proof strength Rp0.2, typical. 47% above the 410 wire rod row in the same table, from 0.08% more carbon. The cold rolled row for this grade, which the datasheet marks as annealed, is 350 MPa — so within one grade and one document the figure runs from 350 to 550 MPa depending on form and condition.
Elongation A, typical. Two thirds of the 410 figure on the same product form, and 8% on the bar row. Carbon buys strength and spends ductility, and the datasheet shows both halves of that trade.
Why we do not just copy an aggregator. Because then this page would be a worse copy of MatWeb with no way for you to tell which rows to trust, and the one thing we have that MatWeb does not is the evidence column. Our coverage and its limits.
What 420 is usually chosen for
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.
And what it is usually rejected for
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.
The number to be more careful with than any of the above is the difference between a specified minimum and a typical value — a floor the standard guarantees, versus what a supplier’s production usually does. The full version, and the most expensive routine mistake in material data.
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What this page 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 the property this grade is specified on.
- No specified minima. Everything here is a mill typical value and cannot be used as a design allowable.
- 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/420.yaml. Regenerate rather than editing this file by hand — edits here are lost on the next build.