EN ISO 4957 — Tool steels
Last updated
Scope
Non-alloy and alloy cold-work, hot-work and high-speed tool steels supplied as bar, rod, wire, forgings, plate and strip: C45U–C120U, 1.2842 (90MnCrV8), 1.2379 (X153CrMoV12), 1.2363 (X100CrMoV5), 1.2344 (X40CrMoV5-1), 1.2343, 1.2767, HS6-5-2 and others. Specifies chemistry, annealed hardness, hardening temperatures and hardness after hardening as reference values.
Grades covered by EN ISO 4957
| Grade | No. | Type | C % | Yield MPa | Tensile MPa | Nearest equivalents |
|---|---|---|---|---|---|---|
| 1.2379 | 1.2379 | Cold-work tool steel, 12 % Cr ledeburitic | 1.45 – 1.6 | — | ≈ 750–850 (typ.) | D2, SKD11, Cr12Mo1V1 |
Revision history and superseded standards
| Year | Change |
|---|---|
| 1999 | EN ISO 4957:1999 — replaced DIN 17350 and national tool-steel standards |
| 2018 | EN ISO 4957:2018 — current; grade list and reference heat-treatment data updated |
Supersedes: DIN 17350:1980; EN ISO 4957:1999.
Where to buy the standard
The full text is copyrighted by ISO / CEN and is not reproduced here. Purchase the current edition from ISO / CEN or your national standards body. The values on this site are the normative limits as published; the standard's own tables, notes and test methods govern.
Related standards
Tool steels are grouped by what they have to survive
ISO 4957 organises tool steels by duty rather than by alloy family. Cold-work grades — 1.2379, 1.2510, 1.2842 — are hard and wear-resistant at room temperature, for blanking, forming and cutting tools. Hot-work grades — 1.2344, 1.2343 — hold their hardness at 500–600 °C and resist thermal fatigue, for die casting and forging dies. Plastic mould grades — 1.2311, 1.2738 — are supplied pre-hardened so that a large cavity can be machined and put to work without a further treatment cycle.
Choosing across those groups on hardness alone is the classic error: a cold-work grade in a hot die softens, and a hot-work grade in a blanking tool wears.
Why the heat treatment is the whole product
A tool steel bar as delivered is soft — annealed, typically 200–250 HB — and carries none of the properties it was bought for. Everything that matters happens afterwards: austenitising at a grade-specific temperature, quenching in the specified medium, and tempering two or three times, because retained austenite transforms on cooling and the fresh martensite needs its own tempering cycle.
That is why a tool steel order names the grade and the heat treatment specification together, and why dimensional change during treatment — different for every grade — belongs on the drawing before the tool is machined.