Tool steel grades
1 tool steel grades from 1 designation systems, each with a full data sheet. Sorted by system; the yield and tensile values are the first line of each grade's mechanical table.
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EN (European)
| Grade | No. | Type | C % | Yield MPa | Tensile MPa | Equivalents |
|---|---|---|---|---|---|---|
| 1.2379 | 1.2379 | Cold-work tool steel, 12 % Cr ledeburitic | 1.45 – 1.6 | — | ≈ 750–850 (typ.) | D2, SKD11, Cr12Mo1V1 |
Cold work, hot work, high speed
Tool steels are grouped by what the tool does, not by chemistry. Cold-work grades (D2, 1.2379, O1) are for shearing, blanking and forming below about 200 °C — maximum hardness and wear resistance, no requirement to hold that hardness when hot. Hot-work grades (H13, 1.2344) are for die casting, extrusion and forging, where the tool must resist thermal fatigue and keep its hardness at 500–600 °C. High-speed grades (M2, HSS) hold a cutting edge at red heat.
Picking across groups is expensive and usually wrong: a cold-work grade in a hot die softens and cracks within a short campaign.
Carbide type decides wear life
What makes a tool steel wear-resistant is not hardness alone but the hard carbides dispersed in the matrix. Chromium carbides are hard; vanadium carbides are much harder and finer. That is why a 1.2379 punch outlasts an O1 punch in an abrasive job even at the same measured HRC.
The price of that wear resistance is toughness. High-carbide grades chip rather than deform, so a die that sees shock loading often does better in a tougher, lower-carbide grade at lower hardness.
Heat treatment is the product
A tool steel bar is a semi-finished product; the heat treatment is what turns it into a tool. Austenitising temperature, quench medium and tempering cycle all move the final hardness and toughness by more than a grade change would.
That is why a tool steel order should state the supply condition — usually annealed for machining — and why the tool drawing, not the steel certificate, carries the target hardness.
faq.h
What is D2 tool steel equivalent to?
EN 1.2379 (X153CrMoV12) is the standard European equivalent, and JIS SKD11 is the Japanese one. All three are high-carbon, high-chromium cold-work grades with similar carbide structures.
What is the difference between cold-work and hot-work tool steel?
Cold-work grades maximise hardness and wear resistance for service below about 200 °C. Hot-work grades trade some hardness for resistance to thermal fatigue and for hot hardness at 500 to 600 °C, which is what die casting and extrusion demand.
How hard should a tool steel be?
It depends on the failure mode. Abrasive wear wants maximum hardness, 60 to 62 HRC on a cold-work grade. Shock and chipping want lower hardness and more toughness, often 56 to 58 HRC. The drawing should state it, not the steel order.
Can tool steel be welded?
Repair welding is possible with matching or tougher filler, preheat to the tempering temperature and immediate post-weld tempering. It is a repair technique, not a fabrication method, and the repaired zone is never as good as the parent.
What does annealed supply condition mean?
The steel has been softened to around 200 to 250 HB so it can be machined. The tool maker then hardens and tempers the finished shape. Ordering a tool steel already hardened is unusual and limits what can be done to it.