Aluminum die casting dies
The dominant H13 application. Aluminum die casting at 700 °C. Service life 100,000+ shots with proper conditioning.
Hot-work tool steel · UNS T20813
H13 Tool Steel
The hot-work tool steel standard. Holds 44 HRC hardness at sustained 540 °C service while resisting thermal fatigue, erosion, and gas pressure from molten aluminum and zinc. The aluminum die casting industry runs almost entirely on H13.
Hardness
44-50 HRC
Service T
540 °C
Modulus
207 GPa
Mach. (ann.)
75 /100
When to use
Pick H13 when tooling runs hot.
H13 is engineered for elevated temperature service. Its 5% chromium and 1.3% molybdenum content forms stable carbides that resist softening at temperature, while a tempered martensite matrix tolerates thermal cycling without cracking. Aluminum die casting dies, hot forging dies, plastic injection molds for high-temp resins, extrusion tooling — H13 dominates these.
For room-temp service, H13 is “just” another tool steel — A2 (better wear), D2 (much better wear), or S7 (better impact) typically beat it. The advantage shows up only above 200 °C, and grows dramatically above 500 °C. Don’t spec H13 for cold-work tooling — it’s wasted money.
Strengths
Why hot-work loves it.
- Holds hardness at temperatureMaintains 44 HRC at 540 °C continuous service. Will eventually soften but slowly — service life on molten Al die casting dies measured in 100,000+ shots.
- Thermal fatigue resistanceTempered martensite + carbide structure cycles between hot and cool without surface cracking (heat checking).
- Excellent toughness for tool steelCharpy ~20 J at 44 HRC. Best toughness/strength balance of common tool steels.
- Air hardeningSame as A2 — minimal HT distortion. Through-hardens up to ~150 mm sections in air.
- Weldable for repairRepair welding with preheat (~340 °C) and matched filler is standard practice for die casting tooling.
- PolishableTakes mirror finish for plastic injection molds. Vacuum-melted (VAR or ESR) grades for premium polishing.
Trade-offs
Where it's wrong.
- Lower max hardness than A2/D2Tops out around 52 HRC vs 60+ HRC for cold-work tool steels. For room-temp wear, the cold-work grades win.
- Lower wear than D25% Cr vs D2's 12% — much less hard carbide content. Wear life on cold tooling is markedly worse than D2.
- Surface heat checkingLong service life eventually fails by thermal-fatigue cracks on the working surface. Routine maintenance / refurbishment required.
- Cost premium over A2~30% more expensive by weight. Worth it for hot-work; wasted money for cold-work.
- Limited cold compressive strength~1500 MPa — half of D2. Don't substitute H13 for blanking dies.
- Tough, gummy grinding behaviorMore tough than wear-resistant. Wheels glaze without aggressive dressing.
Specs
Mechanical, physical & chemical data.
Properties for H13 in standard hardened condition (austenitize 1010-1050 °C, air-cool, double-temper at 540 °C × 2 hr each) — yielding 44 HRC.
Mechanical
Properties (HT 44 HRC)
| Hardness (annealed) | ≤ 235 HB / B98 |
|---|---|
| Hardness (HT typical) | 44 HRC |
| Hardness (HT max) | ~53 HRC (max, as double-tempered) |
| UTS (HT) | 1700 MPa (245 ksi) |
| Yield strength (HT) | 1450 MPa (210 ksi) |
| Modulus of elasticity | 207 GPa |
| Charpy V-notch (HT) | 20 J |
| Compressive yield (HT) | 1450 MPa |
| UTS at 540 °C | 1100 MPa |
Source: Crucible Industries datasheets. ESR/VAR-melted grades retain properties slightly better at sustained temperature.
Physical & thermal
At room temperature
| Density | 7.80 g/cc (0.282 lb/in³) |
|---|---|
| Specific heat | 0.460 J/g·°C |
| Thermal conductivity | 29 W/m·K |
| CTE (20–100 °C) | 10.4 µm/m·°C |
| Austenitize temp | 1010 – 1050 °C |
| Critical temp (Ac1) | 860 °C |
| Quench medium | Air or oil |
| Magnetic | Ferromagnetic |
Higher thermal conductivity than D2 — better at moving heat away from die surface during shot-cycle. Important for die casting longevity.
Composition
Chemistry, weight %
| Carbon (C) | 0.32 – 0.45 |
|---|---|
| Chromium (Cr) | 4.75 – 5.50 |
| Molybdenum (Mo) | 1.10 – 1.75 |
| Vanadium (V) | 0.80 – 1.20 |
| Manganese (Mn) | 0.20 – 0.50 |
| Silicon (Si) | 0.80 – 1.20 |
| Phosphorus (P) | 0.030 max |
| Sulfur (S) | 0.030 max |
| Iron (Fe) | balance |
Compare to A2 — H13 has lower C (0.4 vs 1.0%) for toughness, more Mo and V for high-temp stability.
Specifications
Common purchase specs.
AMS 6408
Bar/forging — H13, annealed
NADCA 207
Specifications for die casting tool steel
ASTM A681
Tool steels — alloy
AISI H13 / SAE H13
Standard designation
UNS T20813
Unified numbering
DIN X40CrMoV5-1 / 1.2344
European equivalent
JIS SKD61
Japanese equivalent
ESR / VAR grades
Premium remelt for highest service life
Machining
How we cut it.
H13 in annealed condition machines well — better than D2, similar to 4140 prehardened. Tempered to ~44 HRC, it’s harder than 4140 prehardened but still machinable. Most die work is rough machined annealed, hardened, and EDM/grind to final.
Cutting speed (annealed)
150-250 SFM with carbide. Better than D2 due to lower carbide content.
Feed rate
Aggressive constant feed. Annealed H13 cuts smoothly.
Tooling
Coated carbide standard. CBN inserts for hardened condition above ~50 HRC.
Coolant
Flood. Through-spindle helpful for deep features.
Stock allowance for HT
0.005-0.020″ on critical surfaces. Distortion smaller than D2 due to lower carbide content.
Wire EDM after HT
Standard for sharp internal corners and complex profiles in hardened H13.
Stress-relieve before HT
Recommended at ~675 °C for 1 hour. Reduces final distortion.
Polish for plastic molds
Sharp tools + light DOC + climb mill produces excellent surface as foundation for hand polishing.
Applications
Where H13 shows up.
Hot forging dies
Forging dies for steel and aluminum. Resists thermal fatigue and impact loading from forging press strokes.
Plastic injection molds (high-temp)
PEEK, Ultem, glass-filled plastics, automotive grades. Mirror-polished H13 mold cavities for technical parts.
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