1.2344 (H13) hot-work tool steel: properties, composition, equivalents
1.2344 (X40CrMoV5-1) is the 5 % Cr hot-work tool steel known as H13: working hardness 44–52 HRC, tempered above its service temperature. Composition, heat treatment, and H13/SKD61/4Cr5MoSiV1 equivalents.
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What is 1.2344?
1.2344 is the hot-work tool steel the whole industry calls H13. Its 5 % chromium, 1.3 % molybdenum and 1 % vanadium form fine alloy carbides that only precipitate when the steel is tempered above 500 °C — the secondary-hardening reaction that lets a tool keep 44–52 HRC while its surface cycles to 600 °C and back thousands of times. Nearly every aluminium die casting die, extrusion die and hot forging insert in the world is made of this steel or a remelted version of it.
The rule that governs its use has nothing to do with maximum hardness. The tempering temperature must be at least 30–50 °C above the working temperature of the tool. A die tempered at 520 °C and then run at 540 °C tempers itself in service: it softens, distorts and cracks, and no amount of extra hardness at delivery prevents it. That is why the standard cycle is two tempers at 550–620 °C and why delivery hardness for die casting sits around 44–48 HRC rather than the 54 HRC the steel can reach.
The second thing to understand is the failure mode. Hot-work dies rarely wear out; they heat-check — a network of thermal-fatigue cracks on the cavity surface from repeated expansion and contraction. Toughness, cleanliness and thermal conductivity therefore decide die life more than hardness does, which is why premium 1.2344 is electro-slag remelted and bought against NADCA #207 instead of against EN ISO 4957 alone. Two blocks can both be legitimate X40CrMoV5-1 and still differ by a factor of three in die life.
1.2344 and AISI H13 are the same steel; JIS SKD61 and GB 4Cr5MoSiV1 are too. Its close relative 1.2343 (H11) carries a third of the vanadium, trading wear resistance for toughness, and is the European preference for large die casting dies.
1.2344 chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | 0.37 – 0.43 | |
| Si | 0.9 – 1.2 | |
| Mn | 0.3 – 0.5 | |
| P | ≤ 0.03 | |
| S | ≤ 0.02 | |
| Cr | 4.8 – 5.5 | |
| Mo | 1.1 – 1.5 | |
| V | 0.9 – 1.1 |
EN ISO 4957:2018 Table 5 (X40CrMoV5-1). AISI H13 to ASTM A681 is wider: C 0.32–0.45, Si 0.80–1.20, Cr 4.75–5.50, Mo 1.10–1.75, V 0.80–1.20. The silicon content near 1 % is deliberate — it raises the tempering resistance and is what separates the hot-work 5 % Cr family from the cold-work 5 % Cr grade 1.2363.
1.2344 mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| +A soft annealed (delivery) | — | ≈ 760–850 (typ.) (≈ 110.2–123.3 (typ.)) | — | ≤ 229 HB |
| Hardened 1020–1050 °C, air/vacuum, as-quenched | — | — | — | 52–56 HRC |
| Tempered 2 × 550 °C | ≈ 1450 (≈ 210.3) | ≈ 1700 (≈ 246.6) | — | 50–52 HRC |
| Tempered 2 × 600 °C | ≈ 1250 (≈ 181.3) | ≈ 1500 (≈ 217.6) | — | 44–46 HRC |
| Tempered 2 × 650 °C | ≈ 1000 (≈ 145.0) | ≈ 1200 (≈ 174.0) | — | 38–40 HRC |
| At 46 HRC, tested at 500 °C | ≈ 1050 (≈ 152.3) | ≈ 1200 (≈ 174.0) | — | — |
EN ISO 4957 specifies chemistry and annealed hardness only; everything below the annealed row is typical for a 100 mm block and depends on the heat-treater. Room-temperature strength matters less than the hot yield and the thermal-fatigue resistance, which is why hot-work dies are specified by hardness band and by impact energy from the supplier's own test, not by a standard mechanical table.
1.2344 equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| H13 | AISI / SAE | Identical | AISI H13 (UNS T20813, ASTM A681): C 0.32–0.45, Cr 4.75–5.50, Mo 1.10–1.75, V 0.80–1.20. Same steel; the ASTM window is wider at both ends, so a certificate to A681 can sit outside the EN ISO 4957 limits while still being correctly labelled H13. |
| 4Cr5MoSiV1 | GB/T (China) | Identical | GB/T 1299 4Cr5MoSiV1 is the direct H13 transcription; 4Cr5MoSiV is the older lower-vanadium grade equivalent to H11. |
| SKD61 | JIS (Japan) | Identical | JIS G4404 SKD61: C 0.35–0.42, Si 0.80–1.20, Cr 4.80–5.50, Mo 1.00–1.50, V 0.80–1.15. For die casting work the two are interchangeable. |
| 1.2343 | EN (European) | Near | X37CrMoV5-1 (H11): the same steel with vanadium at 0.30–0.50 instead of 1.00. Lower wear and temper resistance, noticeably higher toughness — the European default for large aluminium die casting dies, where heat checking rather than erosion ends the tool. |
| 1.2363 | EN (European) | Near | X40CrMoV5-1 (H13): nearly the same alloy content with 0.40 % C and 1 % Si. The low carbon makes it a hot-work steel — it cannot reach 60 HRC, but it holds 45 HRC at 550 °C. |
| 4Kh5MFS | GOST (Russia/CIS) | Near | GOST 5950 4Kh5MFS: C 0.32–0.40, Cr 4.50–5.50, Mo 1.20–1.50, V 0.30–0.50 — vanadium is roughly half, so tempering resistance is lower. |
| 1.2367 | EN (European) | Functional | X38CrMoV5-3: molybdenum raised to 2.8–3.3 %. Better high-temperature strength and thermal-fatigue resistance for large dies and extrusion tooling; it is the usual upgrade when 1.2344 heat-checks too early. |
| 1.2365 | EN (European) | Functional | 32CrMoV12-28: 3 % Mo, 0.30 % C hot-work steel for hot extrusion mandrels and die holders where toughness outranks hardness. |
| 1.2714 | EN (European) | Functional | 55NiCrMoV7 (L6): the nickel hot-work forging-die steel. Tougher and used pre-hardened at 38–44 HRC, but it loses hardness above about 500 °C and is not a die casting steel. |
| 1.2738 | EN (European) | Functional | X40CrMoV5-1 (H13) at 48–52 HRC: the choice when the mould runs hot or abrasively filled polymers erode the cavity. Far more expensive, must be heat treated after machining, and an unnecessary step for ordinary thermoplastics. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for 1.2344 →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| X40CrMoV5-1 | DIN 17350 (withdrawn) | Same number and same short name; only the standard changed to EN ISO 4957. |
| BH13 | BS 4659 (withdrawn) | The British designation of the same steel. |
| Z40CDV5 | NF A 35-590 | The French designation. |
| W302 / Orvar Supreme | Böhler / Uddeholm trade names | Thyrotherm 2344, Cryodur 2344, Vidar Superior. Premium versions are remelted and sold against NADCA #207 rather than against EN ISO 4957 alone. |
Product forms and tolerance standards
Product forms: blocks and flat bar (annealed), round bar (annealed, rough-turned), plate, forgings and die blanks, ESR / remelted premium quality for die casting.
Dimensional tolerances: annealed blocks and flat: supplier tolerances, typically +2/+5 mm machining allowance per face; rough-turned round: DIN 7527-6 forging allowance; die casting dies: NADCA #207 dimensional and cleanliness requirements ordered in addition to EN ISO 4957.
Key property values
1.2344 hardness
Annealed ≤ 229 HB on delivery. As-quenched 52–56 HRC. Working hardness is set by the temper: 50–52 HRC at 550 °C, 44–46 HRC at 600 °C, 38–40 HRC at 650 °C. Typical specifications are 44–48 HRC for aluminium die casting, 46–50 HRC for extrusion dies, 48–52 HRC for plastic moulds and cold-running tooling.
Heat treatment
Soft anneal 750–800 °C, slow cool. Stress relieve at 650 °C after rough machining — on a deep cavity this step is the difference between a usable die and a distorted one. Preheat 650 and 850 °C, austenitise 1020–1050 °C (30 min at temperature per 25 mm), quench in air, vacuum gas or hot oil; interrupt at 50–70 °C, do not cool to room temperature before tempering. Temper twice, 2 h minimum each, at 550–650 °C; a third temper is normal practice on large dies. Ms ≈ 320 °C.
Tempering above the service temperature
The temper curve has a secondary-hardening peak near 520 °C and falls away above it. Tempering on the rising side of that peak looks attractive because the hardness number is higher, but the die then continues to temper in service. Set the temper 30–50 °C above the highest surface temperature the tool will see: 550 °C minimum for zinc, 580–620 °C for aluminium die casting and hot extrusion.
Heat checking and thermal fatigue
The dominant failure mode. Cracking is driven by the temperature swing at the surface, so preheating the die to 200–250 °C before the first shot and keeping the cooling steady matter more than hardness. Lower hardness (44–46 HRC) resists heat checking better; higher hardness (50 HRC) resists erosion and washout better. Remelted (ESR) material with low sulphur and isotropic toughness extends life several-fold on the same hardness.
Nitriding — where it helps and where it hurts
Gas or plasma nitriding at 480–520 °C gives 1000–1200 HV and resists aluminium erosion, but the brittle compound layer initiates heat-check cracks. Practice splits accordingly: nitride extrusion dies, mandrels and forging dies, where erosion dominates; do not nitride a die casting cavity surface unless the compound layer is suppressed and the depth kept below about 0.1 mm. PVD CrN or duplex coatings are the alternative for cores and pins.
Physical properties
Density 7.80 g/cm³, E = 210 GPa at 20 °C and 180 GPa at 500 °C. Thermal conductivity ≈ 25 W/m·K at 20 °C rising to 30 W/m·K at 500 °C — about 20 % better than the cold-work 12 % Cr grades, which is part of why it survives thermal cycling. Expansion 11.5 × 10⁻⁶/K (20–200 °C), 12.6 × 10⁻⁶/K (20–600 °C).
Weldability
Weldable for repair with care, and repair welding is routine on die casting dies. Preheat and hold at 350–450 °C, weld with a matching 1.2344-type filler (or a slightly softer H11-type filler on highly stressed cavities), keep the interpass temperature above 350 °C, cool slowly to 100 °C and temper immediately 20–30 °C below the original tempering temperature. Welding a hardened die without preheat cracks it. Laser and micro-TIG cladding are used for small cavity repairs because the heat-affected zone stays shallow.
Machining, forming and heat treatment
Annealed machinability ≈ 55–60 % relative to 1 % C free-cutting steel: easier than the 12 % Cr cold-work grades because there is no carbide network, but the 1 % silicon makes the chip gummy and promotes built-up edge, so use positive geometry and keep speeds up. Rough machine, stress relieve at 650 °C, then finish — this is the single most skipped step and the most common cause of a die that moves during hardening. Hard milling at 44–52 HRC is standard practice for cavities with coated carbide and light radial engagement. EDM leaves a re-hardened white layer that must be stoned or ground off and the die re-tempered, otherwise the layer cracks on the first thermal cycle. Polishing to Ra < 0.2 µm is achievable; remelted material polishes noticeably better.
Typical applications
- Aluminium, zinc and magnesium die casting dies, cores and inserts
- Hot extrusion dies, die holders, mandrels and liners
- Hot forging dies and trimming tools
- Plastic injection moulds for abrasive or corrosive compounds
- Shear blades for hot cutting, hot punches and piercing tools
- Die casting shot sleeves and plunger tips
- Hot-work rolls and guide tooling
Frequently asked questions
Is 1.2344 the same as H13?
Yes. 1.2344 (X40CrMoV5-1, EN ISO 4957) and AISI H13 (UNS T20813, ASTM A681) are the same steel. The ASTM composition window is wider — carbon 0.32–0.45 % against 0.37–0.43 %, molybdenum up to 1.75 % against 1.50 % — so material correctly certified as H13 can be outside the EN limits. If a drawing calls for X40CrMoV5-1, ask for the analysis, not just the trade name.
What hardness should a 1.2344 die casting die be?
Typically 44–48 HRC for aluminium, 46–50 HRC for zinc and small inserts. Lower hardness resists heat checking, higher hardness resists washout and erosion. The hardness is a consequence of the tempering temperature, which must sit 30–50 °C above the die surface temperature — that constraint comes first and the hardness follows.
What is the difference between 1.2343 and 1.2344?
Vanadium: 0.30–0.50 % in 1.2343 (H11) against 0.90–1.10 % in 1.2344 (H13). Less vanadium means fewer hard carbides, so 1.2343 is tougher and more resistant to heat checking, while 1.2344 holds its hardness better at temperature and resists erosion. European die makers favour 1.2343 for large aluminium dies, North American practice favours H13 almost everywhere.
Why does 1.2344 have to be tempered twice?
The first temper transforms the retained austenite left after quenching; the fresh martensite that forms as it cools is untempered and brittle. The second temper tempers it. On blocks over 150 mm a third temper is standard. Each temper is held for at least two hours at temperature, counted from when the core reaches it.
Can 1.2344 be nitrided?
Yes, at 480–520 °C, and it is standard practice for extrusion dies and forging tools where aluminium erosion or abrasion is the problem. It is deliberately avoided on die casting cavity surfaces, because the brittle compound layer starts thermal-fatigue cracks. If nitriding is used there, the compound layer is suppressed and depth held below about 0.1 mm.
Is 1.2344 a stainless steel?
No. The 5 % chromium raises tempering resistance and scaling resistance, not corrosion resistance; a passive layer needs around 11 %. Dies rust in humid storage and in water-cooled channels, which is why cooling lines are treated and dies are oiled when idle.
What does NADCA #207 add over EN ISO 4957?
EN ISO 4957 fixes the chemistry and the annealed hardness. NADCA #207 is a purchasing specification for premium die casting steel on top of that: microstructural cleanliness, maximum annealed hardness, segregation and banding limits, and a minimum impact energy measured on specified test pieces. Two blocks can both meet EN ISO 4957 and differ by a factor of three in die life; #207 is how that difference is bought.
Related grades
Verified against EN ISO 4957:2018; EN ISO 4957:2018 Table 5; ASTM A681-08 (H13 comparison); JIS G4404:2015 (SKD61 comparison). Last checked: October 2026.