H13 Tool Steel: Composition, Properties, Heat Treatment & Uses
H13 is a chromium–molybdenum–vanadium hot-work tool steel used for die-casting dies, forging tools and extrusion tooling. Its value is the balance of hot strength, toughness and resistance to repeated heating and cooling. To select it well, specify the steel quality and heat-treated condition—not just the grade name or a high hardness number.
What makes H13 a hot-work steel?
A hot-work die must resist more than abrasion. Its surface heats when it contacts hot metal and cools between cycles, while the tool carries pressure or impact. Repeated expansion and contraction can form a network of fine cracks called heat checking. Softening, wear and larger fractures are different failure modes and may require different responses.
H13 is used where these demands overlap. Hudson’s H13 data identifies die cavities, cores, shot sleeves, forging dies, extrusion dies and demanding plastic-mould components as applications. “Hot-work” describes the tool’s duty, not a claim that the material can operate indefinitely at any temperature.
H13 is also described as air-hardening: it has enough hardenability to form a hardened structure with suitable cooling. That does not mean every large die can simply be left in still air. The controlling section, quench arrangement and required properties determine the cooling route.
H13 is not stainless steel. Its roughly 5% chromium content belongs to a hot-work alloy design. Plan corrosion protection for storage and service instead of treating it as a corrosion-resistant mould grade.
H13 composition: read typical chemistry separately from specification limits
Carbon supports hardening; chromium contributes hardenability; molybdenum helps resist softening; and vanadium contributes carbide formation and grain control. Their balance and the resulting microstructure matter more than maximizing any one element.
The two commercial examples below show why a typical analysis is not a universal acceptance range. Values are mass percent, with iron making up most of the balance.
Swipe horizontally to compare both products.
| Element | Uddeholm Orvar Supreme Typical analysis, wt.% | BÖHLER W302 ISOBLOC Average analysis, wt.% |
|---|---|---|
| Carbon (C) | 0.39 | 0.39 |
| Silicon (Si) | 1.00 | 0.90 |
| Manganese (Mn) | 0.40 | 0.40 |
| Chromium (Cr) | 5.20 | 5.20 |
| Molybdenum (Mo) | 1.40 | 1.40 |
| Vanadium (V) | 0.90 | 0.95 |
Sources: Orvar Supreme product data and W302 ISOBLOC product data. These are product examples, not ASTM chemistry limits or a ranking.
For purchasing, use the permitted ranges and residual-element limits in the agreed specification, then check the actual heat analysis on the mill certificate. ASTM A681-24 covers wrought alloy tool-steel products, including requirements beyond chemistry. A matching average analysis alone does not establish cleanliness, microstructure or through-section performance. Additively manufactured H13 also needs its own process and property qualification.
H13 properties depend on temperature and condition
Separate delivery hardness, working hardness and test temperature. A soft bar supplied for machining and a finished hardened die are the same grade in different conditions.
Working hardness follows the application
As product-specific examples, Orvar Supreme guidance lists 42–48 HRC for aluminium/magnesium die-casting dies, 44–50 HRC for aluminium/magnesium extrusion dies and 50–52 HRC for steel-forging tools. These are selection ranges, not a universal H13 target.
Swipe horizontally to see all test temperatures.
| Property | 20°C | 400°C | 600°C |
|---|---|---|---|
| Density, kg/m³ | 7,800 | 7,700 | 7,600 |
| Elastic modulus, GPa | 210 | 180 | 140 |
| Thermal conductivity, W/(m·K) | 25 | 29 | 30 |
Source: Orvar Supreme brochure, pp. 3–4. Physical-data specimens: centre of a 407 × 127 mm bar, hardened at 1025°C for 30 minutes, air quenched and tempered 2 + 2 hours at 610°C; 45 ± 1 HRC. Values are supplier data, not Oceanplayer Laser measurements.
How to use the table: the rising conductivity does not mean the tool becomes stronger as it heats. Stiffness falls, and resistance to deformation must be assessed separately. Do not combine room-temperature strength with a hot-service load case.
For incoming stock, request the specified delivery condition. For example, W302 ISOBLOC lists an annealed maximum of 229 HB. That delivery limit is a different kind of requirement from a finished die’s HRC range. A hardness conversion cannot turn one condition into the other.
Heat treatment must control the whole section
Heat treatment turns machinable stock into a tool with the required balance of hardness and toughness. A furnace setpoint alone does not describe the result: the tool must heat through, cool appropriately and receive the specified tempering treatment.
- Prepare
Rough machine with finishing allowance. Plan stress relief where machining or geometry makes distortion a concern.
- Preheat
Equalize the tool before high-temperature hardening to reduce temperature differences within it.
- Austenitize
Use the selected product’s temperature and hold after the tool has heated through.
- Quench
Control cooling through the governing section, balancing transformation needs against distortion and cracking.
- Temper
Use the specified repeated cycles, cooling between them, to reach a stable working condition.
A published cycle is a starting reference
BÖHLER’s W302 ISOBLOC sheet gives 1020–1030°C for die-casting equipment, with a 15–30 minute hold after temperature equalization. It recommends at least two tempers and notes that a third may help relieve stress. These details belong to that product; they do not establish a complete cycle for an unknown block. See the W302 heat-treatment section.
The heat treater should agree on the target hardness, controlling section, temperature measurement, quench capability and final inspection before loading the furnace. Keep the heat number linked to those records.
Why a small coupon can mislead
A thin coupon can cool more quickly than the centre of a large die. A passing coupon therefore does not, by itself, prove the tool has the same structure throughout. Agree on representative test locations and a hardness map where needed. The cooling guidance in Hudson’s H13 instructions also changes with section thickness.
For a hypothetical replacement insert that cracked at a sharp corner, ordering a harder version without reviewing the corner, machining damage and quench history leaves the cause unresolved. Start with the fracture location and process records; then decide whether hardness, design or steel quality needs to change.
Match H13 to the tool’s actual damage
H13 is a useful baseline for hot-work tooling, but the application label does not identify the limiting problem. Inspect where damage begins and distinguish gradual surface damage from a large fracture.
Heat checking or a broken corner?
A fine crack network calls for a review of thermal cycling, cooling and surface condition. A large fracture calls for closer attention to local stress, support, geometry and toughness. Raising hardness is not an automatic solution to either problem.
Wear or loss of shape?
Grooves and material loss differ from a detail that has rounded or indented under load. Record temperature and support conditions as well as surface hardness. Soldering or material transfer also calls for review of lubrication, finish and the casting process.
Photograph the damage before repair and record when it appeared. A comparison trial is more informative when steel quality, heat treatment, geometry and operating conditions are traceable.
Grade equivalents and premium quality are separate questions
BÖHLER cross-references W302 ISOBLOC to H13, UNS T20813, 1.2344 / X40CrMoV5-1 and JIS SKD61. These names help locate the grade family. Substitution still requires agreement on the governing standard, actual chemistry, product form, delivery condition and test requirements.
What ESR adds—and what still needs checking
Electroslag remelting, or ESR, is a secondary steelmaking step. It can improve material homogeneity and carbide refinement. A premium quotation should identify the actual melt route and acceptance criteria; the word “premium” is not enough. Ask for the required cleanliness and toughness test method, specimen orientation and inspection coverage.
NADCA’s die-steel guidance addresses procurement and heat-treatment acceptance for high-volume or critical-performance die casting. If it governs your tool, put the agreed document revision and material classification on the order. Do not infer compliance from “ESR H13” alone.
When should H11 enter the comparison?
An H11-type product is worth discussing when toughness is a central concern. For example, BÖHLER W300 ISOBLOC is an ESR H11/1.2343 steel positioned for hot toughness and thermal-fatigue resistance. It is a different grade from H13. Compare product-level data at matching hardness and test conditions rather than assuming that every H11 is tougher than every H13.
If the limiting problem is hot deformation, request hot-strength and temper-resistance data for the proposed alternative. If the tool never experiences hot-work duty, reassess whether a hot-work grade is needed at all. The best comparison starts with the job the material must do.
Nitriding changes the surface, not the core specification
Nitriding diffuses nitrogen into a steel surface to form a harder case. It can improve wear resistance while retaining a different core condition. A surface microhardness result and a bulk HRC reading answer different questions.
For H13 hot-work tools, agree on case depth, compound-layer condition, masking and compatibility with the previous temper. An excessively brittle case may crack or spall under shock; greater depth is not automatically better. Orvar Supreme’s nitriding guidance discusses these limits.
PVD adds a deposited coating. In a duplex system, nitriding and PVD are combined, as in Uddeholm’s published coating examples. Ask the treatment provider to review substrate hardness, finish, process temperature and adhesion together. A coating cannot restore a cracked or inadequately supported tool.
Machining and weld repair can change the finished tool
Remove damage from EDM and finishing
Electrical discharge machining (EDM) locally melts material. It can leave a resolidified surface layer, altered hardness and small cracks. A good-looking cavity is not proof that these effects have been removed. Uddeholm’s EDM guide explains fine finishing, removal of the affected layer and appropriate re-tempering. Plan the finishing allowance and post-EDM treatment before machining a hardened tool.
Qualify the repair for the known steel condition
H13 can be weld repaired, including with suitable laser processes, but the filler and thermal procedure must fit the steel and its intended use. Record the existing hardness, previous temper, coating or nitride case, crack depth and repair history. The heat-affected zone can contain hard or softened regions even when the deposited bead looks sound.
Orvar Supreme welding recommendations identify consumables, temperature control, cooling and post-treatment, with different treatment routes for annealed and hardened material. A generic “H13 repair temperature” omits these conditions. Do not assume that using a laser eliminates the need to assess them.
For a repair trial, define crack inspection, hardness checks, dimensional acceptance and any surface-finish requirements before welding. Keep the trial result separate from a claim about production tool life. The Oceanplayer Laser welding guide explains the wider process considerations.
Specify a usable tool condition, not just “H13”
A useful request for quotation connects the material order to the tool’s duty. Include:
- Material identity: exact grade, standard revision, supplier product if required, heat traceability and melt route.
- Stock and delivery: product form, dimensions, machining allowance, orientation and annealed or pretreated condition.
- Performance and inspection: target working hardness, critical section, agreed toughness/cleanliness criteria and any ultrasonic inspection requirements.
- Process history and next steps: heat-treatment records, finishing, nitriding or coating plans, repair requirements and acceptance checks.
Give the supplier the material being formed, joint or cavity geometry, cycle conditions and previous damage. Compare prices on the same specification, usable size and inspection scope; a lower price per kilogram may cover a different delivery condition or testing package.
Considering laser repair of H13 tooling?
Share the exact steel, hardness, repair area and required result with Oceanplayer Laser to discuss whether a process trial is appropriate.
Include a drawing or photographs, crack or wear dimensions, previous heat treatment and any coating history.
Discuss your tooling application