H11 tool steel is an air-cooling hardening hot work tool steel. It has excellent toughness, thermal strength, fatigue performance, and wear resistance at medium temperatures. Additionally, it retains some toughness in the quenched state and demonstrates strong resistance to thermal fatigue. When air-quenched at lower austenitizing temperatures, it exhibits minimal heat treatment deformation and a low tendency to form oxide skin. H11 tool steel can effectively resist the corrosion of molten aluminum, making it a popular choice for manufacturing aluminum die casting molds, hot extrusion tools, stamping and forging molds, and plastic molds.
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The designation for this steel is H11 in the U.S. ASTM A681 system. Similarly, other national standards use comparable designations, such as ISO X37CrMoV5-1, Japan/JIS SKD6, USA/UNS T, Germany/DIN X38CrMoV5-1, Germany/W-Nr. 1., Czech Republic (CSN) , and China/GB 4Cr5MoSiV.
H11 tool steel equivalent grades and the compositions
Tool steel H11 possesses an exceptional combination of attainable hardness, red hardness (hot hardness), toughness, and wear resistance.
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Precise H11 tool steel heat treatment is crucial for achieving its optimal performance as a 5% chromium hot-work die steel and ultrahigh-strength steel, similar to H11 Modified and H13. This process tunes the microstructure for demanding factory tooling.
This steel is easily forged, with a suitable forging temperature range of to °C ( to °F). We recommend preheating the billet to 790 to 815°C ( to °F), then uniformly heating it to the forging temperature. The forging temperature must NOT be lower than 925°C (°F). If the temperature drops near this level, it must be reheated before continuing the forging process.
Austenitizing, the primary hardening step, involves heating to transform its structure into austenite. This allows uniform conversion and dissolution of alloying elements and carbides.
Holding at the austenitizing temperature ensures uniform transformation and dissolution.
After austenitizing, H11 steel is rapidly quenched to form hard martensite. H11 is an air-hardening steel, providing uniform hardening through large sections with minimal residual stress and dimensional change. Air cooling is the standard and preferred method for H11 tool steel. While air cooling is standard, oil quenching from 995 °C ( °F) is a possible alternative. H11 and other hot work tool steels must never be water quenched, as this can lead to cracking.
After hardening, tempering H11 tool steel by reheating to a lower temperature is crucial for improving toughness, relieving stress, and stabilizing properties. Steel H11 is a secondary hardening steel. It achieves its best performance when tempered at temperatures above 510°C (950°F). We recommend performing multiple tempering treatments on it to achieve optimal toughness and extend tool life. Allow parts to cool to room temperature between each tempering cycle to minimize residual austenite.
The annealing temperature is 845-900°C (-°F). The cooling rate is 22-40°C/h (40-75°F/h). The hardness after annealing is 192-229 HB.
The H11 tool steel we supply is available in various forms, including round bars, sheet plates, slabs, flat bars, square bars, and blocks. The dimensions of the flat bar range from: width 20–600 mm × thickness 20–400 mm × length 1,000–5,500 mm. The dimensions of the round bar range from a diameter of 20–400 mm × a length of 1,000–5,500 mm. The block dimensions are obtained by cutting the flat bar.
For smaller sizes, such as round bars with a diameter less than 70 mm, we use the hot-rolled process. For sizes greater than 70 mm, we offer forged products.
UT testing: Sep -84 D/d, E/e.
Surface Treatment: original black, peeled, machined/turned, polished, grounded, or milled surface finishes.
Inventory Status: We do not maintain a stock of H11 tool steel. We arrange production based on customer orders.
Delivery time: Electric Arc Furnace (EAF) materials are 30-45 days. ESR materials are approximately 60 days.
H11 steel is primarily an air-cooling type hot work mold steel, often referred to as DIN 1. or JIS SKD6. It is a chromium-based hot work tool steel highly valued for its exceptional toughness and ability to retain its properties even at elevated temperatures. It is used extensively in the manufacturing of molds.
What are the key characteristics and properties of H11 tool steel?H11 tool steel is noted for its excellent impact toughness, strong resistance to thermal fatigue (also known as heat checking), and high strength, maintaining these qualities at temperatures approaching 600°C. It also offers good wear resistance, hardenability, plasticity, corrosion resistance, high temperature stability, oxidation resistance, and weldability, making it relatively easy to process.
What are the international equivalent grades for H11 steel?H11 steel is recognized globally under various designations, including DIN 1. (Germany), JIS SKD6 (Japan), and BH11 (British Standard). In the USA, it aligns with standards like ASTM A681, FED QQ-T-570, SAE J437, SAE J438, SAE J467, and its Unified Numbering System (UNS) designation is T.
What is the main difference between H11 and H13 steel?H11 steel contains less vanadium than H13 steel. This results in H11 having higher toughness and superior resistance to thermal fatigue cracking (better handling of repeated heating and cooling cycles) compared to H13, though it might have slightly less wear and temper resistance.
Why might H11 steel be preferred over H13 steel for specific applications?H11 steel is often chosen when the application demands maximum resistance to cracking and thermal shock, particularly when water cooling is involved in service or under frequent heating and cooling cycles. Its superior toughness and generally easier machinability (due to lower hardness) also make it a favorable choice over H13 for certain projects.
What are the typical applications of H11 tool steel?H11 tool steel is frequently used in hot tooling applications that require high resistance to cracking. Key applications include die casting dies (especially for aluminum and magnesium alloys), forging dies, hot punches, hot shear blades, and extrusion tooling. It is also utilized in the aerospace industry for critical structural components, such as aircraft landing gear.
Is H11 steel suitable for plastic molds?Yes, H11 steel is widely used in the manufacturing of plastic molds, particularly for the insert parts of the mold.
What forms is H11 tool steel typically supplied in?H11 tool steel is commonly available as round bars, sheets, plates, and flat bars. It can also be supplied as slabs, billets, wire, shapes, steel coils, and pipes. Surface conditions vary, including original black, peeled, polished, machined, hot rolled, ground, turned, drawn, or cold rolled.
How is H11 tool steel typically heat-treated for hardening?For hardening, H11 tool steels are generally preheated to 816°C (°F) and then directly heated to °C (°F), where they are held at that temperature for 15 to 40 minutes. The hardening process is completed by air-quenching, which is effective due to H11’s very high hardenability. Some methods involve oil cooling after quenching from °C to °C, followed by air cooling.
What is the recommended tempering process for H11 steel?Tempering of H11 steel is performed at temperatures ranging from 538 to 649°C ( to °F) to achieve a Rockwell C hardness between 54 and 38. Double tempering is highly recommended, with each tempering step lasting one hour at the chosen temperature, followed by air cooling.
Can H11 steel be welded?Yes, H11 tool steels can be welded using conventional methods. However, special procedures are often necessary, including pre-heating and using filler materials that match the base material’s composition. It’s important to note that H11 is susceptible to hydrogen-induced cracking (HIC) due to its high alloy content and hardenability, so precise temperature control (e.g., 310-370°C for hardfacing) during welding is crucial.
Is H11 steel easy to machine?Yes, H11 steel exhibits good machinability. Its machinability rate is approximately 75% to 80% compared to 1% carbon steel and about 75% of “W” group tool steels. It is often considered easier to machine than H13 steel because of its lower hardness.
What is the forging temperature for H11 tool steel?H11 tool steels are typically forged at around °C (°F). Forging below 899°C (°F) is not recommended. The precise temperature can vary, generally falling within a range of to °C ( to °F), depending on desired deformation properties.
Can H11 steel be nitrided or PVD coated?Yes, H11 steel serves as an excellent substrate for PVD coating. For nitriding, a small diffusion zone is preferred, and the formation of compound and oxidized layers should be avoided. H11 is suitable for bath, gas, and plasma nitriding processes and can be nitrided at temperatures of 500-600°C to achieve a hard surface. Studies have also explored TiN coatings on H11 steel.
What is the typical hardness range for H11 steel after heat treatment?The hardness of H11 steel post-heat treatment varies with tempering. For general applications, a hardness of 50-54 HRC is common. When air-cooled from °C (°F) for 45 minutes, it can reach up to 57 HRC. Tempering within the range of 538-649°C (-°F) can result in a Rockwell C hardness from 54 down to 38.
Can H11 tool steel be produced using additive manufacturing (3D printing)?Yes, H11 tool steel (specifically DIN 1. / AISI H11) can be produced through additive manufacturing processes, such as Laser Powder Bed Fusion (LPBF). Research indicates that subsequent heat treatments after LPBF can be used to precisely tailor the microstructure and hardness of these additively manufactured steels.
What is the machinability of H11 tool steel?H11 is typically rated at 60-70% when compared to water-hardening tool steel W1 (which serves as a benchmark at 100% machinability for tool steels).
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Our ProductsTool steels are indispensable materials in manufacturing and are broadly categorized into two main types based on working temperature conditions: cold work tool steels and hot work tool steels. These two types of steel differ significantly in composition, properties, and applications, making proper understanding and selection crucial for mold longevity and product quality.
Cold work tool steel is used for forming materials at room temperature. During operation, the mold cavity surface temperature typically does not exceed 200–300°C. These steels are primarily used in cold processing techniques such as blanking, bending, drawing, and cold extrusion. Typical applications include automotive sheet metal stamping dies, fastener cold heading dies, and metal casing drawing dies for electronic products.
Hot work tool steel, on the other hand, is employed in high-temperature forming processes, where mold operating temperatures usually exceed 300°C and can reach up to 600–°C. These molds are mainly used for hot forging, die casting, and hot extrusion of metals. Common applications include automotive connecting rod forging dies, aluminum alloy die-casting molds, and copper alloy extrusion dies.
The fundamental difference in working environments leads to distinct performance requirements. Cold work tool steels emphasize hardness, wear resistance, and compressive strength, while hot work tool steels prioritize high-temperature strength, thermal fatigue resistance, and thermal stability.
Cold work tool steel composition characteristics:
High carbon content (0.5%–2.5%) to ensure high hardness and wear resistance
Main alloying elements: Cr (5%–12%), Mo, V (forming hard carbides)
Common grades: D2 (1.5% C, 12% Cr), SKD11, DC53
Sometimes W or Mn is added to improve hardenability and wear resistance
Hot work tool steel composition characteristics:
Medium-to-low carbon content (0.3%–0.6%) to balance strength and toughness
Main alloying elements: Cr (2%–5%), W, Mo, V (enhancing high-temperature strength)
Common grades: H13 (0.4% C, 5% Cr, 1.5% Mo), DIN 1.
Often contains Co or Ni to improve thermal stability and toughness
The key differences lie in carbon content and alloying element ratios. Cold work tool steels achieve wear resistance through high carbon and chromium content, forming hard carbides, while hot work tool steels rely on medium carbon combined with tungsten and molybdenum to provide secondary hardening effects and thermal stability at high temperatures.
Cold work tool steel heat treatment characteristics:
Quenching temperature: 950–°C (for high-carbon, high-chromium steels)
Tempering temperature: 150–550°C (low-temperature tempering to maintain high hardness)
Target hardness: 58–64 HRC
May undergo cryogenic treatment (-70 to -196°C) to transform retained austenite
Surface treatments: Often nitrided or coated with PVD to further improve wear resistance
Hot work tool steel heat treatment characteristics:
Quenching temperature: –°C (higher temperatures ensure alloy element dissolution)
Tempering temperature: 550–650°C (high-temperature tempering for secondary hardening)
Target hardness: 42–52 HRC (moderate hardness to retain toughness)
Multiple tempering cycles (usually 2–3 times) to stabilize microstructure
Surface treatments: May undergo aluminizing or TD treatment to enhance oxidation resistance
The core difference in heat treatment lies in tempering temperature selection. Cold work tool steels use low-temperature tempering to retain martensitic hardness, while hot work tool steels employ high-temperature tempering to induce secondary hardening phases while relieving stress to improve toughness.
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Key properties of cold work tool steels:
High hardness (≥58 HRC) to resist workpiece material wear
Excellent wear resistance to withstand repeated friction without dimensional failure
High compressive strength to endure forming pressures without deformation
Sufficient toughness to prevent brittle cracking
Microstructure: Tempered martensite matrix + uniformly distributed alloy carbides
Key properties of hot work tool steels:
High-temperature strength (maintaining hardness at 500–600°C)
Superior thermal fatigue resistance to resist crack formation from cyclic heating/cooling
Good thermal conductivity to dissipate heat buildup quickly
Oxidation resistance to withstand high-temperature corrosion and molten metal erosion
Microstructure: Tempered martensite/bainite + finely dispersed alloy carbides
The performance comparison highlights that cold work tool steels focus more on "static" mechanical properties, while hot work tool steels emphasize "dynamic" thermomechanical performance. Hot work tool steels must maintain stability under cyclic thermal-mechanical conditions, posing greater challenges in material design.
Cold work tool steel applications:
Blanking dies: Precision stamping dies for electronic component lead frames (e.g., SKD11)
Cold extrusion dies: Bearing ring cold extrusion dies (e.g., DC53)
Drawing dies: Deep-drawing dies for stainless steel cutlery (e.g., powder metallurgy high-speed steels)
Cold heading dies: High-strength bolt forming dies (e.g., high-toughness steels like SLD-MAGIC)
Coining dies: Coin stamping dies (requiring extreme wear resistance)
Hot work tool steel applications:
Die-casting molds: Aluminum alloy engine block die-casting dies (e.g., modified H13 grades)
Hot forging dies: Crankshaft and connecting rod forging dies (e.g., Ni-Cr-Mo steels like DIN 1.)
Hot extrusion dies: Copper tube extrusion dies (e.g., W-Mo-based hot work steels)
Hot blanking dies: High-temperature alloy sheet punching dies
Plastic injection molds: High-temperature engineering plastic injection molds (modified hot work steels)
Material selection depends on accurately assessing actual working conditions. For instance, warm forming processes (300–500°C) may fall in a gray area, requiring either modified cold work steels or hot work steels based on pressure, speed, and cooling conditions.
Cold work tool failure modes:
Abrasive wear: Surface wear from hard particles in workpiece material
Adhesive wear: Material transfer leading to surface damage
Fatigue cracking: Crack propagation under cyclic stress
Chipping: Localized fracture due to impact loads
Plastic deformation: Dimensional changes under extreme pressure
Hot work tool failure modes:
Thermal fatigue cracking: Network cracks from cyclic thermal stress
Erosion: Surface degradation from molten metal flow
Thermal softening: Hardness loss due to prolonged high temperatures
Stress cracking: Macroscopic cracks from thermomechanical loading
Oxidation/corrosion: Surface deterioration from high-temperature exposure
Common strategies to extend mold life:
Optimizing mold design to reduce stress concentrations
Selecting appropriate steel and applying proper heat treatment
Standardizing usage and maintenance (especially preheating and cooling for hot molds)
Applying surface treatments when necessary
For cold work molds, improving surface finish reduces friction wear
For hot work molds, controlling temperature fluctuations delays thermal fatigue
When selecting tool steel, engineers should evaluate:
Working temperature: Whether it exceeds 300°C (the basic dividing line)
Load conditions: Impact loads require higher toughness; static high pressure demands higher hardness
Production volume: High-volume production requires better wear/thermal fatigue resistance
Workpiece material: Hardness, strength, and chemical reactivity influence selection
Cost factors: Includes initial material cost and total lifecycle cost
Machinability: Some high-alloy steels are difficult to machine and heat-treat
Special cases may require intermediate options:
Warm work tool steels (200–400°C): Modified cold work steels
High-speed steels: For extreme wear resistance in cold or hot applications
Powder metallurgy steels: Addressing carbide inhomogeneity in conventional steels
With advancing material technology, the boundary between cold and hot work tool steels is blurring, leading to multipurpose tool steels that perform well in both regimes, offering more flexibility for complex applications.
Key advancements in tool steel technology include:
Clean steel technology: Reducing impurities to improve isotropy
Microstructure control: Precise heat treatment for optimal properties
Surface engineering: Developing wear-resistant, anti-adhesion coatings
Additive manufacturing: 3D-printed molds with graded functionality
Smart heat treatment: AI-optimized, simulation-based processes
Eco-friendly steels: Reducing rare element usage and improving recyclability
Both cold and hot work tool steels are moving toward "tailored solutions"—optimizing material design for specific applications rather than simply maximizing individual properties. Additionally, digital technologies will play an increasingly important role in material selection, application, and lifespan prediction.
Cold work and hot work tool steels, as two major categories of mold materials, each possess unique properties and applications. Understanding their fundamental differences and mastering material selection principles are essential for mold designers and users. In practical engineering, beyond material properties, factors such as cost, machinability, and maintenance must be considered to make optimal technical and economic decisions. With the continuous emergence of new materials and processes, the performance boundaries of tool steels are constantly expanding, providing a solid foundation for high-quality manufacturing development.
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