H13 tool steel is an air-hardening hot work tool steel and is one of the most widely used steels among all hot work tool steels. Similar to D2 tool steel as a benchmark for cold work tool steels, H13 is the benchmark for hot work tool steels. Compared to H11 tool steel, this steel grade has higher thermal strength and hardness. It can be air-hardened, so it performs well in terms of quenching deformation and residual stress, and has a lower likelihood of surface oxidation. Additionally, it can achieve secondary hardening, has excellent thermal stability, and can effectively resist corrosion from aluminum alloy molten metal.
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Manufacturers widely use this steel grade to produce hot extrusion dies and mandrels, drop hammer forging dies, and forging dies. It is also commonly used for inserts in precision forging machines and die-casting dies for aluminum, copper, and their alloys.
The designation in the U.S. ASTM A681 system is H13, and the name in the American AISI system is AISI H13 steel. Similarly, other national standards use comparable designations, such as ISO 40CrMoV5, Japan/JIS SKD61, USA/UNS T, Germany/DIN X40CrMoV5-1, Germany/W-Nr. 1., and Czech Republic (CSN) , BS (BH13), SS (), ANFOR (Z40CDV5), and UNI (X35CrMoV05KU / X40CrMoV511KU).
H13 mold steel is a hot-work tool steel widely used globally. It is characterized by high strength, high toughness, high hardenability, and resistance to thermal cracking. In particular, it can maintain its strength and hardness at high temperatures. Additionally, it has excellent comprehensive mechanical properties and high tempering stability.
The specific properties depend heavily on the tempering temperature. Here are typical longitudinal mechanical properties when air-cooled from °C ( °F) and tempered:
Key Mechanical Properties (Typical Values at Room Temperature, Double Tempered 2h + 2h)
The H13 steel heat treatment involves several critical steps to achieve the desired properties:
It is easy to forge and is typically forged at temperatures between and °C ( to °F). Before forging, we recommend preheating the steel to 790 to 815°C ( to °F), then uniformly heating it to the required forging temperature.
During forging, the material temperature must not drop below 925°C (°F). If it is about to fall below this temperature, it must be reheated to the required forging temperature.
This material is an air-hardening steel that must be cooled slowly to prevent stress cracking. After forging, the material must be placed in a furnace at 790°C (°F) and held until the temperature is uniform; then cooled slowly.
Following the previous step, the H13 material should undergo spheroidizing annealing, which aims to eliminate stress, enhance the toughness and ductility, and form the required microstructure.
The specific details of the annealing process are as follows: heat the steel to 871°C (°F), hold for 1 hour per inch (25.4 mm) of thickness, then cool at a rate of 14°C (25°F) per hour down to 482°C (900°F), followed by air cooling to room temperature.
Because of the risk of cracking, we generally do not recommend normalizing treatment for H13, especially when a controlled atmosphere furnace does not prevent surface decarburization. However, this normalizing treatment can still improve the uniformity of the material. This step must be performed immediately after spheroidizing annealing.
The specific steps are as follows: preheat to approximately 790 °C ( °F), slowly and uniformly heat to to °C ( to °F), hold for 1 hour per 25 mm (1 inch) of thickness, and then air cool.
The hardening temperature is around °C ( °F). Other sources suggest a range of - °C (- °F), or specifically °C ( °F).
H13 is an air-hardening steel, and we recommend performing a preheating treatment. The purpose is to stabilize the crystalline structure, reduce hardness, increase ductility, improve machinability, promote uniform grain structure, and minimize distortion/cracking. The preheating temperature is 815 °C ( °F). For a 1” (25mm) cube, it should be preheated to 650 °C ( °F) and held for 10 to 15 minutes before setting the furnace for the soaking step. For delicate parts, an additional preheat may be necessary.
After preheating, raise the furnace temperature to its austenitizing temperature of °C ( °F). The soaking process then begins, with the soaking time calculated from the moment the material’s temperature is the same as the furnace temperature. Specific details are as follows: For parts thicker than 1“ (25mm), the soak time is typically half an hour per inch of the smallest cross-section. For smaller parts, specific soak times are provided: 1/8” (3.175mm) for 10-15 minutes, 1/4” (6.350mm) for 15 minutes, 1/2“ (12.70mm) for 20 minutes, 3/4” (19.05mm) for 25-30 minutes, and 1” (25mm) for 30 minutes.
Air quenching can minimize residual stress and reduce thermal shock. While air quenching is the most common method for H13, oil quenching is also used in practice, but it increases internal stresses. The hardness after quenching is 52-54 HRC. During the quenching cycle of the material, the next step of tempering should be performed immediately at a temperature no lower than 66°C/150°F to prevent cracking.
The purpose is to reduce brittleness, transform martensite into a more stable microstructure, improve toughness, relieve stresses while retaining hardness.
We recommend tempering H13 twice or even three times to achieve optimal toughness and extend tool life. The first tempering temperature is 565°C (°F), the second tempering temperature is 550°C (°F), with each cycle lasting 2 hours per inch (25mm) of thickness.
After tempering, the hardness varies with the tempering temperature. For example, as-quenched H13 has a hardness of 52-54 HRC. Tempering at 204°C (400°F) results in 51-53 HRC, while tempering at 538°C (°F) yields 47-48 HRC, and at 621°C (°F), it can be 36-38 HRC. Typical tempering temperatures range from 540-620°C (-°F), producing a stable microstructure that makes the material most suitable for high-temperature applications.
It is essential to avoid tempering H13 at around 500°C (930°F), as this temperature yields the lowest toughness.
H13 steel is readily weldable, especially for repair applications in molds, tools, and dies. Gas Tungsten Arc Welding (GTAW or TIG) is the most suitable welding process for H13 molds, tools, and dies, and can also be performed using an inert gas process or coated electrodes. When welding, the minimum recommended arc voltage and current must be used, and the electrode must be moved slowly in a straight line to minimize heat input. Clean slag frequently and peen the welds while they are still hot (above 370°C or 700°F); never peen a cold weld.
H13 steel is used in high-temperature conditions, where it exhibits excellent resistance to softening, thermal fatigue, and impact. Compared to cold-worked steel, however, it has lower wear resistance. D2 steel, on the other hand, performs exceptionally well in cold-working applications, offering high wear resistance and excellent dimensional stability. Compared to H13, however, D2 has lower toughness and poorer performance in high-temperature conditions.
Here is a side-by-side comparison highlighting their key differences and similarities:
M2 tool steel is primarily used for high-speed cutting, boasting excellent wear resistance and thermal hardness.
The H13 tool steel we supply is available in three shapes: flat bar, block, and round bar. 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.
We also offer the ESR (Electroslag Remelting) process, which is tailored to meet customer requirements. The advantage is better internal microstructure, but it comes at a higher cost. Please contact us for specific requirements.
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 H13 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.
Many of our customers choose non-ESR processes when considering cost-effectiveness. Please discuss your specific requirements with us directly.
1. Can H13 steel be welded?
Yes, H13 tool steel can be welded, but it has limited weldability and requires specific procedures due to its air-hardening nature and susceptibility to cracking during and after welding. Preheating before welding, maintaining suitable interpass temperatures, and performing post-weld heat treatment (PWHT) are essential to minimize cracking and preserve its properties. Gas Tungsten Arc Welding (GTAW) is often recommended for its control.
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2. Is H13 high-speed steel?
H13 steel is not classified as a high-speed steel. It is identified as a hot-work tool steel.
3. What is the ultimate strength of H13?
The ultimate strength (also known as tensile strength) of H13 steel varies depending on the tempering temperature and manufacturing process. Typical room-temperature longitudinal mechanical properties of H13 steel, based on bars tempered to different hardness levels, are as follows:
4. Is H13 hard to machine?
Yes, H13 steel can be difficult to machine, especially when hardened. However, its machinability can be influenced by its condition and the specific machining operation.
5. What is the Rockwell hardness of H13 steel?
The recommended hardness range for H13 tool steel is generally 40-55 HRC. Specific applications and tempering temperatures can result in values ranging from 36 HRC (at a tempering temperature of 621°C) to 56 HRC (at a tempering temperature of 500°C). Forging tools in service typically range from 38-52 HRC.
6. What is the difference between H11 and H13 steel?
The primary difference between H11 and H13 steel lies in their vanadium content and the resulting impact on their properties. H13 may show slightly lower toughness than H11, especially during quench embrittlement.
7. What are the main characteristics of H13 tool steel?
Key characteristics include exceptional heat resistance, high toughness, high hot strength, high hot wear resistance, high retention of hardness, and strong resistance to thermal fatigue (heat checking)
8. Does H13 tool steel have good wear resistance?
Yes, H13 tool steel has excellent wear resistance. This property can be further improved by nitriding, which can increase surface hardness to over HV, equivalent to more than 70 HRC.
9. Is H13 tool steel resistant to thermal fatigue (heat checking)?
H13 tool steel has excellent resistance to thermal fatigue cracking.
10. What are the mechanical properties of H13 tool steel?
Typical mechanical properties at room temperature (when double tempered) include an Ultimate Tensile Strength ranging from to MPa (174,000-231,000 psi) and Yield Strength from to MPa (145,000-228,000 psi). Specific values are highly dependent on the tempering temperature. It also possesses good impact strength and ductility, with a Charpy V-notch impact strength of 16-27 J depending on tempering.
11. Does H13 tool steel rust or have corrosion resistance?
No, H13 tool steel is not highly corrosion-resistant compared to stainless steel or other specialized alloys. It is primarily chosen for its strength and heat resistance rather than its corrosion properties, and is prone to rust in aggressive environments, including those with moisture, humidity, or chemically aggressive plastics.
11. What factors can cause H13 tool steel dies to fail prematurely?
Common failure mechanisms include wear, mechanical fatigue, gross cracking, plastic deformation, and thermal fatigue cracking (heat checking). These can be exacerbated by factors such as too low billet temperature, inadequate die design (e.g., sharp radii, thin walls), improper heat or surface treatment, insufficient die support, or high cavity stress levels.
12. How is H13 tool steel heat-treated for optimal hardness and toughness?
The hardening process typically involves preheating to around 815°C (°F), then raising the temperature to an austenitizing range of -°C (-°F), followed by air quenching. Tempering is crucial and usually performed twice or three times, at temperatures typically between 540-620°C (-°F), with each cycle lasting approximately 2 hours per inch of thickness. Avoiding tempering around 500°C (930°F) is critical as it yields the lowest toughness.
13. What maintenance practices are recommended to optimize H13 tool hardness and lifespan?
We recommend performing regular inspections for signs of wear or fatigue, applying recoating or retempering when necessary, and avoiding overheating during operation, which can soften the material. Proper die preheating also significantly reduces the risk of catastrophic failure via cracking.
14. How does surface treatment benefit H13 tool steel?
Surface treatments are commonly applied to H13 tool steel to enhance wear resistance. Nitriding, for example, is a thermochemical treatment that creates a hard surface layer and can induce compressive residual stress, which helps counteract heat checking. However, the nitrided layer can be brittle, so careful control of thickness (e.g., typically no more than 0.3 mm) is necessary.
15. What are the international equivalent standards for H13 tool steel?
H13 tool steel has various international equivalents, including AISI H13 (USA), X40CrMoV5-1 (Europe/Germany DIN 1.), and SKD61 (Japan JIS).
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