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Steel 39NiCrMo3

Steel Alloy EN39 (AISI 9840), a high-performance material offering exceptional strength, toughness, and wear resistance. Ideal for challenging applications.

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Steel 39NICRMO3 CNC machining


  • High strength and toughness
  • Excellent wear resistance and fatigue strength
  • High-stress mechanical applications
  • Widely used in the construction and automotive industries


  • Low corrosion resistance
  • More expensive than other types of steel
  • It requires specialized welding techniques


  • Machining process: CNC machining
  • Tolerances: ISO 2768-1 fine (f) or medium (m) class. Info
  • Max size: 300 x 300 x 120 mm; 11.8 x 11.8 x 4.7 in
  • Lead time: <6 days

Rating 4.81 / 5.00

Based on 634 reviews

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High strength and toughness

Designed through a fine combination of alloying elements and heat treatment processes, AISI 9840 is designed to withstand the most challenging applications, offering both durability and strength.


Excellent wear resistance and fatigue strength

Thanks to careful design and heat treatment processes, AISI 9840 offers greater durability, making it ideal for applications with repetitive stress cycles or abrasive environments. Excellent for projects requiring consistent performance, long life and subject to critical environments.


High-stress mechanical applications

Thanks to its exceptional strength, toughness and wear resistance, AISI 9840 offers reliable performance in challenging conditions. Rely on this robust alloy to meet the stringent requirements of your most complex projects.



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In the constantly changing world of materials engineering, choosing the right steel alloy can be a challenging task. However, for those looking for a versatile, high-performance option, the steel alloy 39NiCrMo3 (AISI 9840) presents itself as an ideal candidate. In this short review, we will explore the strengths and potential drawbacks of this alloy, comparing it with some of its competitors, to demonstrate why it could be the perfect choice for your next project.


Superior strength: EN39 steel boasts an impressive combination of tensile strength, yield strength and hardness. This high-performance alloy is suitable for demanding applications, including gears, axles and heavy-duty machinery components. Its exceptional strength ensures superior durability and reliability under the most extreme conditions, enabling components made with this alloy to maintain their structural integrity even under intense workloads.

Excellent toughness:
The toughness of 39NiCrMo3 ensures its ability to withstand significant impacts and resist breakage, making it suitable for dynamic loading conditions and fatigue-prone applications. This characteristic is crucial in sectors such as the automotive industry, where safety and reliability of components are essential to ensure optimal performance and protection.

Superior hardenability:
This steel has excellent hardenability, allowing uniform hardness to be achieved throughout the material, even in large cross-sections, which can be a challenge for other steel alloys. This means that components produced with this alloy can be subjected to hardening processes with uniform and reliable results, ensuring consistent performance and increased resistance to deformation and wear over time.

Easy machinability: Despite its high strength, 39NiCrMo3 steel is relatively easy to machine, enabling efficient and economical production processes. This characteristic is valuable for industries that require the production of complex components with tight tolerances, allowing precise and accurate machining without compromising the mechanical properties of the material.

Good wear resistance: Due to the combination of hardness and toughness, AISI 9840 offers excellent wear resistance, reducing the need for frequent maintenance and replacement of components. This property is particularly advantageous in applications subject to abrasive stresses or repeated impacts, helping to extend component life and reduce long-term maintenance costs.


Moderate weldability: Although it offers numerous advantages, EN39 exhibits moderate weldability compared to other steel alloys. To avoid cracking and ensure that the desired properties of the alloy are maintained, preventive measures such as preheating and post-production stress relieving are necessary.

Corrosion potential: It is not inherently corrosion resistant, which may necessitate additional surface treatments such as painting, galvanising or coating to protect it from harsh environments. It is important to carefully consider the operating environment in which 39NiCrMo3 alloy will be used and take the necessary precautions to preserve its integrity over time.

Comparison with other steel alloys

Compared to AISI 4140, 39NiCrMo3 steel has similar mechanical properties, but with higher toughness. However, AISI 4140 has a slight advantage in terms of weldability and is more readily available on the market. In addition, EN39 is characterised by higher machinability and corrosion resistance, making it an attractive option for applications requiring a balance between strength and machinability.

Compared to AISI 4340, alloy 39NiCrMo3 offers better machinability and comparable strength. However, AISI 4340 offers better overall corrosion resistance and higher fatigue strength. It is important to carefully evaluate the specific needs of the application to determine which alloy is best suited to the project requirements, considering factors such as the operating environment, mechanical stresses and durability requirements.

Compared to AISI 1045, EN39 offers superior strength, toughness and wear resistance. In contrast, AISI 1045 boasts better weldability and is generally cheaper. The choice between the two alloys will depend on project priorities, considering strength, machinability and cost requirements. It is important to balance these considerations to obtain the best possible result for the specific application.


In conclusion, 39NiCrMo3 steel emerges as a superlative option in materials engineering, offering an impressive combination of strength, toughness and machinability. While recognising challenges such as moderate weldability and corrosion potential, the advantages offered by this alloy are indisputable. Compared to its competitors such as AISI 4140, AISI 4340 and AISI 1045, EN39 stands out for its exceptional toughness, good machinability and corrosion resistance. It is an ideal choice for applications requiring robust, reliable and wear-resistant components, such as gears, axles and heavy-duty machinery. Despite the various considerations to be taken into account, 39NiCrMo3's versatility and superior performance make it a compelling choice for a wide range of industrial projects. With careful evaluation of the application's specific needs and project requirements, 39NiCrMo3 steel proves to be an excellent candidate for those seeking excellent and lasting results.

"Weerg produced high-quality EN39 components for our heavy machinery, exceeding our expectations. Their responsive team ensured our requirements were met, resulting in improved machinery performance. Highly recommended for those seeking a reliable partner in Steel Alloy EN39 production."

steel alloy EN39 PROPERTIES

Tensile breaking load 970 MPa
Modulus of elasticity 205 GPa
Elongation at break 12%
Density 7,87 g/cm³
Melting temperature 1580°C
Hardness 270 Brinell
Yield Strength 700 MPa


"Weerg exceptional EN39 parts and Customer Support made a significant difference in our demanding applications. Their technical team optimized the design for manufacturability, ensuring timely shipping. Weerg is our go-to partner for EN39 parts."



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