4140 steel is a popular alloy steel known for its strength, toughness, and versatility. It belongs to the family of chromium-molybdenum steels, offering a unique combination of mechanical properties that make it a preferred choice for industrial applications. Engineers, fabricators, and manufacturers widely use this steel for everything from automotive parts to machinery components.
In this SEO article, sakysteel presents a comprehensive overview of 4140 steel, including its chemical composition, mechanical properties, heat treatment processes, and common uses.
4140 is a low alloy steel that falls under the SAE-AISI classification system. It is also known as AISI 4140, EN19 (in Europe), and SCM440 (in Japan). The designation “4140” refers to a specific alloy content:
“41” indicates a chromium-molybdenum steel
“40” represents the approximate carbon content (0.40%)
4140 steel is not a stainless steel, as it does not contain sufficient chromium to offer corrosion resistance. Instead, it is prized for its mechanical strength and hardness after heat treatment.
The chemical composition of 4140 is what gives it its enhanced mechanical properties. Typical ranges include:
Carbon (C): 0.38% – 0.43%
Chromium (Cr): 0.80% – 1.10%
Manganese (Mn): 0.75% – 1.00%
Molybdenum (Mo): 0.15% – 0.25%
Silicon (Si): 0.15% – 0.35%
Phosphorus (P): ≤ 0.035%
Sulfur (S): ≤ 0.040%
These elements work together to enhance hardenability, wear resistance, and overall durability, making 4140 a go-to material for demanding mechanical parts.
4140 offers an impressive range of mechanical properties, especially after proper heat treatment. These include:
Tensile Strength: Up to 1100 MPa (160 ksi)
Yield Strength: Around 850 MPa (123 ksi)
Elongation at Break: Approximately 20%
Hardness: Typically 197 to 235 HB in annealed condition, up to 50 HRC after quenching and tempering
These values can vary depending on the form of the steel (bar, plate, forged) and heat treatment condition.
Heat treatment is a key process that enhances the performance of 4140 steel. The steel can undergo the following processes:
Annealing
Slowly cooled from about 850°C to improve machinability and reduce internal stress. This results in a softer structure with improved ductility.
Normalizing
Heated to around 870°C to refine the grain structure. Provides a balance of strength and toughness.
Quenching and Tempering
Hardened by heating to about 845°C and rapidly cooling in oil or water, followed by tempering to desired hardness levels. This greatly increases the strength and wear resistance.
Stress Relieving
Done at around 650°C to minimize residual stresses from machining or welding.
At sakysteel, we provide 4140 steel in various heat-treated conditions based on customer requirements, ensuring maximum performance in your application.
High Strength-to-Weight Ratio: Ideal for weight-sensitive applications.
Good Fatigue Resistance: Withstands cyclic loading, suitable for gears and shafts.
Excellent Hardenability: Achieves high hardness after quenching.
Machinability: Easily machinable in annealed or normalized conditions.
Weldability: Can be welded with proper preheating and post-weld treatment.
These benefits make 4140 steel an economical choice for many high-stress engineering applications.
Due to its mechanical strength and versatility, 4140 steel is used in a wide range of industries:
Axles
Crankshafts
Gears
Steering knuckles
Drill collars
Tool joints
Connecting rods
Landing gear components
Shafts
High-stress structural parts
Couplings
Forged components
Die holders
Spindles
At sakysteel, we have supplied 4140 steel products for customers across these sectors, offering reliable quality and precise customization.
4140 vs. 1045 Carbon Steel:
4140 offers better wear resistance and higher tensile strength due to alloying elements. 1045 is cheaper but less durable.
4140 vs. 4340 Steel:
4340 has higher nickel content, offering better toughness and fatigue resistance. 4140 is more cost-effective for general-purpose use.
4140 vs. Stainless Steel (e.g., 304 or 316):
Stainless steels offer corrosion resistance but lower strength. 4140 is preferable in high-load applications without exposure to corrosive environments.
sakysteel supplies 4140 steel in the following product forms:
Round Bars (Hot Rolled, Cold Drawn, Peeled)
Flat Bars and Plates
Forged Blocks and Rings
Hollow Bars and Tubes (upon request)
Cut-to-size precision blanks
All products are available with EN10204 3.1 certificates, and we also offer CNC machining and heat treatment services.
4140 is a versatile, high-performance alloy steel that meets the needs of various demanding applications. Its combination of strength, toughness, and cost-efficiency makes it a preferred material for mechanical engineers and manufacturers worldwide.
Whether you need raw material supply or finished components, sakysteel is your trusted partner for 4140 alloy steel. Contact our technical team today to discuss your requirements and receive a tailored quote.