In engineering and manufacturing, strength is a decisive factor. Whether it’s a crankshaft in an automotive engine or a high-load pin in construction equipment, tensile strength determines how much load a material can handle before breaking. Among the many alloy steels available, 4140 alloy steel has earned a reputation for its impressive balance of tensile strength, toughness, and machinability.
But how strong is 4140 alloy steel—really? In this article, sakysteel dives deep into the tensile properties of 4140, exploring what makes it a trusted material in demanding structural and mechanical applications.
4140 is a low-alloy chromium-molybdenum steel known for its high tensile strength and good fatigue resistance. It’s widely used in manufacturing, machining, tooling, and heavy-duty components.
Key chemical composition of 4140 includes:
Carbon: 0.38% – 0.43%
Chromium: 0.80% – 1.10%
Molybdenum: 0.15% – 0.25%
Manganese: 0.75% – 1.00%
Silicon: 0.15% – 0.35%
These alloying elements enhance hardenability and strength, making 4140 one of the most dependable steels for structural use.
Tensile strength refers to the maximum amount of tensile (pulling or stretching) stress a material can endure before failing. It is usually measured in megapascals (MPa) or pounds per square inch (psi). A higher tensile strength means the material can withstand greater forces before deforming or breaking.
The tensile strength of 4140 steel depends heavily on its heat treatment condition:
In its softest state (annealed), 4140 steel typically offers:
Tensile Strength: 655 – 850 MPa
Yield Strength: 415 – 620 MPa
Hardness: ~197 HB
After normalization, the steel’s structure becomes more uniform, enhancing mechanical properties:
Tensile Strength: 850 – 1000 MPa
Yield Strength: 650 – 800 MPa
Hardness: ~220 HB
This is the most common condition for high-performance applications:
Tensile Strength: 1050 – 1250 MPa
Yield Strength: 850 – 1100 MPa
Hardness: 28 – 36 HRC
At sakysteel, we offer 4140 alloy steel in a variety of heat-treated conditions, optimized to match specific strength requirements for different industries.
The key factors behind 4140’s high tensile strength include:
Chromium Content: Adds hardness and wear resistance
Molybdenum: Improves strength at high temperatures and enhances hardenability
Heat Treatment Flexibility: Tailors microstructure to match desired strength and toughness
Balanced Carbon Level: Offers a good combination of strength and ductility
These characteristics allow 4140 to outperform many carbon steels and even some tool steels when it comes to tensile strength under load.
4140 vs 1045 Carbon Steel
1045 is a medium carbon steel with tensile strength around 570 – 800 MPa.
4140 offers 30% to 50% more strength, especially when heat-treated.
4140 vs 4340 Steel
4340 includes nickel, which boosts toughness and fatigue resistance.
While 4340 may offer slightly higher toughness, 4140 is more economical with similar tensile performance.
4140 vs Stainless Steel (e.g., 304, 316)
Austenitic stainless steels offer corrosion resistance but lower tensile strength (typically ~500 – 750 MPa).
4140 is nearly twice as strong but must be protected against corrosion in aggressive environments.
Because of its high tensile strength, 4140 is used extensively in parts that endure heavy loads or dynamic forces. Typical applications include:
Drive shafts
Crankshafts
Suspension components
Gear blanks
Drill collars
Tool joints
Valve bodies
Hydraulic fittings
Landing gear components
Engine support brackets
Precision linkages
Punches and dies
Tool holders
Forming tools
The ability to withstand both static and cyclic loads makes 4140 the backbone of countless critical components in global industries.
The theoretical tensile strength of 4140 can vary in real-world applications based on:
Size of the part: Larger cross-sections may cool slower during heat treatment, reducing hardness.
Surface finish: Rougher finishes can act as stress risers.
Machining operations: Improper machining can induce stress concentrations.
Heat treatment control: Precise quenching and tempering temperatures directly impact final strength.
At sakysteel, we use strict quality control during heat treatment and machining to ensure optimal and consistent tensile properties in all our 4140 alloy steel products.
Tensile strength is typically measured using a universal testing machine (UTM) following ASTM or ISO standards. The steel sample is stretched until it breaks, and the results are recorded.
All sakysteel 4140 steel materials can be supplied with:
EN 10204 3.1 certificates
Mechanical test reports
Chemical composition data
This ensures full transparency and compliance with industry norms.
4140 alloy steel is truly one of the most versatile and robust steels available in the global market. With tensile strength exceeding 1000 MPa in treated conditions, it meets the demanding requirements of structural, mechanical, and tooling applications.
When strength, durability, and performance matter most, 4140 delivers—and sakysteel ensures you receive only the highest quality material, tested and certified for your peace of mind.