What is the difference between steel 4140 and 4340?

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There are various differences and similarities between alloy steel 4140 and 4340. This blog about the difference between steel 4140 and steel 4340 can help you make an informed decision when choosing which one to use in your project or product.

1.Properties comparison of steel 4140 and 4340

steel 4340 vs. steel 4140

(1)Chemical Composition of AISI 4140 vs AISI 4340 

①4140 Chemical Composition

②4340 Chemical Composition


4340 steel and 4140 steel have equal traces of sulfur, phosphorus, and silicon. They also have approximately the same amount of molybdenum and manganese. 


However, 4340 has more carbon, while 4140 has more chromium. One of the most significant differences between the two metals is the inclusion of nickel in 4340 steel, which accounts for the metal’s greater strength and fracture toughness.

2. mechanical properties

Due to their difference in chemical composition, 4340 and 4140 have some similar and some different properties. 

Similar to 4340, 4140 steel is highly strong, which is a result of its chromium and molybdenum content. However, since it does not contain nickel, it is less hard and more susceptible to fracturing. 

4340 steel is known for its strength and toughness. These characteristics come from the fine and equal dispersion of carbides within its structures. 

①ASTM 4140 Steel Properties

②ASTM 4340 Steel Properties

3. Products Features of 4140 vs 4340 Alloy Steel 

(1) 4140 steel features

 This steel has good strength, good toughness, high hardenability, good workability, small processing deformation, quite good fatigue resistance, small deformation during quenching, and high creep strength and durable strength at high temperatures.

(2) 4340 steel features

 It has high strength, toughness, excellent hardenability and stability against overheating, good plasticity and heat resistance, uniform material, high working reliability, weldability, non-leakage, and simple steel structure production. Short construction period and good assembly.

4. Common Specifications

(1)Common 4140 Steel Specifications

(2) AISI 4340 Steel Specification and Relevant Standards

5. Applications of 4140 vs 4340 Steel

Given their unique characteristics, these two steel alloys are often used for separate purposes. 

(1)Applications of 4140 Steel 

4140 alloy steel finds many applications as forgings for the aerospace and oil and gas industries, along with myriad uses in the automotive, agricultural, and defense industries, Typical uses are forged gears and shafts, spindles, fixtures, jigs, and collars.

It can also be used for drilling pipe joints and fishing tools in oil wells below 2000m and can be used for molds of bending machines, etc.

(2)Applications of 4340 Steel

4340 steel can be used in machinery and high-load shafts, turbine shafts with a diameter greater than 250mm, helicopter rotor shafts, turbojet engine turbine shafts, Blades, high-load transmission parts, and crankshaft fasteners since it is of good toughness, high strength, and large size.

Moreover, it can also be used for rotor shafts and blades whose operating temperature exceeds 400 ℃。

What’s more, 4340 steel can also be used to manufacture important parts with special performance requirements after nitriding treatment and can be used for ultra-high temperatures after low-temperature tempering or austempering. 

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4340 cnc machining capability of our company

4340 steel is a high-strength alloy that is often used in aerospace, automotive, and other demanding industries. 

We provide 4340 cnc machining services for a variety of applications. We can provide 4340 cnc machinings and can produce 4340 parts with tight tolerances and a smooth finish.

4140 cnc machining capability of our company

4140 is known for its strength and durability, making it an ideal choice for applications where high levels of stress are present,4140 also has excellent weldability properties, making it suitable for fabricating and welding projects. 


What is steel 4130 and its features?

Steel 4130 is a type of alloy steel that is known for its great strength and durability. It has been used in many different industries, from automotive to aerospace, because of its ability to resist corrosion and withstand high temperatures. It is also widely used in the construction of structural components such as bridges and buildings due to its excellent strength-to-weight ratio. Steel 4130 has high tensile strength, good fatigue resistance, and excellent weldability. It is also relatively resistant to wear and tear, making it an ideal choice for numerous applications. Additionally, steel 4130 can be heat treated for increased hardness or ductility depending on the intended application. This makes it a very versatile material that can be used in many different ways. With these features and its affordability, steel 4130 is an ideal choice for many industries needing strong yet resilient materials.

What is Annealed Steel?

Annealed steel is a type of steel that has gone through a process of heating and cooling to increase its strength and ductility. This process, known as annealing, can be used to treat both ferrous and non-ferrous metals. Through the annealing process, the metal is heated to a certain temperature before being cooled in order for its internal structure to become more malleable and uniform. The resulting product is stronger than it was previously, making it highly durable and resistant to wear and tear. Additionally, annealed steel has greater formability due to its harder surface which makes it optimal for cutting, machining, welding, and other manufacturing processes. Annealed steel is commonly used in automotive parts, refrigeration systems, structural supports, piping systems, sheet metal fabrication projects, and much more.

Steel 4140 vs steel 4130

Steel 4140 and Steel 4130 are two of the most commonly used alloy steel grades. Both are hardenable, heat-treatable steels that contain chromium and molybdenum, making them ideal for many engineering applications. However, they do have some differences between them. Steel 4140 is an alloy steel containing chromium and molybdenum, which provides it with better toughness and strength than other alloys. It also has good ductility, making it easier to work with when forming. In contrast, Steel 4130 contains a higher amount of carbon than 4140, providing it with higher tensile strength and wear resistance. Additionally, its lower chromium content gives it superior weldability compared to 4140. Ultimately, which steel grade you use depends on the specific application requirements you may have.


At EJ CNC, we provide 4140 cnc machining services to produce parts and components for a variety of applications. Our 4140 cnc machining services provide customers with parts that meet their specific application requirements. 

Contact us today to learn more about our 4140 or 4340 cnc machining services!