4340 Steel vs 1040 – What’s the Difference

4340 Steel VS 1040 Steel

There are many options when choosing the right type of steel for your project. Two common types of steel are 4340 and 1040. Although they share a few similarities, they differ in many ways and have unique properties that make each suitable for different applications. In this blog post, we will explore the differences between these two types of steel.

What is 4340 Steel?

4340 Steel comprises elements like nickel, chromium, and molybdenum, known for its toughness and high tensile strength. 4340 Steel is often used in applications where extreme strength is needed, such as gears, crankshafts, and aircraft landing gear. But what sets 4340 steel apart from other types is its ability to withstand heat treatment without losing its durability.

What is 1040 Steel?

1040 steel is a medium-carbon steel widely used in various industries, including automotive, machinery, and construction. It’s known for its excellent strength, toughness, and wear resistance, making it a go-to choice for many applications that require durable and reliable materials. It contains 0.40% carbon, giving it the right hardness and flexibility balance. Moreover, it can be easily machined, welded, and heat-treated to further enhance its properties.

Difference between 4340 Steel and 1040

4340 steel is an alloy steel that contains nickel, chromium, and molybdenum. It has a higher strength-to-weight ratio than 1040 steel, making it stronger and more lightweight. Additionally, 4340 resists thermal cycles better than 1040 and is tougher at high temperatures. It also has better weldability and machinability due to its low carbon content.

Composition and Properties

The primary difference between 4340 and 1040 steel is their composition and properties. 1040 steel is mainly composed of iron and carbon, with a carbon content of 0.4% – 0.45%. It also contains small amounts of manganese and silicon, which helps with the strength and toughness of the steel. 4340 steel, on the other hand, is an alloy steel containing nickel, chromium, and molybdenum. It has a carbon content of 0.38% – 0.43% and a higher concentration of other elements. This results in 4340 steel having significantly better toughness than 1040 steel.

Heat Treatment

Heat treatment plays a critical role in determining the properties of steel. Both 4340 and 1040 steel can be heat treated to improve their mechanical properties. However, the heat treatment process for 4340 steel is more complicated and requires more critical attention. When heated, 4340 steel can become brittle and susceptible to cracking. Thus, it requires a more gradual cooling process. This makes manufacturing 4340 steel more challenging and time-consuming than 1040 steel.


4340 steel is a more advanced and complex steel that is best suited for use in high-stress applications. Its superior strength and toughness make it ideal for aircraft landing gear, crankshafts, and other heavy-duty machinery. On the other hand, 1040 steel is known for its durability, and its ability to be easily machined makes it an excellent choice for many industries. It is often used in construction, agricultural machinery, and automotive parts.


The cost of steel is another significant factor to consider when choosing between 4340 and 1040 steel. Because of its superior strength and complexity, 4340 steel is typically more expensive than 1040 steel. Depending on the application, the added cost may be worth it, as the improved properties can lead to safer and more reliable machinery.


In conclusion, 4340 steel and 1040 steel are two different types of steel with unique properties and applications. The primary difference between these two is their composition and mechanical properties, ultimately leading to different performances in specific applications. When deciding which steel to use, it’s essential to consider the intended application, cost, and feasibility of manufacturing. Knowing the differences between these two types of steel can help you make an informed decision to ensure your project’s success.