AISI 4140 steel

AISI 4140 steel is categorized as low alloy steel which contains some significant levels of manganese, molybdenum, and chromium elements. This metal is applicable in a wide range of industries thanks to its physical and structural toughness.

What does the number 4140 mean in this type of steel metal?

4 stands for Molybdenum. It simply means that this steel contains a high level of molybdenum than any other steel that belong in the same series.

1 represents the presence of chromium in the steel.

40 is basically used to differentiate this steel from other types of steel.

How is 4140  Steel Formed?

The major alloys of 4140 steel are carbon and iron. Apart from these two, there are other elements that are added. These are manganese, chromium, and molybdenum.

These elements are placed in an electric furnace or even in an oxygen furnace. They turn into a molten state and combine to form one solid metal. The hot steel is allowed to cool.

In some cases, this form of 4140 steel can be annealed for several times.

After the annealing, the steel, is again heated into molten phase then poured into forms where it will take the desired shape.

Alternatively, this steel can be cold worked through various processes such as rolling, panning, and cutting.

Immense pressure may also be applied during the forming process so as to give this steel the necessary hardness that it should have.

There are other post-processing techniques that can be applied to the newly-formed steel for the purpose of improving its strength and aesthetics.

How is 4140 Steel Annealed Hardened and Tampered?

Before  4140 steel is ready for use, it is usually subjected through these three processes; annealing hardening and tampering. The purpose of these processes is to enhance the physical and mechanical properties of this steel.

4140 steel is annealed at 872°C which is equivalent to 1600°F. After that, the steel is cooled in a furnace.

On the other hand, 4140 steel has tampered at the temperatures of between 200°C and 650°C. The temperature is adjusted depending on the desired level of hardness.

There are various methods of hardening  4140  alloy steel.  These are quenching, heating, and cold working.

Can you case harden 4140 steel? Yes. This steel can be case hardened by simply lowering the temperature during the quenching process. Instead of being quenched at the required temperature of 1575°F, the temperature is reduced to 1375°F.

What are the Mechanical Properties of 4140 Steel?

The presence of chromium and molybdenum tends to give  4140 steel some extra mechanical advantages than ordinary steel.  It is harder than regular steel.

The steel has an excellent weight to strength ratio. This means that despite being physically and mechanically stronger, 4140  is not very heavy.

One of the most outstanding properties of this metal is the high tensile strength. The tensile strength of this metal can be as high as 95,000 PSI. This means that this metal cannot break easily even when subjected to some kind of a heavy load.

Another mechanical property of 4140 steel is excellent ductility. This type of steel can be easily drawn into a wire and be stretched to form different products.

This steel also features an excellent hardenability.  It has a high carbon content and can be hardened and pampered when the need arises.

Is 4140 a Tool Steel?

Is 4140 a Tool Steel?


Does 4140  meet the criteria of being referred to as tool steel? Yes. This is definitely a type of tool steel.

One of the reasons why 4140 qualifies to be tool steel is the high content of chromium and carbon. The higher the chromium content the better. These two elements are responsible for giving this steel some extra level of hardness.

The presence of molybdenum also tends to increase the corrosion resistance of this steel. It also acts as a strengthening agent in this steel alloy.

The hardening and tempering processes tend to increase the suitability of 4140 steel for being used as tooling steel. They not only improve the tensile strength of the steel but also make it resistant to high temperatures.

Does 4140 Steel Rust?

Although steel is known for being resistant to rust, the situation can easily change when exposed to different conditions. The presence of an iron element can still cause some rust.

Most steel rust just after they have corroded. Excellent resistance to corrosion is the reason why 4140 steel does not rust so fast as compared to other types of steel.  This can be attributed to a significant percentage of chromium and molybdenum.

However, once corroded, the  4140 steel will just rust like most steel that undergoes the same damage. The only caveat is it has some degree of protection.

What are the Applications of 4140 Steel?

As a result of its numerous properties, 4140 Steel is used for making a wide range of tools and products.

Some of the most common applications of this steel include;

-In the automotive industry for making gear engine, steering

-For bolts nuts and screws


-Machinery parts

-For steel collet

-Conveyor belts

-Piston rod among many other steel products

Are you planning to build a product using steel but not sure which grade of steel to use? Consider seeking advice from an expert. They will advise you whether 4140 steel is the right steel alloy for the application.

4140 Steel Manufacturer in China-Roche Industry

Are you planning to use  4140  steel to make your products? Let us be your partner. Apart from just manufacturing this steel alloy, we can also implement various finishing processes.

Our 4140  ally steel experts can also give you the necessary advice regarding this steel. Contact us for more information and a free quotation.