Properties Of 4140 Steel Round Bar

4140 Steel Round Bar

Steel has been around for centuries and is used in various applications. It is the preferred material of choice mainly because of its exceptional mechanical, physical, and chemical properties. One prime example of steel is the 4140 steel round bar, a versatile alloy known for its high tensile strength, excellent toughness, and superior corrosion resistance. In this blog post, we will discuss the properties of the 4140 steel round bar in detail, from its composition to its applications.

What Is 4140 Steel Round Bar?

4140 Steel Round Bar, also known as AISI or SAE 4140, is a versatile, high-strength alloy steel commonly used in manufacturing. It contains chromium, molybdenum, and manganese, giving it exceptional strength and toughness. This makes it suitable for automotive, aerospace, oil and gas, and construction applications. Adding carbon also allows for great hardenability, making it ideal for heat treatment processes such as quenching and tempering to achieve desired mechanical properties.


4140 steel round bar comprises various elements, including chromium, molybdenum, manganese, and carbon. Chromium and molybdenum are responsible for the steel’s high tensile and yield strength and the ability to withstand high temperatures. Meanwhile, manganese helps regulate the hardness and strength of the steel, and carbon offers hardenability.

Mechanical Properties

One of the selling points of the 4140 steel round bar is its excellent mechanical properties. It has a high tensile strength of 655 MPa, yield strength of 415 MPa, and elongation at a break of about 25%. The hardness of the steel ranges from 217 HBW to 388 HBW, depending on the heat treatment it underwent.

Physical Properties

Regarding physical properties, the 4140 steel round bar has a density of approximately 7.85 g/cm³, with a melting point of 1416°C. It exhibits good thermal conductivity, meaning it can transfer heat efficiently.

Corrosion Resistance

Another essential characteristic of the 4140 steel round bar is its superior corrosion resistance, which makes it ideal for applications in harsh environments. Chromium in the steel makes it resistant to oxidation and corrosion under high temperatures and pressures.


With its exceptional mechanical, physical, and chemical properties, the 4140 steel round bar finds widespread use in various industries, including oil and gas, automotive, aerospace, and defence. It is used to manufacture critical parts such as gears, shafts, axles, and bolts. In the oil and gas industry, it is used to produce drilling components, while the automotive industry uses it to manufacture chassis and suspension parts.


In conclusion, the 4140 steel round bar is a versatile alloy with exceptional mechanical, physical, and chemical properties that make it ideal for various industrial applications. Its excellent tensile strength, superior corrosion resistance, and good thermal conductivity make it a preferred material for many critical components in various industries. By understanding the properties of 4140 steel round bars, manufacturers can determine the best applications for this versatile alloy and ensure quality end products.

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