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4140 Steel vs 42CrMo Steel Difference:
Let You Choose Better

4140 and 42CrMo are widely used as alloy steel materials in manufacturing, automotive, engineering, and other fields. 4140 steel and 42CrMo steel look similar, but there are actually some differences. For customers who purchase 4140 or 42CrMo steel from Songshun Steel, we will first understand the projects they need to apply in order to most effectively select the ideal steel for application in the project. So this article will provide a detailed introduction to the differences between 4140 steel and 42CrMo steel from several aspects.

4140 Steel vs 42crmo Steel

Grade Standard

1. 4140 steel is the American standard AISI standard and is approved by the ASTM A29 standard
2. 42CrMo is the Chinese GB standard and complies with the T 3077 standard.

Chemical Composition


Judging from the chemical composition of 4140 and 42CrMo, the chemical composition elements of the two overlap. The main difference lies in the Mn composition, and the manganese content of 42CrMo is low. The carbon content and chromium content of 42CrMo are higher than 4140. Although there is only a slight difference in the chemical composition of the two materials, it will also affect their performance and use. For example, 42CrMo steel has higher hardness and strength than 4140, so it is more suitable for manufacturing high-strength, high-load mechanical parts.

Mechanical Properties

4140 Mechanical PropertiesMetric
Tensile Strength655 MPa
Yield Strength415 MPa
42CrMo Mechanical PropertiesMetric
Tensile Strength1080 MPa
Yield Strength930 MPa

Due to the different production process and processing methods of each steel factory, the data of mechanical properties will also be different. The data in the table is the common mechanical performance index and approximate range of our Songshun Steel. It can be seen from the data that the strength of 42CrMo is better than that of 4140, but the plasticity of 4140 is better than that of 42CrMo.

Heat Treatment Process

The heat treatment states of 4140 and 42CrMo are both quenched and tempered, but due to the slight differences in chemical composition and mechanical properties between the two, there are also differences in their heat treatment processes.

(1) Quenching
The quenching temperature of 4140 steel is 840°C, the quenching temperature of 42CrMo steel is 850°C, and the medium is oil or water, but the quenching hardness of 42CrMo steel is higher than that of 4140 steel.

(2) Tempering
After quenching, quickly put it into the medium to cool, and then perform tempering treatment, the purpose is to reduce the brittleness of the steel and provide toughness. 4140 needs to be kept at a tempering temperature of 540°C for a period of time, while the tempering temperature of 42CrMo is 560°C. 42CrMo steel already has good toughness at high temperature, and depending on the requirements, there may be cases where the second tempering treatment is not required.

(3) Normalizing
In terms of normalizing, 4140 steel needs to be kept at 850-880°C for a period of time, and then rapidly cooled to room temperature. The structure after normalizing is pearlite and a small amount of cementite. The normalizing temperature of 42CrMo steel will be higher than that of 4140, at 860-890°C.


4140 is mainly used in the manufacture of mechanical parts, shafts, gears, forgings and weapon parts, etc.

42CrMo can be used not only in mechanical parts, but also in the manufacture of high-strength parts such as large gears, automobile bearings, engine bearings, hydraulic cylinders and transmission shafts. Because 42CrMo has better mechanical properties, 42CrMo is more suitable and widely used in high load and high temperature environments.

To sum up, 4140 has similarities with 42CrMo, but there are also some differences. When purchasing 4140 steel or 42CrMo steel, generally speaking, if you need stronger strength and toughness, or require better wear resistance, it is recommended to choose 42CrMo, but the final choice of material depends on the specific application and requirements.

Our Songshun Steel, are a reliable 42CrMo and 4140 round bar supplier. We not only provide 4140 and 42CrMo round bars, but also steel coils, steel pipes, and steel plates, etc., to help you choose ideal materials and better apply them to projects.


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