Metallographic diagram of 20CrMnMo (normalized after forging)

20CrMnMo (forged and normalized) Microstructure

20CrMnMo forging and normalizing steel is a kind of composite steel with excellent performance and excellent combination of strength, corrosion resistance, wear resistance, plasticity and impact toughness, which can be used in the manufacture of medium and large parts for automobiles, tractors and mining machinery.

The alloy of 20CrMnMo forging and normalizing steel is composed of 1.0-1.3% C, 0.17-0.37% Si, 1.0-1.3% Mn, 0.30-0.60% Cr, 0.50-0.80% Mo and balanced Fe. The steel has excellent hardenability, and it is not easy to produce quenching crack after quenching and tempering. The quenching range is 830-880 degrees, and the tempering temperature is 500~530.

The microstructure of 20CrMnMo forging and normalizing steel is divided into austenite, martensite and carbide. The gross of microstructure is refined and white. The austenite grains are distributed evenly, the grain boundary is smooth, and the grain size is controlled in 8. There are a large number of martensite grains, and the grain size is controlled in 1-2. There are a few carbides, which are distributed along the martensite grains and play an important role in the wear resistance of steel.

The carbide particles in the 20CrMnMo forging and normalizing steel are mostly square type M7C3 and cube type M6C, and their composition is relatively uniform. The carbon content of M7C3 carbide is slightly higher than that of M6C carbide. The M7C3 carbide exists in the form of particles and tetragonal network, while the M6C carbide exists in the form of particles and hexagonal network. The sizes of M7C3 and M6C carbides are all between 2.0 and 2.5 microns, and no graphite is seen.

The 20CrMnMo forging and normalizing steel has excellent performance, and its microstructure plays an important role. The austenite, martensite and carbide are evenly distributed in the steel, making the steel have excellent comprehensive properties such as strength, toughness, plasticity, wear resistance and corrosion resistance. The M7C3 and M6C carbide particles have a great influence on the wear resistance of the steel, which has a promotion effect.

20CrMnMo is a kind of steel commonly used in forging. After being properly forged, the steel can reach its maximum strength. Microstructurally, the 20CrMnMo steel consists mainly of ferrite and pearlite, as shown in the micrograph below.

The bright constituents in the micrograph are the ferrite, which is oriented perpendicular to the direction of rolling. On the other hand, the bluish-gray dim constituents are the pearlite, which forms in between the ferrite. It is worth noting that the composition of ferrite and pearlite in the sample of 20CrMnMo steel is around 94-97.5% ferrite and 2.5-6% pearlite.

In addition, the 20CrMnMo steel displays a certain amount of residual austenite embedded in the pearlite and ferrite matrix. However, the amount of residual austenite present in the 20CrMnMo steel is not as significant as that in its counterpart of low-carbon steel.

From the above micrograph, we can clearly see that the hardness of the 20CrMnMo steel is primarily determined by the amount of ferrite and pearlite in its composition. Since the microstructure consists mostly of ferrite and pearlite, it is expected that the 20CrMnMo steel exhibits a good level of hardness, strength, and wear resistance.

In conclusion, the 20CrMnMo steel exhibits good mechanical properties after being adequately forged and quenched. The well-forged steel consists mainly of ferrite and pearlite with a small amount of residual austenite, which contributes to its good level of hardness and strength.