Metallographic diagram of 30CrMnSiA

30CrMnSiA is a low-alloy hot rolled steel with medium to high strength, excellent heat-resistant properties, and good cold-formed properties. This type of steel is widely used in the manufacture of parts requiring increased strength and corrosion resistance, such as automobile, railway, and aircraft parts.

30CrMnSiA has excellent mechanical and physical properties, including resistance to abrasion, impact and fatigue, as well as good formability and weldability. Additionally, it is resistant to corrosion and has good electrical conductivity. This steel offers high fatigue life and low notch sensitivity, making it an ideal choice for applications with fluctuating loads.

In metallography, 30CrMnSiA can be described as a ferritic hot-rolled steel. Its grain structure is continuous and its ferrite grain boundaries are slightly curved. Its surface is coarse and contains a small amount of pores. The grain is typically small and rod-shaped, and there is no segregation in the grain size. This steel also exhibits good transverse ductility and good stretch formability.

When subjected to a cross-sectional metallographic examination, 30CrMnSiA reveals a microstructure of ferrite and pearlite. The pearlite is formed by a uniform distribution of lamellar ferrite, ductile ferrite and ledeburite carbides. The microstructure also shows carbide bands and carbide clumps dispersed in the ferrite. The carbide clumps are mostly small and the carbide bands form along the grain boundaries.

30CrMnSiA has good hot workability and cold workability, as well as excellent hardenability and forgeability. It is also notable for having a high strength-to-weight ratio and can be machined easily. This steel is also very resistant to hydrogen embrittlement and has a good balance of both tensile and yield strength. Finally, 30CrMnSiA has a notch impact toughness of 68 J/cm2 and an elongation of 36%.

In conclusion, 30CrMnSiA is an excellent choice of low-alloy hot rolled steel that offers a wide range of desirable properties, including exceptional mechanical and physical properties, good formability and weldability, excellent hot workability and cold workability, as well as a high strength-to-weight ratio and good resistance to hydrogen embrittlement. Furthermore, it has a good notch impact toughness and an elongation of 36%. As a result, it is the ideal material for applications requiring increased strength, dimensional stability, and resistance to corrosion and fatigue.

介绍

20CrMnSiA is a kind of low-carbon, high-strength, low-alloy structural steel, which has medium hardenability, good plasticity and weldability, certain strength and low sensitivity to medium-frequency quenching cracking. Its metallographic structure is mainly characterized by evenly distributed ferrite and pearlite.

The yield strength and tensile strength of 20CrMnSiA after normalizing and tempering are above 600 MPa, and the yield ratio is more than 0.70. The main component of the steel is 0.17～0.24%C and the rest is Mn, Si, Cr and other alloying elements. The material is usually composed of ferrite and pearlite, which has the characteristics of uniform composition and fine grain structure, moderate hardness and plasticity, competitive price and good processing performance.

20CrMnSiA is mainly used to manufacture medium and large gears, crankshafts and camshafts with high strength, wear resistance and impact resistance, as well as subcritical parts such as axles, connecting rods, thrust collars and connecting rods of diesel engines. The steel is usually bent after quenching, which can reduce the machining workload and save much cost. In addition, it can also be used to manufacture agricultural machinery parts, machine tool spindles, automobile parts, hot press forming die, machine tool guide rails and industrial robots.

The microstructure of 20CrMnSiA is mostly tempered sorbite structure, which is composed of ferrite, pearlite and retained austenite. In the tempering process, the retained austenite to ferrite transformation generates fine polygonization and its grain grows. The tempered sorbite has a great improvement in both strength and toughness. The faster quenching speed in the quenching process can prevent the grain boundary diffusion and produce the fine polygonization structure, which can further improve the mechanical properties of 20CrMnSiA.