What are the differences between 40Cr steel plate and 45# steel plate

40Cr steel plate is easy to process, and a certain degree of toughness, plasticity and wear resistance can be obtained after proper heat treatment. Normalizing can promote the SPHEroidization of the structure and improve the cutting performance of the blank with a hardness of less than 160HBS. The hardenability of 40Cr steel plate is higher than that of 45# steel plate, which is suitable for surface hardening treatment such as high frequency quenching and flame quenching.

40Cr steel plate is used to manufacture parts with heavy load, low impact and wear resistance, and the solid thickness of the cross section is below 25mm, such as worms, spindles, shafts, collars, etc. In addition, this steel is also suitable for manufacturing various transmission parts, such as gears and shafts with larger diameters and good low temperature toughness.

45# steel plate belongs to GB699"(high quality) carbon structural steel";, and 40Cr steel plate belongs to GB3077 "alloy structural steel". There are differences between them after heat treatment. The main role of Cr in heat treatment is to improve the hardenability of steel. Due to the increase in hardenability, the mechanical properties of 40Cr steel plate after quenching (or quenching and tempering) are significantly higher than that of 45# steel plate, such as strength, hardness, and impact toughness. However, due to the strong hardenability, the internal stress of 40Cr steel plate during quenching is also larger than that of 45# steel plate, the cracking tendency of the workpiece of 40Cr steel plate is greater than that of 45# steel plate under the same conditions. Therefore, in order to avoid the cracking of the workpiece, the oil with lower thermal conductivity is mostly used as the quenching medium when quenching 40Cr steel plate, while the water with higher thermal conductivity is used as the quenching medium for 45# steel plate.

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