40Cr Steel - Alloy Structure Steel40Cr belongs to GB3077 "alloy structural steel". The carbon content of 40Cr steel is 0.37% to 0.44%, which is slightly lower than 45 steel. The content of Si and Mn is equivalent, containing Cr0.80% to 1.10%. In the case of hot rolling supply, this 1% Cr basically does not work, and the mechanical properties of the two are roughly the same. Since the price of 40Cr is about half more expensive than 45 steel, 40Cr is not needed for economic reasons.
Conditioning treatment of 40Cr steel: The main function of Cr in heat treatment is to improve the quenchability of steel. Due to the improvement of quenchability, the mechanical properties such as strength, hardness and impact toughness of 40Cr after quenching (or tempering) are also significantly higher than that of 45 steel, but it is also due to strong quenchability. At quenching, the internal stress of 40Cr is also greater than that of 45 steel. Under the same conditions, the working parts of 40Cr material are also more prone to crack than 4. 5 The workpiece of steel material is large. Therefore, in order to avoid the cracking of the workpiece, 40Cr quenching mostly uses oil with low thermal conductivity as the quenching medium (sometimes also uses the double-liquid quenching method, as the saying goes as water quenching oil cold), while 45 Rigid uses water with high thermal conductivity as the quenching medium. Of course, the choice of water and oil is not absolute, and it is also closely related to the shape of the workpiece. Simple-shaped 40Cr parts can also be quenched with water, while complex 45-shaped steel parts may have to be quenched with oil or even salt baths.
The quenching and tempering of 40Cr workpiece conditioning, and various parameter process cards are stipulated. In practice, we have experienced that:
