What is the difference between 45 steel and 40Cr is as follows:
1, carbon content
40Cr this material has a carbon content of 0.37% to 0.44%, which is slightly lower than 45 steel (0.42% to 0.50%).
2, the price is different
Because the price of 40Cr is more expensive than 45 steel about half, so for economic considerations can be used 45 steel will not use 40Cr.
3, the hardenability of different
The difference lies in the heat treatment later.Cr in the heat treatment of the main role is to improve the hardenability of steel. As hardenability increases, quenching (or tempering) treatment after 40Cr strength, hardness, impact toughness and other mechanical properties are significantly higher than 45 steel.
4, cracking tendency is different
But also due to strong hardenability, in the quenching of 40Cr internal stress is also greater than 45 steel, the same conditions 40Cr material workpiece cracking tendency is also greater than 45 steel material workpiece.
Expanded Information:
40Cr is the standard steel grade of GB in China, and 40Cr steel is one of the most widely used steels in the machinery manufacturing industry. After tempering treatment has good comprehensive mechanical properties, good low temperature impact toughness and low notch sensitivity. Steel hardenability is good, water quenching can be quenched to Ф28 ~ 60mm, oil quenching can be quenched to Ф15 ~ 40mm.
This steel in addition to tempering treatment is also suitable for cyanide and high frequency quenching treatment. Cutting performance is good, when the hardness of 174 ~ 229HB, the relative cutting machinability of 60%. The steel is suitable for making medium-sized plastic molds.
References:
Baidu Encyclopedia-40Cr
Baidu Encyclopedia-45 Steel