Factors Affecting The Hardenability Of Steel

The decisive factor affecting the hardenability of steel is the critical cooling rate (vk). The lower the critical cooling rate, the greater the hardenability. The influencing factors include:
1. Carbon content: Hardenability is best near the eutectoid point, far from the S-point difference.
2. Alloying elements: Except for Co, almost all the alloying elements reduce the critical cooling rate of steel, that is, improve the hardenability of steel.
3. Austenitization: The higher the temperature, the longer the holding time, and the greater the hardenability of the steel.
4、 Determination and expression method of hardenability
Endless quenching method GB225-88
Method for expressing the hardenability of steel
Critical Hardening Diameter Dc - It refers to the maximum diameter at which the center obtains all M or 50% M. As shown in the figure:
5、 The Relationship between Hardenability and Hardening Layer Depth
Under the same conditions, the higher the hardenability of steel, the greater the depth of the hardened layer.
The depth of the hardened layer of the workpiece is not only determined by the hardenability of the steel, but also by external factors such as quenching medium and workpiece size.