The continuous heat treatment of tool steel is applied to low- or medium-alloyed carbon steel strips as well as martensitic stainless steels. The described lines produce high-quality strip with respect to uniform structure, flatness, and bright surface finish. High quenching rates are necessary, especially for plain carbon steels. Cooling gradients of up to 600 K/s are possible in a molten lead-bismuth quench. Because two-stage quenching technology provides considerable advantages over quenching in oil, this method has been adopted worldwide. It is also possible to achieve isothermal transformation to bainite and pearlite using a molten metal quench, so this type of hardening and tempering line is extremely versatile.
The configuration of a high-performance line involves an entry and exit section of the strip handling equipment. The hardening section consists of the austenitizing furnace, the molten metal quench or hydrogen quench, and a martensite cooler.
For more information, click on the link below (subscription required). Then scroll to Figure 10. R Schneider; R. Mesquita; W Schützenhöfer, Distortion in Tool Steels, ASM International, 2014
