Quenching, Double Cascade

After austenitizing, steel rod is prequenched in a salt bath at a temperature just over the Ms point. It is then transformed in a second salt bath at a temperature around 510°C, both baths in tandem. Approximate isothermal transformation is said to take place, providing a fine even structure and, consequently, high tensile strength, higher ductility for a given strength and improved fatigue properties.