Quenching Cooling Characteristic Curve
The time-dependent temperature decrease of a workpiece in the quenchant, divided into vapor blanket, boiling, and convection stages. Precise tuning prevents unacceptable hardening defects or cracking.
The quenching curve shows you how quickly a workpiece cools in the medium. It runs in three phases: First, a vapor film forms, which slows down heat removal. Then the film breaks and the medium boils directly on the workpiece – that's when cooling is fastest. Finally, it only cools via convection. When welding, you have to be careful: If cooling is too severe, the structure becomes hard and prone to cracking. If it's too slow, you might not get a clean structure. The right setting depends heavily on the material – only experience or a look at the data sheet helps. In practice, this means: Monitor the cooling, especially with thick parts or when working with preheating. If you see cracks or unexpected hardness, the cooling wasn't right. Then you need to adjust the parameters, not blindly adopt values.