Quenching Severity
Quenching severity is a characteristic value that measures the heat transfer capability of a quenching medium and influences the cooling rate at the workpiece surface.
Physical-Chemical Mechanism of Action
Quench severity describes how quickly a quenching medium absorbs and removes heat from the weld. A high quench severity means the medium lowers the temperature faster.
Metallurgical Relevance & Risks in Welding
Too high a quench severity can cause too rapid cooling. This can lead to the microstructure becoming glass-hard and increasing the tendency for hot cracking. Conversely, too low a quench severity slows cooling, which can lead to grain coarsening and loss of toughness in the steel.
Shop Practice & Action Guidelines
Choose a quenching medium with the right quench severity for the welding process used. For high-temperature processes like MIG welding, use a medium with medium quench severity (e.g., t8/5 between 10 and 20 seconds). For low-temperature processes like TIG welding, a medium with lower quench severity is suitable to ensure controlled cooling.