Heat-extraction capacity of a quench, expressed as the Grossmann H value with still water set at 1.0. Still oil sits around 0.25 to 0.3, violently agitated oil reaches about 0.8 to 1.1, and still brine is near 2. Severity depends on the medium, its temperature and above all agitation. Matching severity to the steel's hardenability is the core quench decision: too mild leaves soft cores, too harsh cracks and warps parts.
Quench severity dropped when they swapped the pumps, and now the 4140 cores read 32 instead of 38.
Also heard as
- H value
- Grossmann number
- severity of quench
Related terms
Quenchant
The liquid or gas used to quench parts, chosen for its cooling speed and the distortion it produces.
Agitation
Forced movement of quenchant around parts by pumps, propellers or nozzles to speed up and even out cooling.
Hardenability
A steel's ability to form martensite to a given depth, set by its chemistry and grain size, not its hardness.
DI
Ideal critical diameter: the largest bar that would reach 50 percent martensite at its center in a perfect quench.