Jominy Hardenability
The end-quench test that measures how deeply a steel will harden, reported as hardness against distance from the quenched end of a standard bar.
Why it decides the grade
Hardenability is not hardness. Two steels can both reach 60 HRC at the surface, but only the one with sufficient alloy will still be hard 25 mm in. That is the whole reason EN19 and EN24 exist alongside EN8 — carbon sets maximum hardness, alloy content sets how far in you get it.
Reading a Jominy band
Grades are supplied to an H band (for example 20MnCr5H) guaranteeing hardness at set distances. Gear makers specify the band because consistent hardenability means consistent distortion in the furnace, which is what keeps post-carburising grinding stock predictable.
Related terms
Where this applies
Alloy Steel Bright Bars, Case Hardening & Bearing Steel Bars
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