ISO P — Steel · P30
P30 — Case-hardened steel
Hardness range: 58–62 HRC surface. Part of the ISO P — Steels group. Steel is the most widely machined material. Carbon and alloy steels are the target material for the majority of turning and milling operations. Hardness ranges from ~125 HB (low-carbon) to 350 HB (high-strength structural). CVD-coated carbide (TiCN/Al₂O₃ multilayer) dominates. Positive geometry for finishing, negative for heavy roughing.
Material profile — P30
- ISO designation
- P30 (ISO P — Steels)
- Material
- Case-hardened steel
- Hardness
- 58–62 HRC surface
- ISO group colour
- Steel
Tooling guidance — P-group
- Group summary
- CVD-coated carbide at Vc 200–400 m/min. Positive geometry for finishing, negative for roughing.
Insert selection for case-hardened steel — starting point
- ISO application class
- P / H. The first question is whether you cut before carburizing (soft core, normal P-class) or after (hard 58–62 HRC case, effectively hard turning). Match the ISO P class across brands rather than the brand name (Sandvik, Kennametal, Iscar, Walter, Seco and Mitsubishi each publish one), then confirm the exact grade for your condition.
- Grade & coating
- Soft pre-carburized state: P-class CVD carbide. Hardened case (58–62 HRC): CBN or hard ceramic, like hard turning, with a honed/chamfered edge.
- Geometry
- For the hardened case, negative geometry with a chamfer plus hone and a rigid setup; for the soft state, normal turning geometry.
- Starting parameters
- Soft state Vc ≈ 180–280 m/min; hardened case with CBN Vc ≈ 100–180 m/min, fn ≈ 0.05–0.15 mm/rev. Confirm in the advisor or on a sample part.
Selection table: case-hardened steel
| Operation | Geometry | ISO class | Coating family | Coolant | First check |
|---|---|---|---|---|---|
| Roughing | Soft pre-carburized state: normal turning geometry | P (soft state); H (hardened case) | Soft state: P-class CVD carbide | Per process | Confirm before or after carburizing first; it changes everything |
| Finishing | Hardened case: negative with chamfer plus hone, rigid setup | H (hardened case) | CBN or hard ceramic on the 58–62 HRC case | Run as hard turning | White layer on the case: keep the edge fresh, speed in band |
| Interrupted cut | Chamfered honed edge, rigid setup | H (hardened case) | CBN with a robust grade | Run as hard turning | Case-to-core transition shock: favour edge security |
| Low rigidity / thin wall | Rigid setup, negative geometry with chamfer plus hone for the case | P (soft state); H (hardened case) | As state of the part | Per state | Edge chipping cutting the hard case |
case-hardened steel: what goes wrong, and what to check first
- Edge chipping cutting the hard case
- The hard 58–62 HRC case behaves like hard turning; use CBN with a chamfered honed edge and a rigid setup.
- Case-to-core transition shock
- Cutting through the hard case into soft core is an interruption in hardness; favour edge security.
- White layer on the case
- Keep the edge fresh and the speed in band.
- Wrong grade for the state
- Confirm before or after carburizing first; it changes everything.
Reference data
Frequently asked questions
What insert for case-hardened steel?
It depends on the state: P-class carbide before carburizing, CBN or hard ceramic for the hardened 58–62 HRC case. Match the ISO class and confirm in the advisor.
Is machining case-hardened steel hard turning?
Cutting the hardened case (58–62 HRC) is effectively hard turning and needs CBN; the soft pre-carburized state is normal P-class turning.
Should I machine before or after carburizing?
Most stock removal is done soft, before carburizing; only finishing is done on the hardened case with CBN.
Why does my edge chip on case-hardened parts?
The hard case and the case-to-core hardness step chip a fragile edge; use CBN with a chamfered honed edge and a rigid setup.
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Grade designations in this group
Each page cross-references the EN, Werkstoffnummer, AISI/UNS and JIS designations for one material, with the ISO machining group it falls in.
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