31CrMoV9 vs 31CrMo12: Both nitriding steels — 31CrMo12 harder case, 31CrMoV9 tougher core
31CrMoV9 vs 31CrMo12
Side-by-side chemical composition and mechanical property comparison.
Overview
31CrMoV9
1.8519
THE standard nitriding steel — Cr-Mo-V combination optimized for gas nitriding. Vanadium refines grain and forms hard VN nitrides (surface >750 HV). Better core toughness than 31CrMo12 at similar strength. THE default choice when "nitriding steel" is specified without further detail. Used for crankshafts, gears, spindles, extrusion screws, and precision machine components.
31CrMo12
1.8515
Deep nitriding steel with 3% Cr — the highest Cr content in the EN 10085 nitriding series. Produces the deepest and hardest nitrided case (surface hardness >900 HV, case depth >0.5mm). Core strength 800-1000 MPa QT. Used where maximum surface hardness and wear resistance with a tough core is needed: large gears, cylinder liners, spindles, precision measuring tools, and heavy-duty sliding components.
| 31CrMoV9 | 31CrMo12 | |
|---|---|---|
| Material Number | 1.8519 | 1.8515 |
| Category | Alloy Steel | Alloy Steel |
| Standard | EN 10085 | EN 10085 |
Chemical composition (wt%)
| Element | 31CrMoV9 | 31CrMo12 | Overlap |
|---|---|---|---|
| C | 0.27–0.34% | 0.28–0.35% | Partial |
| Si | 0–0.4% | 0–0.4% | OK |
| Mn | 0.4–0.7% | 0.4–0.7% | OK |
| P | 0–0.025% | 0–0.025% | OK |
Mechanical properties
| Property | 31CrMoV9 | 31CrMo12 | Unit |
|---|---|---|---|
| tensile_strength | 800–1000 | 800–1000 | MPa |
| yield_strength | 600–750 | 600–750 | MPa |
| elongation | 12–16 | 12–16 | % |
Compatibility Assessment
31CrMo12 has 3% Cr giving the hardest nitrided surface (>900 HV) and deepest case. 31CrMoV9 has 2.5% Cr + V giving slightly softer case (~750 HV) but better core toughness and grain refinement. Choose 31CrMo12 for max surface hardness; 31CrMoV9 as the default all-rounder.
Frequently Asked Questions
Is 31CrMoV9 the same as 31CrMo12?
31CrMoV9 and 31CrMo12 have a 80% composition overlap. Both nitriding steels — 31CrMo12 harder case, 31CrMoV9 tougher core
Can I replace 31CrMoV9 with 31CrMo12?
In many cases, yes. The compositions overlap significantly (80%). However, always verify mechanical property requirements and heat treatment compatibility for your specific application.
What is the difference between 31CrMoV9 and 31CrMo12?
The main differences are in the following elements: C, Cr, Mo. 31CrMoV9 is a Alloy Steel grade, while 31CrMo12 is a Alloy Steel grade.
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Data provided for reference only. Always verify against the applicable specification for critical applications.
All data is for reference only. Equivalents indicate similarity, not identity. Always verify against the applicable specification for safety-critical applications. materialref.com accepts no liability for decisions based on this data.