Steel 15CrMo4 CARB
Heat-treated state
EN 15CrMo4
CARB = carburized, direct/re-hardened and low-temperature tempered
The in-service condition: 58–62 HRC wear-resistant case over a tough tempered-martensite core for gears and bearing rings.
Values for the CARB condition
Other 15CrMo4 tempers and conditions
15CrMo4 is listed in 9 conditions; see the grade overview at 15CrMo4.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Best condition for cold extrusion, cold heading and deep upsetting — softest, most ductile microstructure. | 320 | 500 | 26 | 155 HB | 7.8 % IACS |
Treated for high shearability | Use for cold-shear billet cut-off in forging/cold-heading lines; hardness deliberately capped for clean shear faces. | 340 | 540 | 23 | 160 HB | 7.8 % IACS |
+ADefault Annealed | Standard stock condition for bar and tube: lowest hardness for machining before carburizing. | 350 | 560 | 22 | 170 HB | — |
Supplied with specified hardenability | Order this when case/core depth must be predictable — the heat is certified to a Jominy hardenability band (15CrMo4H). | 360 | 580 | 21 | 40 HRC | 7.8 % IACS |
Treated to ferrite–pearlite structure with specified hardness range | Choose when a uniform ferrite/pearlite microstructure and consistent hardness are needed for stable high-volume machining. | 370 | 590 | 20 | 165 HB | 7.8 % IACS |
Normalized | Grain-refined condition used after hot forging and before carburizing to reduce distortion. | 400 | 620 | 20 | 185 HB | 7.8 % IACS |
Heat treated to a specified hardness range | Pick when incoming bar hardness must sit in a narrow band for automatic machining or cold forming lines. | 420 | 640 | 18 | 13 HRC | 7.8 % IACS |
Cold drawn | Cold-drawn bright bar for close tolerance and good surface directly from stock. | 560 | 700 | 12 | 17 HRC | 7.8 % IACS |
CARBThis page Carburized, direct/re-hardened and low-temperature tempered | The in-service condition: 58–62 HRC wear-resistant case over a tough tempered-martensite core for gears and bearing rings. | 700 | 1,000 | 10 | 60 HRC | — |
What is 15CrMo4 CARB?
15CrMo4 CARB is 15CrMo4 heat treated to CARB — the in-service condition: 58–62 HRC wear-resistant case over a tough tempered-martensite core for gears and bearing rings. 15CrMo4 CARB has a yield strength of 700 MPa (102 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 81% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi). 15CrMo4 CARB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). +A is the default condition FabDigit quotes; CARB is available on request or by drawing note.
Advantages
- High strength — 700 MPa (102 ksi), better than 81% of steel grades
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Limited ductility — 10%, worse than 91% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
15CrMo4 CARB properties
Typical room-temperature values for 15CrMo4 CARB; 16 are specific to this condition. Other listed values are 15CrMo4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
15CrMo4 CARB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
15CrMo4 CARB has a yield strength of 700 MPa (102 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 81% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
15CrMo4 CARB is rated for continuous service to 180°C (356 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
15CrMo4 CARB conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 15CrMo4 CARB takes about 31 MJ of energy and emits 2.3 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 25%.
Manufacturability7
15CrMo4 CARB's machinability is not recommended (12/100, worse than 99% of steel grades); weldability poor (20/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 15CrMo4 CARB
Is 15CrMo4 easy to machine?
Machine fully in the +A/+AC/+TH condition with carbide at ~150–220 m/min; after carburizing only grinding or hard turning with CBN is practical.
Can 15CrMo4 be welded?
Weldable before carburizing with low-hydrogen consumables, 150–250 °C preheat and post-weld stress relief; carburized surfaces should not be welded.
Can 15CrMo4 be formed, bent or molded?
Cold heading and extrusion are done in the spheroidized +AC state; hot forge 1100–850 °C then normalize to refine grain before case hardening.
What surface finishes work on 15CrMo4?
No anodizing — use case hardening plus grinding/honing, and phosphate, black oxide, zinc or nickel plating (with bake-out) for corrosion protection.
15CrMo4 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Ccase-hardening carbon level | 0.13 – 0.18 | 0.15 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| Slower max (≤0.015) for bearing-quality | ≤ 0.04 | — |
| Cr | 0.8 – 1.15 | 1 |
| Mo | 0.15 – 0.25 | 0.2 |
| Fe | balance | — |
15CrMo4 CARB — frequently asked
What is 15CrMo4 CARB used for?
15CrMo4 CARB is typically used for carburized bearing rings, gears, camshafts, pins and case-hardened shafts. In short: bearing-grade case-hardening steel; hard case, tough core; machine soft, harden after.
What is the yield strength of 15CrMo4 CARB?
15CrMo4 CARB has a typical yield strength of 700 MPa (102 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 81% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 15CrMo4 CARB easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% of steel grades). Machine fully in the +A/+AC/+TH condition with carbide at ~150–220 m/min; after carburizing only grinding or hard turning with CBN is practical.
Can 15CrMo4 CARB be welded?
Not readily — weldability is rated poor (20/100). Weldable before carburizing with low-hydrogen consumables, 150–250 °C preheat and post-weld stress relief; carburized surfaces should not be welded.
What surface finishes work on 15CrMo4 CARB?
No anodizing — use case hardening plus grinding/honing, and phosphate, black oxide, zinc or nickel plating (with bake-out) for corrosion protection.
Can 15CrMo4 CARB be formed, bent or molded?
Cold heading and extrusion are done in the spheroidized +AC state; hot forge 1100–850 °C then normalize to refine grain before case hardening.
What is the maximum service temperature of 15CrMo4 CARB?
15CrMo4 CARB is rated for continuous use to about 180°C (356 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 15CrMo4 +A and 15CrMo4 CARB?
+A is the default condition — standard stock condition for bar and tube: lowest hardness for machining before carburizing. CARB: the in-service condition: 58–62 HRC wear-resistant case over a tough tempered-martensite core for gears and bearing rings. Yield strength is 350 MPa in +A versus 700 MPa in CARB.
Sources
- EN 10084 — Case hardening steels: technical delivery conditions — CEN (2008)
- ISO 683-17 — Heat-treatable steels, alloy steels: ball and roller bearing steels — ISO (2014)
- SAE J404 — Chemical compositions of SAE alloy steels (4118) — SAE International (2009)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carburizing of Cr-Mo case-hardening steels) — ASM International (1991)
- Case-hardening steel bar datasheets (Böhler / Ovako / Dörrenberg equivalent grades) — various producers (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.