Steel S25C CARB
Heat-treated state
JIS S25C
CARB = carburized & hardened
Choose when a wear-resistant hard skin over a tough, moderately strong core is required (pins, small gears, bushings).
Values for the CARB condition
Other S25C tempers and conditions
S25C is listed in 6 conditions; see the grade overview at S25C.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — choose for deep cold forming, heavy upsetting or when maximum dimensional stability before final heat treatment is needed. | 240 | 420 | 33 | 116 HB | — |
Hot rolled | Cheapest stock condition for weldments and non-critical machined parts where scale and looser tolerances are acceptable. | 250 | 440 | 28 | 121 HB | — |
NDefault Normalized | Standard JIS G4051 delivery condition — uniform fine grain, predictable strength/toughness for shafts and general machined parts. | 290 | 470 | 30 | 131 HB | — |
Quenched and tempered | Use on small sections (<25 mm) where somewhat higher yield with good toughness is wanted; poor hardenability limits benefit in thick parts. | 380 | 560 | 25 | 170 HB | — |
CARBThis page Carburized & hardened | Choose when a wear-resistant hard skin over a tough, moderately strong core is required (pins, small gears, bushings). | 400 | 600 | 18 | 58 HRC | 10.2 % IACS |
Cold drawn | Pick for close tolerance, bright surface and higher yield strength on turned/CNC parts; residual stress can cause distortion on unbalanced machining. | 420 | 510 | 15 | 148 HB | — |
What is S25C CARB?
S25C CARB is S25C heat treated to CARB — choose when a wear-resistant hard skin over a tough, moderately strong core is required (pins, small gears, bushings). S25C CARB has a yield strength of 400 MPa (58 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 60% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi). S25C CARB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). N is the default condition FabDigit quotes; CARB is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High electrical conductivity — 10.2 % IACS, better than 87% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
Limitations
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 86% of steel grades
S25C CARB properties
Typical room-temperature values for S25C CARB; 23 are specific to this condition. Other listed values are S25C reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
S25C CARB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
S25C CARB has a yield strength of 400 MPa (58 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 60% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
S25C CARB is rated for continuous service to 180°C (356 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
S25C CARB conducts electricity at 10.2 % IACS, better than 87% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of S25C CARB takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
S25C CARB's machinability is poor (20/100, worse than 97% of steel grades); weldability poor (30/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with S25C CARB
Is S25C easy to machine?
Machines easily at ~65 % of 1212; normalized or cold-drawn stock cuts cleaner than annealed, which tends to smear — use positive-rake carbide and adequate feed to avoid built-up edge.
Can S25C be welded?
Readily weldable by SMAW/GMAW/GTAW with E70/ER70S-6 filler; preheat 100–150 °C only for sections above ~25 mm or restrained joints, and re-normalize if carburized parts are welded.
Can S25C be formed, bent or molded?
Good cold bending and upsetting in annealed/normalized condition (bend radius ≈ 1–1.5 t); hot forming 1100–1250 °C followed by normalizing restores grain size.
What surface finishes work on S25C?
No natural corrosion protection — specify zinc/zinc-nickel plating, manganese phosphate, black oxide plus oil, or paint; surfaces take a good ground/turned finish but only a moderate mirror polish.
S25C 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 |
|---|---|---|
| CJIS G4051 S25C | 0.22 – 0.28 | 0.25 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| P | ≤ 0.03 | — |
| S | ≤ 0.04 | — |
| Curesidual, max | ≤ 0.3 | — |
| Niresidual, max | ≤ 0.2 | — |
| Crresidual, max; Ni+Cr ≤ 0.35 | ≤ 0.2 | — |
| Fe | balance | — |
S25C CARB — frequently asked
What is S25C CARB used for?
S25C CARB is typically used for shafts, gears, fasteners and machine parts. In short: weldable medium-carbon steel; balanced strength and forming; low-cost structural bar stock.
What is the yield strength of S25C CARB?
S25C CARB has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is S25C CARB easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Machines easily at ~65 % of 1212; normalized or cold-drawn stock cuts cleaner than annealed, which tends to smear — use positive-rake carbide and adequate feed to avoid built-up edge.
Can S25C CARB be welded?
Not readily — weldability is rated poor (30/100). Readily weldable by SMAW/GMAW/GTAW with E70/ER70S-6 filler; preheat 100–150 °C only for sections above ~25 mm or restrained joints, and re-normalize if carburized parts are welded.
What surface finishes work on S25C CARB?
No natural corrosion protection — specify zinc/zinc-nickel plating, manganese phosphate, black oxide plus oil, or paint; surfaces take a good ground/turned finish but only a moderate mirror polish.
Can S25C CARB be formed, bent or molded?
Good cold bending and upsetting in annealed/normalized condition (bend radius ≈ 1–1.5 t); hot forming 1100–1250 °C followed by normalizing restores grain size.
What is the maximum service temperature of S25C CARB?
S25C 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 S25C-N and S25C-CD?
N is the default condition — standard JIS G4051 delivery condition — uniform fine grain, predictable strength/toughness for shafts and general machined parts. CD: pick for close tolerance, bright surface and higher yield strength on turned/CNC parts; residual stress can cause distortion on unbalanced machining. Yield strength is 290 MPa in N versus 420 MPa in CD.
Sources
- JIS G4051 — Carbon steels for machine structural use — JSA (2016)
- GB/T 699 — Quality carbon structural steels (25 ) — SAC (2015)
- SAE J403 / ASTM A29 — Carbon steel bars (1025) — SAE / ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook (machinability ratings, heat-treat data) — Industrial Press (2020)
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.