Steel C15E +SR (Stress relieved)
Heat-treated state
EN C15E
Use when drawn bar must stay straight after heavy asymmetric machining or subsequent heat treatment.
Values for the +SR condition
Other C15E tempers and conditions
C15E is listed in 8 conditions; see the grade overview at C15E.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot rolled | Cheapest bar/plate condition for non-critical welded structures and parts that will be heat treated later. | 230 | 380 | 28 | 111 HB | — |
Annealed | Choose for maximum cold formability — deep drawing, cold heading, severe upsetting before carburizing. | 285 | 385 | 37 | 111 HB | — |
+NDefault Normalized | Standard stocked bar condition: uniform fine grain, good toughness and machining behaviour before carburizing or welding. | 325 | 425 | 35 | 121 HB | — |
+SRThis page Stress relieved | Use when drawn bar must stay straight after heavy asymmetric machining or subsequent heat treatment. | 330 | 410 | 21 | 120 HB | 10.8 % IACS |
Cold rolled sheet/strip | Sheet-metal condition for stamped, bent and welded parts needing a smooth surface ready for plating or paint. | 350 | 450 | 20 | 130 HB | 10.7 % IACS |
Cold drawn | Pick for close tolerance, straight bright bar with higher yield strength and better chip control than hot rolled. | 355 | 420 | 18 | 126 HB | — |
Quenched and tempered | Only worthwhile on sections below ~16 mm where water quenching gives a partly martensitic, higher-strength core. | 420 | 650 | 17 | 20 HRC | — |
Carburized and hardened | The main reason to buy C15E: a hard 0.3–1.2 mm wear-resistant case (58–62 HRC) on a tough, still-ductile core. | 450 | 700 | 15 | 60 HRC | — |
What is C15E +SR?
C15E +SR is C15E heat treated to +SR — use when drawn bar must stay straight after heavy asymmetric machining or subsequent heat treatment. C15E +SR has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 410 MPa (59.5 ksi) — weaker than 78% of steel grades. Elongation at break is 21% and the elastic modulus is 205 GPa (29.7 Msi). C15E +SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,460°C (2,660 °F). +N is the default condition FabDigit quotes; +SR is available on request or by drawing note.
Advantages
- Readily welded — 93/100, better than 95% of steel grades
- High electrical conductivity — 10.8 % IACS, better than 94% of steel grades
- Conducts heat well — 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Low strength — 330 MPa (47.9 ksi), worse than 78% of steel grades
C15E +SR properties
Typical room-temperature values for C15E +SR; 22 are specific to this condition. Other listed values are C15E reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
C15E +SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,460°C (2,660 °F).
Mechanical16
C15E +SR has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 410 MPa (59.5 ksi) — weaker than 78% of steel grades. Elongation at break is 21% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
C15E +SR is rated for continuous service to 350°C (662 °F). It conducts heat at 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
C15E +SR conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of C15E +SR takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
C15E +SR's machinability is fair (50/100, worse than 53% of steel grades); weldability excellent (93/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C15E +SR
Is C15E easy to machine?
Soft and gummy — use sharp positive-rake tools, high speed, generous coolant and chip breakers; normalizing or cold drawing improves finish, and C15R (resulphurised) machines noticeably better.
Can C15E be welded?
Excellent weldability by MIG/TIG/MMA/spot with ER70S-type filler; CEV ≈ 0.25 so no preheat or PWHT is needed except on very thick sections, but carburized parts should not be welded.
Can C15E be formed, bent or molded?
Very good cold formability — deep drawing, bending to tight radii, cold heading and roll forming; hot forge at 1100–850 °C followed by normalizing.
What surface finishes work on C15E?
No corrosion resistance of its own: specify zinc/nickel plating, phosphate + oil, black oxide or paint; takes a fair polish but ferrite scratches easily.
C15E 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 |
|---|---|---|
| C | 0.12 – 0.17 | 0.15 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| P | ≤ 0.04 | — |
| SC15R variant is resulphurised 0.020–0.040 | ≤ 0.04 | — |
| Crresidual | ≤ 0.4 | — |
| Niresidual | ≤ 0.4 | — |
| Moresidual; Cr+Mo+Ni ≤ 0.63 | ≤ 0.1 | — |
| Fe | balance | — |
C15E +SR — frequently asked
What is C15E +SR used for?
C15E +SR is typically used for shafts, bolts, case-hardened components and general machine parts. In short: excellent weldability, CEV ≈ 0.25; clean-steel case-hardening base; very high cold formability.
What is the yield strength of C15E +SR?
C15E +SR has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 410 MPa (59.5 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is C15E +SR easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Soft and gummy — use sharp positive-rake tools, high speed, generous coolant and chip breakers; normalizing or cold drawing improves finish, and C15R (resulphurised) machines noticeably better.
Can C15E +SR be welded?
Yes — weldability is rated excellent (93/100). Excellent weldability by MIG/TIG/MMA/spot with ER70S-type filler; CEV ≈ 0.25 so no preheat or PWHT is needed except on very thick sections, but carburized parts should not be welded.
What surface finishes work on C15E +SR?
No corrosion resistance of its own: specify zinc/nickel plating, phosphate + oil, black oxide or paint; takes a fair polish but ferrite scratches easily.
Can C15E +SR be formed, bent or molded?
Very good cold formability — deep drawing, bending to tight radii, cold heading and roll forming; hot forge at 1100–850 °C followed by normalizing.
What is the maximum service temperature of C15E +SR?
C15E +SR is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C15E +N and C15E-CH?
+N is the default condition — standard stocked bar condition: uniform fine grain, good toughness and machining behaviour before carburizing or welding. CH: the main reason to buy C15E: a hard 0.3–1.2 mm wear-resistant case (58–62 HRC) on a tough, still-ductile core. Yield strength is 325 MPa in +N versus 450 MPa in CH.
Sources
- EN 10084 — Case hardening steels, technical delivery conditions — CEN (2008)
- EN 10083-2 — Steels for quenching and tempering: non-alloy steels — CEN (2006)
- JIS G 4051 — Carbon steels for machine structural use (S15C) — JSA (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (AISI 1015) — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carburizing) — ASM International (1991)
- Mysteel / 1688 (2025)
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.