Steel O1-SR (Stress relieved)
Heat-treated state
AISI/SAE O1 · UNS T31501 · EN 1.2510, 100MnCrW4 · JIS SKS3 · GB 9CrWMn
Use between roughing and hardening on long or asymmetric tools to minimise distortion.
Values for the SR condition
Other O1 tempers and conditions
O1 is listed in 7 conditions; see the grade overview at O1.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault soft, as-supplied bar/plate (≤ 212 HB) | Standard stock condition for machining, sawing and drilling before hardening. | 400 | 690 | 25 | 200 HB | — |
SRThis page Stress relieved | Use between roughing and hardening on long or asymmetric tools to minimise distortion. | 400 | 690 | 25 | 200 HB | 7 % IACS |
Cold Drawn / cold finished annealed bar | Cold-finished small-diameter bar for close-tolerance turned parts prior to hardening. | 560 | 780 | 14 | 225 HB | 7 % IACS |
Q&T, tempered ~400 °C | Toughest practical working hardness for heavily shock-loaded chisels, cold heading and forming tools. | 1,600 | 1,900 | 5 | 55 HRC | 6 % IACS |
Q&T, tempered ~300 °C | Balanced hardness/toughness for punches and shear blades that see impact loading. | 1,750 | 2,050 | 3 | 58 HRC | 6 % IACS |
oil quench + 180 °C temper, 60–62 HRC | Standard working condition for blanking dies, punches and gauges where maximum wear resistance is wanted. | 1,900 | 2,200 | 1 | 61 HRC | — |
Hardened & tempered 150–170 °C | Maximum hardness for knife blades, reamers, hand tools and gauges where toughness is secondary. | 2,050 | 2,400 | 0.5 | 63 HRC | — |
What is O1-SR?
O1-SR is O1 heat treated to SR — use between roughing and hardening on long or asymmetric tools to minimise distortion. O1-SR has a yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 60% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi). O1-SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F). Annealed is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 80/100, better than 97% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Poor heat conductor — 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades
O1-SR properties
Typical room-temperature values for O1-SR; 21 are specific to this condition. Other listed values are O1 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
O1-SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
O1-SR has a yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 60% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
O1-SR is rated for continuous service to 200°C (392 °F). It conducts heat at 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
O1-SR conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of O1-SR takes about 32 MJ of energy and emits 2.4 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 40%.
Manufacturability6
O1-SR's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (20/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with O1-SR
Is O1 easy to machine?
Machines and grinds well at 190–210 HB (≈42 % of 1212); after hardening only grinding, EDM or CBN work — rough machine soft, stress relieve, then finish.
Can O1 be welded?
Poor weldability; if repair welding is unavoidable preheat to 300–350 °C, use matching or low-hydrogen high-alloy filler, and temper immediately to avoid quench cracks.
Can O1 be formed, bent or molded?
Cold form only in the annealed state and with generous radii; hot work 900–1050 °C with slow furnace cooling, then spheroidize anneal at 760–790 °C. Harden 790–815 °C, oil quench, temper 150–400 °C; dimensional change is small, ~+0.05 % typical.
What surface finishes work on O1?
Takes a high polish and mirror finish when hardened; protect bare surfaces with oil, black oxide, phosphate or nitride/PVD coating since the steel has no corrosion resistance.
O1 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 |
|---|---|---|
| CASTM A681 O1 | 0.85 – 1 | 0.92 |
| Mn | 1 – 1.4 | 1.2 |
| Si | 0.1 – 0.5 | 0.3 |
| Cr | 0.4 – 0.6 | 0.5 |
| W | 0.4 – 0.6 | 0.5 |
| Voptional / max | ≤ 0.3 | 0.1 |
| Moresidual, not required | ≤ 0.3 | — |
| Niresidual | ≤ 0.3 | — |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
O1-SR — frequently asked
What is O1-SR used for?
O1-SR is typically used for blanking and trimming dies, hand and machine cutting tools, knife and shear blades, gauges and templates, cold forming tools and punches and die inserts. In short: classic oil-hardening tool.
What is the yield strength of O1-SR?
O1-SR has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is O1-SR easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machines and grinds well at 190–210 HB (≈42 % of 1212); after hardening only grinding, EDM or CBN work — rough machine soft, stress relieve, then finish.
Can O1-SR be welded?
Not readily — weldability is rated poor (20/100). Poor weldability; if repair welding is unavoidable preheat to 300–350 °C, use matching or low-hydrogen high-alloy filler, and temper immediately to avoid quench cracks.
What surface finishes work on O1-SR?
Takes a high polish and mirror finish when hardened; protect bare surfaces with oil, black oxide, phosphate or nitride/PVD coating since the steel has no corrosion resistance.
Can O1-SR be formed, bent or molded?
Cold form only in the annealed state and with generous radii; hot work 900–1050 °C with slow furnace cooling, then spheroidize anneal at 760–790 °C. Harden 790–815 °C, oil quench, temper 150–400 °C; dimensional change is small, ~+0.05 % typical.
What is the maximum service temperature of O1-SR?
O1-SR is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between O1 Annealed and O1-SR?
Annealed is the default condition — standard stock condition for machining, sawing and drilling before hardening. SR: use between roughing and hardening on long or asymmetric tools to minimise distortion. Yield strength is 400 MPa in Annealed versus 400 MPa in SR.
Can FabDigit make parts in O1-SR?
Yes — O1-SR is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A681 Standard Specification for Tool Steels, Alloy — ASTM International (2020)
- DIN EN ISO 4957 Tool steels (100MnCrW4 / 1.2510) — DIN/ISO (2018)
- GB/T 1299 (9CrWMn) — SAC (2014)
- ASM Handbook Vol.1: Properties and Selection — Tool Steels — ASM International (1990)
- Uddeholm Arne (AISI O1) datasheet — voestalpine Uddeholm (2023)
- Böhler K460 (1.2510) datasheet — voestalpine Böhler Edelstahl (2022)
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.