Steel O7 HT-205
Heat-treated state
AISI/SAE O7 · UNS T31507
HT-205 = hardened & tempered 205 °C
General-purpose hardened condition for blanking/trimming dies balancing edge retention with slightly better toughness.
Values for the HT-205 condition
Other O7 tempers and conditions
O7 is listed in 6 conditions; see the grade overview at O7.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard as-supplied stock condition for machining tools and dies before hardening. | 400 | 690 | 24 | 202 HB | — |
Cold drawn / precision ground annealed bar | Decarb-free ground stock for drill rod / tool blanks needing close size before hardening. | 520 | 760 | 15 | 17 HRC | 3 % IACS |
Hardened & tempered 260 °C | Higher-temper condition when moderate impact loading or thicker sections demand more toughness. | 1,800 | 2,050 | 3 | 58 HRC | — |
HT-205This page Hardened & tempered 205 °C | General-purpose hardened condition for blanking/trimming dies balancing edge retention with slightly better toughness. | 1,950 | 2,250 | 1.5 | 62 HRC | — |
Hardened & tempered 175 °C | Maximum hardness and wear resistance for cutting edges, taps, reamers and paper/plastic knives. | 2,050 | 2,400 | 1 | 64 HRC | 31 W/m·K |
Water/brine quenched & tempered | Use when O7 is deliberately water-hardened for a very hard shallow case over a tougher unhardened core (thin edge tools, punches). | 2,100 | 2,400 | 1 | 65 HRC | 2.5 % IACS |
What is O7 HT-205?
O7 HT-205 is O7 heat treated to HT-205 — general-purpose hardened condition for blanking/trimming dies balancing edge retention with slightly better toughness. O7 HT-205 has a yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,250 MPa (326 ksi) — stronger than 100% of steel grades. Elongation at break is 1.5% and the elastic modulus is 205 GPa (29.7 Msi). O7 HT-205 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,400°C (2,552 °F). ANN is the default condition FabDigit quotes; HT-205 is available on request or by drawing note.
Advantages
- High strength — 1,950 MPa (283 ksi), better than 100% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to machine — 8/100, worse than 100% of steel grades
- Limited ductility — 1.5%, worse than 99% of steel grades
- Limited service temperature — 190°C (374 °F), worse than 98% of steel grades
- Low electrical conductivity — 3 % IACS, worse than 91% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
O7 HT-205 properties
Typical room-temperature values for O7 HT-205; 12 are specific to this condition. Other listed values are O7 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
O7 HT-205 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
O7 HT-205 has a yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,250 MPa (326 ksi) — stronger than 100% of steel grades. Elongation at break is 1.5% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
O7 HT-205 is rated for continuous service to 190°C (374 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
O7 HT-205 conducts electricity at 3 % IACS, worse than 91% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of O7 HT-205 takes about 33 MJ of energy and emits 2.4 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 30%.
Manufacturability8
O7 HT-205's machinability is not recommended (8/100, worse than 100% of steel grades); weldability poor (15/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with O7 HT-205
Is O7 easy to machine?
Machine only in the spheroidize-annealed state (≈200 HB) with rigid setups and carbide or cobalt HSS; the W/V carbides are abrasive, so use moderate speeds, generous feed and flood coolant, and allow grinding stock for post-hardening finishing.
Can O7 be welded?
Essentially not a weldable grade — repair welding needs 300–400 °C preheat, matching high-carbon filler, slow cooling and immediate re-temper, otherwise quench cracking is likely.
Can O7 be formed, bent or molded?
Hot work at 900–1050 °C with slow cooling and full anneal (≈760–790 °C, slow furnace cool) afterwards; cold forming is limited to gentle bending of annealed thin sections.
What surface finishes work on O7?
Takes a fine polish and holds a keen edge at 62–64 HRC; protect with oil, black oxide, phosphate or PVD/TiN coating (deposition below the tempering temperature) since bare O7 rusts readily.
O7 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 |
|---|---|---|
| Chigh carbon for carbide volume | 1.1 – 1.3 | 1.2 |
| Mn | 0.1 – 1 | 0.4 |
| Si | 0.1 – 0.6 | 0.3 |
| Cr | 0.35 – 0.85 | 0.6 |
| Wforms wear-resistant tungsten carbides | 1 – 2 | 1.5 |
| Vgrain refinement, optional | 0 – 0.4 | 0.2 |
| Mo | 0 – 0.3 | 0.1 |
| Niresidual | 0 – 0.3 | — |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
O7 HT-205 — frequently asked
What is O7 HT-205 used for?
O7 HT-205 is typically used for cutting tools, forming dies and reamers. In short: most wear-resistant O grade; keen-edge tool steel; tungsten-alloyed oil-hardening.
What is the yield strength of O7 HT-205?
O7 HT-205 has a typical yield strength of 1,950 MPa (283 ksi) and a tensile strength of 2,250 MPa (326 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is O7 HT-205 easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). Machine only in the spheroidize-annealed state (≈200 HB) with rigid setups and carbide or cobalt HSS; the W/V carbides are abrasive, so use moderate speeds, generous feed and flood coolant, and allow grinding stock for post-hardening finishing.
Can O7 HT-205 be welded?
Not readily — weldability is rated poor (15/100). Essentially not a weldable grade — repair welding needs 300–400 °C preheat, matching high-carbon filler, slow cooling and immediate re-temper, otherwise quench cracking is likely.
What surface finishes work on O7 HT-205?
Takes a fine polish and holds a keen edge at 62–64 HRC; protect with oil, black oxide, phosphate or PVD/TiN coating (deposition below the tempering temperature) since bare O7 rusts readily.
Can O7 HT-205 be formed, bent or molded?
Hot work at 900–1050 °C with slow cooling and full anneal (≈760–790 °C, slow furnace cool) afterwards; cold forming is limited to gentle bending of annealed thin sections.
What is the maximum service temperature of O7 HT-205?
O7 HT-205 is rated for continuous use to about 190°C (374 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between O7-ANN and O7 WQ-HT?
ANN is the default condition — standard as-supplied stock condition for machining tools and dies before hardening. WQ-HT: use when O7 is deliberately water-hardened for a very hard shallow case over a tougher unhardened core (thin edge tools, punches). Yield strength is 400 MPa in ANN versus 2,100 MPa in WQ-HT.
Sources
- ASTM A681 — Standard Specification for Tool Steels Alloy — ASTM International (2022)
- SAE J437/J438 — Tool and Die Steels — SAE International (2015)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (tool steel section) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- GB/T 1299 (comparable W-Cr cold-work grades) — SAC (2014)
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.