Steel EN8 · supply condition · default condition
Steel EN8-HR
Properties of the HR condition, compared with the other EN8 tempers.
Most stocked form: hot-rolled black bar/plate for general machined parts that will be heat treated or used as-is.
What is EN8-HR?
EN8-HR is EN8 supplied in the HR condition — most stocked form: hot-rolled black bar/plate for general machined parts that will be heat treated or used as-is. EN8-HR has a yield strength of 310 MPa (45 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 83% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi). EN8-HR 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).
Advantages
- Conducts heat well — 50 W/m·K (28.9 BTU/hr·ft·°F), better than 88% of steel grades
- Easy to machine — 60/100, better than 83% of steel grades
- High electrical conductivity — 10 % IACS, better than 82% of steel grades
Limitations
- Low strength — 310 MPa (45 ksi), worse than 83% of steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 83% of steel grades
EN8-HR properties
Typical room-temperature values for EN8-HR — 13 properties are specific to this condition; the rest are grade-level values shared by every EN8 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
EN8-HR 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
EN8-HR has a yield strength of 310 MPa (45 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 83% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
EN8-HR is rated for continuous service to 400°C (752 °F). It conducts heat at 50 W/m·K (28.9 BTU/hr·ft·°F), better than 88% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
EN8-HR conducts electricity at 10 % IACS, better than 82% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of EN8-HR takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
EN8-HR's machinability is good (60/100, better than 83% of steel grades); weldability fair (45/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other EN8 tempers and conditions
EN8 is also supplied in 5 other conditions. The full side-by-side table is on the EN8 overview.
- HRDefaultMost stocked form: hot-rolled black bar/plate for general machined parts that will be heat treated or used as-is.310 MPa yield · 179 HB
- Q&TChoose for loaded shafts, gears, keys and studs needing higher yield and fatigue strength; hardenable depth limited to roughly 30–60 mm diameter.620 MPa yield · 25 HRC
- CDBright, size-accurate bar for shafts and turned parts where no further heat treatment is planned; highest as-supplied yield of the unhardened conditions.540 MPa yield · 201 HB
- CRChoose for thin strip/sheet with good surface and closer thickness tolerance; strength raised, ductility reduced.470 MPa yield · 190 HB
- NormalizedUse for uniform fine-grained structure and predictable machining/strength in larger sections, typically before final machining or induction hardening.370 MPa yield · 185 HB
- AnnealedPick when maximum softness/ductility is needed for cold forming, deep machining or stress relief before hardening.300 MPa yield · 155 HB
Working with EN8-HR
Is EN8 easy to machine?
Machines readily in HR/normalized condition with carbide or HSS (≈60 % of AISI 1212); rough-machine before hardening and expect ~50 % rating and shorter tool life above 250 HB.
Can EN8 be welded?
Weldable with low-hydrogen electrodes but 0.4 % C demands 150–260 °C preheat, controlled interpass and post-weld stress relief/temper to avoid hard martensitic HAZ cracking.
Can EN8 be formed, bent or molded?
Hot forge 1050–1200 °C then normalize; cold bending is limited — use annealed stock and generous bend radii (>3 t).
What surface finishes work on EN8?
No anodizing; protect by zinc/nickel/hard-chrome plating, phosphating, black oxide, paint or oiling — bare bar rusts quickly in humid storage.
EN8 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 |
|---|---|---|
| CBS 970 080M40 / EN8 | 0.36 – 0.44 | 0.4 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn | 0.6 – 1 | 0.8 |
| Smax; EN8M free-cutting version 0.20–0.30 S | ≤ 0.05 | 0.03 |
| P | ≤ 0.05 | 0.03 |
| Fe | balance | — |
EN8-HR — frequently asked
What is EN8-HR used for?
EN8-HR is typically used for crankshafts, shafts and industrial bolts. In short: workhorse English carbon bar.
What is the yield strength of EN8-HR?
EN8-HR has a typical yield strength of 310 MPa (45 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 83% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is EN8-HR easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines readily in HR/normalized condition with carbide or HSS (≈60 % of AISI 1212); rough-machine before hardening and expect ~50 % rating and shorter tool life above 250 HB.
Can EN8-HR be welded?
With care — weldability is rated fair (45/100). Weldable with low-hydrogen electrodes but 0.4 % C demands 150–260 °C preheat, controlled interpass and post-weld stress relief/temper to avoid hard martensitic HAZ cracking.
What surface finishes work on EN8-HR?
No anodizing; protect by zinc/nickel/hard-chrome plating, phosphating, black oxide, paint or oiling — bare bar rusts quickly in humid storage.
Can EN8-HR be formed, bent or molded?
Hot forge 1050–1200 °C then normalize; cold bending is limited — use annealed stock and generous bend radii (>3 t).
What is the maximum service temperature of EN8-HR?
EN8-HR is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between EN8-HR and EN8-CD?
HR is the default condition — most stocked form: hot-rolled black bar/plate for general machined parts that will be heat treated or used as-is. CD: bright, size-accurate bar for shafts and turned parts where no further heat treatment is planned; highest as-supplied yield of the unhardened conditions. Yield strength is 310 MPa in HR versus 540 MPa in CD.
Can FabDigit make parts in EN8-HR?
Yes — EN8-HR is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- BS 970 Part 1 / Part 3 — 080M40 (EN8) wrought steels — BSI (1991)
- GB/T 699 — Quality carbon structural steels (45 ) — SAC (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carbon steel hardenability/tempering) — ASM International (1991)
- SAE J403 / ASTM A576 — AISI 1040/1045 carbon steel bars — SAE / ASTM (2017)
- Mysteel / 1688 — Mysteel (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.