EN8D
EN8D Bright Bar
EN8 held to tighter limits — for parts where batch-to-batch variation costs money.
Also known as 080A42 · AISI 1042
Overview
What EN8D is, and where it belongs
EN8D is not a different steel from EN8. It is the same medium carbon steel supplied to a tighter specification: narrower carbon and manganese bands, and phosphorus and sulphur each capped at 0.035% instead of 0.050%.
That sounds like a small change on paper. On a heat treatment line it is not. A narrower carbon band means a narrower spread of as-quenched hardness, so a batch of parts comes out of the furnace within a tighter hardness range and the tempering cycle does not need re-proving for each new lot of material.
Lower phosphorus and sulphur also mean cleaner steel with fewer inclusions, which shows up as better transverse ductility and better fatigue life. For a rotating shaft under reversing load, that is not a cosmetic difference — it is service life.
Choose EN8D over EN8 when parts are heat treated to a specified hardness, when the component is fatigue loaded, or when a customer audit expects controlled incoming material. Choose plain EN8 when the part is used as-drawn and cost is the priority.
Chemistry
Chemical composition
As per BS 970 Part 1 : 080A42, certified per mill test certificate. Values are percentage by weight.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | 0.410 | 0.450 |
| Silicon | Si | 0.050 | 0.350 |
| Manganese | Mn | 0.700 | 0.900 |
| Phosphorus | P | — | 0.040 |
| Sulphur | S | — | 0.040 |
A dash in the minimum column means only an upper limit applies to that element.
Properties
Mechanical properties
Typical values in the Cold Drawn condition. Certified values for your consignment appear on the test certificate.
- Tensile Strength
- 620 – 780 MPa
- Yield Strength
- 470 – 550 MPa
- Elongation (A5)
- 10 – 16%
- Hardness
- 180 – 235 HB
- Impact (Izod)
- 30 J typical
Availability
Sizes and tolerances
We draw EN8D across the range below. Exact availability for a given size is confirmed on enquiry.
Round bar
6 – 65 mm
Nominal diameter
Hex bar
7 – 46 mm
Across flats (AF)
Tolerance bands
All bands are ISO 286 ‘h’ — the bar is never above nominal size. See exact values for your size.
Where it is used
Typical applications
- Hardened and tempered shafts
- Hydraulic piston rods and cylinders
- Automotive linkages and pins
- Fatigue loaded rotating components
- Precision machine spindles
Application guides
Cross reference
International equivalents
Nearest designations under other standards. Equivalents are close but rarely identical — check the specific requirement that matters for your part.
Full equivalents chart| Standard | Designation |
|---|---|
| BS (UK) | 080A42 / EN8D |
| AISI / SAE (USA) | 1042 |
| DIN (Germany) | C45 / 1.0503 (nearest) |
| JIS (Japan) | S43C |
| IS (India) | 40C8 / 45C8 |
Processing
Heat treatment guidelines
Indicative parameters. Actual cycles depend on section size, furnace and the properties your drawing calls for.
- 01Normalising830 – 860 °C, cool in still air
- 02Hardening820 – 860 °C, quench in oil
- 03Tempering550 – 660 °C, air cool
- 04Stress relieving550 – 650 °C after heavy machining, to control distortion
Index relative to AISI 1212 = 100. Higher is faster to machine.
Machines like EN8 — slightly lower sulphur means marginally longer chips. The tighter chemistry does not make it easier to cut; it makes the finished part more consistent. For machinability with medium carbon strength, specify EN8M.
Weldability: Fair
Related grades
Chemical composition and mechanical properties shown are as per the applicable standard and are indicative. Actual values for your consignment are certified in the Mill Test Certificate supplied with each dispatch. Available sizes and tolerances are confirmed at the time of enquiry.
Need EN8D?
Send us the size and quantity — Round 6–65 mm · Hex 7–46 mm. We will confirm availability and come back with a price.