EN8D STEEL
EN8D steel bars
EN8D is a medium-carbon steel in the BS 970 family, supplied to tighter sulphur and phosphorus limits than plain EN8. At 0.40 to 0.45% carbon and 0.70 to 0.90% manganese it will normalise, or harden and temper, to a target hardness without anyone having to move up to an alloy grade.
It machines well, welds with reasonable care and takes heat treatment predictably, which is why it turns up on so many drawings for shafts, gears, axles and general machined components.
Most bar leaves the mill as rolled. If a drawing calls for a specific hardness or strength band, we can supply it hardened and tempered or annealed instead.
It is a plain carbon steel though, not an alloy one. Once the section gets thick, or the hardness target has to hold through the full section, SAE 4140 is the right specification. Our note on alloying elements covers what the alloying additions actually buy you.
Applications
Typical EN8D parts are shafts, axles, gears, spindles, studs, bolts, crane wheels, couplings, machine tool components and general engineering fabrications. It is also common forging stock for automotive and agricultural work.
The grade suits parts that need moderate strength and a predictable heat treatment response, on sections light enough that the hardness does not have to hold right through the core.
Sizes we offer in EN8D
- Rounds – 23.5mm to 80mm
- Bright Bars – 22mm to 63.5mm
Chemical composition
| Element | Percent by mass |
|---|---|
| Carbon (C) | 0.40 to 0.45 |
| Manganese (Mn) | 0.70 to 0.90 |
| Silicon (Si) | 0.10 to 0.40 |
| Sulphur (S), max | 0.040 |
| Phosphorus (P), max | 0.040 |
Sulphur and phosphorus held to 0.040% maximum each is what separates EN8D from plain EN8. Heat-wise figures for your consignment are on the Mill Test Certificate.
Mechanical properties
As rolled:
| Property | Value |
|---|---|
| Tensile strength (UTS) | 600 to 780 MPa (87,000 to 113,000 psi) |
| Yield strength (0.2% proof) | 355 MPa min (51,500 psi) |
| Elongation (on 5d) | 16% min |
| Reduction of area | 30% min |
| Brinell hardness | 179 to 229 HB |
After heat treatment:
| Condition | Tensile strength, MPa | Yield strength, MPa | Elongation, % | Hardness, HB |
|---|---|---|---|---|
| Normalised | 600 to 750 | 340 to 400 | 14 to 18 | 170 to 220 |
| Hardened and tempered | 700 to 850 | 600 to 700 | 12 to 16 | 205 to 255 |
These are typical values for guidance. What applies to your material is the test certificate issued against the heat number. Properties after heat treatment also depend on section size, since a plain carbon steel cannot hold the same hardness through a heavy section that it reaches at the surface.
Heat treatment
| Operation | Cycle |
|---|---|
| Normalising | 850 to 880 °C, air cool |
| Annealing (sub-critical) | 650 to 700 °C, slow furnace cool |
| Hardening | 830 to 860 °C, oil quench |
| Tempering | 550 to 660 °C, air cool |
| Stress relief | 550 to 650 °C, slow cool |
These are reference values. The cycle that applies depends on section thickness and on the hardness target written on the buyer’s drawing.
Tempering temperature sets the final hardness. Across the 550 to 660 °C range above, EN8D comes out between about 255 HB and 205 HB, the lower tempering temperatures giving the higher hardness. Above that band the drawing is calling for a surface condition: the grade flame or induction hardens to 50 to 55 HRC at the case, with the core left soft. Anything above roughly 35 HRC held right through the section belongs to an alloy steel.
We supply bar hardened and tempered or annealed when the drawing calls for it.
Forging
A large share of the EN8D we roll goes to forge shops making automotive, agricultural and general engineering components. The grade forges readily and normalises to a uniform structure afterwards, which is what most forging drawings ask for.
Typical practice is to forge between 1150 and 1250 °C and to finish above roughly 850 °C, then cool in still air. Working the bar below the finishing temperature risks cracking and leaves an uneven grain structure. Normalising after forging is the usual step once the finished part has to hold consistent mechanical properties.
Reduction ratio matters as much as temperature. Our reduction ratio chart gives the ratios across the billet and bar sizes we roll, and the forging page covers what we supply into forge shops and in what condition.
Machinability
EN8D machines predictably for a medium-carbon steel. On the standard comparison scale that rates free-cutting 1212 at 100%, the carbon grades bracketing it run from 64% at 1040 and 1042 down to 54% at 1050. EN8D falls in that band, nearer the 1040 end at the lower part of its carbon range.
Two things move that number. Normalising before machining gives a more uniform structure and cuts better than as-rolled bar. Machinability then drops as tempered hardness rises, so a part taken to the top of the hardness range will cost more in tool life and cycle time than the same part left soft.
On a component machined in volume with a modest strength requirement, a free-cutting grade such as En1a will cut considerably faster. Our full machinability comparison chart lists the rates for the common carbon, alloy, stainless and tool steels.
International equivalents
| Standard | Designation |
|---|---|
| BS 970 (current) | 080M40 / 080A42 |
| BS 970 (legacy) | EN8D |
| AISI / SAE | 1040 / 1043 / 1045 |
| DIN | C45 / Ck45 (1.0503 / 1.1191) |
| JIS | S45C |
| IS (India) | C45 / 45C8 |
| ISO | C45E / C45R |
These are close matches for enquiry purposes. Order to the standard printed on the drawing rather than to its equivalent. The section below takes the S45C and 1045 comparison further.
EN8D compared with EN8
EN8 and EN8D share the same base chemistry. The difference is control, not composition.
EN8D is supplied to tighter sulphur and phosphorus limits, 0.040% maximum each. Lower residuals mean fewer inclusions, and that shows up as more consistent mechanical properties across a heat and a more predictable response to hardening and tempering.
In practice, if the part is machined and used as rolled, plain EN8 will usually do. If it is heat treated to a hardness band, or if properties have to repeat batch to batch, specify EN8D. The price gap between the two is small enough that most buyers who heat treat simply standardise on EN8D.
EN8D compared with S45C and 1045
The trade treats EN8D, S45C and AISI 1045 as one family, and for most parts that is a fair working assumption. It is still worth knowing how close the match actually is.
| Property | EN8D | S45C / 1045 |
|---|---|---|
| Standard | BS 970 080M40 | JIS G4051 / AISI |
| Carbon, % | 0.40 to 0.45 | 0.42 to 0.50 |
| Position in family | Lower half of the range | Upper half of the range |
| Attainable hardness | Slightly lower | Slightly higher |
| Machinability | Slightly better | Slightly harder to cut |
EN8D sits at the lower end of the carbon band, S45C and 1045 at the upper end. The gap is small. It matters when the part is taken to the top of its hardness range after quench and temper, and again in cycle time on the machine. For shafts, studs and general machined parts either will serve.
Order to the drawing when it names a standard, or when the hardness target sits at the top of the range. We roll S45C as a separate grade for that reason. If the comparison you actually need is against an alloy steel, see the difference between EN8D and SAE 4140.
Ordering information
To place an order we need the following.
| Grade | EN8D |
|---|---|
| Order | Minimum order 5 MT per size |
| Length |
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| Diameter |
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| Condition |
To request a quote, fill in this form.
About our company
Ambhe Ferro Metal Processors Private Limited rolls EN8D round bar at its own mills in Maharashtra, India. The plants are close to JNPT port and to the consumption centres of Mumbai, Thane, Pune, Nashik, Ahmednagar and Aurangabad.
We roll rounds, bright bars, hexagons and RCS across the size range listed above, to domestic and international specifications. We can develop sizes outside the standard list if the requirement is regular and the quantity supports it.
Testing and packaging
Every heat we roll in EN8D is tested before dispatch. On the customer’s request we add ultrasonic testing, macro and micro examination, grain size determination and a decarburisation check.
A heat-wise Mill Test Certificate ships with every consignment, listing chemistry and mechanicals against the heat number. Finished bars are bundled with steel strapping, end-tagged with grade and heat number, and protected for road or container dispatch. Third party inspection can be arranged on request. There is more detail on our quality control page.
Related grades and guides
Frequently asked questions
What is EN8D steel?
EN8D is a medium-carbon steel from the BS 970 family with 0.40 to 0.45% carbon, supplied to tighter sulphur and phosphorus limits than plain EN8. It is used widely in forging, automotive and general engineering for parts that need moderate strength with good machinability and weldability.
What is the chemical composition of EN8D?
EN8D contains 0.40 to 0.45% carbon, 0.70 to 0.90% manganese, 0.10 to 0.40% silicon, with sulphur and phosphorus each held to 0.040% max. The full heat-wise composition is shared on the Mill Test Certificate.
What is EN8D equivalent to in AISI, DIN, JIS and IS?
EN8D is approximately equivalent to AISI 1040 / 1045, DIN C45 / Ck45 (1.0503 / 1.1191), JIS S45C, and IS C45 / 45C8.
What is the difference between EN8 and EN8D?
The base chemistry is similar. EN8D is the variant supplied to tighter sulphur and phosphorus limits, 0.040% max each, and is the one to specify when mechanical properties or heat treatment response have to repeat batch to batch.
What is the difference between EN8D and SAE 4140?
SAE 4140 is a chrome-moly alloy steel with much higher hardenability and through-section hardness response. EN8D is a plain medium-carbon steel. Use 4140 when sections are thick or hardness above 35 HRC is needed, and EN8D when those are not requirements and cost matters.
Can EN8D be heat treated, and to what hardness?
Yes. Normalising at 850 to 880 °C improves grain refinement. For higher strength, harden at 830 to 860 °C with an oil quench, then temper between 550 and 660 °C, which sets the hardness between about 205 and 255 HB. Anything above that is a surface condition: EN8D flame or induction hardens to 50 to 55 HRC at the case, with the core left soft.
Is EN8D weldable?
EN8D is weldable with care. Carbon at 0.40 to 0.45% places it in the medium-weldability range. Preheat at 150 to 250 °C and slow post-weld cooling or stress relief are advisable, especially on thicker sections.
What sizes do you supply EN8D in?
Hot rolled rounds 23.5 to 80 mm, bright bars 22 to 63.5 mm, hexagons 23.5 to 52.5 mm across flats, and RCS in 55, 63 and 75 mm. Standard lengths are 5 to 6 metres, with custom cuts on request.
What is your minimum order quantity for EN8D?
5 MT per size. Consolidated orders across several sizes are accepted on a single consignment.
Do you provide a test certificate with EN8D?
Yes. Every consignment ships with a heat-wise Mill Test Certificate listing chemistry and mechanicals. Third party inspection can be arranged on request.