Two medium-carbon engineering steels that overlap heavily on shaft, axle and stud work. This guide sets out the composition, hardness, machinability and weldability differences so you can specify the right one.
45C8 and EN8D are close medium-carbon cousins. 45C8 (the C45 / 1045 family, ~0.45% C) carries marginally more carbon than EN8D (close-control EN8, ~0.40–0.45% C), so it reaches slightly higher hardness and strength. EN8D's tighter sulphur and phosphorus control gives a more predictable heat-treatment response and is the right call when the drawing specifies EN8. For most shafts, axles and studs the two are interchangeable — choose by the standard your customer names and the hardness you need.
| Property | 45C8 | EN8D |
|---|---|---|
| Type | Medium-carbon unalloyed steel | Medium-carbon, close-control (EN8 family) |
| Carbon (C) | 0.40–0.50% | 0.40–0.45% |
| Manganese (Mn) | 0.60–0.90% | 0.70–0.90% |
| Silicon (Si) | 0.10–0.35% | 0.10–0.35% |
| Sulphur (S) | 0.050% max | 0.045% max |
| Phosphorus (P) | 0.050% max | 0.045% max |
| Tensile (normalised) | 620–720 MPa | 620–700 MPa |
| Yield (normalised) | 340–460 MPa | 340–450 MPa |
| Elongation | 15–20% | 16–20% |
| Hardness (normalised) | 180–230 HB | 180–220 HB |
| Hardenability | Limited (plain carbon); marginally higher max hardness | Limited (plain carbon); consistent response |
| Machinability | Good | Good; consistent due to controlled chemistry |
| Weldability | Fair — preheat on thicker sections | Fair — slightly easier at the lower carbon end |
| Relative cost | Comparable | Comparable |
| Equivalents | 1045, C45 (1.0503), S45C, 080M46 | 1040, C40 (1.0511), S40C, 080M40 |
| Typical applications | Shafts, axles, spindles, studs, gears, forgings | Shafts, axles, crankshafts, gears, crane wheels |
Both grades are supplied with a heat-wise mill test certificate stating the actual chemistry and properties for the heat you receive.
Both grades machine cleanly in the normalised or annealed condition, which is how most bar is turned, milled and drilled before any hardening. Tool life and surface finish are close to identical; the practical edge with EN8D is consistency — its controlled chemistry means one batch behaves much like the next, which matters on a CNC line running unattended. 45C8 can sit at the upper carbon end, so it occasionally feels marginally tougher to cut at the top of its range, though hard spots are rare in properly normalised bar.
Where machinability is the first priority — high-volume turned parts, free-running threads — neither plain medium-carbon grade is the best pick. A free-cutting medium-carbon steel such as EN8M, with added sulphur for chip breaking, will out-machine both. For bright, dimensionally accurate stock straight off the shelf, order either grade as cold-drawn or polished bright bar rather than hot-rolled black bar.
The two grades respond almost identically because their carbon and manganese sit so close together. Both are usually supplied normalised at 850–880 °C for a uniform structure. For a harder, stronger part, both through-harden by quenching from 850–880 °C and tempering at 550–660 °C to the required hardness; oil is preferred over water for anything other than simple sections to limit quench cracking. Temper immediately after quenching.
Because neither grade carries alloying elements, hardenability is limited: the hardened layer is shallow, so full through-hardening only works in small to medium diameters. In larger bar the core stays softer than the surface. The usual answer for a wear face on a bigger part is induction or flame hardening, which both grades accept well. If you need uniform hardness through a large section, that is the point to move to an alloy grade such as EN19 or SAE 4140.
Ambhe Ferro rolls and finishes both grades as rounds (23.5–80 mm diameter), bright bars (21–63.5 mm), hexagons (23.5–52.5 mm across flats) and RCS (55, 63 and 75 mm). Standard length is 5–6 m, with custom cut lengths to order. Supply conditions cover hot rolled, annealed, normalised and bright (cold drawn or polished).
The minimum order quantity is 5 MT per size, and non-standard sizes are often available make-to-order against tonnage. Whichever grade the drawing calls for, every dispatch carries a heat-wise mill test certificate confirming the chemistry and mechanical properties of that heat, with third-party inspection on request.
Both 45C8 and EN8D are mainstream medium-carbon steels, widely rolled and stocked across India, so availability and price track each other closely. Cost is driven more by product form, size, finish and order quantity than by the grade itself — a bright, polished bar costs more than hot-rolled black bar of the same grade. Because the two are so close, buyers sometimes receive one against an order for the other; protect yourself by stating the exact grade and standard on the purchase order and checking the mill test certificate on receipt.
Ambhe Ferro is an engineering-steel manufacturer with two factories in MIDC Murbad, near Kalyan — about 80 km from Mumbai Port and JNPT. We roll and finish 45C8 and EN8D steel at our units and dispatch quickly across the Mumbai–Pune–Nashik corridor and pan-India. Regular dispatches go to buyers in Mumbai, Navi Mumbai, Thane, Vasai–Virar, Pune, Pimpri-Chinchwad, Chakan, Nashik, Ahmednagar, Aurangabad, Kolhapur, Nagpur, Rajkot, Ahmedabad and Bengaluru; exports are arranged on request. Order as hot-rolled rounds, bright bars, hexagons or RCS against your size and tonnage, with a heat-wise mill test certificate on every dispatch.
MOQ is 5 MT per size. Send the grade, form, size and tonnage and we will respond with pricing, availability and lead time.
Tell us the grade, form, size, and tonnage. Ambhe Ferro responds with pricing, availability, and lead time — and a mill test certificate on every heat.
