EN8 also know as 080M40. Unalloyed medium carbon steel. EN8 is a medium strength steel, good tensile strength. Suitable for shafts, stressed pins, studs, keys etc. AISI 1040. Available as normalized or rolled. EN8 is supplied as round drawn/turned, round hot rolled, hexagon, square, flats and plate. EN8 is usually supplied untreated but can be supplied to order in the normalized or finally heat treated (quenched and tempered to ”Q” or “R”properties for limiting ruling sections up to 63mm), which is adequate for a wide range of applications. Please refer to our selection guide for comparisons. EN8 is a very popular grade of through-hardening medium carbon steel, which is readily machinable in any condition. (Refer to our machinability guide). EN8 is suitable for the manufacture of parts such as general-purpose axles and shafts, gears, bolts and studs. It can be further surface-hardened typically to 50-55 HRC by induction processes, producing components with enhanced wear resistance. For such applications the use of EN8D (080A42) is advisable. It is also available in a free-machining version, EN8M (212A42), EN8 in its heat treated forms possesses good homogenous metallurgical structures, giving consistent machining properties. Good heat treatment results on sections larger than 63mm may still be achievable, but it should be noted that a fall-off in mechanical properties would be apparent approaching the centre of the bar. It is therefore recommended that larger sizes of EN8 are supplied in the untreated condition, and that any heat treatment is carried out after initial stock removal. This should achieve better mechanical properties towards the core.
Heat Treatment:
- EN8 or 080m40 can be tempered at a heat of between 550°C to 660°C (1022°F-1220°F), heating for about 1 hour for every inch of thickness, then cool in oil or water.
- Normalizing of EN8 bright mild steel takes place at 830-860°C (1526°F-1580°F) then it is cooled in air.
- Quenching in oil or water after heating to this temperature will harden the steel.
- Chemical Composition of EN8 Steel
Chemical composition:
| Element | Min | Max |
|---|---|---|
| Carbon, C | 0.35 | 0.45% |
| Manganese, Mn | 0.60 | 1.0% |
| Silicon, Si | 0.5 | 0.35% |
| Sulphur | -.– | 0.6 |
| Phosphorus | -.– | 0.6 |
Mechanical Properties:
| Max Stress | 700-850 n/mm 2 | |
|---|---|---|
| Yield Stress | 465 n/mm 2 Min | (up to 19mm LRS) |
| 0.2% Proof Stress | 450 n/mm 2 Min | (up to 19mm LRS) |
| Elongation | 16% Min | (12% if cold drawn) |
| Impact KCV | 28 Joules Min | (up to 19mm LRS |
| Hardness | 201-255 Brinell |
EN8 Equivalents:
| BS970: 1955 | EN8 |
| BS970/PD970: | 080M40 |
| Onwards | 1970 |
| European | C40, C45, Ck40,Ck45, Cm40, Cm45 |
| Werkstoff No. | 1.0511, 1.1186, 1.1189 |
| US SAE (AISI) | 1039, 1040, 1042, 1043, 1045 |
