230M07
EN1A · BS 970
230M07 (EN1A) is a free-cutting steel (Resulfurised family) to BS 970. It has a specified 0.2 % proof stress of 240 MPa and a typical tensile strength of about 420 MPa, with a uniform elongation of 18 %. Nominal carbon content is around 0.07 %. For nonlinear FEA, a bilinear model uses E = 210 GPa up to yield and a tangent modulus of 1018 MPa above it. Sulphur (and sometimes lead) additions make it machine freely at high rates, at some cost to ductility and weldability.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 18.0% · conservative analysis limit ½εu = 9.0%
Bilinear (BISO) approximation. Elastic modulus E up to the 0.2% proof stress R_p0.2, then a single tangent slope Eₜ to the ultimate tensile strength: Eₜ = (Rₘ − R_p0.2) / (εu − R_p0.2/E − 0.002), where εu is the uniform elongation and Rₘ is a typical (nominal) UTS within the specified band. The half-εu figure is a conservative strain limit for the analysis. Treat these as guidance for first-pass models; for critical work use a measured true stress–strain curve for the actual product and condition.
Ratings — engineering judgement
Weldabilitypoor
The high sulphur that makes it machine so well also promotes hot cracking — welds are unreliable. Avoid welded joints; join mechanically.
Formabilitypoor
The sulphide inclusions cut transverse ductility, so heavy bending or forming (especially across the bar) risks splitting.
Machinabilityexcellent
The whole point of the steel — manganese-sulphide inclusions break the chip and lubricate the cut, giving outstanding tool life and surface finish on automatic lathes.
Corrosion resistancepoor
None; and the sulphide inclusions can be corrosion initiation sites.
Hardenabilitylow
Low carbon, no meaningful hardening; not a strength steel.
Toughnesslow
Reduced and directional (anisotropic) because of the inclusions — not for impact or fatigue-critical parts.
Expert notes
230M07 — everyone calls it EN1A — is the classic free-cutting steel. The added sulphur (0.20–0.30 %) forms soft manganese-sulphide inclusions that break the chip and lubricate the tool, so it machines faster, cleaner and with better tool life than anything else. If a part is turned in volume on an automatic lathe and doesn’t need to be strong, this is the default.
Everything that makes it machine well is a liability elsewhere. Those inclusions wreck weldability (hot cracking), cut ductility and toughness — especially across the bar — and offer no strength or hardening. So keep it to non-structural, non-welded, low-stress parts: studs, spacers, fittings and the like.
The leaded version (230M07Pb / EN1APb) machines better still, but lead brings handling, environmental and disposal concerns, and many suppliers are moving to bismuth or calcium-treated alternatives.
If you need free-cutting behaviour with more strength, look at a leaded/resulphurised medium-carbon grade (e.g. 212M36) rather than pushing EN1A beyond its comfort zone.
Mechanical properties
| Condition | Section | Yield (MPa) |
|---|---|---|
| 230M07 (EN1A) · as-rolled/cold-drawn | bar | 240 |
UTS 400–500 MPa · Impact low (sulphur anisotropy) · Hardness ~140–170 HB
Physical properties
| Density | 7850 | kg/m³ |
| Elastic modulus | 210 | GPa |
| Shear modulus | 81 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 12.0 | ×10⁻⁶/°C |
| Thermal conductivity | 50 | W/(m·K) |
| Specific heat | 470 | J/(kg·K) |
Chemical composition (wt %)
Available forms
Equivalent grades
| Standard | Grade | Note |
|---|---|---|
| AISI | 1213 | |
| DIN | 9SMn28 / 1.0715 | |
| BS 970 | EN1A |
Historical designations
| Standard | Grade | Note |
|---|---|---|
| BS 970:1955 | EN1A | The name every UK machinist still uses. |
| BS 970:1970 | 230M07 |
Common applications
- High-volume turned parts on automatic lathes
- Studs, screws, nuts and fittings (non-critical)
- Spacers, bushes and collars
- General low-stress machined components
History
Free-cutting steels were developed to feed the automatic lathe: sulphur (and sometimes lead) is added deliberately to make the steel machine faster and cleaner at the cost of other properties.
- 1920Resulphurised free-cutting steels developed for screw machines
- 1942EN1A defined in BS 970
- 1970BS 970 overhaul — EN1A redesignated 230M07