240M07
EN1B · BS 970
240M07 (EN1B) 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 0.15 %. 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
Weldabilitygood
Low carbon (~0.15%) gives good weldability by all common processes; preheat rarely needed in thin sections.
Machinabilityexcellent
Free-cutting additions (S, and sometimes Pb) give excellent chip breaking and tool life.
Corrosion resistancepoor
No inherent corrosion resistance — protect by paint, galvanising or plating in exposed use.
Hardenabilitylow
Limited hardenability at low carbon — surface hardening is possible but through-hardening is not.
Toughnessmoderate
Adequate toughness for general use at ambient temperature.
Indicative ratings derived from composition and family — engineering guidance, not specification values.
Physical properties
| Density | 7850 | kg/m³ |
| Elastic modulus | 210 | GPa |
| Shear modulus | 80.8 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 12.0 | ×10⁻⁶/°C |
| Thermal conductivity | 48 | W/(m·K) |
| Specific heat | 470 | J/(kg·K) |
| Magnetic | Yes |
Typical values for resulfurised steel — use the mill certificate for the specific product.
Chemical composition (wt %)
Nominal composition per BS 970 for 240M07 — confirm exact limits against the standard.
Available forms
Common applications
- High-volume machined parts
- Studs, screws and fittings
- Automatic-lathe (screw-machine) components
History
Free-cutting steels are deliberately loaded with sulphur (and sometimes lead or bismuth) so they machine fast and clean on automatic lathes — the inclusions break the chip and lubricate the cut. Everything that helps machining hurts weldability, ductility and toughness, so they are strictly for high-volume, low-stress turned parts.
- 1920Resulphurised free-cutting steels developed for automatic screw machines
- 1942BS 970 defines EN1A and the free-cutting series
This profile is generated from the grade's core data and family. Composition is decoded from the designation where its naming system defines it; physical properties are family-typical and ratings are indicative. Confirm critical values against the governing standard or the mill certificate. Equivalents, historical designations and hand-written expert notes are added per grade over time.