250A53
EN45 · BS 970
250A53 (EN45) is a spring steel (Silicon-Manganese family) to BS 970. It has a specified 0.2 % proof stress of 1200 MPa and a typical tensile strength of about 1450 MPa, with a uniform elongation of 6 %. Nominal carbon content is around 0.50 %. For nonlinear FEA, a bilinear model uses E = 210 GPa up to yield and a tangent modulus of 4781 MPa above it. Its high elastic limit and fatigue resistance suit it to springs and resilient components.
Bilinear material model — nonlinear FEA
Uniform elongation εu = 6.0% · conservative analysis limit ½εu = 3.0%
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
Higher carbon (~0.50%) raises the risk of HAZ cracking — preheat and PWHT are usually required, if welding is advisable at all.
Machinabilitygood
Machines well, particularly in the normalised or pre-tempered condition.
Corrosion resistancepoor
No inherent corrosion resistance — protect by paint, galvanising or plating in exposed use.
Hardenabilitygood
Responds well to quench-and-temper (and, for the case-hardening/nitriding grades, to surface treatment).
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 silicon-manganese steel — use the mill certificate for the specific product.
Chemical composition (wt %)
Nominal composition per BS 970 for 250A53 — confirm exact limits against the standard.
Available forms
Common applications
- Coil, leaf and torsion springs
- Suspension and valve springs
- Clips, clutches and resilient components
History
Spring steels are medium-to-high-carbon steels, often with silicon, chromium and vanadium, heat-treated to a high elastic limit and fatigue strength so they store and return energy without taking a set. Silicon raises the yield-to-tensile ratio; Cr and V add hardenability and fatigue resistance.
- 1900Silicon-manganese and Cr–V spring steels developed for vehicle suspension
- 1960Oil-tempered and valve-spring qualities refine fatigue performance
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.