440A
1.4109 · EN 10088 / AISI · 1.4109
440A is a stainless steel (Martensitic family) to EN 10088 / AISI (1.4109). Nominal carbon content is around 0.60 %. Supplied hardened in service; for analysis treat it as elastic (E = 200 GPa) with a hardness- or fracture-based limit. Unusually for a stainless steel it can be hardened by heat treatment, trading some corrosion resistance for strength and wear resistance.
Bilinear material model — nonlinear FEA
This grade is supplied hardened in service and is not represented as a bilinear material — it has a negligible uniform-plastic range. Model it as elastic (E = 200 GPa) with an appropriate fracture / hardness-based limit.
Ratings — engineering judgement
Weldabilitypoor
Difficult — hardens on cooling. Preheat and post-weld tempering are normally required.
Machinabilitygood
Machines well, particularly in the normalised or pre-tempered condition.
Corrosion resistancegood
Good atmospheric and mild-chemical resistance from the chromium content; less resistant than austenitics in chlorides.
Hardenabilitygood
Hardenable by heat treatment (unusual among stainless steels).
Toughnessmoderate
Adequate toughness for general use at ambient temperature.
Indicative ratings derived from composition and family — engineering guidance, not specification values.
Physical properties
| Density | 7750 | kg/m³ |
| Elastic modulus | 200 | GPa |
| Shear modulus | 76.9 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 10.5 | ×10⁻⁶/°C |
| Thermal conductivity | 25 | W/(m·K) |
| Specific heat | 460 | J/(kg·K) |
| Magnetic | Yes |
Typical values for martensitic steel — use the mill certificate for the specific product.
Chemical composition (wt %)
Composition per EN 10088 / AISI for 440A (1.4109).
Available forms
Common applications
- Process, food and pharmaceutical equipment
- Architectural and marine hardware
- Fasteners and fittings for corrosive service
- Tanks, pipework and heat exchangers
History
The martensitic stainless steels are the original stainless — Harry Brearley’s 1913 Sheffield cutlery steel. Higher carbon lets them harden by heat treatment like a tool steel while keeping ~12–18 % chromium for corrosion resistance, trading some of that resistance for strength, hardness and edge-holding.
- 1913Harry Brearley melts the first martensitic stainless steel in Sheffield
- 1915“Stainless steel” cutlery reaches the market
- 1950Higher-carbon 440-series developed for bearings, blades and instruments
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.