Grade dossier
440A Stainless Steel
440A stainless steel is a high-carbon, high-chromium martensitic grade identified as UNS S44002 and commonly cross-referenced to EN 1.4109 / X70CrMo15. Its strongest procurement case is a hardened precision or wear component—such as pivot pins, dental and surgical instruments, cutlery or valve parts—where high hardness is required but the maximum hardness capability of 440C is not necessarily needed.
Identity before substitution
Specify 440A with the required condition, hardness and fabrication route
The grade name alone is not a complete purchase specification. 440A is commonly machined in a soft annealed condition and then hardened and tempered to develop its final hardness. Compared with 440C, its lower carbon range reduces maximum hardness but leaves a wider fabrication and toughness window. Product form, governing standard, dimensions, annealed or hardened condition, heat-treatment responsibility, final hardness target and certification should therefore be stated together.
440A stainless composition
Producer chemistry reference for UNS S44002
Lower carbon than 440C is the key distinction
Carpenter Technology publishes 0.60–0.75% carbon and 16.0–18.0% chromium for 440A, with molybdenum up to 0.75%. This chemistry gives a lower hardness ceiling than 440C while still supporting high hardness after heat treatment. Use the ordered product specification and heat-specific MTC/test report for acceptance.
| C | 0.60–0.75% |
|---|---|
| Cr | 16.00–18.00% |
| Mo | 0.75% max |
| Mn | 1.00% max |
| Si | 1.00% max |
| P | 0.040% max |
| S | 0.030% max |
| Fe | Balance |
440A stainless properties
Mechanical properties depend on the heat-treatment route
Carpenter typical hardened + tempered example
| Heat treatment | 1038°C harden, oil quench, 316°C temper |
|---|---|
| 0.2% yield strength | 1655 MPa |
| Ultimate tensile strength | 1793 MPa |
| Elongation in 50.8 mm | 5% |
| Reduction of area | 20% |
| Brinell hardness | 512 HB |
Selection indicators
| Maximum hardness capability | about 56–57 HRC |
|---|---|
| Annealed hardness reference | about 223 HB |
| Hardness after 315°C temper | about 51–52 HRC |
| Magnetic response | Magnetic in all normal conditions |
| Primary strength | High hardness with more margin than 440C for toughness/fabrication |
The hardened values above are Carpenter producer-published typical data for a 1038°C oil quench followed by a 316°C temper; they are not universal minimums. Section size, austenitizing temperature, quench severity and tempering temperature can materially change hardness, strength and dimensional response. Release the order against the specified condition and actual test/MTC results.
Selection boundary
Use 440A when high hardness is needed without defaulting to the 440C maximum
440A is strongest where a component needs high hardness, moderate stainless corrosion resistance and a heat-treatable martensitic structure, but not necessarily the higher carbon and maximum hardness of 440C. Selection should still account for corrosion environment, impact loading, section size, machining route and final heat treatment.
Good reasons to evaluate it
Pivot pins and precision wear parts requiring high hardness after heat treatment
Dental and surgical instruments where the governing specification permits 440A
Cutlery and blade components where hardness, edge performance and corrosion exposure are balanced
Valve parts and other industrial components exposed to mild environments
Reasons to stop and review
Seawater, aggressive chloride or highly corrosive service without dedicated corrosion data
Applications demanding the maximum hardness and wear resistance available from the 440 series—review 440C instead
Extensive welding without preheat and immediate post-weld annealing, or heavy cold forming outside the soft annealed condition
Orders that state only “440A” but omit final hardness, annealed/hardened condition and heat-treatment responsibility
Fabrication and heat treatment
Machine in the soft condition, then harden and temper to the required result
Carpenter recommends most machining in the dead-soft annealed condition. Carbide or ceramic tooling is suggested, and chip control matters because the chips can be tough and stringy.
A published hardening route is about 1010–1066°C followed by warm-oil quenching or air cooling. Avoid overheating because excessive temperature can reduce the attainable final hardness.
For maximum hardness, Carpenter gives a low-temperature temper reference of about 148–176°C for at least one hour, producing approximately 56–57 HRC in the published example. Tempering temperature must be tied to the required hardness and corrosion performance.
440A is seldom welded. If welding is unavoidable, Carpenter recommends about 260°C preheat and an immediate 732–760°C anneal for 6–8 hours with slow furnace cooling; use a qualified WPS for the actual joint.
440A stainless supplier checklist
Buy by form, specification, size and delivered condition
A 440A stainless supplier should identify the exact mill form, governing standard, dimensions, annealed or heat-treated condition, surface condition, heat-treatment responsibility, final hardness requirement and inspection package. Carpenter lists bar, rounds, billet, strip, wire and rod, but exact current diameters, thicknesses, widths and lengths should be confirmed from live supplier inventory rather than assumed from a generic web range.
Carpenter: bar, rounds, billet, strip, wire and rod
Applicable examples: ASTM A276, A314, A473, A580 and ASTM F899
AMS example: 5631 · legacy QQ-S-763 also listed by Carpenter
EN cross-reference: 1.4109 · X70CrMo15
MTC / test-report checkpoint
Verify heat number and traceability, 440A / UNS S44002 identity, governing specification and edition, chemistry, ordered form and dimensions, annealed or hardened-and-tempered condition, heat-treatment route where supplier-controlled, final hardness or mechanical-test results, surface/straightness requirements and any supplementary inspection. Do not treat a catalog grade name as proof of the delivered condition.
Interactive selection check
Test 440A against the controlling design question
Procurement FAQ
Questions to close before ordering 440A stainless steel
What is 440A stainless steel?
440A is a high-carbon, high-chromium martensitic stainless steel, UNS S44002, commonly cross-referenced to EN 1.4109 / X70CrMo15. It is selected for high hardness after heat treatment together with moderate corrosion resistance and is used for parts such as pivot pins, instruments, cutlery and valve components.
How hard can 440A stainless steel become?
Carpenter publishes approximately 56–57 HRC for a 1038°C hardening treatment followed by a low-temperature temper around 149–176°C. Higher tempering temperatures reduce hardness, so the purchase and heat-treatment instructions should state the required final hardness.
Is 440A stainless steel highly corrosion resistant?
It has moderate stainless corrosion resistance. Carpenter reports resistance in mild atmospheres, fresh water, steam, ammonia, many petroleum products and organic materials, but 440A should not be treated like a 316-type chloride-resistant grade. Review chloride level, temperature, deposits and cleaning conditions before selection.
Is 440A easy to machine or weld?
It is best machined in the dead-soft annealed condition. Welding is uncommon because of the grade's hardening response; if unavoidable, Carpenter calls for preheat and an immediate post-weld anneal, so the actual joint should use a qualified procedure.
What should a 440A RFQ include?
State product form, ASTM/AMS/EN requirement, UNS S44002 or the verified EN 1.4109 / X70CrMo15 cross-reference, dimensions and tolerances, delivered condition, required final hardness, heat-treatment responsibility, surface finish, quantity, service environment, MTC and supplementary inspection requirements.
Sources, scope and RFQ
Trace the 440A data, then certify the actual heat and condition
UNS S44002 identity, 0.60–0.75% C and 16–18% Cr chemistry, approximately 56–57 HRC hardness capability, typical hardened mechanical properties, annealing/hardening/tempering guidance, machining and welding notes, forms and applicable specifications.
Current producer listing for UNS S44002, product forms, applications and applicable ASTM/AMS specifications used for the supply checklist.
EN 1.4109 / X70CrMo15 designation and martensitic classification used as the European cross-reference; final equivalence must still follow the governing order standard.
The current ASTM, AMS or EN product specification and the heat-specific MTC/test report control acceptance. State condition, hardness, dimensions, heat-treatment responsibility and supplementary inspection explicitly.