AISI 440A Forgings
UNS S44002 · SUS440A · EN 1.4109 – Bars, Rings, Discs and Blocks
- UNS
- S44002
- EN number
- 1.4109
- JIS
- SUS440A
- Carbon
- 0.60–0.75 %
- Chromium
- 16.0–18.0 %
- Delivered
- Annealed (+A)
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu, China. We forge AISI 440A high-carbon martensitic stainless steel into round bars, hollow bars, rolled rings, discs, blocks and near-net shapes for bearings, cutlery, surgical instruments, gauge blocks, moulds and valve components.
1.Key data
| Grade type | High-carbon, high-chromium martensitic stainless steel |
|---|---|
| Designations | AISI 440A · UNS S44002 · JIS SUS440A · EN 1.4109 · DIN X70CrMo15 |
| Carbon | 0.60 – 0.75 % |
| Chromium | 16.0 – 18.0 % |
| Molybdenum | 0.75 % max |
| Tensile strength | 725 – 1790 MPa, annealed through hardened |
| Yield strength, 0.2 % | 415 – 1650 MPa, annealed through hardened |
| Hardness, annealed | approx. 95 HRB |
| Austenitising | 950 – 1065 °C, quench in oil, gas or air |
| Tempering | 150 – 370 °C – never 400 – 580 °C |
| Annealing | 850 – 880 °C, furnace or air cool |
| Density | 7.8 g/cm³ |
| Magnetic response | Ferromagnetic in all conditions |
| Delivery condition | Annealed (+A) unless otherwise specified |
| Product forms | Forged bars, hollow bars, rolled rings, discs, blocks, near-net shapes |
2.What is AISI 440A
AISI 440A is the lowest-carbon member of the 440 martensitic stainless family. With 0.60 to 0.75 % carbon and 16 to 18 % chromium it hardens by quenching and tempering much like an alloy tool steel. Chromium carbides give hardness and wear resistance, while the chromium left in solution provides moderate corrosion resistance.
The grade is chromium-molybdenum alloyed and air-hardening, with good hardenability and excellent wear resistance. Against 440B and 440C it carries less carbon, which caps the hardness it can reach but gives it higher toughness than either of the other two grades. That combination is why 440A is chosen where a part has to hold an edge or resist wear without being brittle.
We supply 440A annealed unless the order specifies a hardened and tempered delivery condition.
3.Chemical composition
| Element | Minimum | Maximum |
|---|---|---|
| Carbon (C) | 0.60 | 0.75 |
| Chromium (Cr) | 16.00 | 18.00 |
| Molybdenum (Mo) | – | 0.75 |
| Manganese (Mn) | – | 1.00 |
| Silicon (Si) | – | 1.00 |
| Phosphorus (P) | – | 0.040 |
| Sulfur (S) | – | 0.030 |
| Iron (Fe) | Balance | |
Composition to ASTM A276/A276M. The same limits appear in the AZoM datasheet for grade 440A and in the BGH Edelstahlwerke data sheet for AISI 440A / 1.4109. Tighter customer limits available on request.
4.Mechanical properties
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 725 – 1790 MPa | 105,000 – 260,000 psi |
| Yield strength, 0.2 % offset | 415 – 1650 MPa | 60,200 – 239,000 psi |
| Elongation at break, in 50 mm | 5 – 20 % | 5 – 20 % |
| Modulus of elasticity | 204 – 215 GPa | 29,600 – 31,200 ksi |
| Hardness, annealed | approx. 95 HRB | approx. 95 HRB |
The low end of each range corresponds to the annealed condition, the high end to the hardened and tempered condition. Final hardness depends on the tempering temperature selected within the 150 to 370 °C window. Confirm your target hardness on the enquiry and we will set the tempering schedule to match.
Note on figures circulating online.
Several 440A pages publish a tempering table showing 758 MPa annealed and 2030 MPa at 59 HRC after a 204 °C temper. Those values come from the grade 440C table in the Atlas Steels grade datasheets, and AZoM publishes the same table under the heading "mechanical properties of grade 440C stainless steels". 440A carries at most 0.75 % carbon against 0.95 to 1.20 % for 440C, so it cannot reach 440C hardness. If your drawing needs hardness beyond what 440A delivers, specify 440B or 440C and we will quote that grade instead.
5.440A compared with 440B and 440C
| Property | 440A (S44002) | 440B (S44003) | 440C (S44004) |
|---|---|---|---|
| Carbon, % | 0.60 – 0.75 | 0.75 – 0.95 | 0.95 – 1.20 |
| Chromium, % | 16.0 – 18.0 | 16.0 – 18.0 | 16.0 – 18.0 |
| Molybdenum, % max | 0.75 | 0.75 | 0.75 |
| Silicon / Manganese, % max | 1.00 / 1.00 | 1.00 / 1.00 | 1.00 / 1.00 |
| Attainable hardness | Lowest of the three | Intermediate | Highest |
| Toughness | Highest of the three | Intermediate | Lowest |
All three share the same chromium range, so carbon is the differentiator. More carbon means more carbide, raising attainable hardness and wear resistance while lowering toughness.
Where toughness, forgeability and cost outweigh peak hardness – valve trim, general cutlery, pump wear parts, surgical instruments.
Where maximum hardness and wear life govern – rolling-element bearings and precision gauges.
6.Physical properties
| Density | 7.8 g/cm³ |
|---|---|
| Modulus of elasticity | 204 – 215 GPa |
| Magnetic response | Ferromagnetic, annealed and hardened |
Thermal conductivity, thermal expansion, specific heat and electrical resistivity for a specific heat and section size are available from us on request.
7.Forging and heat treatment
7.1 Forging
The grade air-hardens. Forgings must be preheated before hot working, cooled slowly after forging rather than quenched, and fully annealed before machining. Skipping the slow cool or the anneal is the usual cause of cracking in this grade. Contact us for the forging temperature range and reduction schedule we run on a given section size.
7.2 Annealing
| Temperature | 850 – 880 °C |
|---|---|
| Cooling | Furnace or air |
| Result | Annealed (+A), the standard delivery condition |
7.3 Hardening and tempering
| Austenitising | 950 – 1050 °C for 1.4109; 1010 – 1065 °C for the 440 family |
|---|---|
| Quench | Oil, gas or air – heavier sections oil quenched |
| Subzero | Optional, where dimensional stability matters |
| Tempering | 150 – 370 °C, to the required hardness |
Avoid the embrittlement window.
Tempering between 400 and 580 °C carries a risk of temper embrittlement and must not be used.
7.4 Machining
Machine in the annealed condition. Carbide or ceramic tooling with chip breakers handles the chips this grade produces.
7.5 Welding
Welding is not recommended. The carbon content makes the grade crack-sensitive and matching fillers are not readily available. If a joint cannot be avoided in your design, contact us before releasing the drawing so we can review it.
8.Equivalent grades and specifications
| System | Designation |
|---|---|
| AISI | 440A |
| UNS | S44002 |
| EN / DIN | 1.4109, approximately X70CrMo15 |
| JIS, Japan | SUS440A |
| ASTM product specifications | A276, A314, A473, A511 |
| ASTM surgical implant specification | F899 |
| Aerospace material specifications | AMS 5631, AMS 5632 |
EN 1.4109 and X70CrMo15 are approximate rather than exact equivalents of AISI 440A. Confirm the governing specification on your enquiry and we will certify to it. For a specification not listed here, send us the number and we will confirm whether we can meet it.
9.Product forms supplied
| Form | Description |
|---|---|
| Forged bars | Round, square, rectangular, flat and hexagonal – rough turned or black as forged |
| Rolled rings | Ring-rolled rings and forged flanges for bearing races and valve seat rings |
| Hollow bars and sleeves | Bushes, bushings, cylinders, barrels, casings, shells, hubs and housings |
| Discs, blocks and plates | Upset forged discs, blanks and blocks for gauge blocks, moulds and die inserts |
| Shafts and near-net shapes | Stepped shafts, pivot pins, nozzles and stem blanks forged close to final profile |
| Valve components | Bodies, bonnets, stems, seats and seat rings in hardened and tempered 440A |
10.Typical applications
Ball and roller bearings and races, cutlery and knife blades, surgical instruments, fuel injection system parts, cutting tools, gauge blocks and measuring instruments, moulds and dies, valve components and seats, pump parts, pivot pins and nozzles.
The grade suits parts facing high demands on wear and on cutting edge retention, and parts needing high surface quality.
11.Why buy from us
- Forged in our own shopBars, rings, discs, blocks and hollows forged on our presses in Jiangyin, with direct control of the forging schedule.
- Certified to your specificationChemistry and mechanical test reports per heat, certified to the ASTM, AMS or customer specification on your order.
- Heat treatment and testingAnnealing, hardening, tempering and subzero treatment, plus ultrasonic and hardness testing, arranged as part of the order.
- Engineering supportSend a drawing and we will advise on forging allowance, grain flow direction and whether 440A, 440B or 440C fits the duty.
12.Frequently asked questions
What is AISI 440A stainless steel?
AISI 440A, UNS S44002, is a high-carbon, high-chromium martensitic stainless steel with 0.60 to 0.75 % carbon, 16.0 to 18.0 % chromium and up to 0.75 % molybdenum. It combines moderate corrosion resistance with good hardenability and excellent wear resistance after hardening and tempering.
What is the difference between 440A, 440B and 440C?
Carbon content. 440A has 0.60 to 0.75 %, 440B has 0.75 to 0.95 % and 440C has 0.95 to 1.20 %, all with the same 16 to 18 % chromium. More carbon raises attainable hardness and wear resistance, while 440A has the highest toughness of the three.
What hardness can AISI 440A reach?
Hardness depends on the tempering temperature selected within the 150 to 370 °C window. Annealed, the grade sits near 95 HRB. 440A cannot match 440C hardness because of its lower carbon ceiling, so published figures of 59 HRC for 440A are in fact 440C values. Tell us your target hardness and we will confirm whether 440A meets it.
At what temperature is 440A annealed?
850 to 880 °C, cooling in the furnace or in air. Annealed is the standard delivery condition.
At what temperature is 440A hardened?
950 to 1050 °C for EN 1.4109, with the wider 440 family range given as 1010 to 1065 °C, quenched in oil, gas or air. Heavier sections are oil quenched.
Which tempering temperatures must be avoided?
400 to 580 °C, because of temper embrittlement risk.
Is AISI 440A magnetic?
Yes. As a martensitic stainless steel it is ferromagnetic in both the annealed and the hardened condition.
How corrosion resistant is 440A?
Moderate. The 16 to 18 % chromium gives stainless behaviour in mild service, but this is a hardness-and-wear grade rather than a corrosion grade, and it does not match austenitic stainless steels in aggressive media. Corrosion resistance is best in the hardened and polished condition.
Can AISI 440A be welded?
Welding is not recommended, because of the carbon content and the resulting crack sensitivity, and because matching fillers are not readily available.
What sizes of 440A forgings can you produce?
We forge 440A as bars, hollow bars, rolled rings, discs and blocks to customer drawings. Send dimensions, quantity and the governing specification to sales@steelforgepieces.com and we will confirm feasibility and lead time.
Related stainless grades
13. Request a quotation
Send your drawing, specification and quantity to Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory, Jiangyin, Jiangsu, China.
- Telephone, WhatsApp, WeChat
- +86-189-2135-9659
- Address
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
14.References
Composition and property data compiled from ASTM A276/A276M, the AZoM datasheet for stainless steel grade 440A (UNS S44002), the AZoM datasheet for grade 440 (UNS S44000), and the BGH Edelstahlwerke material data sheet for AISI 440A (~X70CrMo15 / 1.4109). Grade comparison data drawn from published ASTM A276/A276M composition limits for 440A, 440B and 440C.
Figures are typical values for guidance and first orientation and are not guaranteed properties. Certified values for your order appear on the mill test certificate issued with each heat.
Page last reviewed 30 September 2026 by the technical sales team, Jiangyin Jiangnan Metal Co., Ltd.