---
title: "UNS S44004 (AISI 440C) Forgings: Bars, Rings, Discs and Sleeves"
canonical: "https://www.steelforgepieces.com/Stainless-Steel/UNS-S44004.html"
grade: "UNS S44004 / AISI 440C / SAE 51440C / EN 1.4125 / X105CrMo17 / SUS440C"
manufacturer: "Jiangyin Jiangnan Metal Co., Ltd."
address: "No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China"
telephone: "+86-189-2135-9659"
email: "sales@steelforgepieces.com"
updated: "2026-10-09"
---

# UNS S44004 (AISI 440C) Forgings: Bars, Rings, Discs and Sleeves

UNS S44004 is the UNS designation for AISI/SAE 440C, a high-carbon, high-chromium
martensitic stainless steel with 0.95 to 1.20 % carbon and 16.00 to 18.00 % chromium,
plus up to 0.75 % molybdenum. It reaches the highest hardness of any stainless steel,
around 58 to 60 HRC, after hardening and low-temperature tempering, with high wear
resistance and moderate corrosion resistance close to grade 410.

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu,
China. We forge UNS S44004 into round bars, seamless rolled rings, discs, blocks,
hollow bars and sleeves to customer drawings, supplied annealed at 269 HBW max hot
finished or 285 HBW max cold finished, or hardened and tempered.

Contact: sales@steelforgepieces.com / +86-189-2135-9659

## Key data

| Attribute | Value |
|---|---|
| UNS number | S44004 |
| AISI / SAE | 440C, SAE 51440C |
| EN / Werkstoff | 1.4125, X105CrMo17 |
| JIS | SUS440C |
| AFNOR | Z100CD17 |
| Structure | Martensitic stainless steel |
| Carbon | 0.95 to 1.20 % |
| Chromium | 16.00 to 18.00 % |
| Molybdenum | 0.75 % max |
| Annealed hardness, hot finished | 269 HBW max |
| Annealed hardness, cold finished | 285 HBW max |
| Hardness capability | 58 to 60 HRC |
| Density | 7 650 kg/m3 |
| Forging range | 1 050 to 1 150 C, finish above 900 C |
| Forms supplied | Forged bars, seamless rolled rings, discs, blocks, hollow bars, sleeves, shafts |

## What UNS S44004 / 440C is

UNS S44004 carries the most carbon of any grade in the AISI 400 series. The 0.95 to
1.20 % carbon level separates it from 440A and 440B. That carbon forms chromium
carbides, which is where the abrasive wear resistance comes from and why the steel can
be through hardened to roughly 60 HRC, a figure no other stainless grade reaches. The
cost is corrosion performance: carbon locked into carbides is chromium no longer
available to protect the matrix, so 440C sits close to grade 410 and below grade 431,
the ferritic 400-series grades and every austenitic 300-series grade.

Annealed, the grade machines acceptably and behaves a little like a high-speed steel,
throwing tough stringy chips. Hardened, it is hard to machine, so nearly every 440C part
is rough machined soft, hardened, then finish ground. Thin sections can be air cooled.
Heavier sections need an oil quench to harden through.

Open-die forging and ring rolling break up the as-cast carbide network and line the
grain flow up with the shape of the part. On bearing races, valve seats and sleeves that
continuous grain flow gives better fatigue and wear behaviour than a part machined out
of oversize stock, and on large or hollow shapes it saves a lot of material.

## Equivalent grades and specifications

| Region or body | Standard | Designation |
|---|---|---|
| USA (UNS) | UNS | S44004 |
| USA (AISI / SAE) | ASTM A276 / A276M | Type 440C, SAE 51440C |
| Europe | EN 10088 | 1.4125, X105CrMo17 |
| Japan | JIS G4303 | SUS440C |
| France | AFNOR | Z100CD17 |
| Aerospace | SAE AMS | AMS 5630, AMS 5618 (vacuum melted), AMS 5880 (bearing quality) |

440C material also falls under ASTM A276/SA276, A314 (billets and bars for forging),
A473 (stainless forgings), A484, A493, A580, A756 and QQ-S-763.

## Chemical composition (ASTM A276/A276M Type 440C)

| Element | Min % | Max % |
|---|---|---|
| Carbon | 0.95 | 1.20 |
| Silicon | - | 1.00 |
| Manganese | - | 1.00 |
| Chromium | 16.00 | 18.00 |
| Molybdenum | - | 0.75 |
| Phosphorus | - | 0.040 |
| Sulphur | - | 0.030 |
| Nickel | - | optional addition |
| Iron | Balance | |

Specification differences to watch: EN 10088 grade 1.4125 narrows molybdenum to 0.40 to
0.80 %. AMS 5630 calls for Mo 0.40 to 0.65 %, Ni 0.75 % max and Cu 0.50 % max.

## Mechanical properties

### Annealed, specification requirements

| Specification | Finish | Brinell hardness | Hardening capability |
|---|---|---|---|
| ASTM A276 440C | Hot finished | 269 HBW max | 58 HRC min, 9.50 mm bar air cooled from 1 020 C |
| ASTM A276 440C | Cold finished | 285 HBW max | 58 HRC min, 9.50 mm bar air cooled from 1 020 C |
| AS 2837 440C | - | 269 HBW max | 59 HRC min, 10 mm bar oil quenched from 1 010 to 1 070 C |

### Annealed, typical as-supplied values

| Property | Typical value |
|---|---|
| Tensile strength | 785 MPa |
| Yield strength, 0.2 % proof | 420 MPa |
| Elongation in 50 mm | 15 % |
| Impact, Charpy | 6 J |
| Hardness | 240 HB, about 24 HRC |

Other published datasheets give around 758 MPa tensile, 448 MPa yield and 14 %
elongation at 269 HB max. These are typical values, not guaranteed minima.

### Hardened and tempered

| Temper C | Tensile MPa | 0.2 % yield MPa | Elongation % | Hardness HRC | Charpy V, J |
|---|---|---|---|---|---|
| 204 | 2 030 | 1 900 | 4 | 59 | 9 |
| 260 | 1 960 | 1 830 | 4 | 57 | 9 |
| 316 | 1 860 | 1 740 | 4 | 56 | 9 |
| 371 | 1 790 | 1 660 | 4 | 56 | 9 |

A typical hardened bar, austenitised at 1 038 C, oil quenched and tempered at 316 C,
reports around 1 965 MPa tensile, 1 896 MPa yield, 2 % elongation, 10 % reduction of
area and about 580 HB. Ductility and impact energy are low in this grade by nature.

## Physical properties

| Property | Value |
|---|---|
| Density | 7 650 kg/m3 |
| Modulus of elasticity | 200 GPa |
| Mean thermal expansion, 0 to 100 C | 10.1 um/m.C |
| Mean thermal expansion, 0 to 200 C | 10.3 um/m.C |
| Mean thermal expansion, 0 to 600 C | 11.7 um/m.C |
| Thermal conductivity at 100 C | 24.2 W/m.K |
| Specific heat, 0 to 100 C | 460 J/kg.K |
| Electrical resistivity | 600 nOhm.m |
| Magnetic response | Ferromagnetic in all conditions |

## Forging and heat treatment

**Forging.** Preheat 760 to 820 C slowly and evenly. Heat to 1 050 to 1 150 C, soak until
uniform, forge at once. Do not forge below 900 C; reheat instead. Cool slowly in a
furnace, warm dry lime or ashes. Anneal straight away. Air cooling directly from the
forge can crack the part.

**Annealing.** 843 to 871 C, slow furnace cool, for maximum softness and machinability.
This is the normal shipping condition for bars, rings and discs.

**Hardening and tempering.** Preheat around 760 C, austenitise near 1 010 C (published
practice runs to about 1 063 C), quench in warm oil or air cool by section size, then
temper without delay. At least one hour at 149 to 177 C holds around 60 HRC. Avoid
overheating during austenitising, since retained austenite and coarse grain prevent full
hardness.

**Welding.** Seldom welded. Where unavoidable, preheat to about 260 C and post-weld
anneal at 732 to 760 C for roughly 6 hours with slow furnace cooling. Matching
composition consumables preferred, otherwise AWS E/ER309 may be considered.

## Forged product range

- Forged bars: round, square, rectangular, flat and hexagon. Rough turned, peeled, black or proof machined.
- Seamless rolled rings: bearing races, valve seat rings, spacers, retaining rings, rectangular and contoured profiles.
- Hollow bars and sleeves: bushes, bushings, cylinders, barrels, casings, shells, hubs, housings.
- Discs, blocks and plates: upset forged discs, rectangular blocks, forged plate for die blocks, gauge blocks, mould bases.
- Shafts and stepped forgings: valve stems, pivot pins, nozzles, spindles.
- Near-net custom shapes: valve bodies, bonnets, flanged and contoured components.

All items are made to customer drawing. There is no fixed catalogue.

## Applications

Ball bearings and bearing races, cutlery and knife blades, moulds and dies, gauge blocks
and measuring instruments, surgical and dental instruments, valve seats, seat rings,
stems, bodies and bonnets, needle valves, ball check valves, pump parts, nozzles, pivot
pins, and wear parts in textile machinery.

Industries served: oil and gas valve manufacture, petrochemical processing, bearing
production, food and pharmaceutical processing equipment, precision instrumentation,
general wear-part engineering.

## Testing and documentation

- Spectrographic heat analysis against ASTM A276, EN 10088 or AMS 5630 limits.
- Tensile, hardness (HBW / HRC) and impact testing on a representative test piece or prolongation.
- Hardenability response test confirming specified minimum HRC after the agreed cycle.
- Ultrasonic, magnetic particle, dye penetrant and dimensional inspection on request.
- EN 10204 3.1 mill test certificate as standard; third-party 3.2 inspection by agreement.

## FAQ

**What is UNS S44004?**
The UNS designation for AISI/SAE 440C, a high-carbon martensitic stainless steel with
0.95 to 1.20 % carbon and 16.00 to 18.00 % chromium, reaching roughly 58 to 60 HRC after
hardening and low tempering.

**What is the equivalent of UNS S44004?**
EN 1.4125 / X105CrMo17 in Europe, SUS440C in Japan, Z100CD17 in France, AMS 5630 /
AMS 5618 / AMS 5880 in aerospace.

**How hard can 440C be heat treated?**
Roughly 58 to 60 HRC. ASTM A276 requires 58 HRC min on a 9.50 mm bar air cooled from
1 020 C. AS 2837 requires 59 HRC min on a 10 mm bar oil quenched from 1 010 to 1 070 C.

**Is 440C corrosion resistant?**
Moderately. Close to grade 410, below grade 431 and all austenitic 300-series grades.
Not a replacement for duplex or 316 in chloride service.

**What is the forging temperature?**
Preheat 760 to 820 C, forge from 1 050 to 1 150 C, never finish below 900 C, cool slowly
and anneal immediately.

**Does 440C machine well?**
Acceptably when annealed, poorly when hardened. Hardened parts are normally finish
ground. Free-machining variants 440F and 440F Se exist.

**What sizes can you forge?**
All forms listed above, made to drawing. Send drawing, specification, delivery condition
and quantity for size capability and lead time.

**Can you supply heat treated and machined?**
Yes: as forged, annealed, or hardened and tempered to an agreed hardness band, with
rough, proof or finish machining to drawing.

## Supplier

Jiangyin Jiangnan Metal Co., Ltd. (open-die forging factory)
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Tel +86-189-2135-9659
Email sales@steelforgepieces.com
Web https://www.steelforgepieces.com/

Technical data compiled from ASTM A276/A276M Type 440C, EN 10088 (1.4125), JIS G4303
(SUS440C) and AMS 5630 published data. Values are typical or specification limits for
guidance and are not a guarantee of properties for any specific forging.