Printed from Kezuriba (kezuriba.net/en/materials/440c/)
440C
ISO P (steel)Martensitic stainless steel (high carbon). Number: UNS S44004. Standard: AMS 5630, 5618, 5880 (SAE), ASTM A276/A276M and others (shown by Carpenter as corresponding).
🌐JIS and international equivalents
“Close” means composition or properties are not exactly the same. Before substituting, check the values in each standard.
| System | Designation | Number | Relation | Confidence |
|---|---|---|---|---|
| AISI | 440C | UNS S44004 | — | |
| JIS | SUS440C | JIS G 4303 (bar) | equivalent | Agrees in 2+ sources[3][9][10][6] |
| EN | X105CrMo17 | 1.4125 | close | Agrees in 2+ sources[2][8][3] |
| GB | — | S44096 (China column of the Japan Stainless Steel Association cross-reference) | close | One source / reference[3][9] |
Differences between the equivalents (from the sources)
- JIS SUS440C: Agrees between the Japan Stainless Steel Association (SUS440C ↔ S44004 / 440C) and Kyocera (SUS 440C ↔ S44004 440C). The Japan Stainless Steel Association notes that "equivalence is not guaranteed". The JIS composition (agrees between the Japan Stainless Steel Association and Sanyo's Red Book) is C 0.95-1.20, Si ≤1.00, Mn ≤1.00, P ≤0.040, S ≤0.030, Cr 16.00-18.00, Mo ≤0.75 (may be contained), Ni ≤0.60 (may be contained). JIS covers bar only (no plate)
- EN X105CrMo17: Böhler N695 (440C / 1.4125 / X105CrMo17 / S44004) and Aubert & Duval (X105CrMo17, 1.4125, UNS S44004, AISI 440C) are shown in the same row. On the other hand, the Japan Stainless Steel Association cross-reference (sourced from ISO 15510) marks the European column "not confirmed" and gives the ISO symbol as X110Cr17 (ISO number 4023-440-04-I). The composition range of EN 1.4125 is not confirmed in primary sources
- GB : Kyocera's cross-reference lists three (former) grade designations in the GB column for SUS440C: 9Cr18, 11Cr17 and 9Cr18Mo, so it cannot be narrowed to one. Which designation S44096 corresponds to has not been checked in Chinese primary sources
📄Related specifications (AMS, ASTM etc.)
Specifications called up on purchase orders and drawings. AMS are SAE aerospace material specifications, split by product form (bar, plate, forging), melting practice and heat treatment. Standard texts are paid, so only titles and scopes checked on the publishers’ public pages are shown.
| Spec | Scope | Confidence |
|---|---|---|
| AMS 5630 | Steel, Corrosion-Resistant, Bars, Wire, and Forgings and Forging Stock 17Cr - 0.52Mo (0.95 - 1.20C) (440C)Bar, wire, forgings and forging stock. Revision letter M confirmed on SAE Mobilus | Agrees in 2+ sources[5] |
| AMS 5618 | Steel, Corrosion-Resistant, Bars, Wire, and Forgings, 17Cr - 0.52Mo (0.95 - 1.20C), (440C), Consumable Electrode Vacuum MeltedBar, wire and forgings. Consumable electrode vacuum melted. Revision letter K confirmed | Agrees in 2+ sources[11] |
| AMS 5880 | Steel, Corrosion-Resistant, Bars, Wire, Forgings and Forging Stock 17Cr - 0.52Mo (0.95 - 1.20C) (SAE 51440C) for Bearing ApplicationsBar, wire, forgings and forging stock for bearings. Revision letter F confirmed | Agrees in 2+ sources[12] |
| ASTM A276/A276M | Standard Specification for Stainless Steel Bars and ShapesHot-finished and cold-finished stainless steel bars and shapes. Condition classes include annealed (A) and quenched and tempered (H, T). The A276/A276M-25 page was confirmed at store.astm.org | Agrees in 2+ sources[13] |
All ASTM standards on Kezuriba: ASTM standards quick reference.
✈Main aerospace uses (as stated in the sources)
- Balls, rollers, needles and races for bearings requiring corrosion resistance; aerospace turbine and engine parts (Böhler N695)[2]
- Widely used for instrument bearings, and traditionally the choice for bearings in cryogenic rocket engine turbopumps such as those of the Space Shuttle. Below 149°C it is the first choice among corrosion-resistant bearing steels (NASA)[14]
- Aerospace valves and ball bearings (Carpenter)[15]
⚗Chemical composition (mass %)
Ranges differ between specifications, so each one has its own column (dark figures agree in several sources, light figures come from one source).
| Element | Spec ① | Spec ② | Spec ③ | Spec ④ |
|---|---|---|---|---|
| C | 0.95 – 1.20[1][5][2] | — | — | — |
| Si | — | ≤ 1[1][2] | — | — |
| Mn | — | — | ≤ 1[1][2] | — |
| P | — | — | ≤ 0.04[1][2] | — |
| S | — | — | ≤ 0.03[1][2] | — |
| Cr | — | — | 16 – 18[1][2] | — |
| Mo | ≤ 0.75[1] | — | — | 0.40 – 0.65[2] |
| Ni | — | — | — | ≤ 0.75[2] |
| Cu | — | — | — | ≤ 0.5[2] |
- Spec ① Carpenter 440C composition table (UNS S44004). Also agrees with the C range (0.95-1.20) in the titles of AMS 5630, 5618 and 5880, and with Böhler (AMS 5630 related)
- Spec ② Agrees between Carpenter 440C (UNS S44004) and Böhler N695 (AMS 5630 related)
- Spec ③ Agrees between Carpenter 440C and Böhler N695 (AMS 5630 related)
- Spec ④ AMS 5630 related (Böhler N695 table). The nominal in the AMS 5630 title is 0.52Mo
⚖Density
7.7 g/cm³
Aubert & Duval (1.4125) gives 7.7 and Sanyo Special Steel (SUS440C) gives 7.75, a slight difference
Calculate weight in 440C →💪Mechanical properties
“Reference” values are not specified minimums from the standard but figures published by makers and others.
| Condition | Tensile MPa | Yield MPa | Elong. % | Hardness | Type of value |
|---|---|---|---|---|---|
| Annealed (JIS G 4303 SUS440C) | — | — | — | HBW 269 max | JIS specified value (from the JIS G 4303 table in Sanyo Special Steel's "Red Book" catalog). Annealing is 800-920°C, slow cooling One source / reference[6][7] |
| Annealed (delivery condition) | — | — | — | HB 255 max (cold-finished bar up to 69.85 mm diameter) / HB 230 (typical value) | Upper limit of the delivery condition for Böhler N695 (AMS 5630 related), and typical value from Aubert & Duval (1.4125) One source / reference[2][8] |
| Quenched and tempered (JIS G 4303 SUS440C: 1010-1070°C oil cooled + 100-180°C air cooled) | — | — | — | HRC 58 min | JIS specified value (Sanyo Special Steel "Red Book" catalog and English-language stainless steel catalog) One source / reference[6][7] |
| Quenched and tempered | — | — | — | About HRC 60 (Carpenter) / HRC 59 (Aubert & Duval: 1040°C oil quench + subzero + 140°C temper) | Typical value (manufacturer). Böhler describes it as for parts requiring hardness up to HRC 58 One source / reference[1][8][2] |
1 MPa ≈ 145 psi (0.145 ksi). Hardness conversion · unit converter
🔧Machinability notes (as stated in the sources)
📚Sources
Primary sources (public documents from makers, industry associations and standards bodies), numbered where each value is cited. Many are in Japanese.
- carpentertechnology.com https://www.carpentertechnology.com/alloy-finder/440C
- bohler-edelstahl.com https://www.bohler-edelstahl.com/app/uploads/sites/248/productdb/api/n695-aerospace_en_gb.…
- jssa.gr.jp https://www.jssa.gr.jp/contents/products/standards/comparisons/
- sandvik.coromant.com https://www.sandvik.coromant.com/en-us/knowledge/materials/workpiece-materials
- saemobilus.sae.org https://saemobilus.sae.org/content/ams5630m/
- sanyo-steel.co.jp https://www.sanyo-steel.co.jp/product/special_steel/images/pdf/akahon_201906.pdf
- sanyo-steel.co.jp https://www.sanyo-steel.co.jp/english/product/special_steel/images/pdf/stainless_201712.pd…
- aubertduval.com https://www.aubertduval.com/wp-content/uploads/2024/12/XDBD_GB.pdf
- kyocera.co.jp https://www.kyocera.co.jp/prdct/tool/wp-content/uploads/2016/06/R_2016.pdf
- jssa.gr.jp https://www.jssa.gr.jp/contents/products/standards/jis/martensite/
- saemobilus.sae.org https://saemobilus.sae.org/content/ams5618k/
- saemobilus.sae.org https://saemobilus.sae.org/content/ams5880f/
- store.astm.org https://store.astm.org/a0276_a0276m-25.html
- ntrs.nasa.gov https://ntrs.nasa.gov/api/citations/20120008557/downloads/20120008557.pdf
- carpentertechnology.com https://www.carpentertechnology.com/hubfs/Alloy%20Cards/440C_snapshot.pdf
Other materials
Aerospace steel