About AMS 5630 / AMS 5618
AMS 5630 and AMS 5618 are SAE aerospace material specifications for 440C (UNS S44004), a high carbon martensitic stainless steel with 16-18 % chromium. AMS 5630 covers air melted bars, wire, forgings and forging stock. AMS 5618 covers consumable electrode remelted material with tighter cleanliness limits. After hardening, 440C reaches 58 HRC minimum and about 60 HRC is possible. It gives high hardness and wear resistance with moderate corrosion resistance.
440C has more carbon than 440A and 440B, so it hardens to a higher level. The steel is magnetic, and it resists corrosion best in the fully hardened condition.
Updated 2 October 2026 | Jiangyin Jiangnan Metal Co., Ltd.
AMS 5630, AMS 5880 and AMS 5618 compared
| Specification | Melting | Cleanliness | Typical use |
|---|---|---|---|
| AMS 5630 | Air melt | Standard | Valve parts, tooling, general wear parts |
| AMS 5880 | With cleanliness testing | Bearing quality | Bearing components |
| AMS 5618 | Consumable electrode remelt (CEM) | Premium, P 0.020 % max, S 0.010 % max | Anti-friction bearing parts needing both corrosion and wear resistance |
Chemical composition
| Element | AMS 5630 | AMS 5618 |
|---|---|---|
| Carbon (C) | 0.95 - 1.20 | 0.95 - 1.20 |
| Manganese (Mn) | 1.00 max | 1.00 max |
| Silicon (Si) | 1.00 max | 1.00 max |
| Phosphorus (P) | 0.040 max | 0.020 max |
| Sulfur (S) | 0.030 max | 0.010 max |
| Chromium (Cr) | 16.00 - 18.00 | 16.00 - 18.00 |
| Molybdenum (Mo) | 0.40 - 0.65 | 0.40 - 0.65 |
| Nickel (Ni) | 0.75 max | 0.75 max |
| Copper (Cu) | 0.50 max | 0.50 max |
Orders follow the current revision of the AMS specification. Mill test certificates are supplied.
Physical and mechanical properties
| Property | Value |
|---|---|
| Hardness, annealed | 255 HB max |
| Hardness after heat treatment | 58 HRC min, about 60 HRC possible |
| Density | 0.28 lb/in3 (about 7.75 g/cm3) |
| Thermal expansion, 32-212 F | 5.7 x 10-6 in/in/F |
| Machinability | About 40 % of AISI 1212 |
| Magnetic | Yes |
Heat treatment
Annealing
843-899 C (1550-1650 F), slow cool.
Hardening
982-1066 C (1800-1950 F), air or oil quench depending on section size.
Tempering
Temper to the required hardness. Best corrosion resistance is in the fully hardened condition.
Forging, machining and welding
Forging
Preheat to 760 C (1400 F), then raise slowly to 1038-1204 C (1900-2200 F). Do not forge below 927 C (1700 F). Cool slowly after forging and fully anneal once the part reaches room temperature.
Machining
Machine in the annealed condition. Chips are tough and stringy, so chip breakers help. Use carbide or ceramic tools.
Welding
440C is seldom welded because it air hardens. If welding is needed, preheat to 260 C (500 F), post weld heat treat at 732-760 C (1350-1400 F) for 6 hours and furnace cool slowly to avoid cracking. Use matching filler metal and high heat input.
440C forged products
Forged bars
Round, square, rectangular, flat and hex bars.
Hollow forgings
Hollow bars, sleeves, bushings, tubes, barrels, casings, shells, cylinders, hubs and housings.
Rings
Seamless rolled rings, bearing races and valve seat rings.
Discs and blocks
Forged discs, blocks and plates.
Custom parts
Valve bodies, bonnets, stems and seats, pump parts, pivot pins, nozzles and other parts to drawing.
Applications
Ball bearings and races, gauge blocks, molds and dies, cutlery and knives, valve seats, stems, bodies and bonnets, pump parts, pivot pins, nozzles, surgical instruments and measuring instruments.
Equivalent grades
| Standard | Grade |
|---|---|
| UNS | S44004 |
| AISI / SAE | 440C / 51440C |
| EN / W.Nr. | 1.4125 / X105CrMo17 |
| JIS | SUS440C |
| AFNOR | Z100CD17 |
| Federal | QQ-S-763 Class 440C |
| Related AMS | AMS 5880, AMS 5618 |
Chemistry limits of these grades are close but not identical. Check your drawing before substituting.
FAQ
What is the difference between AMS 5630 and AMS 5618?
Both cover 440C. AMS 5630 is air melted. AMS 5618 is consumable electrode remelted with tighter cleanliness limits (P 0.020 % max, S 0.010 % max) and is mainly used for anti-friction bearing parts.
What hardness can 440C reach?
58 HRC minimum after heat treatment, about 60 HRC possible. Annealed hardness is 255 HB max.
What is the equivalent grade of AMS 5630?
AISI 440C / UNS S44004. Comparable grades are 1.4125 (X105CrMo17), SUS440C, Z100CD17 and QQ-S-763 Class 440C.
Can 440C be welded?
Seldom. If needed, preheat to 260 C, post weld heat treat at 732-760 C for 6 hours and furnace cool slowly.
Where can I buy AMS 5630 / AMS 5618 forgings in China?
Jiangyin Jiangnan Metal Co., Ltd. in Jiangyin, Jiangsu forges 440C bars, rings, discs, blocks, sleeves and custom parts to AMS 5630 and AMS 5618. Email sales@steelforgepieces.com or call +86-189-2135-9659.
Request a quote
Send your drawing or sizes, the specification (AMS 5630, AMS 5880 or AMS 5618), quantity and delivery condition. We will reply with price and lead time.
Jiangyin Jiangnan Metal Co., Ltd. | Open-Die Forging FactoryNo.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Tel: +86-189-2135-9659
Email: sales@steelforgepieces.com Email RFQ