Description
440C AMS 5618 Round Bar
440C AMS 5618 is a premium, vacuum-melted grade of 440C martensitic stainless steel, specified by SAE International, known for exceptional hardness (to 60 HRC), wear resistance, and corrosion resistance, primarily used in demanding aerospace applications like anti-friction bearings, precision instruments, and high-performance valve components where reliability is critical.
AMS 5618 provides aircraft-quality 440C steel for applications demanding the utmost in hardness and wear performance, with enhanced purity due to its vacuum melting process.
AISI 440C is available in either Standard Melted (AMS 5630) or Vacuum Melted (AMS 5618) versions. AMS 5618 is typically used for anti-friction bearing components where resistance to both corrosion and wear is essential. SS 440C is capable of hardnesses in excess of 58 HRC after heat treatment.
As a stainless steel, 440C is a great go-to grade for many applications where moderate corrosion resistance is needed, offering superior performance to SAE 52100.
440C is a high carbon martensitic stainless steel that is AOD, AOD + ESR or AOD + VAR melted. It has slightly more carbon than 440A and 440B giving it the highest hardness of any martensitic stainless alloy. This grade has excellent wear resistance making it perfect as a bearing steel used as ball bearings and bearing races. It also is readily used as cutlery.
440C Chemical Composition of AMS 5618 :
| Element | Min. | Max. |
| C | 0.95 | 1.20 |
| Mn | – | 1.00 |
| Si | – | 1.00 |
| Cr | 16.00 | 18.00 |
| P | – | 0.040 |
| S | – | 0.030 |
| Mo | – | 0.75 |
Comparison to Other Grades:
AMS 5618 is a higher-quality, premium version of the standard air-melted AMS 5630 (also 440C), offering superior cleanliness for critical applications.
Applications of 440C :
Aerospace: Anti-friction bearings, control components, high-reliability parts.
Precision Parts: Gage blocks, ball screws, measuring instruments.
Industrial: Valves, knives, medical instruments, tooling.
Cutting Instruments
Ball Bearings and Ball Screws
Knife Blades, Chisels, and Swords
Surgical Instruments
Heat Treatment :
As a steel with relatively high hardness, 440C is often supplied as Annealed for easier machinability. Following this, 440C can be hardened and quenched to increase strength and prevent cracking. Tempering can be performed to reduce brittleness without sacrificing hardness.
Designations :
DIN 1.4125, AMS 5618 , AMS 5630 , ASTM A276 , ASTM A314 , ASTM A473 , ASTM A493 , ASTM A580 , FED QQ-S-763 , MIL SPEC MIL-S-862 , SAE 51440C , SAE J405 (51440C) , UNS S44004, AS 2837-1986 440C, W.Nr 1.4125 X105CrMo17, JIS G4303 SUS 440C, UNS S44004
Applicable Specifications :
AMS 5618
AMS 5880
AMS 5630
ASTM A276
ASTM A314
ASTM A493
ASTM A756
ASTM A473
ASTM A580
AMS-QQ-S-763
ASTM F899
Barden SA 1254
Federal QQ-S-763
NHBB PES 1.102
NHBB SM3
Woodward SP-1197
