06 Jan All about Stainless Steel – Grade 440C (UNS S44004)
Introduction
Stainless steels are high-alloy steels that have a higher corrosion resistance than other steels due to the presence of a high concentration of chromium. They are classified into three categories based on their crystalline structure: ferritic, austenitic, and martensitic steels. Precipitation-hardened steel is another type of stainless steel. They are made up of a mix of martensitic and austenitic steels.
Grade 440C stainless steel is a martensitic stainless steel with a high carbon content. It is strong, has moderate corrosion resistance, and is hard and wear-resistant.
The datasheet that follows provides an overview of grade 440C stainless steel.
Chemical Composition
The chemical composition of grade 440C stainless steel is shown in the table below.
|
Element |
Content (%) |
|
Iron, Fe |
79.15 |
|
Chromium, Cr |
17 |
|
Carbon, C |
1.1 |
|
Manganese, Mn |
1 |
|
Silicon, Si |
1 |
| Molybdenum, Mo |
0.75 |
Physical Properties
The physical parameters of grade 440C stainless steel are shown in the table below.
|
Properties |
Metric | Imperial |
| Density | 7.80 cm³ | 0.282 lb/in³ |
| Melting point | 1483°C |
2700°F |
Mechanical Properties
The mechanical parameters of grade 440C stainless steel are shown in the table below.
| Properties | Metric | Imperial |
| Tensile strength | 760-1970 MPa | 110000-286000 psi |
| Yield strength (@ strain 0.200%) | 450-1900 MPa | 65300-276000 psi |
| Bulk modulus | 166 GPa | 24100 ksi |
| Shear modulus | 83.9 GPa | 12200 ksi |
| Elastic modulus | 200 GPa | 29008 ksi |
| Poisson’s ratio | 0.27-0.30 | 0.27-0.30 |
| Elongation at break | 2-14 % | 2-14 % |
| Hardness, Rockwell B (converted from Brinell hardness) | 97 | 97 |
Thermal Properties
The thermal characteristics of 440C stainless steel are shown in the table below.
|
Properties |
Metric | Imperial |
|
Thermal expansion coefficient |
10.2 µm/m°C |
5.67 µin/in°F |
| Thermal conductivity | 24.2 W/mK | 168 BTU in/hr.ft².°F |
Other Designations of SS440C
Other grades of stainless steel that are equal to grade 440C include:
AMS 5618
AMS 5630
AMS 5880
ASTM A276
ASTM A314
ASTM A473
ASTM A493
ASTM A580
DIN 1.4125
QQ S763
MIL-S-862
SAE 51440C
SAE J405 (51440C)
Fabrication and Heat Treatment
Machinability
In the annealed state, stainless steel grade 440C may be machined. Chip breakers are useful for dealing with difficult and stringy chips. This alloy is best suited to carbide or ceramic tooling.
Welding
Because it is readily air-hardened, grade 440C stainless steel is not welded. To minimize cracking, this alloy should be warmed to 260°C (500°F) and post-weld treated at 732-760°C (1350-1400°F) for 6 hours before gently cooling in the furnace.
Hot Working
The stainless steel grade 440C is pre-heated to 760°C (1400°F). The temperature may be raised to 1038-1204° C (1900-2200° F). It should not be heated any lower than 927°C (1700°F). After that, it is progressively cooled to ambient temperature and totally annealed.
Cold Working
Grade 440C stainless steel is somewhat cold-workable when utilizing standard techniques.
Annealing
The stainless steel grade 440C is annealed at 843-871°C (1550-1600°F), then progressively cooled in the furnace.
Tempering
Tempering 440C stainless steel at 148°C (300°F) is possible.
Hardening
Hardening 440C stainless steel at 760°C (1400°F) is possible. Temperatures may be raised to 1010°C (1850°F), then cooled in air or oil.
Applications
Stainless steel grade 440C is used in the following applications:
Gage blocks
Cutlery
Ball bearings and races
Molds and dies
Knives
Valve components
Measuring instruments
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