Sep 26 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
Machinability
Welding
Hot Working
Cold Working
Annealing
Tempering
Hardening
Applications
Introduction
Stainless steels are high-alloy steels which have high corrosion
resistance compared to other steels due to the presence of large
amounts of chromium. Based on their crystalline structure, they are
divided into three types such as ferritic, austenitic, and martensitic
steels. Another group of stainless steels are precipitation-hardened
steels. They are a combination of martensitic and austenitic steels.
Grade 440C stainless steel is a high carbon martensitic stainless
steel. It has high strength, moderate corrosion resistance, and good
hardness and wear resistance.
The following datasheet gives an overview of grade 440C stainless
steel.
Chemical Composition
The chemical composition of grade 440C stainless steel is outlined
in the following table.
| 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 following table shows the physical properties of grade 440C
stainless steel.
| Properties |
Metric |
Imperial |
| Density |
7.80 cm³ |
0.282 lb/in³ |
| Melting point |
1483°C |
2700°F |
Mechanical Properties
The mechanical properties of grade 440C stainless steel are
displayed in the following table.
| 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 properties of grade 440C stainless steel are given in
the following table.
| Properties |
Metric |
Imperial |
| Thermal expansion co-efficient |
10.2 µm/m°C |
5.67 µin/in°F |
| Thermal conductivity |
24.2 W/mK |
168 BTU in/hr.ft².°F |
Other Designations
Other designations that are equivalent to grade 440C stainless steel
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
Grade 440C stainless steel can be machined in the annealed
condition. Chip breakers can be used to handle tough and stringy chips.
Carbide or ceramic tooling is preferred for this alloy.
Welding
Grade 440C stainless steel is not welded because it can be easily
air hardened. To weld this alloy, it should be preheated to 260°C
(500°F) and post weld treated at 732-760°C (1350-1400°F) for 6 h
followed by slowly cooling in the furnace to prevent cracking.
Hot Working
Grade 440C stainless steel is pre-heated at 760°C (1400°F).
Temperature can be increased up to 1038-1204°C (1900-2200°F). It should
not be heated below 927°C (1700°F). It is then slowly cooled at room
temperature and fully annealed.
Cold Working
Grade 440C stainless steel is slightly cold workable using common
practices.
Annealing
Grade 440C stainless steel is annealed at 843-871°C (1550-1600°F)
followed by slowly cooling in the furnace.
Tempering
Grade 440C stainless steel can be tempered by soaking at 148°C
(300°F).
Hardening
Grade 440C stainless steel can be hardened by heating at 760°C
(1400°F). Temperature can be increased up to 1010°C (1850°F) followed
by cooling in air or oil.
Applications
Grade 440C stainless steel is used in the following applications:
- Gage blocks
- Cutlery
- Ball bearings and races
- Molds and dies
- Knives
- Valve components
- Measuring instruments