440A is a high carbon martensitic stainless steel that is AOD melted. This alloy can be heat treated to extremely high hardnesses. It has slightly less carbon than 440B and 440C giving it better machinability but less hardness. The combination of good wear resistance and high hardness makes this alloy an excellent candidate for cutting tools and knife blades. It also is often used for dental and surgical equipment.
Chemical Composition
The chemical composition of grade 440A stainless steel is outlined in the following table.
| Element | Content (%) |
|---|---|
| Iron, Fe | Balance |
| Chromium, Cr | 16-18 |
| Manganese, Mn | 1 |
| Silicon, Si | 1 |
| Molybdenum, Mo | 0.75 |
| Carbon, C | 0.60-0.75 |
| Sulfur, S | 0.03 |
| Phosphorous, P | 0.04 |
Mechanical Properties
The mechanical properties of grade 440A stainless steel are displayed in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Tensile strength | 725-1790 MPa | 105000 - 260000 psi |
| Yield strength (@strain 0.200 %) | 415-1650 MPa | 60200 - 239000 psi |
| Modulus of elasticity | 204 - 215 GPa | 29600 - 31200 ksi |
| Elongation at break (in 50 mm) | 5- 20% | 5- 20% |
| Hardness, Rockwell B | 95 | 95 |
Other Designations
Equivalent materials to grade 440A stainless steel are given below.
| AISI 440A | AMS 5631 | AMS 5632 | ASTM A276 | ASTM A314 |
| ASTM A473 | ASTM A511 | ASTM A580 | QQ S763 | SAE 51440A |
| FED QQ-S-763 | MIL SPEC MIL-S-862 | SAE J405 (51440A) |