Introduction
Stainless steels are high alloy steels which have higher corrosion resistance compared to other steels due to the presence of large amounts of chromium. Based on their crystalline structure, they are further divided into ferritic, austenitic, and martensitic steels.
Grade 309 stainless steel has high corrosion resistance and strength compared to 304 stainless steel. The following datasheet gives an overview of grade 309 stainless steel.
Chemical Composition
The following table shows the chemical composition of grade 309 stainless steel.
| Element | Content (%) |
| Iron, Fe | 60 |
| Chromium, Cr | 23 |
| Nickel, Ni | 14 |
| Manganese, Mn | GBP 2 |
| Silicon, Si | GBP 1 |
| Carbon, C | GBP 0.20 |
| Phosphorous, P | GBP 0.045 |
| Sulfur, S | GBP 0.030 |
Physical Properties
The physical properties of grade 309 stainless steel are given in the following table.
| Properties | Metric | Imperial |
| Density | 8 g/cm3 | 0.289 lb/in3 |
| Melting point | 1455 C | 2650 F |
Mechanical Properties
The following table outlines the mechanical properties of annealed grade 309 stainless steel.
| Properties | Metric | Imperial |
| Tensile strength | 620 MPa | 89900 psi |
| Yield strength (@ strain 0.200%) | 310 MPa | 45000 psi |
| Izod impact | 120 - 165 J | 88.5 - 122 ft-lb |
| Shear modulus (typical for steel) | 77 GPa | 11200 ksi |
| Elastic modulus | 200 GPa | 29008 ksi |
| Poisson's ratio | 0.27-0.30 | 0.27-0.30 |
| Elongation at break (in 50 mm) | 45% | 45% |
| Hardness, Brinell | 147 | 147 |
| Hardness, Rockwell B | 85 | 85 |
| Hardness, Vickers (converted from Rockwell B hardness) | 169 | 169 |
Thermal Properties
The thermal properties of grade 309 stainless steel are displayed in the following table.
| Properties | Metric | Imperial |
| Thermal expansion co-efficient (@ 0-100 C/32-212 F) | 14.9 m/m C | 8.28 in/in F |
| Thermal conductivity (@ 0-100 C/32-212 F) | 15.6 W/mK | 108 BTU in/hr.ft2 .F |
Other Designations
Other designations equivalent to grade 309 stainless steel are included in the following table.
| ASTM A167 | ASME SA249 | ASTM A314 | ASTM A580 |
| ASTM A249 | ASME SA312 | ASTM A358 | FED QQ-S-763 |
| ASTM A276 | ASME SA358 | ASTM A403 | FED QQ-S-766 |
| ASTM A473 | ASME SA403 | ASTM A409 | MIL-S-862 |
| ASTM A479 | ASME SA409 | ASTM A511 | SAE J405 (30309) |
| DIN 1.4828 | ASTM A312 | ASTM A554 | SAE 30309 |
Fabrication and Heat Treatment
Machinability
Grade 309 stainless steel can be machined similar to that of 304 stainless steel.
Welding
Grade 309 stainless steel can be welded using fusion or resistance welding methods. Oxyacetylene welding method is not preferred for welding this alloy.
Hot Working
Grade 309 stainless steel is hot worked at 1177°C (2150°F) followed by reheating at 982°C (1800°F). It can be then quenched rapidly. Post work annealing can be done to restore its corrosion resistance property.
Cold Working
Grade 309 stainless steel can be headed, upset, drawn, and stamped even though it has high work hardening rate. Annealing is performed after cold working in order to reduce internal stress.
Annealing
Grade 309 stainless steel is annealed at 1038-1121°C (1900-2050°F) followed by quenching in water.
Hardening
Grade 309 stainless steel does not react to heat treatment. Strength and hardness of this alloy can be increased by cold working.
Applications
Grade 309 stainless steel is used in the following applications:
Boiler baffles
Furnace components
Oven linings
Fire box sheets
Other high temperature containers
Source - www.azom.com
(www.steelguru.com)
