Stainless steel alloys are popular and sometimes seem to be identical. But these grades hold important substantial value for certain applications. A minuscule difference can impact great consideration for the intended use. Manufacturers and designers pay a significant contribution towards the perfect match.
Grade 304, 316, and 317 are austenitic stainless steel with different chemical compositions. These alloys offer some greater benefits like corrosion resistance, tensile strength, and high-temperature resistance. Among these grades, grades 304 and 316 are the most popular and commercially used.
Chemical composition of grades 304, 316 and 317
Austenitic grades are characterized by a higher concentration of chromium and nickel. Grade 316 and 317 has more amalgamation than grade 304, i.e. molybdenum. Molybdenum helps in providing corrosion resistance in the presence of chlorides. The nickel concentration enhances formability, strength, and weldability. Besides, grade 317 has more molybdenum and the resultant is the cost.
| Grade | Carbon
(max)% |
Manganese
(max)% |
Silicon
(max)% |
Phosphorus
(max)% |
Sulfur
(max)% |
Chromium
(max)% |
Nickel
(max)% |
Nitrogen
(max)% |
Molybdenum
(max)% |
| 304 | 0.07 | 2.0 | 1.0 | 0.045 | 0.030 | 17.5-19.5 | 8-10.5 | 0.10 | – |
| 316 | 0.07 | 2.0 | 1.0 | 0.045 | 0.030 | 16-18% | 10-13.0 | – | 2.0-2.5 |
| 317 | 0.07 | 2.0 | 1.0 | 0.045 | 0.030 | 17.5-19.5 | 13.0-16.0 | – | 3.0-4.0 |
Properties
Grade 304 and 316 offers effective corrosion resistance in demanding environmental conditions. However, grade 317 has more endurance than grade 304 and 316. It offers excellent service in high and cryogenic temperatures. Grade 317 can perform under extreme conditions. That’s the reason; grade 317 is highly used in chemical plants, refineries, marine industry.
Is the extra cost of grade 317 worth over grade 316 and 304?
Grade 316 has considerable significant corrosion resistance to high corrosive mediums. However, grade 317 offers better resistance in acidic mediums. It performs extremely well in presence of sulfuric acid. The PREN values are superior for grade 317. Grade 317 can be a good choice for heat exchangers, Gasoil refineries, pulping paper, etc.
To draw an inference, comprehensive data of an application is required before the selection of stainless steel grades. The budget for the project is also an important acquaintance. Grade 317 has advantages over grades 316 and 304, but it’s a little more expensive than both.
