Stainless Steel: 317 (UNS S31700)
Since its invention, Stainless Steel has gained huge popularity because of its highly useful properties including corrosion resistance, high strength and durability. Based on the chemical composition of stainless steel, it is available in different grades. Characterized by different properties these grades are used for varied applications. One of the common grades of stainless steel is grade 317 also known as UNS S31700.
What Is 317 Stainless Steel?
Grade 317 is a modified version of grade 316. 317 Stainless Steel is highly resistant to corrosion even in extreme environments. It also provides good mechanical properties at high temperatures. Furthermore, it can be easily fabricated and welded. This grade is particularly known for its resistance to corrosion in acidic environments. It is widely used for chemical and petrochemical processing, marine applications, and food processing. It is also used in medical implants and surgical instruments.
AISI 317 Chemical Composition
The main differentiation factor between the various grades of stainless steel is its chemical properties. Even a small variation in the chemical composition of these stainless steel grades can lead to major differentiation in their properties.
Let us have a quick look at the chemical composition of AISI 317
| Element | Content (%) |
| Carbon (C) | 0.08 max |
| Manganese (Mn) | 2.00 max |
| Silicon (Si) | 1.00 max |
| Phosphorus (P) | 0.045 max |
| Sulfur (S) | 0.03 max |
| Chromium (Cr) | 18.00–20.00 |
| Nickel (Ni) | 11.00–15.00 |
| Molybdenum (Mo) | 3.00–4.00 |
| Nitrogen (N) | 0.10 max |
| Iron (Fe) | Balance |
Physical Properties
| Property | Value |
| Density | 8.00 g/cm³ |
| Melting Point | 1390–1440°C |
| Modulus of Elasticity | 200 GPa |
Mechanical Properties
he mechanical properties of grade 317 are the determining factors of its uses in various applications. Here are the various mechanical properties of grade 317:
| Property | Value |
| Tensile Strength | 515 MPa (75 ksi) min |
| Yield Strength (0.2% offset) | 205 MPa (30 ksi) min |
| Elongation at Break | 35% min |
| Hardness, Brinell | 217 HB max |
| Hardness, Rockwell B | 95 HRB max |
Thermal Properties
The thermal properties of various grades of stainless steel vary based on their chemical composition. Below are the thermal properties of grade 317.
| Property | Value |
| Thermal Conductivity (at 100°C) | 16.2 W/m·K |
| Specific Heat | 500 J/kg·K |
| Thermal Expansion (0–100°C) | 16.0 x10⁻⁶/K |
Applications
Grade 317 is an austenitic chromium-nickel-molybdenum grade of stainless steel with high corrosion resistance and formability. This thus easily fits into usages directly or indirectly related to various industries including:
- Chemical and petrochemical industry
- Fertilizer, and power generation;
- Food processing,
- Water supply systems
- Medical instruments.
317 vs 316 Stainless Steel: What's the Difference?
| Property | 317 Stainless Steel | 316 Stainless Steel |
| Molybdenum content | 3.00–4.00% | 2.00–3.00% |
| Pitting/crevice corrosion resistance | Higher | Good |
| Cost | Higher | Lower |
| Best fit | Aggressive acidic/chloride environments | General-purpose corrosion resistance |
Frequently Asked Questions
Q1. What is 317 stainless steel used for?
317 stainless steel is used in chemical processing equipment, pulp and paper plants, marine components, and food processing equipment, wherever resistance to acidic and chloride-rich environments is required.
Q2. Is 317 stainless steel magnetic?
317 stainless steel is austenitic and is essentially non-magnetic in the annealed condition. Cold working can introduce slight magnetic permeability, but it stays far less magnetic than ferritic or martensitic grades.
Q3. What is the difference between 316 and 317 stainless steel?
317 stainless steel carries a higher molybdenum content (3.00–4.00%) than 316 (2.00–3.00%), giving 317 stronger resistance to pitting and crevice corrosion in chloride and acidic environments.
Q4. Can 317 stainless steel be welded?
Yes. 317 stainless steel welds well using standard fusion methods without losing corrosion resistance, provided the weld zone is cleaned of heat tint afterward.