Introduction
SUS316 is one of the most widely used austenitic stainless steels, often described as the superior alternative to SUS304. The key differentiator is the addition of 2.0–3.0% molybdenum (Mo), combined with higher nickel content, which dramatically improves resistance to chloride-induced pitting and crevice corrosion — making SUS316 the material of choice for marine, chemical, and food-grade applications.
Compared to SUS304 (18% Cr, 8% Ni, no Mo), SUS316 contains approximately 16% Cr, 10–14% Ni, and 2–3% Mo. This composition gives SUS316 superior corrosion resistance, particularly in saltwater and chloride-rich environments, at a higher material cost.
SUS316 also offers higher tensile and yield strength than SUS304, making it the standard material for A4-70 and A4-80 grade fasteners.
SUS316 (JIS G4303) and 316 (ASTM A276) are essentially interchangeable designations with identical compositions. This page uses JIS G4303 as the primary reference.
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SUS316 Chemical Composition
Reference standard: JIS G4303
| Grade | C (%) | Mn (%) | Si (%) | P (%) | S (%) | Ni (%) | Mo (%) | Cr (%) |
|---|---|---|---|---|---|---|---|---|
| SUS316 | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | ≤ 0.045 | ≤ 0.03 | 10.00–14.00 | 2.00–3.00 | 16.00–18.00 |
SUS316 Composition Across Different Standards
| # | Standard | Grade | UNS | C | Mn | P | S | Si | Cr (%) | Ni (%) | Mo (%) | N |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | ASTM A276/A276M | 316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 2 | ASTM A959 | 316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 3 | ASTM A240/A240M | 316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤0.75 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | ≤0.1 |
| 4 | ASTM A182/A182M | F316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | ≤0.1 |
| 5 | ASTM A193/A193M | 316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 6 | ASTM A269/A269M | TP316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 7 | ASTM A312/A312M | TP316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 8 | ASTM A320/A320M | 316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 9 | ASTM A493 | 316 | S31600 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | ≤0.1 |
| 10 | ASTM A554 | MT-316 | — | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 11 | JIS G4303:2012 | SUS316 | — | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 12 | JIS G4304:2012 | SUS316 | — | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 13 | JIS G4305:2012 | SUS316 | — | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
| 14 | GB/T 20878-2007 | 06Cr17Ni12Mo2 | S31608 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | — |
Physical and Mechanical Properties
Mechanical Properties (JIS G4303)
| Grade | Tensile Strength σb (MPa) | Yield Strength σ0.2 (MPa) | Elongation δ5 (%) | Reduction of Area ψ (%) | Hardness | Density (g/cm³) | Melting Point (°C) |
|---|---|---|---|---|---|---|---|
| SUS316 | ≥ 520 | ≥ 205 | ≥ 40 | ≥ 60 | ≤ 187 HB / ≤ 90 HRB / ≤ 200 HV | 7.98 | 1375–1450 |
Other Physical Properties
| Property | Value |
|---|---|
| Melting Point | 1375–1450 °C |
| Solution Annealing Temperature | 1010–1150 °C |
| Microstructure | Austenitic |
| Electrical Resistivity | 73.0 μΩ·cm |
| Specific Heat Capacity | 0.45 J/(g·K) |
| Magnetic Permeability | Non-magnetic in annealed / fully austenitic state (μ ≤ 1.02 at 200H); may increase slightly after cold working |
SUS316 vs SUS304: Key Differences
| Criteria | SUS304 | SUS316 |
|---|---|---|
| Cr content | 18% | 16% |
| Ni content | 8% | 10–14% |
| Mo content | None | 2–3% |
| Corrosion resistance | Good | Superior (especially in chloride/marine environments) |
| Tensile / yield strength | Similar | Similar (slightly higher in practice) |
| Machinability | Better | Slightly lower |
| Cost | Lower | Higher (due to Mo and Ni) |
| Typical fastener grade | A2-70 / A2-80 | A4-70 / A4-80 |
| Best for | General purpose, indoor, cost-sensitive | Marine, chemical, food-grade, coastal environments |
Summary: SUS316 is better but more expensive; SUS304 offers the best value for general use.
SUS316 vs SUS316L
The "L" in SUS316L stands for Low Carbon (C ≤ 0.03%), analogous to the relationship between SUS304L and SUS304. The lower carbon content of SUS316L provides two key advantages:
- Better weldability — reduced risk of sensitization (carbide precipitation at grain boundaries) in the heat-affected zone
- Superior corrosion resistance post-welding — since carbon cannot combine with chromium to form chromium carbides, the passive film remains intact
Sensitization occurs when heat from welding or heat treatment causes carbon and chromium to combine, depleting chromium at grain boundaries and reducing corrosion resistance. SUS316L’s low carbon content minimizes this risk. For welded assemblies in corrosive environments, SUS316L with low-carbon filler metal is the recommended choice.
Applications of SUS316 Stainless Steel
- Marine & Coastal Infrastructure — pumps, valves, and piping in contact with seawater; coastal building facades and structural components exposed to sea spray
- Shipbuilding — hull fittings, deck hardware, and components on chemical tankers and offshore vessels
- Chemical Processing — tanks, reactors, and pipelines handling chloride-containing or acidic media
- Snow-melt regions — pipeline components in areas where NaCl/CaCl₂ de-icing agents are used
- Food & Beverage — commercial food storage containers, processing equipment handling salt-containing products
- Fasteners — A4-70 and A4-80 grade bolts, nuts, and screws for marine and chemical environments
Browse our marine-grade stainless steel fastener products: Marine Carriage Bolts (DIN 603) – A4, Marine Castle Nuts (DIN 935) – A4, Marine Dome Nuts (DIN 1587) – A4, and Marine Eye Bolts (DIN 444) – A4.
Fabrication Characteristics
Machinability & Forming
SUS316 can be machined by turning, milling, drilling, punching, and stamping using the same equipment as carbon steel. Its good ductility allows cold forming by bending, drawing, and deep drawing. However, due to its higher strength and work-hardening rate compared to carbon steel, greater machine power is required. For high-volume precision turning, SUS303 remains the preferred free-machining alternative.
Weldability
SUS316 is considered readily weldable by all fusion methods and resistance welding. Two key considerations apply:
- Hot cracking prevention: A small amount of ferrite is intentionally included in the alloy to reduce crack sensitivity in fully austenitic welds.
- Corrosion resistance of the weld zone: For components used in corrosive environments, low-carbon SUS316L filler metal and consumables are strongly recommended to prevent sensitization and intergranular corrosion. Higher Mo content in filler metal may be needed in aggressive environments to compensate for Mo micro-segregation in the weld pool.
Standards reference: JIS G4303 | JIS G4304 | JIS G4305 | ASTM A276/A276M | ASTM A959 | ASTM A240 | GB/T 20878 | GB/T 1220
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