What is the difference between S31600 and S31603 stainless steel?
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Differences Between S31600 and S31603 Stainless Steels
1. Standards and Designations
S31600
Corresponding to ASTM/AISI 316 stainless steel (UNS number: S31600), a medium-carbon austenitic stainless steel.
Equivalent to:
JIS SUS316 (Japan), KS STS316 (Korea), EN 1.4401 (Europe, with minor compositional variations but similar properties).
S31603
Corresponding to ASTM/AISI 316L stainless steel (UNS number: S31603), an ultra-low carbon (L-grade) austenitic stainless steel.
"L" stands for "Low Carbon," with significantly reduced carbon content.
Equivalent to:
JIS SUS316L (Japan), EN 1.4404 (Europe).
S31600 and S31603 Stainless Steels Chemical Composition
| Element | S31600 (316) | S31603 (316L) |
|---|---|---|
| Carbon (C) | ≤0.08% | ≤0.03% |
| Chromium (Cr) | 16.0–18.0% | 16.0–18.0% |
| Nickel (Ni) | 10.0–14.0% | 10.0–14.0% |
| Molybdenum (Mo) | 2.0–3.0% | 2.0–3.0% |
S31600 and S31603 Stainless Steels Mechanical Properties
| Property | S31600 (316) | S31603 (316L) |
|---|---|---|
| Tensile Strength | ≥515 MPa | ≥485 MPa |
| Yield Strength | ≥205 MPa | ≥170 MPa |
| Elongation | ≥40% | ≥40% |
| High-Temperature Strength | Slightly better than S31603 | Slightly lower but better high-temperature toughness |
| Weldability | Requires controlled heat input to avoid intergranular corrosion | No post-weld heat treatment needed; excellent intergranular corrosion resistance |
S31600 and S31603 Stainless SteelsCorrosion Resistance
Intergranular Corrosion Resistance
S31600: Higher carbon content (≤0.08%) may cause chromium depletion at grain boundaries (due to Cr₂₃C₆ precipitation) when exposed to 400–850°C (sensitization temperature range), leading to intergranular corrosion.
S31603: Ultra-low carbon (≤0.03%) virtually eliminates Cr₂₃C₆ formation, providing inherent resistance to intergranular corrosion even without post-weld treatment, ideal for welded structures.
Other Corrosion Resistance
Both offer equal resistance to chloride-induced pitting/crevice corrosion (due to identical Mo content), superior to 304 stainless steel.
S31600 has slightly better high-temperature oxidation resistance (above 870°C) due to minor carbon effects, though the difference is negligible in most applications.
