Comparison Of SUS316 And SUS316L: Standard Molybdenum-Containing Vs Low-Carbon Molybdenum-Containing Austenitic Stainless Steel

SUS316 and SUS316L are core grades of the 316 series, with the core difference being carbon content (SUS316: C≤0.08%, SUS316L: C≤0.03%). The low carbon content of SUS316L eliminates intergranular corrosion after welding, while maintaining the molybdenum-containing corrosion resistance of the 316 series, making them suitable for different welding process and corrosion environment requirements.

Core Parameter Comparison

Parameter	SUS316 Stainless Steel	SUS316L Stainless Steel
Chemical Composition (wt%)	C≤0.08, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=16.00-18.00, Ni=10.00-14.00, Mo=2.00-3.00, Fe=Balance	C≤0.03, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=16.00-18.00, Ni=10.00-14.00, Mo=2.00-3.00, Fe=Balance
Mechanical Properties (Annealed)	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤217HB	Tensile Strength ≥485MPa, Yield Strength ≥170MPa, Elongation ≥40%, Hardness ≤217HB
Service Temperature	-196℃ to 870℃ (continuous service)	-196℃ to 870℃ (continuous service)
Equivalent Grades	EN 1.4401, UNS S31600, AISI 316	EN 1.4404, UNS S31603, AISI 316L

Key Performance Differences: 1. Intergranular corrosion resistance: SUS316L's ultra-low carbon content prevents the formation of chromium-depleted zones at grain boundaries during welding, eliminating intergranular corrosion; SUS316 requires post-weld annealing for harsh corrosion environments. 2. Strength: SUS316 has slightly higher tensile and yield strength than SUS316L due to higher carbon content. 3. Weldability: SUS316L has better welding stability, no post-weld heat treatment required for most thin-plate welding scenarios; SUS316 needs post-weld annealing for thick plates. 4. Cost: SUS316L is 5-10% more expensive than SUS316. 5. Low-temperature performance: Both have excellent ultra-low temperature performance, with no obvious difference.

Applicable Scenario Distinction: SUS316 is suitable for non-welding or post-weld heat-treatable components in medium corrosion environments, such as forged valve bodies, non-welding chemical pipelines, and high-temperature furnace components. SUS316L is suitable for welding-intensive components in harsh corrosion environments, such as chemical reaction vessels (welding structure), seawater desalination equipment, pharmaceutical equipment, and marine engineering parts.

Practical Q&A

Q1: Why is SUS316L widely used in the pharmaceutical industry? A1: Its excellent welding corrosion resistance and low carbon content avoid metal ion precipitation, meeting the high-purity requirements of the pharmaceutical industry; it can withstand cleaning with various chemical disinfectants without rusting.

Q2: Can SUS316 replace SUS316L in welding scenarios? A2: Only if post-weld annealing is possible; in welding-intensive scenarios where post-weld heat treatment cannot be performed (such as large-scale equipment), SUS316's weld area will have intergranular corrosion risks, and SUS316L must be used.

Q3: What is the difference in heat treatment between SUS316 and SUS316L? A3: Both use solution treatment at 1050-1150℃, water cooling; SUS316 requires post-weld annealing at 850-900℃ for thick plates (≥10mm), while SUS316L generally does not require post-weld heat treatment.

Q4: What is the service life difference between SUS316 and SUS316L in coastal welding components? A4: SUS316L's service life (8-10 years) is longer than SUS316 (5-7 years); SUS316's weld area is prone to rust first, while SUS316L's weld area maintains good corrosion resistance.

Q5: How to select between SUS316 and SUS316L? A5: Choose SUS316 if the component is non-welding or post-weld heat-treatable and cost is a concern; choose SUS316L if the component is welding-intensive or used in harsh chloride corrosion environments.