SUS304L Stainless Steel

SUS304L is a low-carbon variant of SUS304 (C ≤0.03%), optimized for weldability and intergranular corrosion resistance. Reduced carbon prevents chromium carbide precipitation at grain boundaries during welding, eliminating the need for post-weld heat treatment, ideal for large welded structures.

Chemical Composition (wt%): C ≤0.03, Si ≤1.00, Mn ≤2.00, P ≤0.045, S ≤0.030, Cr=18.00-20.00, Ni=8.00-12.00, Fe=Balance

Mechanical Properties: Tensile Strength ≥485MPa, Yield Strength ≥170MPa, Elongation ≥40%, Hardness (HB) ≤201

Performance Advantages: Excellent intergranular corrosion resistance after welding; good low-temperature toughness; similar corrosion resistance to SUS304; easy to weld and form.

Equivalent Grades: ASTM A240 304L, EN 1.4306, UNS S30403

Applications: Large welded chemical containers, pressure vessels, offshore oil platforms, pipeline systems, pharmaceutical equipment.

FAQ

1. Q: What's the key role of low carbon in SUS304L? A: Low carbon (≤0.03%) avoids chromium carbide formation at grain boundaries during welding. In SUS304 (C≤0.08%), high heat from welding makes carbon react with chromium, depleting Cr near boundaries and causing intergranular corrosion. SUS304L's low carbon eliminates this risk, keeping Cr uniformly distributed. This makes it suitable for welded structures like chemical tanks without post-weld heat treatment.

2. Q: How does SUS304L compare to SUS304? A: SUS304L has lower carbon, better weld corrosion resistance but slightly lower strength (485MPa vs 515MPa). Both have similar Cr/Ni content and general corrosion resistance. SUS304 is cheaper for non-welded parts (kitchenware), while SUS304L is preferred for welded heavy-duty equipment (pressure vessels). For low-temperature applications (-196°C), SUS304L's toughness is better, reducing brittle failure risk.

3. Q: Can SUS304L be used in cryogenic environments? A: Yes, it's excellent for cryogenics. Its low carbon content and stable austenitic structure retain high toughness at -196°C (liquid nitrogen temp), avoiding cold brittleness. Unlike ferritic steels that become brittle at low temps, SUS304L maintains ductility, making it suitable for liquid oxygen storage tanks, cryogenic pipelines, and aerospace cryogenic components.

4. Q: What welding methods are suitable for SUS304L? A: It's compatible with TIG, MIG, SMAW, and SAW methods. TIG is preferred for thin sheets (high precision, no spatter); MIG for thick plates (high efficiency). Use ER308L filler metal to match low carbon content. Welding parameters: current 80-120A for TIG, voltage 18-22V for MIG. No pre-heat or post-heat is needed, simplifying fabrication of large structures.

5. Q: Is SUS304L suitable for seawater environments? A: It has limited seawater resistance. Short-term contact (coastal decorations) is okay, but long-term immersion causes pitting due to high chloride. Seawater contains 3-5% NaCl, breaking the oxide film. For marine parts (ship hulls, offshore platforms), choose SUS316L (with Mo) for better pitting resistance. SUS304L is cost-effective for inland or low-chloride marine applications only.