1. Core Definition & Standard Compliance

1.1 Fundamental Overview

• Nomenclature & Key Differences:
  • “SUS304”: JIS G4303 designation for standard 18-8 austenitic stainless steel (carbon ≤0.08%);
  • “SUS304L”: “L” = Low Carbon (≤0.03%), engineered to prevent carbide precipitation during welding;
  • Common Aliases: SUS304 (ASTM A240 304, EN 1.4301), SUS304L (ASTM A240 304L, EN 1.4306);
  • Core Distinction: Carbon content—SUS304L’s ultra-low carbon eliminates intergranular corrosion (IGC) risk in welded assemblies, especially thick sections (>12mm).
• Equivalent Grades:

  JIS Grade	ASTM Equivalent	EN Equivalent	Chinese Equivalent	ISO Equivalent
  SUS304	A240 304	1.4301	GB/T 3280 06Cr19Ni10	X5CrNi18-10
  SUS304L	A240 304L	1.4306	GB/T 3280 022Cr19Ni10	X2CrNi18-10

1.2 Core Standards

• Primary Standards: JIS G4303 (Japanese), ASTM A240/A240M (American), EN 10088-2 (European), GB/T 3280 (Chinese);
• Quality Certifications: ISO 9001, ISO 13485 (medical), FDA (food contact), CE (European), JIS Mark (Japanese market), third-party certifications (SGS, BV, TÜV);
• Critical Requirements:
  • SUS304: Cr 18.00–20.00%, Ni 8.00–12.00%, C ≤0.08%, passes ASTM A262 Practice A (IGC test for thin sections);
  • SUS304L: Cr 18.00–20.00%, Ni 8.00–12.00%, C ≤0.03%, passes ASTM A262 Practice E (strict IGC test for welded thick sections);
  • Weldability: Both compatible with all standard welding processes; SUS304L requires no post-weld heat treatment (PWHT) for thick sections.

2. Chemical Composition Comparison

Key Alloy Advantage Comparison

• SUS304: Balances cost and performance for non-critical welding applications; higher carbon offers slightly better strength than SUS304L.
• SUS304L: Ultra-low carbon eliminates intergranular corrosion in welded thick sections and corrosive environments (e.g., chemicals, seawater); superior long-term durability in harsh service.

3. Mechanical & Physical Properties Comparison

3.1 Physical Properties (Common to Both)

• Density: 7.93 g/cm³;
• Melting Point: 1400–1450°C (SUS304), 1405–1455°C (SUS304L);
• Thermal Conductivity: 16.3 W/m·K (room temperature);
• Electrical Conductivity: 14% IACS;
• Thermal Expansion Coefficient: 17.2×10⁻⁶/℃ (20–100°C);
• Service Temperature Range: -270°C to 870°C (both); SUS304L preferred for continuous high-temperature welding scenarios.

4. Product Forms & Dimensional Range

4.1 Core Product Forms

• Sheets/Plates: Hot-rolled (HR) and cold-rolled (CR, 2B/BA finishes);
• Coils: Cold-rolled coils (CRC) and hot-rolled coils (HRC);
• Bars/Rods: Round, square, hexagonal (machining, fasteners);
• Pipes/Tubes: Seamless (SMLS) and welded (ERW) for fluid transport;
• Wire: Annealed/cold-drawn (springs, mesh, fasteners);
• Profiles/Shapes: Angles, channels, I-beams (architecture/structural);
• Custom Fabrications: Stamped parts, welded assemblies, precision components.

4.2 Dimensional Range (Common to Both)

• Sheets/Plates: Thickness 0.4mm–100mm; width 1000mm–4000mm; length 2000mm–12000mm;
• Coils: Thickness 0.15mm–3.0mm; width 1000mm–1500mm; weight up to 30 tons;
• Bars: Diameter 6mm–300mm (round); side 6mm–100mm (square/hexagonal); length 3m–6m;
• Pipes/Tubes: OD 6mm–630mm; wall thickness 0.8mm–20mm; length 3m–12m;
• Dimensional Tolerance: Thickness ±0.02mm (CR sheets) to ±0.5mm (HR plates); OD ±0.1mm (seamless tubes).

5. Production Process & Quality Control

1. Raw Material Preparation: High-purity iron + Cr/Ni master alloys; SUS304L uses low-carbon scrap to meet ≤0.03% C requirement;
2. Smelting: EAF + AOD/VOD (Argon/Vacuum Oxygen Decarburization); SUS304L requires extended decarburization to reduce carbon;
3. Continuous Casting: Slabs/billets/blooms;
4. Hot/Cold Working: Same as standard stainless steel processing;
5. Annealing: 1010–1120°C (air/water cooling); SUS304L’s annealing ensures complete carbide dissolution;
6. Pickling & Passivation: Nitric-hydrofluoric acid treatment to form passive film;
7. Quality Inspection:
   • Chemical Testing: Spectrometric analysis (JIS G1253) to verify C content (critical for SUS304L);
   • Mechanical Testing: Tensile, bend, hardness tests;
   • Corrosion Testing: ASTM A262 Practice A (SUS304) vs. Practice E (SUS304L); salt spray test;
   • NDT: Ultrasonic (UT), eddy current (ECT) testing.

6. Core Applications (Key Differences Highlighted)

6.1 SUS304 Key Applications

• General-purpose scenarios: Food processing equipment (small tanks, conveyors), home appliances (refrigerator doors, washing machine drums), architectural trim, consumer goods;
• Non-critical welding: Thin-walled pipes, small structural components, decorative parts;
• Rationale: Cost-effective balance of corrosion resistance and formability for non-harsh environments.

6.2 SUS304L Key Applications

• Corrosive/welded environments: Chemical processing (pipes, valves, tanks), offshore/marine components, thick-walled pressure vessels;
• High-hygiene/critical applications: Medical devices (surgical instruments), pharmaceutical processing equipment, nuclear power auxiliary systems;
• Rationale: Ultra-low carbon prevents intergranular corrosion in welded thick sections and harsh media.

6.3 Shared Applications

• Food service (kitchen sinks, countertops), automotive trim, electronic device casings, cryogenic storage (both retain toughness at -270°C).

7. Comparison with Similar Grades

8. Pricing Analysis (2025 Q4 Data)

8.1 Global Price Ranges (by Product Form: 1.0mm CR Sheet, 2B Finish)

8.2 Key Pricing Drivers

• Carbon Control Cost: SUS304L requires extended decarburization (AOD/VOD) and high-purity raw materials, adding 5–8% to production cost;
• Product Form: CR sheets cost 15–20% more than HR plates; seamless pipes cost 40–50% more than welded pipes (applies to both grades);
• Surface Finish: BA finish costs 25–30% more than 2B finish (same for both);
• Order Volume: Bulk orders (≥50 tons) unlock 10–15% discounts for both grades; small orders (<5 tons) add 8–12% premium;
• Market Demand: Peak demand in chemical/pharmaceutical sectors (Q2–Q3) increases SUS304L prices by 5–7%;
• Certifications: FDA/ISO 13485 certification adds 3–5% to both grades (higher for SUS304L in medical applications).

8.3 Cost Optimization Strategies

• Right-Grade Selection: Use SUS304 for general-purpose/thin-walled applications (saves 5–10% vs. SUS304L); reserve SUS304L for thick-welded/corrosive scenarios;
• Bulk Purchasing: Annual supply agreements lock in pricing and reduce unit costs for both grades;
• Standard Sizes: Opt for common dimensions (1220×2440mm sheets, 10mm round bars) to avoid custom cutting premiums (10–15%);
• Regional Sourcing: Chinese-manufactured SUS304/SUS304L offers 20–30% cost savings vs. Japanese/European suppliers with identical JIS compliance;
• Avoid Over-Specification: Do not use SUS316/SUS316L unless chloride exposure is extreme (saves 20–30% vs. upgrading from SUS304L).

9. Supply Chain & Value-Added Services

• Minimum Order Quantity (MOQ): 1kg (wire/bars); 1 ton (sheets/plates); 5 tons (coils/pipes) for both grades;
• Delivery Lead Time: 7–14 days (stock products); 20–35 days (custom sizes/finishes); SUS304L may add 3–5 days due to stricter quality control;
• Packaging: Seaworthy export packaging (moisture-proof plastic + wooden crates) for sheets/plates; anti-rust oil + plastic caps for pipes/bars;
• Value-Added Services:
  • Precision cutting (laser/waterjet/plasma); bending/welding/fabrication;
  • Surface customization (brushing, polishing, passivation);
  • Certification support (JIS Mark, FDA, ISO 13485);
  • Third-party testing (SGS/BV/TÜV) for corrosion resistance and carbon content (critical for SUS304L);
• Global Supply Hubs: Core production bases in Japan (Osaka, Kobe), China (Guangdong, Jiangsu), South Korea, USA (Indiana, Texas), Europe (Germany); key ports: Yokohama, Shanghai, Busan, Houston, Hamburg.

10. Conclusion