1. Core Definition & Standard Compliance

1.1 Fundamental Overview

• Nomenclature Logic:
  • “304”: ASTM/SAE grade designation (the most recognized global identifier);
  • “1.4301”: European EN standard number (EN 10088-2);
  • “SUS304”: Japanese Industrial Standard (JIS G 4303) designation;
  • “18-8 Stainless Steel”: Common alias (18% Cr, 8% Ni—core alloy composition);
  • Variants: 304L (low carbon ≤0.03% for welding thick sections), 304H (high carbon 0.04–0.10% for high-temperature strength).
• Key Aliases: A240 304, EN 1.4301, SUS304, 18/8 Stainless Steel.
• Equivalent Grades:
  • ASTM: A240 304 (plates/sheets), A480 304 (bars), A312 304 (pipes);
  • European: EN 10088-2 1.4301, DIN X5CrNi18-10;
  • Chinese: GB/T 3280 06Cr19Ni10;
  • Japanese: JIS G 4303 SUS304;
  • ISO: ISO 15510 X5CrNi18-10.

1.2 Core Standards

• Primary Standards: ASTM A240/A240M (plates/sheets), ASTM A480 (bars), EN 10088-2 (European stainless steels), JIS G 4303 (Japanese), GB/T 3280 (Chinese);
• Quality Certifications: ISO 9001, ISO 13485 (medical grade), FDA (food contact), CE (European market), and third-party certifications (SGS, BV, TÜV);
• Critical Requirements:
  • Minimum chromium (18.00–20.00%), nickel (8.00–12.00%) content for corrosion resistance;
  • Carbon ≤0.08% (304), ≤0.03% (304L);
  • Corrosion resistance: Passes ASTM A262 Practice A (intergranular corrosion test);
  • Weldability: Compatible with all standard welding processes (no post-weld heat treatment required for 304L).

2. Chemical Composition

Key Alloy Advantage

3. Mechanical & Physical Properties

3.1 Physical Properties

• Density: 7.93 g/cm³ (higher than carbon steel, lighter than nickel-based alloys);
• Melting Point: 1400–1450°C;
• Thermal Conductivity: 16.3 W/m·K (room temperature); 21.5 W/m·K (500°C);
• Electrical Conductivity: 14% IACS (lower than carbon steel, suitable for electrical shielding);
• Thermal Expansion Coefficient: 17.2×10⁻⁶/℃ (20–100°C); higher than carbon steel (requires consideration in high-temperature assemblies);
• Corrosion Resistance: Excellent—resists atmospheric corrosion, food acids, mild alkalis, and freshwater; susceptible to chloride pitting in high-salt environments (use 316 for marine/critical applications);
• Weldability: Outstanding—compatible with SMAW, GMAW, GTAW, and SAW; 304L recommended for thick sections (>12mm) to avoid intergranular corrosion.

4. Product Forms & Dimensional Range

4.1 Core Product Forms

• Sheets/Plates: Hot-rolled (HR) and cold-rolled (CR); CR offers a smoother surface (2B, BA finishes) for decorative/appliance use;
• Coils: Cold-rolled coils (CRC) and hot-rolled coils (HRC) for continuous processing (stamping, slitting);
• Bars/Rods: Round bars, square bars, hexagonal bars (for machining, fasteners, and structural components);
• Pipes/Tubes: Seamless (SMLS) and welded (ERW) pipes/tubes (for fluid transport, plumbing);
• Wire: Annealed, cold-drawn wire (for springs, fasteners, and mesh);
• Profiles/Shapes: Angles, channels, I-beams (for architectural and structural use);
• Custom Fabrications: Stamped parts, welded assemblies, and precision components.

4.2 Dimensional Range

• 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); length ±5mm.

4.3 Surface Finishes

5. Production Process & Quality Control

1. Raw Material Preparation: High-purity iron ore + chromium/nickel master alloys (Cr ≥99.5%, Ni ≥99.9%) to meet composition requirements;
2. Smelting: Melting in Electric Arc Furnaces (EAF) + Argon Oxygen Decarburization (AOD) or Vacuum Oxygen Decarburization (VOD) to reduce carbon content and remove impurities;
3. Continuous Casting: Molten steel cast into slabs (for plates/sheets), billets (for bars), or blooms (for pipes);
4. Hot Working: Slabs/billets heated to 1150–1250°C; hot-rolled to target thickness (HR plates/coils) or pierced into tube shells (seamless pipes);
5. Cold Working: Cold rolling (for CR sheets/coils) to achieve precise thickness and surface finish; multiple passes with intermediate annealing;
6. Annealing: 1010–1120°C (air or water cooling) to restore ductility and dissolve carbides (critical for corrosion resistance);
7. Pickling & Passivation: Immersion in nitric-hydrofluoric acid to remove oxide scale and form a passive Cr₂O₃ film;
8. Quality Inspection:
   • Chemical Testing: Spectrometric analysis (ASTM E1086) to verify Cr/Ni/C content;
   • Mechanical Testing: Tensile, bend, and hardness tests for each batch;
   • Corrosion Testing: ASTM A262 Practice A (intergranular corrosion) and salt spray test (ASTM B117);
   • Non-Destructive Testing (NDT): Ultrasonic testing (UT) for internal defects; eddy current testing (ECT) for surface flaws;
   • Surface Inspection: Visual and tactile checks for finish uniformity and defects.

6. Core Applications

6.1 Food Processing & Catering

• Food production equipment (mixers, conveyors, tanks), commercial kitchen sinks, countertops, and cutlery;
• Rationale: Hygienic (non-porous surface, easy to clean), corrosion-resistant to food acids, and FDA-compliant.

6.2 Medical & Pharmaceutical

• Surgical instruments, medical device housings, drug delivery systems, and pharmaceutical processing equipment;
• Rationale: Biocompatible (no tissue rejection), corrosion-resistant to bodily fluids, and non-magnetic (compatible with MRI machines).

6.3 Architecture & Construction

• Building facades, curtain walls, handrails, elevators, and roofing;
• Rationale: Aesthetic appeal (customizable finishes), weather resistance, and low maintenance (no painting required).

6.4 Chemical & Petrochemical Industry

• Pipes, valves, pumps, and storage tanks for mild corrosive media (acetic acid, ethanol);
• Rationale: Corrosion resistance to industrial chemicals; weldability for large-scale assemblies.

6.5 Home Appliances & Consumer Goods

• Refrigerator doors, washing machine drums, microwave ovens, and stainless steel cookware;
• Rationale: Durable, easy to clean, and aesthetically pleasing; resists humidity and food stains.

6.6 Automotive & Transportation

• Exhaust systems, decorative trim, and electric vehicle (EV) battery enclosures;
• Rationale: Corrosion resistance to road salts; lightweight vs. carbon steel (improves fuel efficiency).

6.7 Electronics & Aerospace

• Electronic device casings, aerospace fasteners, and cryogenic storage tanks;
• Rationale: Non-magnetic, high toughness at cryogenic temperatures, and corrosion resistance.

7. Comparison with Similar Grades

8. Cost & Pricing Considerations (2025 Q4 Data)

8.1 Key Pricing Drivers

• Nickel Price Fluctuation: Accounts for 30–40% of total cost (LME nickel 2025 Q4: ~$18,000/ton);
• Product Form: CR sheets cost 15–20% more than HR plates; seamless pipes cost 40–50% more than welded pipes;
• Surface Finish: BA finish costs 25–30% more than 2B finish;
• Order Volume: Bulk orders (≥50 tons) unlock 10–15% discounts vs. small orders (<5 tons);
• Variant: 304L costs 5–8% more than 304; 304H costs 10–12% more than 304.

8.2 Cost Optimization Strategies

• Choose the Right Variant: Use 304 for general applications (cost-effective); 304L for thick weldments; avoid over-specifying 316;
• Bulk Purchasing: Partner with manufacturers for annual supply agreements to lock in pricing;
• Standard Sizes: Opt for common dimensions (1220×2440mm sheets, 10mm round bars) to avoid custom cutting premiums (10–15%);
• Domestic Sourcing: Chinese-manufactured 304 offers 20–30% cost savings vs. Western suppliers with comparable quality.

9. Supply Chain & Value-Added Services

• Minimum Order Quantity (MOQ): 1kg (wire/bars); 1 ton (sheets/plates); 5 tons (coils/pipes);
• Delivery Lead Time: 7–14 days (stock products); 20–35 days (custom sizes/finishes);
• Packaging: Seaworthy export packaging (moisture-proof plastic film + wooden crates) for sheets/plates; anti-rust oil + plastic caps for pipes/bars;
• Value-Added Services:
  • Precision cutting (laser, waterjet, plasma) to custom dimensions;
  • Bending, welding, and fabrication into finished components;
  • Surface customization (brushing, polishing, passivation);
  • Certification support (FDA, ISO 13485, CE);
  • Third-party testing (SGS/BV/TÜV) for corrosion resistance and composition;
• Global Supply Hubs: Core production bases in China (Guangdong, Jiangsu), South Korea, Japan, USA (Indiana, Texas), and Europe (Germany, Italy); key loading ports: Shanghai, Tianjin, Busan, Houston, Hamburg.

10. Conclusion