1. Core Definition & Standard Compliance

1.1 Fundamental Overview

• Standard Nomenclature (JIS G3115):
  • “S”: Denotes “Steel” in JIS classification;
  • “P”: Abbreviation for “Pressure” (pressure vessel application);
  • “V”: Abbreviation for “Vessel” (vessel-specific use);
  • “355”: Minimum yield strength in MPa (at room temperature);
  • Full Designation: JIS G3115 SPV355 (officially “Carbon Steel Plates for Pressure Vessels, Grade SPV355”).
• Key Aliases: SPV355 Pressure Vessel Steel, JIS G3115 SPV355 Plate, Carbon-Manganese Boiler Steel SPV355.
• Equivalent Grades:
  • ASTM: SPV355 ≈ ASTM A516 Gr. 70 (closest match in strength and application);
  • European: SPV355 ≈ EN 10028-2 P355GH (similar yield strength and high-temperature performance);
  • Chinese: SPV355 ≈ GB/T 713 Q345R (domestic equivalent for pressure vessels);
  • API: SPV355 ≈ API 6A F31 (compatible with oilfield pressure equipment).
• Service Temperature Range: ≤400°C (continuous service); suitable for intermittent operation up to 450°C.

1.2 Core Standards

• Primary Standard: JIS G3115 (2015 Edition) – “Carbon Steel Plates for Pressure Vessels” (defines chemical composition, mechanical properties, and quality requirements for SPV355);
• Complementary Standards:
  • JIS G0315 (inspection methods for pressure vessel steels);
  • JIS G0551 (ultrasonic testing for steel plates);
  • JIS Z3101 (welding procedure qualification);
  • ASME Section VIII Div. 1 (pressure vessel design compatibility for global applications);
• Quality Certifications: ISO 9001, JIS Mark Certification (for Japanese market), third-party certifications (SGS, BV, TÜV) for material and weld quality;
• Critical Requirements:
  • Minimum yield strength (YS) ≥355 MPa (room temperature);
  • Mandatory impact testing (≥27 J at -20°C for plates ≥12mm thick);
  • Strict impurity control (P ≤0.035%, S ≤0.035%) to prevent brittle fracture;
  • Weldability validation (compatible with standard welding processes without pre-heat for thin plates);
  • 100% ultrasonic testing (UT) for plates ≥20mm thick (per JIS G0551 Level 2).

2. Chemical Composition

2.1 Key Alloy Advantage

3. Mechanical & Physical Properties

3.1 Physical Properties

• Density: 7.85 g/cm³ (standard carbon steel density);
• Melting Point: 1450–1510°C;
• Thermal Conductivity: 48 W/m·K (room temperature); 32 W/m·K (400°C);
• Thermal Expansion Coefficient: 11.6×10⁻⁶/℃ (20–100°C); 13.2×10⁻⁶/℃ (300–400°C);
• Corrosion Resistance: Moderate—resists high-temperature oxidation and neutral aqueous corrosion; requires protective coatings (e.g., FBE, high-temperature paint) for acidic or marine environments;
• Weldability: Excellent—compatible with SMAW (Shielded Metal Arc Welding), GMAW (Gas Metal Arc Welding), GTAW (Gas Tungsten Arc Welding), and SAW (Submerged Arc Welding); pre-heat required only for thick plates (>25mm) or high-restraint joints; post-weld stress relieving (580–620°C) recommended for critical applications.

4. Product Forms & Dimensional Range

4.1 Core Product Forms

• Hot-Rolled Plates: Primary form for pressure vessel shells, boiler drums, flanges, and heads;
• Normalized Plates: Standard heat treatment form (ensures uniform grain structure and consistent mechanical properties);
• Cut Blanks: Custom-cut shapes for vessel nozzles, manholes, and specialized components;
• Welded Plates: Large-diameter vessel shells (via submerged arc welding of plates for ultra-large equipment).

4.2 Dimensional Range

• Thickness: 6mm–200mm (common gauges: 10mm, 16mm, 20mm, 30mm, 50mm); maximum thickness up to 300mm for heavy-duty boilers;
• Width: 1000mm–4000mm (standard widths: 1500mm, 2000mm, 2500mm);
• Length: 2000mm–12000mm (standard lengths: 6000mm, 8000mm, 10000mm); custom lengths up to 15000mm available;
• Dimensional Tolerance: Thickness ±0.5mm (≤50mm) to ±1.0mm (>50mm); width ±1mm; length ±50mm (per JIS G3193).

4.3 Surface & Heat Treatments

• Surface Finishes:
  • Hot-Rolled Mill Finish: As-rolled surface (for immediate fabrication or welding);
  • Shot Blasted Finish: Cleaned to Sa 2.5 standard (preparation for anti-corrosion coatings);
  • Pickled Finish: Acid-washed to remove oxide scale (for critical weld joints and high-quality coatings);
• Heat Treatments:
  • Normalizing: 880–920°C (air cooling) – Standard for SPV355; refines grain structure and improves high-temperature toughness;
  • Stress Relieving: 580–620°C (air cooling) – Mandatory after welding to reduce residual stress and prevent cracking;
  • Quenching & Tempering (Q&T): Optional for thick plates (>50mm) to enhance strength uniformity and impact toughness.

5. Production Process & Quality Control

1. Raw Material Preparation: High-purity low-carbon steel scrap + manganese additions (certified composition) to meet JIS G3115 standards;
2. Smelting: Melting in basic oxygen furnaces (BOF) or electric arc furnaces (EAF); vacuum degassing to remove impurities (O₂, H₂) and ensure chemical uniformity;
3. Continuous Casting: Molten steel cast into slabs; homogenization annealing (850–900°C for 4–6 hours) to eliminate segregation;
4. Hot Rolling: Slabs heated to 1150–1200°C; hot-rolled to target thickness; controlled cooling to prevent grain coarsening;
5. Heat Treatment: Normalizing (standard) or Q&T (for thick plates) to optimize mechanical properties;
6. Surface Preparation: Shot blasting or pickling to remove oxide scale and contaminants;
7. Quality Inspection (JIS G3115 Mandatory):
   • Chemical Testing: High-precision spectrometric analysis (JIS G1253) to verify composition;
   • Mechanical Testing: Tensile, bend, and hardness tests for each production batch; impact testing (-20°C) for plates ≥12mm; creep testing (for high-temperature service validation);
   • Non-Destructive Testing (NDT):
     • Ultrasonic Testing (UT): 100% thickness inspection and internal flaw detection (JIS G0551 Level 2);
     • Magnetic Particle Testing (MT)/Liquid Penetrant Testing (PT): Surface flaw detection on edges and weld joints (JIS G0565/JIS G0567);
     • Radiographic Testing (RT): Weld inspection for critical components (JIS G0566);
   • Dimensional Inspection: Laser measurement for thickness, width, flatness, and straightness;
   • Material Test Report: JIS Z2343 Type 3.1 or 3.2 certification (mandatory for pressure vessel applications).

6. Core Applications

6.1 Power Generation Industry

• Boiler drums, superheaters, and economizers for thermal power plants;
• Pressure vessels for nuclear power plant auxiliary systems (e.g., coolant storage);
• Rationale: Withstands high-temperature steam (up to 400°C) and cyclic pressure; excellent creep resistance for long-term (20+ years) operation.

6.2 Petrochemical & Chemical Industry

• Medium-temperature reactors, distillation columns, and heat exchangers;
• Storage tanks for high-temperature chemicals (e.g., ethylene, propane, and petroleum products);
• Rationale: Resists chemical corrosion and thermal cycling; weldability enables on-site fabrication of large-scale equipment.

6.3 Boiler & Pressure Vessel Manufacturing

• Industrial boilers (steam boilers, hot water boilers) for commercial and industrial use;
• Pressure vessels for food processing, pharmaceutical, and textile industries (e.g., sterilization tanks);
• Rationale: Complies with global pressure vessel safety standards; balances performance and cost for medium-temperature applications.

6.4 Oil & Gas Industry

• Offshore and onshore oilfield pressure vessels (e.g., separators, accumulators);
• Natural gas processing plants (medium-temperature separation units);
• Rationale: Resists harsh oilfield environments (high pressure, temperature fluctuations, and mild corrosion); compatible with oilfield chemicals.

7. Comparison with Similar Grades

8. Cost & Pricing Considerations (2025 Q4 Data)

8.1 Key Pricing Drivers

• Thickness: Plates >50mm cost 25–35% more than thin plates (<20mm) due to rolling complexity and heat treatment requirements;
• Certification: JIS Z2343 Type 3.2 certification adds 10–15% vs. Type 3.1; third-party (SGS/BV) certification adds 5–8%;
• Order Volume: Bulk orders (≥100 tons) unlock 10–15% discounts vs. small orders (<20 tons);
• Regional Origin: Japanese-manufactured SPV355 costs 50–60% more than Chinese-manufactured grades with equivalent JIS certification;
• Market Demand: Peak demand in power generation and petrochemical sectors (Q2–Q3) may increase prices by 5–10%.

8.2 Cost Optimization Strategies

• Bulk Purchasing: Partner with manufacturers for project-wide orders to reduce unit costs;
• Regional Sourcing: Chinese-manufactured SPV355 offers 50–60% cost savings vs. Japanese suppliers with identical JIS certification;
• Standard Thickness: Opt for common gauges (10–30mm) to avoid custom rolling premiums (15–20%);
• Certification Right-Sizing: Use Type 3.1 certification for non-critical applications (saves 10–15% vs. Type 3.2).

9. Supply Chain & Value-Added Services

• Minimum Order Quantity (MOQ): 10 tons (standard thicknesses); 50 tons (custom thicknesses >100mm);
• Delivery Lead Time: 15–30 days (stock 10–30mm plates); 30–45 days (custom thicknesses); 45–60 days (Japanese-manufactured grades);
• Packaging: Seaworthy export packaging (steel bundles + wooden skids + moisture-proof film) to prevent corrosion and damage during transportation; plates ≥50mm packaged with anti-deformation supports;
• Value-Added Services:
  • Precision cutting (plasma, laser, waterjet) to custom dimensions and beveling for welding;
  • Heat treatment (normalizing, stress relieving);
  • Welding and fabrication of vessel components (e.g., heads, nozzles);
  • JIS Z2343 Type 3.1/3.2 certification and third-party testing (SGS/BV/TÜV);
  • Technical support (pressure rating calculation, welding guidelines, material selection);
• Global Supply Hubs: Core production bases in China (Hebei, Jiangsu), Japan (Osaka, Kobe), and South Korea; key loading ports: Shanghai, Tianjin, Yokohama, Busan.

10. Conclusion