SHANGHAI RUICHAO INDUSTRIAL
SHANGHAI RUICHAO INDUSTRIAL
Pressure vessel steel is a specialized category of high-strength steel engineered to safely contain gases or liquids at high pressures and temperatures. Its key characteristics include high yield and tensile strength, exceptional toughness to prevent brittle fracture, superior weldability for fabrication integrity, and enhanced resistance to corrosion and hydrogen-induced cracking. This steel is primarily used in the construction of storage tanks, boilers, heat exchangers, and reactors within the oil and gas, petrochemical, power generation, and nuclear industries, where operational safety and reliability under extreme conditions are paramount.
Specification Parameters
| Parameters of Pressure Vessel Steel | |||
| Parameter Category | Specific Parameter | Typical Value / Description | Importance for Pressure Vessel Applications |
| Mechanical Properties | Yield Strength (YS) | 205 MPa to 550 MPa+ (e.g., SA-516 Gr. 70 has 260 MPa Min. YS) | Must resist deformation under sustained internal pressure. |
| Tensile Strength (TS) | 415 MPa to 725 MPa+ | Provides safety margin against fracture; must be well above yield strength. | |
| Elongation | Minimum 17% - 22% | Ensures ductility to accommodate stress concentrations and prevent brittle behavior. | |
| Impact Toughness (Charpy V-Notch) | Very High (e.g., > 40 J @ -29°C to -46°C is common) | Critical. Prevents brittle fracture, especially during start-up/shut-down or in low-temperature service. | |
| Hardness (HBW) | Often limited to max. 200-225 HBW | Controlled to minimize risk of Stress Corrosion Cracking (SCC) and Hydrogen-Induced Cracking (HIC), especially in weld zones. | |
| Chemical Composition | Carbon (C) Content | Low to Medium: 0.10% - 0.25% | Balanced to provide strength while maintaining excellent weldability and toughness. |
| Manganese (Mn) | 0.90% - 1.60% | Increases strength and hardenability. Ratio to Carbon (Mn/C) is carefully controlled. | |
| Microalloying Elements | Niobium (Nb), Vanadium (V), Titanium (Ti) | Used in higher-strength grades for grain refinement and precipitation strengthening. | |
| Sulfur (S) & Phosphorus (P) | Kept extremely low (e.g., S < 0.015%, P < 0.025%) | "Clean steel" practice is essential to maximize toughness and weldability. | |
| Special Properties | Creep Strength | Critical for high-temp service (> 400°C) | Resistance to slow, continuous deformation under stress at high temperatures over long periods. |
| Hydrogen Resistance | Tested per NACE Standards | For vessels in hydrogen service or processing "sour" hydrocarbons (H₂S), resistance to HIC and SSC is mandatory. | |
| Fine Grain Practice | ASTM grain size of 5-7 or finer | A fine, uniform grain structure is a fundamental requirement for achieving high toughness and consistent properties. | |
| Governing Standards | Material Specifications | ASTM/ASME SA-516 (Carbon Steel), SA-537 (HSLA), SA-533 (Alloy Steel) | These standards define the precise chemical and mechanical requirements for plates. |
| Design Code | ASME Boiler and Pressure Vessel Code, Section VIII | The overarching code that mandates all material, design, fabrication, and testing requirements. | |
