1. Brief Introduction
Q245R is a high-strength low-alloy steel plate for pressure vessels, widely used due to its excellent comprehensive mechanical properties, workability, and high safety. It is a classic grade from the Chinese National Standard GB 713 "Steel Plates for Boilers and Pressure Vessels," commonly used for manufacturing shells and heads of medium-low pressure vessels.
2. Grade Designation Explanation
- Q: Stands for "Qū", the first character of "Yield Strength" in Chinese, from the Hanyu Pinyin system.
- 245: Represents the minimum yield strength value (in MPa) for plates with a thickness of ≤ 16mm, i.e., 245 MPa.
- R: Stands for "Róng", the first character of "Pressure Vessel" in Chinese.
3. Physical Properties
Typical physical properties of Q245R at room temperature include:
- Density: Approximately 7.85 g/cm³
- Elastic Modulus: Approximately 201 GPa
- Poisson's Ratio: Approximately 0.3
- Thermal Conductivity: Approximately 47.0 W/(m·K) (at 100°C)
- Coefficient of Thermal Expansion: Approximately 12.0 × 10⁻⁶ /K (between 20-100°C)
Mechanical properties (such as tensile strength, impact energy) must meet different standard requirements corresponding to different plate thickness grades.
4. Chemical Composition (Ladle Analysis, %)
The chemical composition of Q245R is designed to ensure good strength, plasticity, and weldability, with strict control of harmful elements. Its typical composition range is as follows:
- C (Carbon): ≤0.20
- Si (Silicon): ≤0.35
- Mn (Manganese): 0.50~1.00
- P (Phosphorus): ≤0.025
- S (Sulfur): ≤0.015
- Als(Acid-Soluble Aluminum): ≥0.020
Features: Low carbon content ensures good weldability and toughness; low phosphorus and sulfur content improves steel purity and ensures good low-temperature impact toughness.
5. Application Fields
Q245R is primarily used to manufacture welded pressure vessels with low working pressure and service temperatures between 0°C and 400°C. Typical applications include:
- Reactors, heat exchangers, separators, and storage tanks (drum shells) in the petrochemical industry.
- Liquid nitrogen and carbon dioxide storage tanks in the gas industry.
- Fermentation tanks and storage tanks in the pharmaceutical and food industries.
- Air receivers, water treatment equipment in the construction industry, etc.
6. Testing and Production Methods
Production
Typically produced by basic oxygen or electric arc furnace smelting, followed by secondary refining (e.g., LF refining) and vacuum degassing to ensure purity and homogeneity. The rolling process employs controlled rolling, and normalizing heat treatment (NR, N condition) is applied if necessary to refine the grain structure and improve mechanical properties.
Testing and Inspection
Strict inspections must be carried out before delivery, mainly including:
- Mechanical Property Tests: Tensile test (measuring yield strength, tensile strength, elongation), Charpy V-notch impact test (typically required at 0°C or 20°C).
- Non-Destructive Testing: Ultrasonic inspection (according to order requirements, divided into different classes).
- High-Temperature Tensile Test (if required): Used to verify the strength characteristics of the material at design temperatures.
7. Corresponding/Similar Grades in International Standards
Q245R is generally equivalent or similar to commonly used international grades for pressure vessel steel plates, though slight differences in specific chemical composition and mechanical properties may exist and should be compared against the respective standards.
American Standard (ASTM/ASME): SA-516 Gr. 60 or SA-516 Gr. 65. Most equivalent; specific choice depends on thickness and property requirements.
European Standard (EN): P265GH (EN 10028-2). This is a common European grade for pressure vessel steel, with properties very similar to Q245R.
Japanese Standard (JIS): SB410 or SB450.
