Q235B Carbon Structural Steel
Q235B carbon structural steel is the most common and widely used material in the manufacturing of lamp posts in the mainland Chinese market, almost becoming the default material for lamp post production. According to the Chinese national standard GB/T 700-2006, the main chemical composition of Q235B is as follows: Carbon (C): ≤ 0.20%, Manganese (Mn): ≤ 1.40%, Silicon (Si): ≤ 0.35%, Sulfur (S): ≤ 0.045%, Phosphorus (P): ≤ 0.045%. Additionally, it may contain trace residual elements such as Chromium (Cr), Nickel (Ni), Copper (Cu), Arsenic (As), etc., typically not exceeding 0.30%, and Nitrogen (N) content not exceeding 0.008%.
The mechanical properties of Q235B vary depending on the thickness of the material, with the core indicators as follows:
Yield Strength:
- - For thickness ≤ 16mm: ≥ 235MPa
- - For thickness > 16~40mm: ≥ 225MPa
- - For thickness > 40~60mm: ≥ 215MPa
- - For thickness > 100~150mm: ≥ 195MPa
- - For thickness > 150~200mm: ≥ 185MPa
Tensile Strength:
Stabilized between 370–500MPa, unaffected by thickness.
Elongation after Fracture:
- - For thickness ≤ 16mm: ≥ 26%
- - For thickness up to 200mm: ≥ 21%, demonstrating excellent plastic deformation capability.
Impact Toughness:
B-grade requires an impact test at 20°C, with impact energy (Akv) ≥ 27J, suitable for dynamic load applications in normal temperature environments.
Design Stress Values:
- - Bending and axial stress design value: 215MPa
- - Shear stress design value: 125MPa.
The advantages of Q235B lie in its excellent combination of performance and high cost-effectiveness, specifically reflected in the following aspects:
- 1. Good Mechanical Properties: It has moderate strength (yield strength ≥ 235MPa) and excellent plasticity (elongation after fracture ≥ 26%), capable of withstanding static and general dynamic loads, making it suitable for most conventional engineering structures.
- 2. Excellent Processability: It has excellent weldability and strong cold bending formability, with no cracks after 180° bending, suitable for various processing methods such as stamping, bending, and welding.
- 3. Significant Cost Advantage: As one of the most common carbon structural steels, it has low raw material costs and stable production and supply, making it suitable for large-scale applications, especially offering significant economic benefits in projects with limited budgets.
- 4. Wide Applicability: It can be used in various scenarios such as building structures, bridges, mechanical manufacturing, vehicle chassis, supports, profiles, and others, truly a "national material."
- 5. Reliable Quality Grades: B-grade steel requires impact energy ≥ 27J at 20°C, offering better toughness assurance compared to A-grade, making it suitable for structural components with certain safety requirements.
It is worth noting that if the material for the custom lamp post requires other different materials, it may increase production costs. Additionally, due to low order quantities, it may increase the difficulty of purchasing steel from upstream suppliers and raise transportation costs.