How to Choose Steel Sections? Angle, Channel, I-Beam and Square Tube
AI Summary: Structural sections include angle steel, channel steel, I-beams, H-beams and square/rectangular tubes. Selection depends on material grade, cross-section dimensions, wall thickness, mechanical properties and application. Q235 is commonly used for general structures, while Q355 can be considered for critical load-bearing applications. Procurement should verify theoretical weight, dimensional tolerances, corrosion level and mill test certificates. Specifications for load-bearing structures should be determined by design calculations.
Procurement Checklist
| Review Item | Selection Points |
|---|---|
| Material Grade | Different strength grades for general structures and load-bearing structures |
| Section Specifications | Section height, leg width and wall thickness should meet design requirements |
| Mechanical Properties | Request yield strength, tensile strength and mill test certificates |
| Surface Condition | Corrosion, deformation and dimensional tolerances should be within allowable limits |
| Weight Verification | Check by theoretical weight or actual weighing to avoid excessive negative tolerances |
Procurement, Installation and Usage Points
1. Load-bearing must be based on calculations
Section specifications cannot be selected by intuition; they should be calculated based on span, load and connection method.
2. Material grades must not be mixed
Q235 and Q355 differ in welding and strength; critical structures should be clearly identified.
3. Negative tolerances must be controlled
Excessive negative wall thickness tolerance affects load-bearing capacity and should be inspected according to standards.
4. Welded connections must be standardized
Joint welding quality and anti-corrosion treatment determine structural service life.
FAQ Quick Answers
What is the difference between I-beam and H-beam?
Cross-section and manufacturing process differ; H-beams have equal flange thickness and more flexible specifications.
Square tube or rectangular tube — which is better?
Choose based on load and appearance requirements; specifications and wall thickness are more critical.
Can rusty steel still be used?
Light surface rust can be treated; severe corrosion and pitting affect cross-section and performance.
Why is a mill test certificate needed?
To confirm material grade and mechanical properties for engineering traceability.
Case Study
A canopy frame was selected based on experience alone and later showed deflection. After design verification, replacing with higher-strength and larger-section sections and standardizing welding stabilized the structure.
Questions to Ask the Supplier
- Can you provide material grade and mill test certificates?
- What are the tolerance standards for section dimensions and wall thickness?
- How is theoretical weight verified against actual delivery weight?
- Do you offer cutting, processing and delivery?
- What are your recommendations for welding different material grades?
Key Takeaways: Section procurement should be based on design calculations and material certificates, verifying cross-section, wall thickness and negative tolerances, with standardized joint welding and anti-corrosion treatment.