Versatile Steel Square and Rectangular Tubes Gain Prominence in Global Construction and Manufacturing

Steel square and rectangular tubes, collectively known as "Fangjuguan" (F for square, J for rectangular), are hollow structural components widely recognized for their durability and adaptability. Manufactured through precision cold-forming processes, these tubes are produced by uncoiling, flattening, rolling, and welding Steel Strips into circular pipes, which are then shaped into square or rectangular profiles. With applications spanning construction, automotive, agriculture, and beyond, these tubes are becoming indispensable in modern engineering.

Key Specifications and Tolerances

1. Wall Thickness Tolerance:

   • For walls ≤10mm: ±10% of nominal thickness.

   • For walls >10mm: ±8% of nominal thickness (excludes weld and corner regions).

2. Delivery Length:

   • Standard lengths: 4,000–12,000mm (6,000mm and 12,000mm most common).

   • Short/non-fixed lengths (≥2,000mm) permitted, capped at 5% of total order weight (10% for tubes >20kg/m). Joint pipes may be supplied but must be removed before use.

3. Straightness Requirements:

   • Maximum bending: 2mm per meter or 0.2% of total length.

Production and Classification

• Manufacturing Processes:
  Hot-rolled seamless, cold-drawn seamless, extruded seamless, and welded (subdivided into arc welding, resistance welding, gas welding, and furnace welding).

  • Welded types include straight-seam and spiral-welded tubes.

• Material Grades:

  • Carbon Steel: Q195, Q215, Q235, SS400, 20#, 45#, etc.

  • Low-Alloy Steel: Q345, 16Mn, Q390, ST52-3, etc.

• Global Standards:
  Compliant with Chinese (GB), Japanese (JIS), American (ASTM), European (EN), and other international specifications.

• Cross-Section Profiles:

  • Basic: Square, rectangular.

  • Complex: Floral, corrugated, open-shaped, and custom designs.

• Surface Treatments:
  Hot-dip galvanized, electro-galvanized, oil-coated, or acid-washed finishes.

Applications Across Industries
Square and rectangular tubes are critical in:

• Construction: Structural frameworks, roofing, glass curtain walls, railings.

• Manufacturing: Machinery, automotive frames, shipbuilding, container skeletons.

• Infrastructure: Oil/gas pipelines, agricultural greenhouses, power transmission.

• Consumer Goods: Furniture, fitness equipment, bicycles, and decorative elements.

Sustainability and Innovation
With advancements in production efficiency and eco-friendly coatings, these tubes align with global demands for sustainable infrastructure. Their lightweight yet robust nature reduces material waste while enhancing structural integrity.

Industry Outlook
As urbanization and industrial automation accelerate, the demand for high-performance steel tubes is projected to grow. Manufacturers are increasingly focusing on precision tolerances and specialized alloys to meet diverse sector needs, reinforcing the role of square and rectangular tubes as backbone materials in modern engineering.