Galvanized Square and Rectangular Tubes

Galvanized square and rectangular tubes, also known as galvanized square and rectangular cold-formed hollow steel sections, are hollow long steel strips with square and rectangular cross-sections, made from hot-rolled or cold-rolled strip steel as raw material. The strips are bent into shape and then treated with hot-dip galvanizing or electro-galvanizing processes. Square and rectangular tubes are designated as F and J, respectively.

The core advantages of galvanized square and rectangular tubes are reflected in the following aspects:
1. Excellent corrosion resistance: The galvanized layer forms a dual mechanism of physical barrier and electrochemical protection on the steel pipe surface, significantly extending its service life.
2. High structural strength: Square and rectangular cross-sections have excellent mechanical properties in terms of bending and torsion resistance, resulting in high load-bearing capacity.
3. Regular cross-section and uniform stress: The regular shape facilitates welding, bolting connections, and decorative treatments.
4. High surface finish: The surface is smooth after galvanizing, making it easy to paint and further process.
5. Strong processing adaptability: Supports various processing methods such as cutting, welding, and drilling.

Galvanized square and rectangular tubes can be classified in various ways, including galvanizing process, production process, material, and cross-sectional shape.
1. Classification by Galvanizing Process: Galvanized square and rectangular tubes are mainly classified into two categories based on their galvanizing process: hot-dip galvanized square and rectangular tubes and electro-galvanized (cold galvanized) square and rectangular tubes.

2. Classification by Manufacturing Process
Welded Square and Rectangular Tubes: Made from steel strip as raw material, cold-bent and then welded.
2.1 By Weld Seam: Straight seam welded square tubes, spiral welded square tubes
2.2 By Process: Arc welded square tubes, resistance welded square tubes (high frequency/low frequency), gas welded square tubes, furnace welded square tubes
Seamless Square and Rectangular Tubes: Hot-rolled seamless square tubes, cold-drawn seamless square tubes, extruded seamless square tubes

3. Classification by Material

4. Classification by Cross-sectional Shape
Simple Cross-section: Square tubes, rectangular square tubes
Complex Cross-section: Flower-shaped square tubes, open-shaped square tubes, corrugated square tubes, special-shaped square tubes

5. Classification by Surface Treatment
Hot-dip galvanized square tubes, electro-galvanized square tubes, oiled square tubes, pickled square tubes

6. Classification by Application
Decorative square tubes, machine tool equipment square tubes, mechanical industry square tubes, chemical industry square tubes, steel structure square tubes, shipbuilding square tubes, automotive square tubes, steel beam and column square tubes, special purpose square tubes

Schematic diagram of the processing of Galvanized square and rectangular tubes :

Key Performance Characteristics
1. Excellent Corrosion Resistance: The hot-dip galvanized layer forms a dual mechanism of physical barrier and electrochemical protection on the steel pipe surface. The galvanized layer also forms an oxide protective layer, effectively resisting corrosion from the atmosphere, water, and soil.
2. High Structural Strength: Square and rectangular cross-sections exhibit excellent mechanical properties in terms of bending and torsional resistance. Square and rectangular tubes are lighter in weight while maintaining the same bending and torsional strength.
3. Regular Cross-Section and Uniform Stress Distribution: Galvanized square and rectangular tubes have regular cross-sections and an aesthetically pleasing appearance, facilitating welding, bolting connections, and decorative treatments.
4. High Surface Finish: After galvanizing, the surface is smooth and free of iron oxide scale, facilitating painting and further processing.
5. Strong Processing Adaptability: Supports various processing methods such as cutting, welding, bending, and drilling, facilitating the fabrication of various structural components and connection nodes.

Application of galvanized square and rectangular tubes:
(1) Construction field: Galvanized square and rectangular tubes are also widely used in construction and decoration. For example, partitions, display racks, chairs, doors, steel and wood floor grids, etc., are beautiful and practical.
(2) Agricultural field: In modern agriculture, rectangular tubes are used more and more widely. For example, steel frame greenhouses, fruit and vegetable sheds, etc. are all made of square tubes.
(3) Industrial field: It is also widely used in the industrial field. For example, oil, gas and other water well pipes, air pipes, filter materials, etc. are all made of square rectangular pipes.

The product combines the structural strength of square and rectangular tubes with the corrosion resistance of a galvanized coating, and is widely used in building steel structures, underground pipe corridors, curtain walls, machinery manufacturing, solar panel supports, power engineering, automobile chassis, and other fields. Currently, galvanized square and rectangular tubes are continuously developing towards larger diameters, seamless designs, and higher coating requirements.

The following are the national standards of China, Britain, the United States and Japan:

Chinese national standard
GB/T 13237-2013 "High-quality Carbon Structural Steel Cold-rolled Plates and Strips", GB/T 34201-2017 "Square and Rectangular Hot-Rolled Seamless Steel Tubes for Structural Use"

British standard
BS 1387 "Heavy welded galvanized steel pipe", BS 1139 "Specification for metal pipe scaffolding"

American standard:
ASTM A500 "Standard Specification for Cold-Formed Welded and Seamless Carbon Steel Structural Pipe", ASTM A53 "Seamless and Welded Black and Galvanized Steel Pipe"

Japanese standard
JIS G 3466: "Carbon steel parts for square steel tubes"

This standard specifies the order content, dimensions, shape and weight, technical requirements, inspection and test methods, inspection rules, packaging, marks and quality certificates of square and rectangular hot-rolled seamless steel pipes for structural use.

Relevant standards

The deviation of galvanized square and rectangular tubes specifications generally includes outer diameter, wall thickness, length and so on. The reason is mainly due to the precision limitation of the process and equipment in the manufacturing and the physical influence in the process of transportation and storage, etc.

The specifications of galvanized square and rectangular tubes are expressed as "side length × side length × wall thickness" (square tube) or "long side × short side × wall thickness" (rectangular tube).

1. Specification Range
Square tube: Side length range 16×16 ~ 1000×1000 mm
Rectangular tube: Side length range 10×20 ~ 800×1000 mm
Wall thickness range: 0.7 ~ 30 mm

2. Delivery Length
Typically, the delivery length is 4000mm ~ 12000mm, with 6000mm and 12000mm being the most common.
Short lengths and non-standard lengths of not less than 2000mm are allowed.
The weight of short lengths and non-standard lengths shall not exceed 5% of the total delivery quantity (theoretical weight > 20kg/m shall not exceed 10%).

In view of various situations of specification deviation of galvanized square and rectangular tubes, the Chinese national standard GB/T 3091-2015 "Welded Steel Pipe" stipulates the allowable deviation range, the specific content is as follows:
1. Outer diameter deviation: ±0.5%D, where D is the outer diameter of the square tube.
2. Wall thickness deviation: should meet the following requirements:
(1) When the wall thickness is ≤0.5mm, the allowable deviation is ±0.1mm;
(2) When the wall thickness is >0.5mm, the allowable deviation is ±10% of the wall thickness.
3. Length deviation: The allowable deviation is ±5mm of the pipe length.

The content of the above specifications stipulates the allowable maximum deviation of the specification deviation of galvanized square and rectangular tubes under different circumstances. Strictly following the national standards can effectively guarantee product quality and use effect, and ensure building quality and construction safety.