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Help CenterSquare Steel & Square Steel Pipe，Q195、Q235B、S235JR、Q355B/C/D、S355JR、ASTM A500 C/D、20#、45#、40Cr
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Steel Billet，Main Materials Q195, Q235B, Q355B, 20#, 45#, SS400, A36, S235JR,NegotiableMOQ: 1 Metric Ton
1. Product Overview
Square tube, fully named square hollow structural section, is hollow sectional material with square cross-section, manufactured by cold forming & high-frequency welding or seamless extrusion. Rectangular tubes are produced on the same production line. Featuring uniform wall thickness, excellent bending and welding performance, high structural rigidity and neat appearance.
Our company mainly supplies welded square tubes and seamless square tubes covering carbon steel, low alloy steel and alloy steel. Products comply with GB, ASTM, EN and JIS standards with sufficient stock. Goods are delivered from Tianjin Port within 5–7 working days. English Mill Test Certificate (MTC) is provided for each batch to facilitate customs clearance.
2. Executive Standards
Domestic GB Standards
Welded square and rectangular tubes for general structures: GB/T 3094-2012
Cold-formed hollow structural sections: GB/T 6728-2017
Seamless square tubes: GB/T 14976
Low alloy high strength steel: GB/T 1591
International Standards
ASTM A500 Grade B/C/D, EN 10210, EN 10219, JIS G3466SGS third-party test reports are available for export markets of Europe, America and Southeast Asia.
3. Classification of Material Grades
3.1 Ordinary Carbon Steel Square Tubes (General Construction)
Grades: Q195, Q235B, S235JRAdvantages: Low cost, easy cutting, welding and painting. Widely used for temporary supports, guardrails, storage racks and light steel frames.
3.2 Low Alloy High Strength Square Tubes (Heavy-Duty Structures)
Grades: Q355B/C/D, S355JR, ASTM A500 Grade C/DHigh tensile strength, strong bearing capacity and favorable low-temperature toughness. Suitable for engineering frames, vehicle chassis, container frames and mechanical supports.
3.3 Special Alloy Square Tubes (Custom Mechanical Parts)
Grades: 20#, 45#, 40CrSeamless square tubes applied for heavy-load mechanical equipment, hydraulic supports and special machinery fittings.
3.4 Surface Treated Square Tubes
Hot-dip galvanized square tubes, black painted square tubes and anti-rust oil coated square tubes for outdoor anti-corrosion projects.
4. Specification Parameters
4.1 Outer Dimension Range
Small sizes: 10×10mm ~ 50×50mm
Medium sizes: 60×60mm ~ 150×150mm
Large sizes: 160×160mm ~ 400×400mm
Common rectangular sizes: 20×40, 30×50, 40×60, 50×100, 100×200, 150×300mm, etc.
4.2 Wall Thickness
0.8mm ~ 16mm. Thin-wall tubes for decoration, thick-wall tubes for load-bearing structures.
4.3 Standard Lengths
Standard fixed lengths: 6m, 9m, 12m. Custom lengths from 1m to 12m are acceptable, with the proportion of short-length tubes ≤10%. Length tolerance: 0~+50mm.
4.4 Surface Types
Black anti-rust oil coated square tubes: Original welded surface coated with anti-rust oil for internal structural processing.
Hot-dip galvanized square tubes: Complete zinc coating with outstanding anti-corrosion performance, specially for outdoor construction and municipal engineering.
Cold galvanized square tubes: Thin zinc coating for decorative purposes.
Sandblasted & painted square tubes: Uniform coating with attractive surface finish for equipment frames.
4.5 Dimensional Tolerance
Outer dimension tolerance: ±0.5mm ~ ±1.5mm according to different sizes
Wall thickness tolerance: ±0.1mm ~ ±0.8mm
Straightness ≤2mm/m; square angle deviation ≤1.5°, free of twisting, dents and bulges.
5. Core Product Advantages
Stable raw material supply: Steel strips sourced from formal steel mills with traceable chemical composition and mechanical properties, complete set of MTC documents provided.
Precise forming technology: High-frequency straight seam welding with fully penetrated welds free of cracks and leakage. Seamless square tubes feature uniform inner and outer wall thickness.
Superior structural performance: Strong torsion resistance, less material consumption than solid round steel under equal load capacity to reduce customers’ material costs.
Multiple anti-corrosion options: Black oil coating, hot-dip galvanizing and painting available to fit various service environments.
Full range of stock specifications: Small decorative tubes, medium engineering tubes and large thick-wall structural tubes all in stock, mixed batch orders supported.
Export-specialized packaging: Bundled with steel straps, plastic end caps for pipe ends, reinforced wooden pallets to prevent collision and rust during ocean transportation.
Fast delivery: Ordinary carbon black square tubes dispatched within 3 days from warehouse; galvanized, thick-wall and deep-processed customized products loaded at Tianjin Port within 5–7 days.
6. Main Application Fields
Construction Steel Structure: Workshop frames, light steel villas, factory supports, curtain wall keels, bridge guardrails, municipal road barriers.
Machinery Manufacturing: Equipment bases, conveying supports, forklift frames, agricultural machinery brackets, hydraulic supporting components.
Automobile Industry: Truck chassis, cargo box frames, supporting fittings for new energy vehicles.
Logistics & Warehousing: Warehouse racks, storage shelves, metal pallet frames.
Decoration Engineering: Indoor partition frames, stair handrails, landscape modeling frameworks.
Municipal & Outdoor Works: Hot-dip galvanized square tubes for street lamp poles, greenhouse frames, pipeline supports.
7. Delivery Conditions
As-welded black finish (standard supply): Coated with anti-rust oil after production, ready for direct cutting, welding and painting processing.
Hot-dip galvanized finished products: Whole tube hot galvanized, zinc coating thickness adjustable as per customer requirements.
Custom deep processing: Fixed-length cutting, chamfering, punching, bending, surface sandblasting and painting available on request.
Seamless supply state: Annealed seamless square tubes for convenient CNC machining.
8. Quality Inspection Standards
Dimensional inspection: Full inspection of outer size, wall thickness, length, straightness and torsion degree.
Mechanical performance test: Tensile strength, yield strength, elongation and bending test; flattening test added for welded tubes.
Weld inspection: Eddy current testing or hydrostatic leakage test to eliminate welding defects.
Galvanized coating test: Zinc layer thickness, adhesion and salt spray anti-rust test (exclusive for galvanized tubes).
Batch marking: Each bundle sprayed with bilingual Chinese & English marks including grade, dimension, wall thickness, length, weight and heat number. English MTC issued per batch, third-party re-inspection supported.
9. Packaging & Ocean Shipment
Bundling specification: Small & medium square tubes bundled with steel straps, 1–3 tons per bundle; large square tubes individually fitted with plastic end caps for protection.
Anti-rust protection: Wrapped with inner VCI anti-rust film to reduce oxidation and rust during long-term sea transportation.
Labeling: Bilingual labels attached to each bundle indicating material grade, dimension, wall thickness and net weight.
Loading Port:Stock goods loaded within 3 days, customized products complete container loading within 5–7 days.
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