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Help CenterSquare Steel & Square Steel Tube，Q195, Q235B / S235JR, A500 Grade B、Q355B / S355JR, A500 Grade C、20#, 45#
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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, also known as square hollow section, is a hollow rectangular steel tube with equal side length. It is processed by cold forming and high-frequency welding of steel coil or steel plate, featuring uniform wall thickness, neat corners, high structural strength and convenient construction. Widely used as structural raw materials for construction, machinery, engineering support and frame manufacturing.
Theoretical weight formula: Weight per meter (kg/m) = (Side width - Wall thickness) × 4 × Wall thickness × 0.00785
2. Product Classification & Specifications
2.1 By Manufacturing Process
1. Welded Square Tube
Executive Standards: GB/T 6728, EN 10219, ASTM A500Side size range: 10×10mm ~ 500×500mmWall thickness range: 1.0mm ~ 20mmStandard length: 6m / 9m / 12m, custom fixed cutting length availableFeatures: Stable size, low cost, full complete sizes, mainstream stock productApplication: Building frames, guardrails, workshop supports, equipment brackets, logistics racks
2. Seamless Square Tube
Executive Standards: GB/T 8162Side size range: 30×30mm ~ 300×300mmWall thickness range: 4mm ~ 30mmFeatures: No welding seam, uniform internal stress, high pressure and impact resistanceApplication: Mechanical transmission frames, hydraulic equipment, heavy load engineering structures
2.2 By Surface Treatment
Black Square Tube (Original Surface): Without surface treatment, with oxidation skin, for secondary painting, spraying or galvanizing
Pickled Bright Square Tube: Remove oxide scale by acid washing, smooth surface for direct processing
Hot Dipped Galvanized Square Tube: Anti-rust coating, suitable for outdoor, humid and corrosive environment
3. Common Material Grades
Q195, Q235B / S235JR, A500 Grade BLow carbon steel, good weldability, cost-effective, most widely used for general structures
Q355B / S355JR, A500 Grade CHigh strength low alloy steel, higher bearing capacity, for heavy load workshop, bridge support
20#, 45#Medium carbon square tube, for mechanical parts requiring post heat treatment
4. Core Technical Indicators
Dimensional ToleranceSide width tolerance ±0.5~±1.5mm; wall thickness tolerance ±0.1~±0.5mm; straightness ≤2mm/m; right angle error controlled within standard range
Weld Seam QualityWeld joint flat without crack, penetration full; seamless tube free of internal fold and hole defects
Surface QualityNo crack, fold, severe pits, burrs; galvanized products with uniform zinc coating, no exposed steel substrate
Test CertificateMill Test Certificate (MTC) attached per batch, including chemical composition, tensile strength, yield strength and bending test data, support customs clearance and incoming inspection
5. Main Application Fields
Construction Engineering: Factory building steel frame, steel structure villa, curtain wall keel, bridge temporary support
Municipal Engineering: Road guardrail, landscape frame, traffic signal support, municipal pipeline support
Mechanical Manufacturing: Machine tool frame, logistics storage rack, transport vehicle chassis bracket
Agricultural Facilities: Greenhouse skeleton, breeding shed support, agricultural machinery frames
Ship & Heavy Industry: Light load ship structural parts, mining equipment auxiliary supports
6. Packing, Marking & Delivery
6.1 Export Packing Standard
Small specification square tubes bundled with high-tensile steel strips, wrapped with waterproof plastic film inside; large size square tubes single bundled. Fumigated wooden pallets optional for container loading to avoid collision and sea rust. Galvanized square tubes separated with partition paper to prevent zinc layer scratch.
6.2 Marking Content
Each bundle hangs metal or plastic label, marked with material grade, side size × wall thickness × length, heat number, net weight, execution standard and manufacturer logo.
6.3 Delivery Time (Ship from Tianjin Port)
Conventional stock specifications: 5–7 days loading and shipmentCustom wall thickness, special length, galvanized processing: 7–15 days
6.4 Order Terms
MOQ: 1 ton, mixed sizes acceptable; fixed-length cutting, punching, bending, galvanized processing available; trade terms FOB, CIF, CFR; payment term: 30% TT deposit + 70% TT balance before shipment
7. Product Advantages
Complete size series, welded and seamless types for selection, matching light and heavy load usage scenarios
Stable raw material chemical composition, good welding and bending performance, low processing scrap rate
Multiple surface treatments optional to meet indoor, outdoor and anti-corrosion demands
Support diversified deep processing: cutting, punching, bending, galvanizing, spraying
Sufficient spot inventory, direct delivery from Tianjin Port, complete test documents for export clearance
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