Product Highlights
- Large-size carbon square hollow structural section, side dimension range 10×10mm up to 1000×1000mm, wall thickness 0.8–30mm for heavy-load large engineering projects
- Fully compliant with global industrial standards: ASTM A36, ASTM A500, GB/T 6728, GB/T 3094, EN 10210, EN 10219, JIS G3466
- Adopts mature high-frequency ERW welding production line, full online non-destructive inspection to eliminate welding internal defects
- Multiple customizable surface finishes: black bare, anti-rust oil, hot galvanizing, paint, powder coating, PVC coated for indoor/outdoor/marine environments
- Complete material grade portfolio: Q235B, S235JR, Q345B, S355JR, ASTM A36, A500 A/B/C, SS400, St37, St52
- Flexible length customization: fixed standard lengths (5.8m / 6m / 12m) or arbitrary cut-to-length per customer technical drawings
- Stable monthly production capacity up to 10,000 tons, low MOQ of 25 tons; flexible trade & payment terms: FOB/CFR/CIF, T/T & L/C available
- Standard export bundled packaging with steel strips + waterproof plastic inner bag, safe for long-distance ocean transportation
Product Overview
Large-diameter square steel pipe is heavy-duty cold-formed ERW welded hollow structural section, specially designed for large-span building frames, heavy machinery supports, municipal infrastructure and oversized engineering equipment.
The whole production workflow includes uncoiling, flattening, roll forming, high-frequency welding, deburring, water cooling, NDT inspection, sizing cutting and surface finishing. All finished large square tubes pass strict dimensional tolerance inspection (side tolerance ±0.5mm, wall tolerance ±0.05mm) before warehousing.
Compared with small square tubes, this large series features thicker wall options and ultra-wide side sizes to bear heavier static & dynamic loads. We support custom surface anti-corrosion treatment and secondary cutting, punching, bending processing, widely supplied to global construction, machinery, municipal and agricultural engineering customers.
Material Grade Characteristics
ASTM A36 General Structural Carbon Steel
- Universal low-carbon structural grade for medium-load frames, min tensile strength 400–550MPa, min yield ≥250MPa
- Excellent cold forming, punching and welding performance, low impurity sulfur & phosphorus, stable long-term service indoors
- Cost-effective conventional structural material for general building & decoration projects
ASTM A500 Grade Structural Square Tube (A/B/C)
- Cold-formed welded hollow section dedicated for structural load-bearing
- Grade A: Min tensile 310MPa, yield 269MPa, elongation ≥25% for light load structures
- Grade B: Min tensile 400MPa, yield 317MPa, elongation ≥23% — most widely used standard grade
- Grade C: Min tensile 427MPa, yield 345MPa, elongation ≥21% for heavy-load large-span engineering
- Uniform wall thickness and symmetrical square cross-section with superior torsional rigidity
Q235B / S235JR Mild Carbon Steel
- Economical general structural steel, min yield strength ≥235MPa, outstanding weldability for ordinary construction frames
- Stable mechanical property under normal temperature, suitable for indoor structure, fence and light equipment supports
Q345B / S355JR High Strength Low Alloy Steel
- High-strength structural grade, min yield ≥345MPa, higher load capacity than Q235/S235
- Ideal for large-span workshops, bridge auxiliary supports, heavy machinery base frames
Chemical Composition (Weight %)
1. Q235B / S235JR
| Element |
C (Max) |
Si |
Mn |
P (Max) |
S (Max) |
| Content Range |
0.17~0.22 |
≤0.35 |
0.30~0.70 |
0.045 |
0.045 |
2. Q345B / S355JR
| Element |
C (Max) |
Si (Max) |
Mn (Max) |
P (Max) |
S (Max) |
| Content Range |
0.24 |
≤0.55 |
≤1.60 |
0.035 |
0.035 |
3. ASTM A500 Grade B
| Element |
C (Max) |
Si |
Mn (Max) |
P (Max) |
S (Max) |
| Content Range |
0.26 |
Optional |
≤1.35 |
0.035 |
0.035 |
4. ASTM A36
| Element |
C (Max) |
Si (Max) |
Mn (Max) |
P (Max) |
S (Max) |
| Content Range |
0.25 |
≤0.40 |
≤1.00 |
0.04 |
0.05 |
Related Material Grades
We supply matching square, rectangular, round hollow sections and alloy pipes for full structural & pipeline projects:
- Carbon Structural Hollow Section: Q235B/S235JR, Q345B/S355JR, ASTM A36, ASTM A500 A/B/C, SS400, St37/St52
- Conventional Round Carbon Pipe: ASTM A53, ASTM A106 Gr.B, API 5L line pipe
- High Temperature Alloy Pipe: ASME SA335 P11/P22/P91, ASTM A519 mechanical alloy tube
- Stainless Structural Tube: 304, 316L, 321 square & rectangular hollow sections
- Corrosion-Resistant Special Alloy: Alloy 28 seamless pipe, ASTM B167 nickel alloy tube
Key Advantages
Heavy Load Large-Size Capacity
Side size up to 1000×1000mm and wall thickness up to 30mm, perfect for large-span workshop columns, heavy equipment bases and municipal large support frames.
Precise Dimensional Tolerance
Side width tolerance ±0.5mm, wall thickness tolerance ±0.05mm, flat square surface for easy bolt connection and assembly.
Reliable ERW Welding Quality
High-frequency integrated welding line with online UT/eddy current non-destructive inspection, no hidden crack defects inside the weld seam.
Diversified Anti-Corrosion Surface Options
Black bare, oiled, hot galvanized, powder coated finishes available to adapt indoor, outdoor and coastal corrosive service environments.
Excellent Machinability & Weldability
Low-carbon steel matrix supports cutting, drilling, punching, bending and all mainstream welding processes for on-site fabrication.
Stable Production & Flexible Order
Monthly output 10,000 tons, accept small batch orders starting from 25 tons, controllable delivery cycle for global engineering orders.
Typical Applications
- Large building engineering: Factory workshop columns, roof trusses, large-span steel frame structures
- Municipal infrastructure: Large traffic guardrail, bridge auxiliary support, tunnel structural components
- Heavy mechanical manufacturing: Large equipment base, conveying rack, mining machinery frame
- Logistics & storage: Oversized warehouse shelf, heavy load storage rack structure
- Agricultural facilities: Large greenhouse main skeleton, breeding equipment heavy supports
- Decoration & engineering: Oversized exhibition stand, large outdoor billboard support frame
Processing Service
We provide integrated forging and precision machining services, and can produce finished components strictly according to customer drawings:
Turning, milling, planing, drilling, boring, grinding
Gear cutting, CNC precision machining
Sizing cutting, surface treatment and finishing
We have supplied a wide range of forged and machined parts including shafts, cylinders, hollow bars, pistons, tube sheets, rings and disc bearings to customers worldwide.
Quality Assurance
We have a professional QC inspection team and complete testing equipment to ensure stable and reliable product quality:
Ultrasonic testing (UT) for internal defects
Tensile and hardness testing for mechanical properties
High-precision dimensional measurement
Spectrometer for chemical composition verification
Metallographic microstructure inspection
Every batch of products undergoes strict inspection before delivery to meet the quality requirements of various engineering projects.
Packing & Delivery
Packing
Inner packaging: waterproof polybag for moisture and dust protection
Outer packaging: reinforced wooden case / wooden pallet, suitable for long-distance international transportation
Custom packaging solutions available upon request
Lead Time
Normally 10 – 45 days after receipt of advance payment
Exact delivery time depends on order quantity, specification complexity and machining requirements