Application description

Widely used in building frames, scaffolding, handrails, fences, gates, furniture (tables, chairs, shelves), machinery supports, automotive components, trailers, and agricultural equipment. The square shape provides easy joining and high strength-to-weight ratio. Cost-effective for structural and general fabrication projects.

Production description

Carbon steel strip is slit to required width, then fed into a series of forming rolls to be gradually shaped into a round tube. The edges are welded together by high-frequency ERW (electric resistance welding). The welded tube passes through sizing rolls where it is shaped into a square profile. It is then cut to length, straightened, and optionally annealed to relieve stress. The finished tube is inspected for weld integrity, dimensions, and surface quality.

Shipping Packaging

For export, welded square tubes are bundled with plastic end caps, wrapped in VCI paper and moisture-proof polyethylene, packed in wooden crates or on ISPM-15 pallets, secured with steel straps, and fitted with edge protectors. Labels include grade, dimensions, length, quantity, and heat number for safe sea freight.

Why Choose Us?

1.Factory Strength:Direct manufacturer with high-frequency ERW lines, in-line forming and sizing rolls, ensuring consistent outer dimensions, straightness, and weld integrity for square tubes.

2.Quality Assurance:Strict control of dimensional tolerances (outer dimension ±0.5mm, wall thickness ±0.1mm), weld seam strength, and corner radius; 100% eddy current or hydrostatic testing; compliant with ASTM A500, EN 10219, JIS G3466, GB/T 6728.

3.Certifications & Reports:Mill test certificates (MTC) with each shipment; third-party inspections (SGS, BV) and weld ultrasonic test reports available upon request.

4.Customization & Service:Wide carbon steel range (Q195–Q345, S235JR–S355JR, ST37–ST52), sizes 10×10–500×500mm, wall 0.5–16.0mm, custom lengths, surface finishes (black, pickled & oiled, galvanized, pre-painted), and corner radius options with fast lead times.

5.Export Packaging:Plastic end caps + VCI paper + moisture-proof wrapping + wooden crates/ISPM-15 pallets + steel strapping + edge protectors for safe sea freight and damage-free delivery.

FAQ

1. How to prevent rust on welded square tubes?

Store in dry, elevated area, keep original packaging. For black (as-welded) tubes, apply primer if used outdoors. Galvanized or pre-painted options are recommended for humid or corrosive environments.

2. Can welded square tubes be bent or welded further?

Yes. Use mandrel bending for tight radii. Re-welding is fine, but clean the weld area first. Avoid excessive heat near the original weld seam to maintain integrity.

3. What is the difference between ERW welded and seamless square tubes?

ERW welded tubes are cost-effective, with consistent dimensions and good for most structural and general fabrication uses. Seamless tubes have no weld seam, offering higher pressure resistance and uniform grain structure for critical or high-pressure applications.