ASTM A36 S235JR Black Square Hollow Section Pipe , Electric Resistance Welding ERW Steel Tube

ASTM A36 / S235JR Black Square Hollow Section (SHS) ERW Welded Steel Tube

Uncoated Mill Finish | ERW Welded | Structural Grade

Product Overview

This Black Square Hollow Section (SHS) is an ERW welded steel tube produced from ASTM A36 and EN S235JR equivalent structural steel grades. It is supplied in uncoated, mill-finish condition — the term "Black" refers to the natural oxidized surface retained from the steel mill, not a painted or coated product.

The tube is manufactured by the ERW (Electric Resistance Welding) process: steel strip is cold-formed into a square section and the longitudinal seam is welded using high-frequency current. This is the mainstream production method for square hollow sections, offering high efficiency, uniform wall thickness, and precise dimensional accuracy.

Material Grades

Note: Both grades offer good weldability and ductility. They are widely accepted in international markets and are often specified interchangeably for general structural applications. Mill test certificates can be issued to either ASTM or EN standard upon request.

Surface Condition

Supplied in Black (uncoated) condition, typically with a light anti-rust oil applied at the mill for protection during transport and short-term storage. This surface is ideal for:

• Components to be painted, powder-coated, or hot-dip galvanized after fabrication

• Indoor structural frames, machinery bases, and welded assemblies

• Heavy fabrication where anti-corrosion treatment is applied after welding

Note: Black SHS is not intended for direct outdoor or moisture-exposed service. For outdoor applications, hot-dip galvanizing or painting after welding is recommended.

Size Range (Typical)

Standards

Manufactured to ASTM A500, EN 10219, or equivalent standards. Mill test certificates are available upon request.

Typical Applications

• Indoor building structural frames

• Machinery manufacturing and equipment bases

• Conveyor line supports and welded structural components

• Semi-finished parts requiring subsequent painting or galvanizing

• General construction and fabrication projects

Why Choose This Black SHS ERW Welded Tube

• International grade recognition — ASTM A36 and S235JR are widely accepted worldwide

• Cost-effective — lower unit price than galvanized or painted tube

• Fabrication-friendly — excellent weldability for cutting, drilling, and joining

• Versatile — suitable for a wide range of structural and mechanical applications

• Customizable — sizes, wall thicknesses, and lengths can be produced to order