CARBON STEEL · SQUARE & RECTANGULAR TUBE

Q235B Carbon Steel Square Tube
国标/T 6728 Cold-Formed Welded Hollow Section

Strong, straight and easy to weld — the workhorse square and rectangular hollow section for steel structures, racks, frames and machinery.

STANDARD: 国标/T 6728 GRADE: Q235B CUSTOM SIZE AVAILABLE

YIELD STRENGTH

≥235兆帕

TENSILE STRENGTH

370–500兆帕

SIZE RANGE

20×20–200×200

01 · 产品概述

Q235B square and rectangular hollow sections are cold-formed from hot-rolled strip and longitudinally welded to GB/T 6728. The section is square to tight corners, straight and torsion-resistant, delivering predictable strength for structural and mechanical use at a very competitive cost.

WHY CHOOSE Q235B TUBE

One material, one grade — Q235B only, no mixed chemistries in the batch. Uniform wall thickness, clean weld seam, precise outer dimensions and cut-to-length service for every order.

02 · 主要特点

Square Precision

Sharp, even corners and straight sidewalls improve joint fit-up and speed up frame assembly.

High Strength-to-Weight

Closed hollow section gives excellent bending and torsional stiffness per kilogram — lighter structures than open profiles.

Easy Welding

Low carbon Q235B welds cleanly in all positions — joints are strong and free of hard spots.

Consistent Wall Thickness

Roll-formed from controlled strip, wall and corner thickness stay uniform along the full length.

Seaworthy Packing

Bundles steel-banded and weather-protected, safe for long sea freight to any destination.

Cut-to-Length Service

Any length from 1 m to 12 米, precise mitre or square cutting available for ready-to-use parts.

03 · 化学成分 (Cast Analysis, %) — Q235B

元素	C	和	锰	磷	S
Max Content	0.20	0.35	1.40	0.045	0.045

笔记: Values are maximum cast analysis in percent. Mill test certificates accompany each batch.

04 · 机械性能 (Base Metal)

财产	价值	Test Method
屈服强度 (ReH)	≥ 235 兆帕	国标/T 228.1
抗拉强度 (Rm)	370 – 500 兆帕	国标/T 228.1
伸长 (A)	≥ 26 %	国标/T 228.1
Charpy Impact (20 ℃)	≥ 27 J	国标/T 229
Weld Seam	Flattening test — no crack	国标/T 246

TENSILE STRENGTH — COMMON GRADES COMPARISON

Q235B Tube (370–500兆帕)RANGE

Q355B (470–630 MPa)HIGHER

05 · 物理性能

DENSITY

7.85 g/cm³

MELTING POINT

≈ 1490 ℃

MODULUS OF ELASTICITY

200 – 210 GPa

THERMAL EXPANSION

≈ 12×10⁻⁶ /K

06 · 通用规格

Section	尺寸 (毫米)	室壁厚度 (毫米)	长度 (米)
Square Tube	20×20 – 100×100	1.5 / 2.0 / 2.5 / 3.0 / 4.0	6 / 12
Square Tube (Large)	120×120 – 200×200	4.0 / 5.0 / 6.0 / 8.0 / 10.0	6 / 12
Rectangular Tube	20×30 – 150×200	1.5 – 10.0	6 / 12
表面	铣削加工; galvanized, painted or oiled on request