CARBON STEEL · SQUARE & RECTANGULAR TUBE

Q235B Tub pătrat din oțel carbon
GB/T 6728 Cold-Formed Welded Hollow Section

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

STANDARD: GB/T 6728 GRADE: Q235B DIMENSIUNE PERSONALIZATĂ DISPONIBILĂ

FORTA DE CANDIDAT

≥235 MPa

REZISTENȚĂ LA TRACȚIUNE

370-500 MPa

SIZE RANGE

20×20–200×200

01 · PREZENTARE GENERALĂ A PRODUSULUI

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

Un singur material, o singură clasă — numai Q235B, no mixed chemistries in the batch. Uniform wall thickness, clean weld seam, precise outer dimensions and cut-to-length service for every order.

02 · CARACTERISTICI CHEIE

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 la 12 m, precise mitre or square cutting available for ready-to-use parts.

03 · COMPOZIȚIA CHIMĂ (Analiza distribuției, %) — Q235B

Element	C	Si	Mn	P	S
Conținut maxim	0.20	0.35	1.40	0.045	0.045

Nota: Valorile sunt analiza maximă a turnării în procente. Certificatele de testare la moara însoțesc fiecare lot.

04 · PROPRIETĂȚI MECANICE (Base Metal)

Proprietate	Valoare	Metoda de testare
Puterea de curgere (ReH)	≥ 235 MPa	GB/T 228.1
Rezistență la tracțiune (Rm)	370 – 500 MPa	GB/T 228.1
Elongaţie (O)	≥ 26 %	GB/T 228.1
Impactul Charpy (20 °C)	≥ 27 J	GB/T 229
Weld Seam	Flattening test — no crack	GB/T 246

REZISTENȚA LA TRACȚIUNE — COMPARAȚIE DE GRADE COMUNE

Q235B Tube (370-500 MPa)GAMĂ

Q355B (470-630 MPa)SUPERIOR

05 · PROPRIETĂȚI FIZICE

DENSITATE

7.85 g/cm³

PUNCT DE TOPIRE

≈ 1490 °C

MODUL DE ELASTICITATE

200 – 210 GPa

THERMAL EXPANSION

≈ 12×10⁻⁶ /K

06 · SPECIFICAȚII COMUNE

Section	Dimensiune (mm)	Grosimea peretelui (mm)	Lungime (m)
Tub pătrat	20×20 – 100×100	1.5 / 2.0 / 2.5 / 3.0 / 4.0	6 / 12
Tub pătrat (Large)	120×120 – 200×200	4.0 / 5.0 / 6.0 / 8.0 / 10.0	6 / 12
Tub dreptunghiular	20×30 – 150×200	1.5 – 10.0	6 / 12
Suprafaţă	Finisaj moara; zincat, painted or oiled on request