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  • Q235 Galvanized square pipe

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Q235 Galvanized square pipe
Q235 galvanized square pipe is manufactured from GB/T 700 Q235 carbon steel and formed into square shape, then processed through hot-dip galvanizing. This product combines good weldability, excellent formability, and superior corrosion resistance, making it suitable for structural applications, construction, and various industrial uses.
Phone：+86 18954208811
Email：info@hwdsteel.com
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Add：Keda Xunfei Weilaigang Building, No. 1 Jiangshan South Road, Huangdao District, Qingdao City, Shandong Province
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◉ PRODUCT SPECIFICATION


1. Material Standards & Grades


Primary Standards:

  • GB/T 700 - Carbon Structural Steels

  • GB/T 3091 - Welded Steel Pipes for Low-Pressure Fluid Transmission

  • GB/T 6728 - Cold-Formed Welded Steel Sections


Grade Designations:

Grade

Yield Strength (MPa)

Quality Level

Equivalent Standards

Q235A

≥235

Commercial

ASTM A36

Q235B

≥235

Better quality

S235JR

Q235C

≥235

Good impact value

-

Q235D

≥235

Best impact value

-


2. Chemical Composition (% by weight)


Element

Q235A

Q235B

Q235C

Q235D

Carbon (C)

0.14-0.22

≤0.20

≤0.18

≤0.17

Manganese (Mn)

0.30-0.65

0.30-0.70

0.35-0.80

0.35-0.80

Silicon (Si)

≤0.30

≤0.30

≤0.30

≤0.30

Phosphorus (P)

≤0.045

≤0.045

≤0.040

≤0.035

Sulfur (S)

≤0.050

≤0.045

≤0.040

≤0.035


3. Mechanical Properties


Property

Q235A

Q235B

Q235C

Q235D

Yield Strength (MPa)

≥235

≥235

≥235

≥235

Tensile Strength (MPa)

375-500

375-500

375-500

375-500

Elongation (%)

≥26

≥26

≥26

≥26

Impact Temperature

-

20°C

0°C

-20°C

Impact Energy (J)

-

≥27

≥27

≥27


4. Galvanized Coating Specifications


Coating Requirements (GB/T 3091):

Coating Class

Coating Mass (g/m²)

Coating Thickness (μm)

Service Life

Standard

≥500

≥70

15-20 years

Heavy

≥600

≥85

20-30 years

Extra Heavy

≥700

≥100

30+ years


Coating Quality Tests:

  • Zinc coating adherence test

  • Uniformity test

  • Bending test (d=2a, 90°)

  • Sulfate copper test


5. Physical Properties


Property

Typical Value

Test Standard

Density

7.85 g/cm³

GB/T 223

Modulus of Elasticity

200-210 GPa

GB/T 223

Poisson's Ratio

0.25-0.30

-

Thermal Expansion Coefficient

11.5×10⁻⁶/°C

GB/T 4339

Thermal Conductivity

48-52 W/m·K

-


6. Product Specifications


Parameter

Standard Range

Tolerance

Customization Available

Outer Size

20×20mm - 400×400mm

±0.5-1.5mm

10×10mm - 500×500mm

Wall Thickness

1.0-12.0mm

±10%

0.8-16.0mm

Length

3-12m

+10mm/-0mm

1-18m

Straightness

≤1.5mm/m

-

≤1.0mm/m

Squareness

≤1.5°

-

≤1.0°


7. Manufacturing Process


Production Flow:

  • Steel strip uncoiling and leveling

  • Cold forming into square shape

  • High-frequency welding (HFW)

  • Weld seam treatment

  • Sizing and straightening

  • Hot-dip galvanizing (445-460°C)

  • Cooling and passivation

  • Final inspection and packaging


Key Process Parameters:

  • Welding speed: 20-40 m/min

  • Galvanizing temperature: 445-460°C

  • Zinc bath composition: Zn≥99.5%

  • Passivation treatment: Chromate or non-chromate


8. Testing & Inspection


Standard Tests:

  • Tensile test (GB/T 228)

  • Bend test (GB/T 244)

  • Flattening test (GB/T 246)

  • Zinc coating test (GB/T 1839)

  • Hydrostatic test (GB/T 241)

  • Visual inspection

  • Dimensional inspection


Optional Tests:

  • Salt spray test (GB/T 10125)

  • Impact test (GB/T 229)

  • Chemical analysis (GB/T 223)

  • NDT inspection

  • Third-party inspection


9. Applications


Construction Applications:

  • Building structural frameworks

  • Steel structure workshops

  • Construction scaffolding

  • Fencing and guardrails

  • Roof truss systems


Industrial Applications:

  • Machinery manufacturing

  • Equipment support frames

  • Conveyor system structures

  • Storage rack systems

  • Industrial work platforms


Infrastructure Applications:

  • Bridge railings

  • Highway sound barriers

  • Transmission towers

  • Agricultural greenhouses

  • Sports facilities

◉ Surfcae selection

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SURFACE CHARACTERISTIC SUMMARY OF MANUFACTURING METHOD APPLICATION
NO.1 Silvery white Hot rolled to specified thickness Do not need to have a glossy surface use
lackluster
NO.2D Silvery white After cold rolling, heat treatment and pickling are carried out General material, deep material
NO.2B Gloss is stronger than No.2D After No.2D treatment, the final light cold rolling is carried out through the polishing roller The general material
BA As bright as a sixpence No standard, but usually a bright annealed surface with high reflectivity. Building materials, kitchen utensils
NO.3 Rough lapping Grind with 100~200# (unit) strop tape Building materials, kitchen utensils
NO.4 Intermediate grinding Polished surface obtained by grinding with 150~180# strop abrasive tape Building materials, kitchen utensils
NO.240 Fine lapping Grinding with 240# strop abrasive tape kitchenware
NO.320 Very fine grinding Grinding was carried out with 320# strop abrasive tape kitchenware
NO.400 The luster is close to BA Use 400# polishing wheel to grind General timber, building timber, kitchen appliances
HL Hairline grinding Suitable particle material for hair stripe grinding (150~240#) with many grains Building, construction material
NO.7 It's close to mirror grinding Use a 600# rotary polishing wheel to grind For art or decoration
NO.8 Mirror ultrafinish The mirror is ground with a polishing wheel Reflector, for decoration

◉ PRODUCTION AND WAREHOUSING

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