Q235B Carbon Steel Square Bar, GB/T 702 Hot Rolled & Cold Drawn Solid Square Steel Bar

Compliant with GB/T 702 standard, stable and consistent material performance
Excellent weldability and machinability for easy fabrication
Available in hot rolled & cold drawn forms to meet different precision needs
Wide size range from 5×5mm up to 200×200mm
Suitable for structural frames, mold blanks and general mechanical parts

Product Overview

Q235B Carbon Steel Square Bar is solid square-section carbon steel bar produced according to GB/T 702 standard, supplied in both hot-rolled and cold-drawn options. Hot rolled Q235B square bar covers sizes 10×10mm to 200×200mm with black oxide surface and standard dimensional tolerance ±0.5~2mm. Cold drawn version provides smaller precision sizes starting from 5×5mm, featuring bright smooth surface and tighter tolerance ±0.1~0.3mm. This grade offers balanced ductility, reliable weldability and good cutting performance. It is widely applied for general steel structures, mechanical frames, mold blanks, equipment base frames and container accessory fabrication. Custom cut-to-length service and Mill Test Certificate are available for overseas customers.

Carbon Steel Square Bar

Chemical & Mechanical Property Snapshot

Grade	Standard	C (%)	Mn (%)	Si (%)	S (%) Max	P (%) Max	Yield Strength (MPa) Min	Tensile Strength (MPa)	Elongation (%) Min
Q235B	GB/T 702	≤0.20	0.30–0.70	≤0.35	0.045	0.045	235	370–500	26

Detailed Technical Specifications

Item	Specification
Product Name	Q235B Carbon Steel Square Bar
Material Grade	Q235B
Standard	GB/T702
Cross Section	Square Section
Product Forms	Hot-rolled / Cold-drawn
Hot-Rolled Size Range	10×10mm–200×200mm
Cold-Drawn Minimum Size	5×5mm
Common Hot-Rolled Sizes	12mm, 16mm, 20mm, 25mm, 30mm, 40mm, 50mm, 60mm, 80mm, 100mm, 120mm, 150mm, 200mm
Hot-Rolled Dimensional Tolerance	±0.5mm to ±2mm
Cold-Drawn Dimensional Tolerance	±0.1mm to ±0.3mm
Cutting Service	Custom cutting according to customer drawings
Quality Certificate	Mill Test Certificate with heat number, chemical composition and mechanical test results
Packaging	Steel strapped bundles for seaworthy export packing
MOQ	5 Ton
Payment Terms	T/T, L/C at Sight
Delivery Time	7–15 working days after receiving deposit

Size Specification Table

Type	Size Range	Available Side Dimensions (mm)	Tolerance
Hot Rolled Carbon Steel Square Bar	10×10 mm–200×200 mm	10, 12, 16, 20, 25, 30, 40, 50, 60, 80, 100, 120, 150, 200	±0.5–±2 mm
Cold Drawn Carbon Steel Square Bar	5×5 mm–50×50 mm	5, 6, 8, 10, 12, 14, 16, 20, 25, 30, 40, 50	±0.1–±0.3 mm

Product Comparison Table

Comparison Item	Q235B Carbon Steel Square Bar	Q355B Carbon Steel Square Bar	S235JR Carbon Steel Square Bar	S355JR Carbon Steel Square Bar	A36 Carbon Steel Square Bar
Equivalent Standard	GB/T 702	GB/T 702	EN 10059	EN 10059	ASTM A675
Manufacturing Process	Hot-Rolled / Cold-Drawn	Hot-Rolled / Cold-Drawn	Hot-Rolled / Cold-Drawn	Hot-Rolled / Cold-Drawn	Hot-Rolled / Cold-Drawn
Size Range	Hot Roll:10×10–200×200 mm; Cold Drawn:5×5–50×50 mm	Hot Roll:10×10–200×200 mm; Cold Drawn:5×5–50×50 mm	Hot Roll:10×10–200×200 mm; Cold Drawn:5×5–50×50 mm	Hot Roll:10×10–200×200 mm; Cold Drawn:5×5–50×50 mm	Hot Roll:10×10–200×200 mm; Cold Drawn:5×5–50×50 mm
Surface Condition	Hot-rolled black surface / Bright cold-drawn surface	Hot-rolled black surface / Bright cold-drawn surface	Hot-rolled black surface / Bright cold-drawn surface	Hot-rolled black surface / Bright cold-drawn surface	Hot-rolled black surface / Bright cold-drawn surface
Dimensional Tolerance	Hot Roll: ±0.5–2 mm; Cold Drawn: ±0.1–0.3 mm	Hot Roll: ±0.5–2 mm; Cold Drawn: ±0.1–0.3 mm	Hot Roll: ±0.5–2 mm; Cold Drawn: ±0.1–0.3 mm	Hot Roll: ±0.5–2 mm; Cold Drawn: ±0.1–0.3 mm	Hot Roll: ±0.5–2 mm; Cold Drawn: ±0.1–0.3 mm
Yield Strength (Min)	235 MPa	355 MPa	235 MPa	355 MPa	250 MPa
Main Application	General steel structures, mechanical frames, mold blanks	Heavy-load supports, engineering structures, lifting parts	European-standard structural fabrication, mechanical bases	High-strength European engineering structures	American-standard machinery, structural components
Cost Level	Medium	Medium-High	Medium	Medium-High	Medium
Feature	Good weldability & machinability	High strength, good impact resistance	Excellent weldability, CE compliance	High strength, CE certified	Stable performance, ASTM standard

App Market

Reliable Steel Coil Solutions For Diverse Industrial Applications

Hardware Stamping Blanking

Steel Structure Support

Machine Frame

Product Packaging

Secure Export Packaging For Safe Handling And Delivery

FAQs

What standard is Q235B carbon steel square bar produced to?

Our Q235B square bar is manufactured in accordance with GB/T 702 standard.

What is the difference between hot rolled and cold drawn Q235B square bar?

Hot rolled Q235B square bar has black surface, larger size options and looser tolerance for structural use. Cold drawn type has bright smooth surface, tighter tolerance for precision machining.

What are the main applications of Q235B square bar?

It is widely used for general steel structures, mechanical frames, mold blanks, equipment bases and container accessory fabrication.

Can you cut Q235B square bar into custom lengths?

Yes, we provide custom cutting service according to customer drawings and required lengths.

What is MOQ and lead time for Q235B carbon steel square bar?

MOQ is 5 tons, lead time 7–15 working days after receiving deposit.

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Q235B Carbon Steel Square Bar, GB/T 702 Hot Rolled & Cold Drawn Solid Square Steel Bar