Q235B Carbon Steel Plate – GB/T 700 Factory Direct Supplier | Huaxia-Steel

Q235B is the most widely used Chinese general-purpose carbon steel plate grade, defined by the standard GB/T 700 “Carbon Structural Steels”. With minimum yield strength of 235 MPa and impact testing at 20 °C, Q235B is the practical Chinese equivalent of ASTM A36 and is used for structural fabrication, plant construction, container frames, ship sections, and general engineering across China and global export markets.

Huaxia-Steel supplies factory-direct Q235B carbon steel plate in thickness 3 mm to 200 mm, width up to 3,000 mm, and length up to 12,000 mm. Hot-rolled, controlled-rolled, and normalized deliveries are available. Plates are supplied per GB/T 700 with EN 10204 3.1 mill test certification.

1. Q235B Standard and Naming

Q235B grade is defined by GB/T 700-2006 “Carbon Structural Steels”. The naming convention breaks down as follows:

Q – the first letter of “Qu” (屈服, yield strength) in Chinese pinyin.
235 – minimum yield strength in MPa at thickness up to 16 mm.
B – the quality grade, determined by impact test temperature: A = no impact, B = 20 °C, C = 0 °C, D = -20 °C.

Q235B has the widest application of all Q grades because the 20 °C impact requirement covers the majority of building and general engineering service environments.

2. Chemical Composition

Element	Range / Max (percent)
Carbon (C)	0.20 max
Silicon (Si)	0.35 max
Manganese (Mn)	1.40 max
Phosphorus (P)	0.045 max
Sulfur (S)	0.045 max
Carbon Equivalent (CEV)	typically 0.30-0.38

For thicknesses above 100 mm, the Mn range can be reduced to 1.20-1.60 max and the CEV is reported per heat. Q235B has very good weldability due to its low carbon and CEV, comparable to ASTM A36.

3. Mechanical Properties

Property	Thickness 3-16 mm	Thickness 16-40 mm	Thickness 40-100 mm	Thickness 100-200 mm
Yield Strength (MPa, min)	235	225	215	205
Tensile Strength (MPa)	370-500	370-500	370-500	370-500
Elongation (percent, min)	26	26	26	26
Impact @ 20 °C (J, min)	27	27	27	27
Bending 180 deg	d = 1.5a	d = 1.5a	d = 1.5a	d = 1.5a

Note that the yield strength decreases with thickness. For plate thickness selection in structural design, refer to GB 50017 “Code for Design of Steel Structures”.

4. Size Range and Tolerance

Dimension	Range	Tolerance (per GB/T 709)
Thickness	3 – 200 mm	+/- 0.30 to +/- 1.5 mm depending on thickness
Width	1,500 – 3,000 mm	+/- 5 to +/- 25 mm
Length	3,000 – 12,000 mm	+/- 10 to +/- 50 mm
Flatness	per GB/T 709	3-8 mm per meter
Edge	mill edge or cut edge	cut edge +/- 5 mm

For thicknesses below 6 mm, the plate is typically produced as hot-rolled strip and slitted. Above 25 mm, the plate is rolled from continuously-cast slab.

5. Delivery Conditions

Q235B plate is supplied in the following conditions:

Hot-rolled (HR): Default condition. Rolled at 900-1,050 °C, cooled in air. Standard mechanical properties.
Controlled rolling (CR): Final rolling passes at 800-900 °C with controlled reduction. Improved mechanical properties, especially notch toughness.
Normalizing (N): Heated to 890-920 °C, held, air-cooled. Refines grain, restores properties after hot rolling at heavy gauge.
Stress relieving (SR): Heated to 600-650 °C to relieve residual stress from rolling or forming.
Shot blasting and priming: Surface cleaned and shop-primed with anti-corrosion primer for fabrication shop use.

For structural use in buildings, bridges, and machinery bases, hot-rolled Q235B is the default. For low-temperature service or critical impact, Q235C (0 °C) or Q235D (-20 °C) is required.

6. Cross-Reference to Other Standards

Q235B is widely cross-referenced to foreign standards for export and procurement purposes:

Standard	Closest Grade	Notes
ASTM (US)	A36 / A283 Gr.C	Yield 250 MPa; slightly higher than Q235B but generally interchangeable
EN (Europe)	S235JR / S235J0	Direct equivalent in chemistry and yield
JIS (Japan)	SS400	Yield 245 MPa; chemistry slightly different (SS400 has higher Mn)
ISO	Fe 360 B	Withdrawn, but cross-reference survives
GOST (Russia)	St3sp / St3ps	Similar grade in GOST 380-2005
DIN (Germany)	St37-2 / RSt37-2	Withdrawn, replaced by S235JR

Be aware of two cross-reference pitfalls: (1) when going from a foreign spec to Q235B, ensure the foreign spec’s thickness-tapering yield rule and impact requirement match; (2) when going from Q235B to ASTM A36, note A36 has slightly higher Mn and may require a different grade of welding consumable for matched strength.

7. Welding and Fabrication

Q235B plate has excellent weldability with all common arc welding processes – SMAW, GMAW, FCAW, GTAW, and SAW. Recommended consumables:

SMAW (stick): E6013, E7018 (for higher strength matching to weld metal).
GMAW (MIG/MAG): ER70S-6 wire with CO2 or Ar/CO2 shielding gas.
FCAW (flux-cored): E71T-1 or E71T-GS for general fabrication.
SAW (submerged arc): H08A / H08MnA wire with HJ431 flux.

No preheat is required for thicknesses up to 25 mm with combined carbon + Mn/6 + Cr/5 + Mo/5 + V/5 + Cu/15 + Ni/15 below 0.40 CEV. For thicknesses above 25 mm or higher CEV, a 75-150 °C preheat is recommended for heavy restraint welds.

Q235B plate can also be flame-cut, plasma-cut, laser-cut, waterjet-cut, sheared, blanked, formed, and bent. Cold-formed sections should be specified to the as-formed strength or stress-relieved if the part carries cyclic load.

8. Applications

Q235B plate is used in:

Building structures: Beams, columns, base plates, gusset plates, brackets, stair stringers, handrails.
Bridge construction: Girders, deck plates, diaphragms, bearing plates.
Industrial equipment: Machine bases, gearbox housings, motor frames, pump casings (non-pressure).
Container and trailer fabrication: Container floor plates (3-6 mm), side plates, end frames.
Power and substations: Transformer tanks, switchgear enclosures, support frames.
Material handling: Storage tank shells (non-pressure), conveyor frames, crane girders.
Agriculture and mining: Dumper bodies, hopper liners, chute liners (wearing applications may need higher hardness grades).

For pressure vessels, low-temperature service, sour service, and high-strength applications, Q235B is replaced by grades like Q345R, Q245R, A516 Gr.70, A537 Class 1, etc.

9. Quality Assurance and Certification

Huaxia-Steel Q235B plate carries the following QA documentation:

GB/T 700 compliance: Chemistry, mechanical, and impact tested per the standard.
EN 10204 3.1 mill test certificate with full heat traceability.
Ultrasonic testing per GB/T 2970 for plates above 20 mm (Class A, B, or C as specified).
Dimensional report: Thickness, width, length, flatness, edge condition.
Visual examination: No cracks, laps, scabs, or surface defects.
Third-party inspection by SGS, BV, TUV, or customer-nominated inspector accepted.

We also accept pre-shipment inspection by the buyer’s representative in our mill.

10. Packaging and Shipping

Standard export packing: Plates bundled with steel straps, edge-protected with cardboard or timber. Mill scale intact for hot-rolled plate.
Anti-rust protection: VCI paper for sea shipment, or shot-blasted + shop-primed.
Marking: Heat number, grade, size, weight stencilled on each plate. Packing list on the bundle.
Container loading: Thin plates (3-6 mm) fit 20-ft or 40-ft containers. Thicker plates above 30 mm go on flat-rack or in bulk carriers.

Lead time: 10-20 days for standard sizes, 25-35 days for custom-cut dimensions.

11. Ordering Information

To order Q235B plate, specify:

Grade: Q235B (or Q235A / Q235C / Q235D)
Standard: GB/T 700
Thickness, width, length (mm)
Delivery condition: hot-rolled / normalized / controlled rolled
Surface: mill / shot-blasted + primed / galvanized
Quantity: in tonnes or pieces
Inspection: factory / third-party / with NDT / with witness

Huaxia-Steel supplies Q235B carbon steel plate direct from the mill at factory prices. Thickness 3-200 mm, width up to 3,000 mm, length up to 12,000 mm, hot-rolled and normalized. GB/T 700, EN 10204 3.1 MTC, container or bulk shipment. Send your inquiry with size, quantity, and destination port for a same-day quotation.