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Help CenterFlat Steel & Flat Steel Bar，Q235B / SS400 / A36、Q355B / S355JR、20#、35#、45#、65Mn、60Si2Mn
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1. Product Overview
Flat steel bars are long rectangular section profiles whose width is far larger than thickness, divided into hot rolled flat bars and cold drawn precision flat bars. They are rolled from carbon steel, low alloy and medium carbon steel billets with neat vertical edges, uniform stress distribution and excellent performance for welding, bending, punching and cutting. Three surface finishes are available: black hot rolled scale, pickled bright and hot-dip galvanized anti-corrosion. Widely used for steel structure supports, embedded parts, machinery fittings, guardrails, earthing strips, construction machinery, ship auxiliary structures and factory reinforcement as universal basic section steel.
Main Implementation Standards
Chinese National StandardsGB/T 704-2016 Hot Rolled Flat Steel BarsGB/T 3078-2014 Cold Drawn Section SteelGB/T 700 Carbon Structural SteelGB/T 1591 Low Alloy High Strength Structural SteelGB/T 13912 Hot-dip Galvanizing Metal Coatings
International Export StandardsASTM A36 / A572 Gr50EN 10058, S235JR, S355JRJIS G3101 SS400
Supporting Test StandardsTensile test, 180° cold bending test, sectional dimensional tolerance inspection, zinc coating weight test, neutral salt spray corrosion test
2. Main Steel Grades & Applicable Working Conditions
2.1 Q235B / SS400 / A36 Ordinary Carbon Flat Bars
Mechanical index: Yield strength ≥235MPa, good ductility & weldability with optimal cost performance
Application: Factory steel structures, building embedded plates, guardrails, common earthing strips, simple supports, small municipal components
Optional surfaces: Hot rolled black scale, pickled finish, hot-dip galvanized
2.2 Q355B / S355JR Low Alloy High Strength Flat Bars
Mechanical index: Yield strength ≥355MPa, high strength, impact resistance and stable low-temperature toughness
Application: Heavy machinery bases, bridge auxiliary components, ship frames, heavy load supports, open-air high-load steel structures
2.3 20#, 35#, 45# Medium Carbon Machining Flat Bars
Performance: Can be quenched & tempered for adjustable hardness and strength, suitable for turning and milling precision machining
Application: Machinery sliding blocks, positioning baffles, shaft blanks, stamping die substrates, precision transmission fittings
2.4 65Mn, 60Si2Mn Spring Flat Bars
Performance: High elastic limit, excellent fatigue resistance, stable rebound & wear resistance after quenching
Application: Construction machinery spring plates, shock absorber shims, agricultural machinery elastic parts, stamped elastic components
3. Specification Parameters
Thickness RangeHot rolled flat bar: 3mm～60mmCold drawn precision flat bar: 2mm～30mm
Width RangeHot rolled: 12mm～300mm; Cold drawn: 5mm～100mm
Standard Fixed Length: 6m, 9m, 12m; customized random lengths from 1–12m available
Dimensional ToleranceStraightness of hot rolled flat bar ≤2mm/m; cold drawn flat bar high precision tolerance ±0.03～±0.08mm, vertical sides free of collapse and burrs
Surface Types
Hot rolled black scale: Original oxide surface, lowest cost, suitable for subsequent painting anti-corrosion
Pickled bright flat bar: Oxide scale removed, clean gray-white surface for direct welding & painting
Hot-dip galvanized flat bar: Thick zinc coating for long-term rust prevention in outdoor, humid and underground buried environments
Theoretical Weight Formula: Weight per meter (kg) = 0.00785 × Width(mm) × Thickness(mm)
4. Complete Production Process
4.1 Hot Rolled Flat Bar Process
Steel billet heating → Vertical continuous hot rolling forming → Cooling & straightening → Cut to fixed length → Shot blasting / pickling / galvanizing (on request) → Visual & dimensional inspection, marking & packing
4.2 Cold Drawn Precision Flat Bar Process
Hot rolled base material pickling, phosphating & saponification → Multi-pass precision cold drawing forming → Stress relief annealing → Straightening & deburring → Bright surface treatment, full inspection & bundling
5. Mandatory Factory Inspection Items
Spectral composition analysis: Strict control of C, Mn, S, P impurities to match grade strength requirements
Mechanical performance test: Room-temperature tensile test, 180° cold bending test without cracks or lamination after bending
Full sectional dimensional inspection: Thickness, width, straightness, side verticality, end flatness
Special galvanized coating test (for galvanized flat bars): Zinc coating weight, coating adhesion, neutral salt spray resistance duration
Visual surface inspection: Free of cracks, scabs, lamination, burrs, missing plating and rust spots
6. Main Application Fields
Building Steel Structure: Factory beam & column supports, roof purlin reinforcement, foundation embedded flat iron, lightning earthing strips
Machinery Manufacturing: Equipment bases, sliding blocks, limit baffles, gear shaft blanks, stamping processing substrates
Municipal Transportation: Road guardrails, bridge reinforcement parts, bus station supports, underground pipe network earthing
Ship & Offshore Engineering: Ship deck supports, cabin fixing components, lightweight load-bearing profiles for offshore platforms
Construction & Agricultural Machinery: Heavy equipment bases, shock absorber spring plates, agricultural machinery elastic parts, forklift auxiliary supports
Power Anti-corrosion Engineering: Hot-dip galvanized earthing flat steel, substation frames, fixing parts for outdoor power transmission equipment
7. Core Product Advantages
Regular section with uniform stress distribution: Flat rectangular cross-section provides stable lateral bending & bearing capacity, tight fitting during assembly and splicing
Wide processing compatibility: Arbitrary cutting, bending, punching, welding and heat treatment available for rough machining and precision finish machining
Complete anti-corrosion surface solutions: Black scale, pickled and hot-dip galvanized finishes cover dry indoor, humid outdoor and underground buried working conditions
Dual production options: Low-cost large-size hot rolled, high-precision cold drawn with minimal machining allowance to meet different tolerance requirements
Full grade coverage: Complete series including ordinary carbon, high-strength low alloy, medium carbon machining and spring steel
Rich width & thickness combinations with abundant spot stock, customizable cut lengths to reduce customer waste
8. Delivery, Packing & Logistics
Delivery States
Hot rolled flat bar: Black oxide raw surface, pickled gray-white surface, matte hot-dip galvanized anti-corrosion surface
Cold drawn flat bar: Bright oxide-free precision surface coated with anti-rust oil
Bar Marking: Metal tag attached to each bundle marked with material grade, dimension, execution standard, bundle weight and heat batch number
Packing Standard: Cross-bound with steel strips, reinforced wooden pallets covered with rainproof film; export heavy-duty seaworthy packing with inner moisture-proof paper
Delivery Lead TimeRegular in-stock Q235B hot rolled flat bars: Delivery within 3–7 days; customized cold drawn precision, Q355 high strength, spring flat bars and galvanized processing: 7–10 days, container shipment available from Tianjin Port
Attached Shipping Documents: Original Mill Test Certificate, tensile & cold bending mechanical test report, galvanized salt spray test record, factory certificate
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