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Help CenterFlat Steel & Steel Flat Bar，ASTM A36、EN10025、JIS G3101、DIN1017、ISO 630
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1. Product Overview
Flat steel, also called flat iron, is long section steel with rectangular cross-section and blunted edges, only manufactured by carbon steel, HSLA steel, quality carbon steel and spring steel without stainless steel grades. Divided into four categories: hot rolled flat steel, cold drawn precision flat steel, hot-dip galvanized flat steel and forged flat steel. It features flat surface and convenient installation, with excellent performance in welding, bending, stamping and heat treatment. It can be directly used as finished product or blank for welded pipe & thin slab rolling, widely applied in steel structure, mechanical processing, electric power cable tray, guardrail, bridge, agricultural machinery and spring fixture construction & manufacturing industries.
2. Applicable Standards
Domestic Chinese Standards
GB/T 704-2016 Dimension, Shape, Weight and Tolerance for Hot Rolled Flat Steel
GB/T 3078-2019 Cold Drawn Quality Structural Steel (for cold drawn flat steel)
GB/T 700 Carbon Structural Steel, GB/T 1591 HSLA Structural Steel
GB/T 13912 Technical Specification for Hot-Dip Galvanized Coating
GB/T 1222 Spring Steel Standard (special for spring flat steel)
International Export Standards
ASTM A36, EN10025, JIS G3101, DIN1017, ISO 630
Supporting Certifications
SGS mechanical & salt spray test report, original Mill Test Certificate (MTC), CE steel structure building material certification, zinc coating adhesion test report
3. Main Material Grades (Stainless Steel Excluded)
3.1 Ordinary Carbon Structural Flat Steel (General Construction, Support, Guardrail)
Q195, Q235B; export equivalent S235JR, ASTM A36, good ductility & weldability with high cost performance
3.2 HSLA High Strength Flat Steel (Heavy Load Steel Structure, Bridge, Machinery Base)
Q355B, Q390B, Q420B; export S355JR, high yield strength, impact resistance & anti-deformation under load
3.3 Quality Carbon Mechanical Flat Steel (CNC machining, flange, fastener blank)
20#, 35#, 45# uniform internal structure, support quenching & tempering for precision mechanical parts
3.4 Alloy Structural Flat Steel (Heavy load shaft base, high strength mold accessories)
40Cr, 42CrMo excellent hardenability for high pressure wear-resistant equipment components
3.5 Special Spring Flat Steel (Leaf spring, fixture, shock absorption elastic parts)
65Mn, 60Si2Mn high elastic limit & anti-fatigue performance without fracture under repeated deformation
4. Product Classification by Production Process & Features
Hot Rolled Flat Steel (Mainstream for Engineering)Integrally rolled at 1100–1250℃ with uniform mill scale on surface, wide size range & low cost, medium dimensional tolerance, suitable for steel structure support, embedded parts, guardrail and grounding flat steel.
Cold Drawn Precision Flat Steel (Special for Precision Machining)Cold drawn from hot rolled blank at ambient temperature, dimension tolerance ±0.02~±0.05mm, bright oxide-free surface without polishing for direct machining, first choice for precision equipment & automatic stamping parts.
Hot-Dip Galvanized Flat Steel (Anti-corrosion Outdoor & Power Grounding)Whole finished flat steel hot-dip galvanized, zinc coating 60–275g/㎡ with superior salt spray resistance, dedicated for substation grounding, outdoor guardrail & coastal steel structure.
Forged Flat Steel (Ultra-Heavy Load Equipment)Dense metallographic structure after forging without internal looseness & pores, tensile & impact performance far superior to rolled flat steel, for heavy mining & lifting equipment load-bearing accessories.
5. Complete Production Process
Hot Rolled Flat Steel Process
Slab high temperature heating → High pressure water descaling → Multi-pass mill rolling for rectangular section → Uniform cooling on cooling bed → Straightening to eliminate bending → Fixed-length flame cutting → Shot blasting / simple anti-rust treatment → Sampling mechanical test → Steel marking, steel strapping & wooden pallet warehousing
Cold Drawn Flat Steel Process
Hot rolled flat blank pickling, phosphating & lubrication → Multi-pass cold drawing for fixed width & thickness → Annealing to eliminate work hardening → Precision straightening → Fixed-length cutting → Bright surface inspection → Packaging & warehousing
Galvanized Flat Steel Process
Degreasing & cleaning of black flat steel → Pickling rust removal → Flux treatment → Hot dip galvanizing → Cooling & passivation → Edge trimming, zinc coating thickness inspection → Anti-rust film covering & packaging
6. Core Technical Parameters
6.1 Size Range
Thickness: 3mm～60mm; Width: 12mm～300mm
Standard fixed length: 6m, 9m, 12m, customized cutting length 0.5–15m available
Single piece weight calculated by theoretical weight, weight tolerance ±4% per national standard
Surface roughness Ra≤3.2μm for cold drawn flat steel; straightness ≤4mm/m for hot rolled flat steel
6.2 Reference Key Mechanical Properties
Q235B: Yield ≥235MPa, Tensile 375–500MPa, Elongation ≥25%, intact after 180° cold bending without cracks
Q355B: Yield ≥355MPa, Tensile 470–630MPa, Elongation ≥21%, anti-deformation under heavy load
Quenched & tempered 45# flat steel: Tensile 600–800MPa, heat treatable to improve hardness for wear-resistant parts
65Mn spring flat steel: Min tensile ≥980MPa, excellent elasticity without fracture after repeated bending
6.3 Surface & Anti-Corrosion Index
Black hot rolled steel: free of lamination, scar & penetrating cracks; galvanized flat steel with uniform zinc coating without missing plating or peeling; neutral salt spray test 500–1200h for hot-dip galvanized products.
6.4 Machining Performance
Controllable carbon equivalent, compatible with SMAW, SAW & spot welding; suitable for bending, stamping, drilling, turning & heat treatment tempering without brittle fracture after processing.
7. Core Product Advantages
Integrally formed rectangular section for easy assembly & splicingFlat double sides facilitate welding & bolt fixing, no secondary edge trimming for steel structure columns, cable trays and grounding grids to greatly shorten construction cycle.
Multi-process grades matching all working conditionsLow-cost hot rolled for civil construction; high precision cold drawn without polishing; long-life galvanized for coastal outdoor; high strength forged for heavy load equipment.
Complete grade system covering light to heavy load scenariosOne-stop supply of ordinary carbon steel for civil buildings, HSLA steel for bridge machinery, quality carbon steel for machining and spring steel for elastic accessories.
Full size stock & customized deep processing supportFull range thickness & width in stock, support cutting, beveling, punching, hot-dip galvanizing & shot blasting pretreatment for bulk container export orders.
High material utilization rate to reduce processing wasteFactory fixed-length delivery, customers cut as required with less blanking loss compared with steel plate to save raw material cost.
Complete anti-corrosion solutions for long outdoor service lifeBlack bare steel can be painted on site; integrated hot-dip galvanizing reduces frequent maintenance cost for long-term stable service of municipal & power outdoor projects.
8. Main Application Fields
8.1 Steel Structure Construction (Largest Consumption)
Factory support frame, embedded grounding flat steel, stair keel, boundary guardrail, photovoltaic support, factory reinforcement tie rod
8.2 Electric Power & Communication Industry
Substation grounding flat steel, cable tray, tower reinforcement, communication base station support, distribution box base
8.3 Mechanical Manufacturing Processing
Flange blank, agricultural machinery parts, machine tool base, fixture, conveying equipment load-bearing parts, stamping components
8.4 Transportation & Bridge Engineering
Bridge reinforcement tie bar, semi-trailer frame parts, road anti-collision guardrail, tunnel embedded steel structure
8.5 Spring & Elastic Equipment
Vehicle leaf spring, mechanical snap spring, shock absorption fixture, textile machinery elastic pressing parts
8.6 Municipal, Water Conservancy & Coastal Anti-Corrosion Engineering
River protection steel structure, water plant equipment support, coastal galvanized guardrail, sewage treatment equipment frame
9. Packaging, Shipment & Lead Time
Packaging Methods
Domestic hot rolled black flat steel: Stacked by same size, multi-circumferential steel strapping, supported by steel-wood pallets, iron corner guards to prevent collision, simple anti-rust film wrapped on ends
Cold drawn bright flat steel / galvanized flat steel: Whole pallet wrapped with thickened waterproof plastic film to avoid scratches on surface & zinc coating
Export dedicated packaging: Fixed on IPPC fumigated wooden pallets with full moisture-proof film covering, fit for 20GP / 40HC container sea transportation
2. Delivery Warehouse: Spot goods shipped directly from Tianjin Port
3. Lead Time: 5–7 days for regular Q235B hot rolled flat steel stock goods; 10–15 days for customized cold drawn precision flat steel, galvanized steel & special grades 40Cr/65Mn
4. Payment Term: 30% TT advance deposit, balance settled before shipment, L/C letter of credit is not accepted.
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