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Help CenterSteel Round Bar & Round Steel Bar，Q195、Q235B、Q355B、10#、20#、35#、45#、27SiMn、40Cr、42CrMo、20CrMnTi
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1. Product Overview
Round bar is a solid long steel product with a circular cross-section, specified by diameter (mm). It is a core raw material widely used in machinery manufacturing, construction, heavy industry and auto parts. Featuring uniform stress distribution, excellent cutting, forging and welding performance, it can be applied for rough blanks and high-precision component production.
Formula for theoretical weight per meter:Weight per meter (kg/m) = Diameter (mm) × Diameter (mm) × 0.00617
2. Production Process Classification & Parameters
2.1 Hot Rolled Round Bar (General Main Grade)
Applicable Standards: GB/T702-2017, ASTM A36, EN10060, JIS G3101
Diameter range: Φ5.5mm ~ Φ500mm
Standard length: 4–12m; custom fixed lengths of 3m/6m/9m available, short length ratio ≤10%
Surface condition: Black oxide scale, dimensional tolerance ±0.4~±1.2mm
Advantages: Low cost, good plasticity, easy welding and forging
Applications: Building embedded parts, equipment base, bolt blanks, steel structure supports, rough blanks for common shafts
2.2 Cold Drawn Round Bar (Precision Bright Grade)
Applicable Standards: GB/T3078, GB/T905
Diameter range: Φ3mm ~ Φ100mm
Surface: Bright surface without oxide scale, roughness Ra ≤0.8~1.6μm
Dimensional tolerance: ±0.03~±0.10mm, high precision for direct finish machining
Advantages: Accurate dimension, smooth surface, improved hardness, eliminating rough turning process
Applications: Hydraulic components, precision gears, mold guide pins, precision auto shafts, standard fasteners
2.3 Forged Round Bar (Heavy-Duty High Strength Grade)
Diameter range: Φ80mm ~ Φ600mm
Process: Repeated high-temperature forging to form continuous internal metal flow lines, free of looseness and segregation
Advantages: High compactness, outstanding impact resistance and fatigue resistance superior to hot rolled materials
Applications: Large gears, lifting hooks, mining main shafts, pressure vessel flanges, load-bearing parts for heavy construction machinery
3. Main Material Grades, Characteristics & Applications
3.1 Common Carbon Structural Round Bar (Low-Cost General Grade)
Q235B / A36 / S235JRLow carbon grade with excellent weldability and medium strength; for building supports, anchor bolts, simple pin shafts and welded structural parts.
Q355B (Former Q345)Low-alloy high-strength steel; for engineering machinery bases, bridge components and heavy-duty supports.
3.2 High-Quality Carbon Structural Round Bar (Main Grade for Machining)
10# / 20# (1010 / 1020)Low carbon with high plasticity, suitable for stamping and carburizing; for pins, bushings, welded parts and small standard fasteners.
35#Medium strength with good toughness after quenching & tempering; for common gears, connecting rods and medium-small shafts.
45# (1045 / S45C)Most widely used medium carbon steel with balanced strength and toughness after heat treatment; for transmission shafts, gears, flanges, mold bases and various general mechanical parts.
3.3 Alloy Structural Round Bar (High Strength & Wear Resistance for Heavy Loads)
40CrChromium alloy quenched and tempered steel with balanced strength and wear resistance; for automobile half shafts, gears, machine tool main shafts and high-strength bolts.
42CrMo / 35CrMoResistant to high temperature, high pressure and fatigue; for wind power main shafts, petroleum pipeline fittings and large transmission components.
20CrMnTiSpecial steel for carburized gears; for gearbox gears and precision transmission gears.
GCr15Bearing steel; for bearing inner & outer rings, rollers and wear-resistant guide rods.
4. Core Technical Performance Indicators
Mechanical Property Range
Low carbon steel: Tensile strength 400–550MPa, Hardness 120–160HB, Elongation 20%–30%
Medium carbon 45#: Tensile strength ≥600MPa, Hardness 170–220HB, Elongation 10%–18%
40Cr / 42CrMo alloy steel: Tensile strength ≥980MPa, Hardness ≤207HB, Excellent impact toughness
Dimensional ToleranceCommon hot rolled grade: ±1mm; high-precision cold drawn grade up to h9/h10 tolerance; forgings follow agreed forging tolerance.
Surface QualityHot rolled: Slight oxide scale and minor scratches acceptable; Cold drawn: Free of cracks, pits and peeling; Forgings: No lamination, inclusion or air holes.
Non-Destructive Testing RequirementsUT ultrasonic testing and MT magnetic particle testing are available for forged and high-end alloy round bars, complying with NDT standards for heavy industry and pressure vessels.
5. Packaging, Delivery & Logistics
5.1 Packaging Methods
Small diameter Φ5.5–Φ30mm: Bundled with steel strips, 1–3 tons per bundle; labels with material grade, size and heat number attached at both ends.
Large diameter hot rolled & forged round bars: Marked individually, bare packing; cold drawn bright bars wrapped with plastic film for rust prevention.
Export packing: Wrapped with moisture-proof film and steel strips, wooden pallets optional for sea transportation moisture protection.
5.2 Delivery Lead Time
Standard in-stock specifications: Shipment within 5–7 days; special alloys, large forgings and custom fixed lengths: 7–15 days.
5.3 Shipping Ports
Tianjin Port, Qingdao Port. Full container & LCL shipments available, complete with material certificates, test reports and inspection documents.
5.4 Payment Terms
30% TT advance payment, balance settled before shipment. Letter of Credit (LC) is not acceptable.
6. Applicable Industries
Machinery Manufacturing: Various transmission shafts, gears, flanges, molds, bolts & nuts
Construction Engineering: Anchor bolts, steel structure supports, embedded components
Automobile & Auto Parts: Half shafts, gearbox gears, chassis load-bearing parts
Mining & Heavy Industry: Lifting hooks, main shafts, hydraulic cylinder rods
Petrochemical Industry: Pipeline flanges, high-pressure valve forgings
7. Product Advantages
Complete material range: Full stock of common carbon steel, high-quality carbon steel, alloy steel and bearing steel; production compliant with GB, ASTM, EN, JIS standards.
Wide size coverage: One-stop supply from small-diameter precision cold drawn bars to large-size forged round bars.
Stable performance: Raw materials from official steel mills, full material test certificates and traceable heat numbers provided.
Wide machining adaptability: Support sawing, turning, milling, forging, stamping, welding, quenching & tempering, carburizing heat treatment.
Complete export support: English material certificates, packing list, commercial invoice supplied; FTA certificate of origin available.
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