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Help CenterSteel Round Bar & Good Machinability，ASTM A36、ASTM A108、EN10060、JIS G4051（S45C）
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1. Product Overview
Steel round bar is a solid long steel with a circular cross-section, measured by diameter (mm) in the industry. It is the most basic and universal profile for machinery manufacturing, construction, heavy industry and hardware processing. The circular symmetrical cross-section features uniform stress distribution and excellent fatigue resistance, compatible with turning, forging, welding and heat treatment. Custom specifications, materials, lengths and surfaces are available with sufficient stock. Delivery cycle: 5-7 days, shipped from Tianjin Port.
2. Classification & Characteristics by Production Process
2.1 Hot Rolled Round Bar (Main Spot Product)
Standard: GB/T 702-2017
Diameter range: Φ5.5mm–Φ500mm
Regular length: 4–12m random length; customized fixed/double length from 1–12m available, short length proportion ≤10%
Surface: Black oxide scale, ordinary dimensional tolerance, cost-effective
Advantages: Complete specifications, high output, good cost performance; suitable for rough machining, forging and structural construction
Applications: Bolts, building embedded parts, shaft blanks, seamless tube blanks and general mechanical components
2.2 Cold Drawn Round Bar (For Precision Machining)
Standard: GB/T 905
Diameter range: Φ3mm–Φ120mm
Regular length: 3–6m with high-precision fixed cutting
Surface: Bright surface without oxide scale, tight dimensional tolerance and good straightness, no secondary turning required
Advantages: Strict tolerance and smooth surface, directly used for finish machining to save processing time
Applications: Precision shafts, piston rods, mass-produced lathe parts and raw materials for standard parts
2.3 Forged Round Bar (High-Strength Large-Diameter Type)
Standard: GB/T 3078
Diameter range: Φ120mm–Φ800mm super large size
Advantages: Compact internal structure free of porosity, high impact resistance, high temperature resistance and qualified flaw detection
Applications: Heavy-duty main shafts, hydraulic equipment, wind power, mining machinery and high-pressure flange blanks
3. Main Material Grades, Properties & Applications
3.1 Carbon Structural Round Bar (General Basic Material)
Q235B, Q345BLow-carbon general steel with excellent welding and cold bending performance and lowest cost; applied to building supports, fences, simple bases, embedded components and general hardware.
Low-carbon quality steel: 10#, 20#High plasticity for stamping and carburizing; used for rivets, chains, thin-walled pipe fittings and gear carburizing blanks.
Medium carbon steel: 35#, 45# (Most widely used grade)Balanced strength and toughness with ideal quenching & tempering performance; universal raw material for shafts, gears, ordinary bolts and construction machinery standard parts.
High carbon steel: 65Mn, 70#High elasticity and hardness; for springs, shock-absorbing parts, wear-resistant spring sheets and tool blanks.
3.2 Alloy Structural Round Bar (For Heavy-Duty High-Strength Scenarios)
40Cr: Much higher strength than 45# after quenching & tempering, good wear and fatigue resistance; for automobile half shafts, gears, high-strength bolts and transmission shafts.
42CrMo / 35CrMo: High temperature and impact resistance for high-pressure heavy load; heavy machine tool spindles, hydraulic cylinders, power station equipment and forgings.
20CrMnTi: Special carburizing steel with hard surface and tough core; automobile transmission gears and precision transmission shafts.
60Si2Mn: Dedicated spring alloy steel; shock-absorbing springs for construction machinery and rail transit elastic components.
3.3 Special Round Bar
Free-cutting steel Y12/Y40Mn: For mass small parts processed by CNC lathes without tool sticking.
Bearing steel GCr15: Bearing inner/outer rings and wear-resistant rollers.
Tool steel Cr12MoV: Molds and wear-resistant stamping tooling.
4. Core Specification Parameters
4.1 Diameter Coverage
Hot rolled: Φ5.5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 25, 28, 30, 32, 35, 40, 45, 50, 60, 70, 80~500mmCold drawn: Full series precision small specifications Φ3~120mmForged: Super large round bar Φ120~800mm
4.2 Theoretical Weight Calculation Formula
Weight per meter (kg/m) = Diameter (mm) × Diameter (mm) × 0.00617Example: Φ50 round bar: 50×50×0.00617=15.425kg/m
4.3 Optional Surface Treatments
Hot rolled black finish, cold drawn bright finish, peeled finish, ground finish, sandblasted finish, anti-rust oil coated finish
5. Executive Standards (Domestic & International)
National Standards: GB/T702, GB/T905, GB/T3078, GB/T699, GB/T3077International Equivalent Standards: ASTM A36, ASTM A108, EN10060, JIS G4051 (S45C)Mill test certificates, SGS/CE/ISO inspection reports are supplied with goods; third-party flaw detection and mechanical property re-inspection are supported.
6. Core Product Advantages
Stable cross-section performance: Uniform stress in all directions, less cracking under alternating loads with longer fatigue life compared to square and flat steel.
Wide processing compatibility: Fully adaptable to turning, milling, grinding, drilling, forging, welding and heat treatment, the preferred raw material for rotary parts.
Complete specification range: Supply covers tiny precision cold drawn bars to hundreds-millimeter large forgings, both in stock and customized.
Complete material system: One-stop supply of carbon steel, alloy steel, tool steel and free-cutting steel.
Stable delivery: Ten-thousand-ton self-owned warehouse inventory, goods delivered within 5-7 days, loaded at Tianjin Port with FOB/CIF/CFR trade terms available.
Perfect packaging protection: Small sizes bundled tightly; large diameters wrapped with waterproof plastic film with end caps to avoid rust during sea transportation.
7. Industrial Application Fields
Machinery Manufacturing: Various transmission shafts, gears, lead screws, flanges, mold blanks and hydraulic piston rods.
Automobile Industry: Half shafts, transmission gears, high-strength fasteners and chassis shock-absorbing springs.
Construction Infrastructure: Embedded steel bars, supports, railings and steel structural components.
Mining, Heavy Industry & Wind Power: Large main shafts, hydraulic equipment, wind power forgings and wear-resistant fittings.
Hardware Standard Parts: Raw materials for mass production of bolts, nuts, rivets and pins.
Pipe Industry: Seamless tube blanks and high-pressure pipe fitting blanks.
8. Packaging, Logistics & Commercial Terms
Packaging: Φ6–Φ32 small round bars bundled with galvanized steel strips (1–3 tons per bundle); large-diameter bars wrapped with waterproof plastic film with plastic end caps for both ends.
Loading Port: Tianjin Port, loadable into 20GP/40HQ containers.
Lead Time: 5-7 days for regular spot goods; 10-15 days for special large forgings or special materials.
Payment Term: 30% TT advance payment, balance paid before shipment; L/C is not accepted.
Quality Warranty: Material composition guaranteed. Free return & replacement for defective goods with unqualified composition, dimension or cracks; original mill test certificate delivered together with goods.
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