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High-Quality 4140/4130/4340 Carbon Alloy Steel Round Bars from China's Leading Suppliers and Factory

Discover our premium carbon steel round bars, sourced from a leading China factory and trusted by suppliers worldwide. Our product range includes grades Q235B, A36, 1045, and 45#, available in customizable diameters from 5 to 300mm and lengths up to 6m (or cut-to-size). Renowned for their exceptional machinability, weldability, and tensile strength, these bars undergo precision forging and rolling, complemented by stringent quality checks to ensure compliance with ASTM and GB standards. They are ideal for various industrial applications, including machinery parts, fasteners, shafts, construction brackets, and automotive components.

Product Details

Carbon Steel Round Bar

🔩 Low-Carbon Steel (1018, Q235B, A36) — Excellent cold formability, weldability & ductility. Ideal for bending, stamping, and general structural support.
⚙️ Medium-Carbon Steel (1045, 45#, 20#) — Tensile strength up to 600MPa after Q&T. Suitable for load-bearing shafts and mechanical parts.
🔧 High-Carbon Steel (40Cr, 45Mn2) — Enhanced hardness & wear resistance. Ideal for gears and tool blanks.

We offer flexible, project-specific specifications: diameters ranging from 3 mm (micro precision pins) to 500 mm (heavy-duty structural bars), standard lengths up to 6 meters, with custom cutting, chamfering, or threading services available. Large-diameter structural bars are hot-rolled (ensuring grain refinement and toughness), while small-diameter precision bars are cold-drawn (achieving tight dimensional tolerances of ±0.03 mm and a smooth surface with Ra≤1.6μm).

Optional surface treatments include blackening (black anodizing), phosphating (rust prevention), or polishing (meeting aesthetic and friction reduction requirements).

These round bars play a crucial role across multiple industries — machinery manufacturing (precision shafts, bearings, fasteners), automotive (suspension components, engine connecting rods), construction (reinforcing bars, scaffolding pins), agricultural equipment (plow shafts, gear components), and mold making (mold blanks, drill bits). Products fully comply with GB/T 702, ASTM A108, and ISO 683-1 standards, with rigorous quality verification including ultrasonic testing, tensile/impact testing, and hardness (HB/HRC) measurement.

✔ GB/T 702 ✔ ASTM A108 ✔ ISO 683-1 ✔ Ultrasonic Tested ✔ Bulk Supply Available

High-quality 414041304340 carbon alloy steel round bars, hot-rolled/cold-rolled, thickness 6-600mm

Product Parameters

Product Name	Aisi 4140 Flat Angle 1060 C45 Ck45 1095 1020 A36 Q235 Sae 1016 1084 Low Round Carbon 1045 1050 1055 Steel Bar
Standard	ASTM A106, ASTM A53, API 5L Gr.B, DIN17175, DIN1629
Outer Diameter	20mm – 610mm
Wall Thickness	4mm – 70mm
Dia Tolerance	Controlled within standard: OD ±1%, WT ±10%
Materials	10#, 20#, 45#, 16Mn, A106(B, C), A53(A, B), API J55, API K55, Q235, Q345, ST35.8, ST37, ST42, ST45, ST52
Inspection	ISO, BV, SGS, MTC
Packing	Waterproof paper and steel strip packed. Standard Export Seaworthy Package. Suitable for all kinds of transport, or as required.
Supply Ability	1,000 metric tons / month
MOQ	5 metric tons; sample order accepted

Packing And Shipping

High-quality round metal bars (2mm, 3mm, 6mm) made of 201, 321, 304, 316, ASTM A479, or 410 stainless steel

High Quality Stainless Steel 201 304 316L Stainless Steel Sheet Plate

Frequently Asked Questions

❓ What carbon steel grades are available for your round bars?

We supply a wide range of grades including low-carbon steel (1018, Q235B, A36), medium-carbon steel (1045, 45#, 20#), and high-carbon/alloy steel (40Cr, 45Mn2). Each grade is selected to match specific mechanical and processing requirements.

❓ What diameter and length options are available?

Diameters range from 3 mm (micro precision pins) to 500 mm (heavy-duty structural bars). Standard lengths are up to 6 meters. Custom cutting, chamfering, and threading services are also available upon request.

❓ What is the difference between hot-rolled and cold-drawn round bars?

Hot-rolled bars are used for large-diameter structural applications, offering grain refinement and improved toughness. Cold-drawn bars are suited for small-diameter precision applications, providing tight dimensional tolerances of ±0.03 mm and a smooth surface finish of Ra≤1.6μm.

❓ What surface treatment options are offered?

Available surface treatments include blackening (black anodizing) for appearance and mild corrosion resistance, phosphating for enhanced rust prevention, and polishing for aesthetic and friction-reduction requirements.

❓ What quality standards and testing methods do you follow?

All products comply with GB/T 702, ASTM A108, and ISO 683-1 standards. Each batch undergoes rigorous quality verification including ultrasonic testing, tensile and impact testing, and hardness measurement (HB/HRC). Third-party inspection by ISO, BV, SGS, and MTC is also supported.

❓ What is the minimum order quantity and how are products packaged for export?

The minimum order quantity is 5 metric tons, with sample orders accepted. Products are packed with waterproof paper and steel strip in a standard export seaworthy package, suitable for all types of international transport.

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