High-Quality 4140/4130/4340 Carbon Alloy Steel Round Bars from China Suppliers | Factory Hot-Rolled/Cold-Rolled
Carbon Steel Round Bar
Precision-machined carbon steel round bars are designed to meet structural load-bearing and precision machining requirements, encompassing a variety of grades: Low-carbon steel (1018, Q235B, A36) offers excellent cold formability, weldability, and ductility, making it ideal for components requiring bending, stamping, or general structural support; Medium-carbon steel (1045, 45#, 20#) balances machinability and heat-treatable strength, achieving a tensile strength of up to 600MPa after quenching and tempering, suitable for load-bearing shafts and mechanical parts; High-carbon steel (40Cr, 45Mn2) incorporates alloying elements, enhancing hardness and wear resistance, making it ideal for gears and tool blanks.
Grade Versatility
Encompasses low-carbon (1018, Q235B), medium-carbon (1045, 45#), and high-carbon steel (40Cr, 45Mn2).
Precision Processing
Diameters from 3 mm to 500 mm, tight dimensional tolerances of ±0.03 mm, and smooth finishes (Ra≤1.6μm).
Certified Quality
Complies with GB/T 702, ASTM A108, and ISO 683-1. Rigorously tested via ultrasonic and tensile methods.
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, and custom cutting, chamfering, or threading services are available. Manufacturing processes are matched to steel grades—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 offer both cost-effectiveness and versatility, playing a crucial role in 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, and each batch undergoes rigorous quality verification, including ultrasonic testing, tensile/impact testing, and hardness (HB/HRC) measurement. We offer bulk supply, just-in-time delivery, and technical consulting services to help global customers balance performance, cost, and processing efficiency in a variety of industrial applications.
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 Dia | 20mm-610mm |
| Wall Thickness | 4mm-70mm |
| Dia Tolerance | Control within the 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. Suit for all kinds of transport, or as required |
| Supply Ability | 1000 metric tons/month |
| MOQ | 5 metric ton, sample order accepted |
Packing And Shipping
Frequently Asked Questions
Q: What steel grades do you provide for carbon steel round bars?
We offer a wide range of carbon steel grades categorized by carbon content: Low-carbon steel (such as 1018, Q235B, A36) for excellent formability and weldability; Medium-carbon steel (1045, 45#, 20#) for balanced strength and machinability; and High-carbon steel (40Cr, 45Mn2) for superior hardness and wear resistance.
Q: What are the size specifications and tolerances of your round bars?
Our round bars range in diameter from 3 mm (micro precision pins) up to 500 mm (heavy-duty structural bars), with standard lengths up to 6 meters. Cold-drawn precision bars achieve tight dimensional tolerances of ±0.03 mm and smooth surface finishes with Ra≤1.6μm.
Q: What surface treatments are available?
To meet aesthetic, friction-reduction, and anti-rust requirements, we offer optional surface treatments including blackening (black anodizing), phosphating (rust prevention), and professional polishing.
Q: Which standards do your products comply with?
All our carbon steel round bars fully comply with international manufacturing standards, including GB/T 702, ASTM A108, and ISO 683-1. Every batch undergoes rigorous quality verifications such as ultrasonic, tensile, and hardness testing.
Q: What is your minimum order quantity (MOQ) and packaging standard?
Our Minimum Order Quantity (MOQ) is 5 metric tons, and we accept sample orders. For shipping, products are securely packed with waterproof paper and steel strips to ensure a standard export seaworthy package suitable for all modes of transport.