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.
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 grades of carbon steel round bars do you offer?
We offer a wide range of grades classified by carbon content: Low-carbon steel (1018, Q235B, A36) for cold 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 size range and customization services are available?
Our round bars come in diameters ranging from 3 mm up to 500 mm with standard lengths up to 6 meters. We also provide custom services including precision cutting, chamfering, and threading tailored to your project requirements.
Q: What are the surface treatment options?
To meet different aesthetic and functional requirements, we offer optional surface treatments such as blackening (black anodizing), phosphating for rust prevention, and polishing for reduced friction.
Q: Which industry standards do your products comply with?
All of our carbon steel round bars fully comply with major international standards including GB/T 702, ASTM A108, and ISO 683-1. Each batch is shipped with standard quality verifications.
Q: What quality testing methods do you perform?
To ensure high reliability, each batch of our steel bars undergoes rigorous quality testing, including ultrasonic testing, tensile and impact testing, and hardness measurements (HB/HRC).
Q: What is the 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 wrapped in waterproof paper and secured with steel strips to meet seaworthy export standards.