High-quality 4140/4130/4340 carbon alloy steel round bars, hot-rolled/cold-rolled, thickness 6-600mm

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.