High Precision Cold Drawn Hexagonal Carbon Steel Bar for Machinery Parts Manufacturing

● Low-Carbon Steel (10#, 20#): With carbon content between 0.07%-0.23%, these grades offer excellent ductility and weldability. 20# steel, for instance, has a tensile strength of 410-550MPa and elongation after fracture ≥24%, making it suitable for parts that require cold forming, such as hexagon bolts, nuts, and washers. Its good machinability also reduces tool wear during threading or drilling processes.​

● Medium-Carbon Steel (35#, 45#): Featuring carbon content of 0.32%-0.50%, these grades strike a balance between strength and toughness. 45# steel stands out with a tensile strength of 600-750MPa and yield strength ≥355MPa, ideal for load-bearing machinery parts like gear shafts, connecting rods, and valve cores. After quenching and tempering, its hardness can reach HRC 28-35, further enhancing wear resistance.​

● High-Carbon Steel (60#, 70#): With carbon content ranging from 0.57%-0.75%, these grades deliver superior strength and hardness. 60# steel has a tensile strength of 750-900MPa and can be heat-treated to a hardness of HRC 38-45, making it suitable for high-wear parts like precision bearings, guide rails, and tool holders in heavy-duty machinery.​

● Ultra-High Dimensional Accuracy: Our cold-drawn hexagonal steel bar adheres to ISO h8-h9 tolerance standards. For a hexagon with a nominal side length of 10mm, the tolerance is only ±0.022mm (h8), far tighter than the ±0.3mm tolerance of hot-rolled hexagonal steel. This precision eliminates the need for secondary machining (such as milling or grinding) for most machinery parts, reducing material waste by 15%-20% and shortening production cycles. For example, when manufacturing hexagon bolts, the precise side length ensures a perfect fit with wrench sockets, preventing slippage during assembly and use.​

● Enhanced Mechanical Properties: The plastic deformation induced by cold-drawing refines the steel’s grain structure, increasing tensile strength by 15%-25% and yield strength by 20%-30% compared to hot-rolled steel. It also significantly improves fatigue resistance—a critical property for machinery parts that undergo repeated loading, such as connecting rods and camshafts. Tests show that our cold-drawn 45# steel bar has a fatigue life 30% longer than its hot-rolled counterpart, reducing the risk of part failure due to fatigue cracking.​

● Superior Surface Quality: Our cold-drawn hexagonal steel bar features a smooth surface with a roughness of Ra ≤0.8μm, compared to Ra 3.2μm for hot-rolled steel. The smooth surface not only improves the aesthetic appearance of machinery parts but also reduces friction between mating components (e.g., between a hexagonal shaft and a sleeve), minimizing wear and energy loss. Additionally, the smooth surface enhances the adhesion of subsequent surface treatments (such as galvanization, electrophoresis, or oil coating), further improving corrosion resistance—essential for machinery used in humid or dusty environments (e.g., agricultural machinery or construction equipment).​

● Quenching and Tempering: For high-load, high-wear parts like gear shafts and connecting rods, quenching (820-860℃) followed by tempering (500-600℃) is used. This process increases the steel’s hardness while maintaining toughness—for example, 45# steel treated this way has a hardness of HRC 28-35 and excellent impact resistance, ensuring it can withstand high torque and shock loads without deformation or fracture.​

● Annealing: For parts that require complex machining (such as precision gear blanks), annealing (650-700℃) softens the steel, reducing its hardness to HB 170-210. This lowers cutting resistance during machining operations like hobbing, milling, and drilling, extending tool life by 25%-30% and improving the surface finish of the final part.​

● Case Hardening (Carburizing and Quenching): For parts that need a hard surface and a tough core (e.g., transmission gears and cam followers), carburizing at 900-950℃ followed by quenching creates a hard outer layer (HRC 58-62) and a ductile core. The hard surface resists wear, while the tough core absorbs impact, making the part suitable for high-speed, high-load machinery operations.​

● Reduced Production Costs: The high precision and excellent machinability of our steel bar reduce machining time by 20%-30%. For example, manufacturing a 45# steel gear shaft from our cold-drawn bar takes only 2.5 hours, compared to 4 hours for a hot-rolled bar. Additionally, the tight dimensional tolerance minimizes material waste, and the smooth surface reduces tool wear—collectively lowering production costs by 10%-15%.​

● Improved Part Reliability and Longevity: The enhanced mechanical properties of our cold-drawn steel bar ensure that machinery parts have a longer service life and higher reliability. For instance, precision bearings made from our 60# steel bar can operate continuously for 80,000-100,000 hours without replacement, compared to 50,000-60,000 hours for bearings made from hot-rolled steel. This reduces maintenance frequency and downtime for machinery, particularly critical for industrial production lines where downtime can cost thousands of dollars per hour.​

● Enhanced Assembly Efficiency: The precise dimensional accuracy of our hexagonal steel bar ensures that parts fit together seamlessly during assembly. For example, hexagon bolts and nuts made from our bar require no additional adjustment during installation, reducing assembly time by 25% and minimizing the risk of assembly errors (such as cross-threading) that can lead to part damage or equipment failure.​

● Adaptability to Diverse Machinery Types: Our steel bar is suitable for a wide range of machinery, including industrial robots, agricultural machinery, construction equipment, and precision machine tools. Whether it’s a small hexagon screw in a robot arm or a large hexagonal shaft in a construction crane, our steel bar can meet the specific performance and precision requirements of the part.​

● Incoming Material Inspection: Raw steel billets are tested for chemical composition (using spectral analysis) and mechanical properties (including tensile strength, yield strength, and elongation) to ensure they meet the requirements of the specified grade. Only billets that pass these tests are used for cold-drawing.​

● In-Process Monitoring: During the cold-drawing process, laser dimensional measuring instruments and surface roughness testers are used to monitor the dimensions and surface quality of the steel bars in real time. Any deviations from the standard are corrected immediately to ensure consistency.​

● Final Testing: Each batch of finished steel bars undergoes a series of rigorous tests, including dimensional inspection (using coordinate measuring machines), mechanical property testing (tensile, hardness, and impact tests), and non-destructive testing (ultrasonic flaw detection to check for internal defects). Only batches that pass all tests are shipped.​

● Dimensional Customization: We provide hexagonal steel bars with side lengths ranging from 5mm to 80mm, covering the size requirements of most machinery parts. For non-standard sizes, we can design and manufacture custom dies to produce bars that match the exact specifications of the customer’s parts.​

● Length Customization: The bars can be cut to lengths ranging from 1m to 12m, depending on the customer’s production line requirements. For example, we can supply 6m-long bars for continuous machining of gear shafts, reducing the number of cuts and improving production efficiency.​

● Surface Treatment Customization: Optional surface treatments include galvanization (for corrosion resistance in outdoor or humid environments), phosphating (to improve paint adhesion for aesthetic or protective purposes), and oil coating (for temporary rust prevention during storage and transportation).​