1.What is the relationship between diameter and load capacity?
Tensile/compressive strength: cross-sectional area determines the basic bearing capacity
Actual impact: large diameter round bars are more suitable for heavy-loaded structures (such as bridge supports), and small diameters are suitable for light-loaded parts (such as bolts).
Bending and torsional stiffness: high-order power effect of diameter
Small diameter (≤20mm) is easy to bend and is suitable for scenes requiring elastic deformation (such as springs); ◦ Large diameter (≥50mm) has high stiffness and is suitable for anti-bending parts such as beams and shafts.
Stability: aspect ratio affects the critical buckling load
Under the same length, the larger the diameter, the greater the moment of inertia and the stronger the anti-buckling ability.
2.What effect does diameter have on coating thickness uniformity?
Small diameter (d≤10mm): The surface area/volume ratio is large, the current distribution is more uniform during galvanizing, and the coating thickness (such as 5-15μm for electrogalvanizing) is more consistent, but it is easy to cause local over-thickness (such as the end) due to the "tip effect".
Large diameter (d≥50mm): The surface curvature is small, and the current density difference between the edge and the center may occur during galvanizing, resulting in uneven coating thickness (slightly thicker at the edge), which needs to be improved through process adjustment (such as moving the anode).
3.What effect does diameter have on the corrosion resistance of the coating?
Corrosion amount per unit area: Under the same environment, the corrosion rate of the coating is consistent, but the total surface area of the large diameter round rod is larger and the total amount of corrosion is higher.
4.What impact does diameter have on production process selection?
Small diameter (d≤20mm): Commonly used cold drawing process, high surface accuracy (roughness Ra≤1.6μm), small dimensional tolerance (such as h11), mechanical properties slightly improved due to cold work hardening (yield strength increased by 5-10%).
Large diameter (d≥50mm): Mostly use hot rolling process, rough surface (Ra≥12.5μm), large dimensional tolerance (such as h14), and subsequent machining (turning, grinding) is required to meet the accuracy requirements.
5.What effect does diameter have on welding and joining performance?
Small diameter: The heat-affected zone is small during welding and is not easy to deform (for example, argon arc welding can be used for direct welding if the diameter is less than 10mm);
Large diameter: Preheating is required for welding (for example, preheating to 150-200℃ for Q345 diameter ≥50mm), and stress concentration is likely to occur after welding, requiring annealing.