300 Series 316/316L Stainless Steel Pipe DN 800 Bending

1. Excellent Ductility: Key to Avoiding Cracks During Bending

• High Elongation: Both grades have an elongation at break of ≥ 40% (316: ≥40%; 316L: ≥45%), far exceeding that of carbon steel or martensitic stainless steel. This ductility allows the pipe wall to stretch/compress uniformly during bending (outer wall stretches, inner wall compresses) without brittle cracking—critical for large-diameter pipes (DN 800), where bending imposes greater stress on the wall.

• Low Yield Strength: 316 has a yield strength of ≥ 205 MPa, 316L ≥ 170 MPa. Lower yield strength reduces the force required for bending, minimizing deformation defects (e.g., wall thinning, wrinkling) that often occur in rigid materials.                                                      

2. Molybdenum-Enhanced Corrosion Resistance: Retained Post-Bending

Chloride Ion Resistance: 316/316L contain 2-3% molybdenum (Mo), which forms a more stable chromium-molybdenum oxide passive film on the surface. Unlike 304 (no Mo), this film resists pitting, crevice corrosion, and stress corrosion cracking (SCC) in high-chloride environments (e.g., seawater, salt spray)—even after bending (which may locally disrupt the passive film, but the alloy’s self-healing ability restores protection).                                                                                                               

316L’s Low-Carbon Advantage: 316L has a carbon content ≤ 0.03% (vs. 316’s ≤ 0.08%), which eliminates sensitization (chromium carbide precipitation at grain boundaries) during high-temperature bending or post-bending heat treatment. This prevents intergranular corrosion (IGC) in corrosive media (e.g., chemicals, coastal air)—a must for large-diameter pipes in long-term critical service.

3.Controlled Wall Thickness Uniformity: Prevents Local Fracture/Thinning

• Large-diameter pipes (DN 800) are prone to uneven wall thickness during manufacturing (e.g., seamless extrusion, welded forming). Bending-ready pipes undergo strict thickness inspection (tolerance: ±5% of nominal thickness) to ensure no "thin spots"—these would stretch excessively during bending and risk cracking.                                                                                                                                    

• For critical applications (e.g., offshore pipelines), some manufacturers use thicker wall sections at the bending zone (e.g., increasing thickness by 10-15% locally) to compensate for outer-wall stretching and inner-wall compression.                                                                                                 

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