The Role of Forming Stands in Second-Hand Welded Pipe Machines​

Forming stands are the core structural components in second-hand welded pipe machines, responsible for gradually shaping flat steel strips into cylindrical or rectangular pipe profiles. Their design and performance directly determine the geometric accuracy and structural integrity of the final welded pipes.​

Profile Forming Precision​

In second-hand welded pipe machines, forming stands (typically arranged in 8-12 passes for ERW pipes) use 渐进式 (progressive) roll contours to bend steel strips. High-quality stands maintain roll gap accuracy of ±0.05mm, ensuring consistent pipe diameter tolerance (≤±0.3mm for DN50-DN200 pipes) and roundness deviation (≤1% of outer diameter). This precision is critical for pipes used in pressure systems (e.g., gas pipelines complying with API 5L), where irregular profiles can cause leakages or pressure drops. For second-hand machines with worn stand rolls, regrinding the roll contours to original design specifications can restore forming accuracy, reducing pipe scrap rates by 18-22%.​

Material Adaptability​

Well-designed forming stands in second-hand welded pipe machines accommodate diverse material thicknesses (1.5mm-12mm for carbon steel) and strengths (up to 550 MPa for high-strength low-alloy steel). The stands’ roll material—typically forged alloy steel (50CrNiMo) with surface hardening (HRC 58-62)—resists wear when processing hard materials. For example, when retrofitting second-hand machines to process stainless steel (304/316L), replacing standard rolls with those coated in tungsten carbide (WC) increases roll life by 3-4 times and prevents material sticking, a common issue with uncoated rolls.​

Production Stability Enhancement​

Sturdy forming stand frames (made of Q345B structural steel with reinforcement ribs) in second-hand welded pipe machines minimize vibration during high-speed forming (up to 100m/min). Excessive vibration can cause uneven strip feeding, leading to longitudinal weld seam misalignment (deviation ≥0.5mm). By tightening stand bolts to the recommended torque (350-400 N·m for M24 bolts) and reinforcing loose frame joints, operators can reduce vibration amplitude to ≤0.02mm, improving weld seam qualification rates by 25-30%.​

Maintenance Guidelines​

To preserve the performance of forming stands in second-hand welded pipe machines:​

• Inspect roll surface wear weekly using a profilometer; regrind rolls when surface roughness exceeds Ra 0.8μm.​

• Check roll bearing temperature daily (normal range: 35-55°C); replace bearings if overheating (≥65°C) occurs.​

• Lubricate roll shafts monthly with molybdenum disulfide grease to reduce friction.​

• Align stands annually using a laser alignment tool to ensure consistent roll centerline alignment (deviation ≤0.03mm).​

Upgrading the forming stand control system in older second-hand welded pipe machines to a servo-driven roll gap adjustment system allows real-time gap modifications, reducing setup time for pipe size changes by 40-45%.​

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