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How to Prevent Tube Rupture When Welding Stainless Steel Bellows with Medium Frequency Seam Welders
Jul 09,2026
Stainless steel bellows are corrosion-resistant, fatigue-resistant and retractable, widely used in aerospace, petrochemical industries for pipeline compensation and isolation sealing. They feature ultra-thin corrugated walls, requiring ultra-precise welding and force control for circumferential & longitudinal seams between bellows and flanges/end pipes. Medium frequency seam welders deliver concentrated, accurate heat input and are mainstream equipment for this process. However, thin corrugated structures and mismatched parameters often cause tube rupture, scrapped parts and higher costs.
1 Core Root Causes of Tube Rupture
(1) Unbalanced Heat Input
1.Excessive heat: High current & slow speed burn through walls or coarsen grain structure with reduced ductility, cracking during cooling.
2.Insufficient heat: Low current & fast speed lead to incomplete fusion and concentrated stress that ruptures tubes after cooling.
3.Uneven heat: Unstable current & inconsistent roller contact create localized thermal stress and cracking.
(2) Uneven Welding Force
1.Unbalanced roller pressure: Overpressure crushes thin walls; underpressure causes localized overheating and burn-through, especially at wave crests/troughs.
2.Improper fixture positioning: No dedicated tooling, loose clamping or severe roller misalignment creates uneven force and crushing damage.
3.Irregular welding sequence: Non-symmetric skip welding accumulates heat and stress, triggering post-weld cracks.
(3) Mismatched Material & Process
1.Base material defects: Impurities or inherent flaws in stainless steel, incompatible filler accelerate cracking.
2.Missing pre-treatment: Surface oil/oxides hinder fusion; excessive edge misalignment causes rupture.
3.Poor roller matching: Unsuitable rollers stick to metal and tear thin walls; poor contact leads to local overheating.
(4) Improper Post-Weld & Environmental Control
1.Sudden cooling: Hot bellows exposed to air or water quenching create huge temperature gradients and cracks.
2.Unrelieved residual stress: Excess residual stress gradually expands into full rupture.
3.Humid/low-temperature environment: Humidity generates pores; cold conditions induce cold cracks without preheating.
2 Key Control Difficulties
1.Heat balance: Ultra-thin walls are sensitive to minor parameter changes; hard to achieve full fusion without burn-through.
2.Force balance: Corrugated tubes deform easily under roller contact; precise pressure & alignment are hard to maintain.
3.Customized process: Different bellows sizes & grades require independent parameter sets.
3 Anti-Cracking Prevention Measures
1.Optimize welding parameters to strictly control heat input and roller pressure; adopt segmented pulse welding.
2.Regular roller calibration, grinding and maintenance to stabilize equipment performance.
3.Use dedicated positioning fixtures, adjust clamping force and adopt symmetric skip welding to reduce stress concentration.
4.Standard pre-weld cleaning, slow cooling and stress relief to eliminate hidden cracking risks.
5.Standardize operation, maintain dry, mild-temperature welding environments and avoid human error.
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Wuxi HAIFEI Intelligent Equipment Co., Ltd.
Wuxi HAIFEI Welding Equipment Co., Ltd.
Add: 28 Shuiyun Road, Yuecheng, Jiangyin, Jiangsu Province, China. (Postal Code: 214404)
Mobile: +86 18915302352
Email: wushijie@jshaifei.com