Seam Welding

Resistance seam welding creates continuous, leak‑tight welds along overlapping sheets using rotating electrodes and high-frequency resistance weld nuggets.

Overview

Seam welding, or resistance seam welding, forms a continuous weld along overlapping sheet or tube joints using rotating wheel electrodes and controlled electrical current. The process creates a series of overlapping resistance spot welds at high speed, producing a near-continuous seam. It excels at making fluid- and gas-tight lap joints in thin sheet metals with consistent quality and repeatability.

Use seam welding for straight or gently curved seams where you need leak-tight joints, strong lap welds, and medium to high production volumes. The process is fast and highly automated, but it requires good joint fit-up, clean material, and access to both sides of the joint. It works best on thin, weldable metals and is less suitable for very thick sections, complex 3D joints, or applications needing deep penetration fillet welds. Equipment setup cost is higher than manual welding, so the process pays off when you run repeat parts or long production batches.

Common Materials

  • Low carbon steel
  • Stainless steel 304
  • Aluminum 5052
  • Galvanized steel
  • Nickel alloys

Tolerances

±0.010" on seam location and consistency, assuming good fixturing and sheet fit-up

Applications

  • Fuel tanks and hydraulic reservoirs
  • Automotive exhaust components and mufflers
  • HVAC ducts and sealed sheet metal housings
  • Metal drums and containers
  • Battery cans and sealed tubular shells
  • Radiator and heat exchanger assemblies

When to Choose Seam Welding

Choose seam welding for overlapping sheet or tube joints that need continuous or near-continuous welds, especially when leak tightness is critical. It fits thin-gauge metals, repeatable geometries, and medium to high production volumes where automation and cycle time matter. Use it when you can design lap joints with good access for wheel electrodes on both sides.

vs Spot Welding

Pick seam welding instead of spot welding when you need a continuous or leak-tight joint rather than discrete weld nuggets. It is better for tanks, ducts, and containers where spacing between welds would cause leaks or reduced structural continuity, and where production volume justifies the more complex equipment and tooling.

vs MIG Welding

Choose seam welding over MIG when joining thin sheet in simple lap joints where speed, automation, and minimal filler metal are priorities. It reduces spatter, post-weld cleanup, and operator variability, but requires accessible, mostly straight or gently curved seams and consistent sheet thickness.

vs TIG Welding

Use seam welding instead of TIG when you need much higher throughput on thin sheet and can accept a resistance-type lap weld instead of a cosmetic fusion seam. Seam welding gives more consistent weld nugget size and lower labor content, but offers less flexibility on joint type and contour than manual TIG.

vs Laser Welding

Select seam welding over laser welding when you want a robust, lower-cost process for typical steel and aluminum sheets without needing extremely narrow welds or deep penetration. Seam welding tolerates small gaps less well than laser, but the equipment cost and maintenance are usually lower, making it attractive for standard lap seams in volume production.

vs Adhesive Bonding

Choose seam welding instead of adhesive bonding when you need metal-metal fusion, pressure or impact resistance, and temperature resilience beyond typical adhesive limits. Seam welding provides immediate handling strength and long-term durability for tanks and structural seams, at the cost of higher heat input and the need for conductive, weldable materials.

Design Considerations

  • Design lap joints with consistent overlap width, typically 3–5 times the sheet thickness, to maintain uniform nugget formation and strength
  • Keep sheet thicknesses within the machine’s rated range and avoid large thickness mismatches that cause uneven heating and weak seams
  • Ensure tight fit-up with minimal gaps; specify flatness and edge quality so the wheel electrodes maintain consistent pressure along the seam
  • Provide straight or large-radius paths and clear line-of-sight for both wheel electrodes, avoiding flanges, steps, or hardware near the weld path
  • Call out whether the seam should be truly continuous or intermittent (weld pitch) and define leak-tightness or pressure test requirements on the drawing
  • Keep sensitive features, coatings, and thin gaskets away from the weld zone, and note any post-weld forming operations so the shop can account for heat-affected areas