Electroslag Welder

Electroslag welding (ESW) with a consumable nozzle welds thick plate vertically in a single pass. Wire is fed through a flux-coated consumable nozzle into a cavity formed by water-cooled copper shoes. An arc first melts flux at the bottom to form a slag bath; the process then switches to electroslag, where current passing through the conductive slag generates resistive heat that continuously melts the wire, the nozzle and the parent edges. The pool solidifies from the bottom up, completing a vertical seam in plate from 30 mm to well over 100 mm in one run.

Why ESW is the default for vertical seams in thick plate

Welding a 60 mm vertical seam by conventional SAW or GMAW means a double-V preparation, dozens to hundreds of filler passes and days of work. ESW uses an I or simple V preparation and finishes the joint in one continuous run — several times faster, with concentrated heat input, a narrow HAZ and far less risk of inter-run lack of fusion.

Process essentials

1. Water-cooled shoes must seal tightly. Leaks or poor contact stop the weld immediately by draining the pool.
2. Match slag bath depth to voltage. Too high a voltage deepens the bath and widens the weld uncontrollably; too low risks lack of fusion.
3. Treat start and finish separately — run-on and run-off tabs are normally used and cut off afterwards.
4. Plan post-weld heat treatment. ESW puts in a lot of heat and coarsens the grain, so important load-bearing members are usually normalised, or normalised and tempered.

Typical applications

Diaphragm welds inside box columns of high-rise steel, vertical seams in heavy machinery, thick-wall components for hydro and thermal power, large forged-welded structures and bridge box-girder diaphragms. The common pattern is thick plate, vertical position, repetitive joints — exactly where ESW pays off.

Frequently asked questions

How thick can ESW weld?

Consumable-nozzle ESW routinely covers 30 mm to over 100 mm. The upper limit depends on source capacity, nozzle length and the shoe system; beyond that a dedicated procedure qualification is required.

What if weld toughness is too low?

Normalise after welding to refine the grain, or use titanium/boron micro-alloyed consumables with controlled heat input. Critical structures must pass specified impact testing.

Can it weld horizontally or flat?

No. The process relies on gravity to hold the slag and molten pool in the cavity, so it can only run vertically, or close to vertical.

For vertical-seam welding scheme assessment, contact the Icyrobot engineering team.