CEMP-E
1 March 2000
a. Process Principles. Electroslag Welding (ESW) is used for welding thick sections, typically 50 mm
to 500 mm (2 to 20 in.) in thickness, for short to moderate lengths. The plates to be joined are positioned
40 mm (3/4 to 1-1/2 in.), depending on welding equipment and material thickness, with no edge
preparation generally required. Water-cooled copper shoes are placed on each side of the joint, forming
used. Shielding of the arc and weld pool is provided by the addition of flux into the joint as welding
progresses. To start the weld, an arc is struck in a sump at the bottom of the joint, underneath a deposit
The arc is extinguished by the slag, but the fed electrode wire and adjacent base metal melts from the
heat generated by the high electrical resistance of the slag. The weld proceeds as more electrode is fed
weld termination. Both the starting sump and finishing run-off tab are removed after completion of
welding.
specified in AWS A5.25, Specification for Carbon and Low-Alloy Steel Electrodes and Fluxes for
. Electrode wires may be either solid or composite. The classification system is
summarized in Table C-18.
deposition rates, in the range of 20 kg (40 lb.) per hour, offering considerable cost and time savings for
vertical welding of thick steels. Time and expense is also saved in the avoidance of joint preparation,
distortion upon completion.
(1) ESW, if interrupted during welding, can leave major discontinuities in the joint that are difficult
may cause low toughness properties, as well as make ultrasonic testing more difficult.
(2) ESW can be used for joints over 12 mm (1/2 in.) thick, but generally does not become the most
including the number of joints to be welded. ESW is not prequalified under AWS D1.1
qualification testing following AWS D1.1
vertical require special setups and procedures, although ESW has been performed at angles to 45
degrees.
C-33
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