Hybrid electroslag cladding (H-ESC): an innovation in high speed electroslag strip cladding

Abstract

Application of strip cladding using electroslag welding process to cover large surface areas of vessels for oil and gas industries has been a common weld cladding method in last few decades. There has been continuous development by welding consumable suppliers to improve this method further through introduction of high-speed ESW flux and specially designed over-alloyed welding strips to achieve required weld metal chemistry in single layer for some of the alloys. However, the conventional method had limitations in achieving desired chemistry with single layer for certain alloys—Ni-625 alloy with max. 5% Fe is one among them. A new variant of electroslag cladding technique (Hybrid Electro Slag Cladding or H-ESC) has successfully been developed and introduced in the market, wherein a 3rd dimension has been added to the conventional ESW strip cladding method of using strip and flux in the form of addition of multiple hot metal cored wires into the molten electroslag weld pool. Addition of multiple hot MCW wires with a particular proportion into the molten weld pool by a uniquely designed digital weld control system helps in controlling the dilution level, thereby achieving clean undiluted cladding chemistry coupled with at least 50% higher welding speed and nearly double the weld deposition rate as compared to conventional ESW cladding technique. In this new high-speed single-layer cladding technique using neutral flux, it is possible to achieve Fe content < 5% for Ni-625 cladding and > 40% Ni for Ni-825 cladding in single layer. Similarly, this new technique offers unique solution in case of high-speed single-layer austenitic stainless steel cladding, wherein only one standard stainless steel strip type is used along with neutral flux and desired AWS clean weld metal chemistry is easily achieved for SS 308L, SS 316L, SS 347, and SS 317L by using suitably designed MCW wires. Such solution would immensely help fabricators to minimize their working capital and faster delivery of weld consumables in addition to reaching desired 3.0 mm undiluted weld chemistry in high-speed single-layer cladding of 3.5-mm thick.