Electroslag welding

History

The process was patented by Robert K Hopkins in the United States in February 1940 (patent 2191481) and developed and refined at the Paton Institute, Kiev, USSR during the 1940s. The Paton method was released to the west at the Bruxelles Trade Fair of 1950. The first widespread use in the U.S. was in 1959, by General Motors Electromotive Division, Chicago, for the fabrication of traction motor frames. In 1968 Hobart Brothers of Troy, Ohio, released a range of machines for use in the shipbuilding, bridge construction and large structural fabrication industries. Between the late 1960s and late 1980s, it is estimated that in California alone over a million stiffeners were welded with the electroslag welding process. Two of the tallest buildings in California were welded, using the electroslag welding process - The Bank of America building in San Francisco, and the twin tower Security Pacific buildings in Los Angeles. The Northridge earthquake and the Loma Prieta earthquakes provided a "real world" test to compare all of the welding processes. After the Northridge earthquake, one billion dollars were needed to repair weld cracks propagated in welds made with the gasless flux cored wire process, while no failures or crack propagations were initiated in any of the hundreds of thousands of welds made on continuity plates welded with the Electroslag welding process.

However the Federal Highway Administration (FHWA) monitored the new process and found that electroslag welding, because of the very large amounts of confined heat used, produced a coarse-grained and brittle weld and in 1977 banned the use of the process for many applications. The FHWA commissioned research from universities and industry and Narrow Gap Improved Electro Slag Welding (NGI-ESW) was developed as a replacement. The FHWA moratorium was rescinded in 2000.