Some references site Robert Hopkins for having invented the Electroslag welding process in the 1930's. Most of his patents relate to Electroslag melting for ingot manufacture, not welding. However one US patent, number 2,191481 filed in June, 1939 does describe the surfacing of one material on another. The illustration, however looks more like a melting furnace than welding. In fact the fellow who invented Submerged Arc Welding, Harry Kennedy, was granted a US patent in October of 1950, number 2,631,344, assigned to Linde Division of UCC that more closely related to Electroslag welding. However it too falls short of defining what we know today as this simple welding process.
A unique version of the Consumable Guide Electroslag Welding Process was developed and patented (US Patent Number 2,868,951 filed in March 1957, assigned to the Linde Division of UCC) by a colleague, Harry Shrubsall. The figure on the left is from that patent. It clearly shows the process as it is known today. Harry's patent includes the use of a flux coated tube to replace part of the flux that plates out on the copper molds. It also insulates the metal guide tube from the work.
The Paton Institute in Russia introduced the process and did a great deal of development work. They published a book, "Electroslag Welding" in 1959 with an English translation published by The American Welding Society in 1962. Of the 92 references sited in that text, most range in dates from 1955 to 1959. The first mention of Electroslag is in a paper entitled "Electroslag Welding," published in Avtomaticicheskaya Svarka in 1953 by Voloshkevich.
Harry Shrubsall and I worked as engineers in the Linde Development Labs (although I started after his invention!). Harry had several subsequent patents on the use of the process to butt weld Railroad Rails. Patent numbers 3,192,356 and 3,291,955 filed on September 1962 and February 1963 respectively describe Railroad Rail welding with Consumable Guide Electroslag.
I worked on a Plate Electrode Electroslag Welding development with Harry, It used a triangular shaped electrode with two holes that spread two electrodes at the bottom to weld the Rail Base then narrowed them to weld through the Rail Web and the Rail Head on top. Welds were excellent and passed all required Railroad tests. The resulting welds were far better quality than the Thermite deposits often employed but did take longer to make. This extra time ultimately caused resistance to its use. If a train happens to be coming down the track, all workers want to be able to move fast! Can't blame them.
Refer to the schematic below copied from the original Linde Publication 51-220 "Procedures for Consumable Guide Electroslag Welding." In the Electroslag Welding process current transfers from the guide tube to the welding wire and in turn though a molten flux bath. The resistance of the flux bath creates the heat and temperature that melts the wire and surrounding base material. The guide tube itself will also contact the molten flux bath periodically which will cause an increase in welding current as the end is consumed. The molten flux will solidify on the copper retaining molds which are placed on the sides on the weld joint. This flux layer protects the copper molds from having direct contact with the weld.
The Linde Flux Coated Guide Tube defined in Harry's original patent looked like a big stick electrode! They were made with a hole down the center and a thin flux coating that protected the tube from shorting to the plate side walls and also automatically compensated for a portion of the flux that plated out on the copper retaining shoes. The tubes were purposely coated with a quantity of flux that was less than the amount that plated out on the copper molds (see schematic on left showing flux layer that plates out on the copper molds ) This avoided excess flux build-up in the joint as welding progressed. Therefore additional flux was always needed and was added by the operator but far less frequently than when uncoated tubes were used. ( The concept of adding flux by listening to the sound, works great in a Laboratory environment. However in a noisy shop it is not effective. There are some simple tricks at measuring flux depth.) For multiple tube welding of heavy sections (up to 4 tubes for 8 inch thick plates) a special very thinly flux coated tube (referred to as Type M) was used so as not to produce excess flux burden as welding progressed up the joint. Special slip-on metal guide tube clips centered the tubes and prevented vibration and shorting. This was possible since the tubes flux coating was an insulator. Little preparation was needed to center the tubes. Those fabricators that employed bare tubes could have shorting problems that caused equipment failures and the worse thing that can happen during an Electroslag weld - - having to restart!
Linde's patented Flux Coated Guide Tube Process was very successful for the user since a great deal of welding time and plate preparation were saved. It was also very successful for Linde who obtained a substantial patent royalty (> $1/foot of tube) built into the sale of the Flux Coated Guide Tubes. They were used extensively with some the notable applications being:
1. Over 100,000 feet of Flux Coated Consumable Guide Tubes were used by Kaiser Steel to weld massive columns for the Bank of America Headquarters in San Francisco. This process was very successful and made some difficult to do any other way, transitions joints. Thin coated tubes were used in locations where there were only captive steel weld dams. The operator at left is placing a copper dam on a box beam reinforcing plate. Four Electroslag welds will secure the plate to the heavy wall box beam. An article entitled "Electroslag Welding with Consumable Guide on the Bank of America World Headquarters Building," published in The Welding Journal in 1968 by Tommy Agic of Kaiser Steel and Jim Hampton of Linde, mention that a total of 23,000 welds were made for the job. Plate thickness ranged from 1/2 to 5 inches. The massive columns ranged from 26 to 42 feet long. The operator on the right is making a beam splice joint with the consumable guide Electroslag process.
2. Thousands of feet of Electroslag welds made on the John Hancock building in Chicago:
(Above photos from a Linde publication F-51-220. On right are two simultaneous welds being made on beam flanges splices on the edge of the John Hancock building under construction. Each weld is being made with two Linde Flux Coated Guide Tubes. The photo on the left shows the weld joint being prepared)
3. 12 foot long seams made in 1 ½ to 2 inch steel for the 72 cubic yard bucket for Texas Gulf Sulfur dragline. A standard sub arc tractor was used to make these welds with the simple addition of a guide tube holder, see below:
When welded with manual stick electrodes these 12 foot seams required 150 pounds of electrodes and 40 man hours to complete. With Consumable Guide Electroslag the electrode requirements reduced to 40 pounds and the weld was completed in 1 3/4 hours.
4. Detailed application information was described in a Welding Journal Article entitled “Vertical Submerged Arc Welding,” by Paul Masters from American Bridge Division of US Steel and Bob Zuchowski from Linde (Linde Publication 52-539).
5. In addition to the high speed conventional Electroslag used at National Shipbuilding in San Diego (mentioned above), they also made many hundreds of welds splicing deck stiffeners on Roll-On-Roll-Off ships with Flux Coated Consumable Guide Tubes. The process was also used for other applications and other shipyards.
The royalty income derived from the sale of the Patented Guide Tubes allowed my Welding Process R & D Group to develop numerous applications and procedures for the Consumable Guide Electroslag Welding Process. At one time we had 7 engineers/technicians working on the process in our Laboratory. After successfully welding steel anode bars in an aluminum pot line (with the line in operation) and a market evaluation, we decided to do extensive research on the welding of massive aluminum busbars used in aluminum production.
Other companies also introduced Electroslag systems in the US. Arcos marketed both conventional Electroslag and Consumable Guide Electroslag products. They produced a plate electrode, some of which were dip coated with flux as I recall. Arcos also marketed products for an Electrogas process. The Electrogas process utilized a cored wire with flux added to replace that which coated the weld retaining copper shoes.
Hobart developed a simple oscillator which allowed the welding of heavier plate without the need for additional guide tubes and related equipment.
Airco marketed an Electrogas process which used a solid wire and argon based gas mixture. In was used by the Litton Shipyard in Erie Pennsylvania to make the vertical hull welds in ship tankers.
Lincoln introduced a vertical welding process which used a self shielded flux cored wire and operated with moving shoes.
Electrogas welding (EGW) is a continuous vertical position arc welding process developed in 1961, in which an arc is struck between a consumable electrode and the workpiece. A shielding gas is sometimes used, but pressure is not applied. A major difference between EGW and its cousin electroslag welding is that the arc in EGW is not extinguished, instead remains struck throughout the welding process. It is used to make square-groove welds for butt and t-joints, especially in the shipbuilding industry and in the construction of storage tanks.
In EGW, the heat of the welding arc causes the electrode and workpieces to melt and flow into the cavity between the parts being welded. This molten metal solidifies from the bottom up, joining the parts being welded together. The weld area is protected from atmospheric contamination by a separate shielding gas, or by the gas produced by the disintegration of a flux-cored electrode wire. The electrode is guided into the weld area by either a consumable electrode guide tube, like the one used in electroslag welding, or a moving head. When the consumable guide tube is used, the weld pool is composed of molten metal coming from the parts being welded, the electrode, and the guide tube. The moving head variation uses an assembly of an electrode guide tube which travels upwards as the weld is laid, keeping it from melting.
Electrogas welding can be applied to most steels, including low and medium carbon steels, low alloy high strength steels, and some stainless steels. Quenched and tempered steels may also be welded by the process, provided that the proper amount of heat is applied. Welds must be vertical, varying to either side by a maximum of 15 degrees. In general, the workpiece must be at least 10 mm (0.4 in) thick, while the maximum thickness for one electrode is approximately 20 mm (0.8 in). Additional electrodes make it possible to weld thicker workpieces. The height of the weld is limited only by the mechanism used to lift the welding head—in general, it ranges from 100 mm (4 in) to 20 m (50 ft).
Like other arc welding processes, EGW requires that the operator wear a welding helmet and proper attire to prevent exposure to molten metal and the bright welding arc. Compared to other processes, a large amount of molten metal is present during welding, and this poses an additional safety and fire hazard. Since the process is often performed at great heights, the work and equipment must be properly secured, and the operator should wear a safety harness to prevent injury in the event of a fall.
EGW uses a constant voltage, direct currentwelding power supply, and the electrode has positive polarity. The welding current can range from 100 to 800 A, and the voltage can range between 30 and 50 V. A wire feeder is used to supply the electrode, which is selected based on the material being welded. The electrode can be flux-cored to provide the weld with protection from atmospheric contamination, or a shielding gas—generally carbon dioxide—can be used with a solid wire electrode. The welding head is attached to an apparatus that elevates during the welding process. Also attached to the apparatus are backing shoes which restrain the weld to the width of the workpieces. To prevent them from melting, they are made of copper and are water-cooled. They must be fit tightly against the joint to prevent leaks.
- Cary, Howard B. and Scott C. Helzer (2005). Modern Welding Technology. Upper Saddle River, New Jersey: Pearson Education. ISBN 0-13-113029-3. Pages 153-56.