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Birth of Welding
The history of joining metals goes back several millennia called “forge welding”, the earliest examples came from the Bronze and Iron Ages in Europe and Middle East. The ancient Greek historian Herodotus states in The Histories of the 5th century BC that ‘Glaucus of Chios’ was the man who single-handedly invented iron welding”. Welding was strategically used in the construction of the Iron pillar of Delhi named Qutub Minar erected in Delhi, India about 310 AD and weighing 5.4 metric tons.
The Middle Ages brought advances in forge welding, in which blacksmiths pounded heated metal repeatedly until bonding occurred. In 1540, Vannoccio Biringuccio published De la pirotechnia, which includes descriptions of the forging operation. Renaissance craftsmen were skilled in the process and the industry continued to grow in the coming centuries.
In 1800, Sir Humphry Davy discovered the short-pulse electrical arc and presented his results in 1801. In 1802, Russian scientist Vasily Petrov created the continuous electric arc and subsequently published news of “Galvanic-Voltaic Experiments” in 1803, in which he gave the description of a stable arc discharge and the indication of its possible use for many applications. One of the applications was melting metals which turned out to be the most crucial invention in the field of welding technology. In 1808, Davy, who was unaware of Petrov’s work, rediscovered the continuous electric arc. In 1881–82 inventors Nikolai Benardos (Russian) and Stanisław Olszewski (Polish) created the first electric arc welding method known as carbon arc welding using carbon electrodes. The advances in arc welding continued with the invention of metal electrodes in the late 1800s by a Russian, Nikolai Slavyanov (1888), and an American, C. L. Coffin (1890). Around 1900, A. P. Strohmenger released a coated metal electrode in Britain, which gave a more stable arc. In 1905, Russian scientist Vladimir Mitkevich proposed using a three-phase electric arc for welding. In 1919, alternating current welding was invented by C. J. Holslag but did not become popular for another decade.
Resistance welding was also developed during the final decades of the 19th century, with the first patents going to Elihu Thomson in 1885who made further advances over the next 15 years. In 1893, Thermite welding was introduced and during the same time additional welding process known as Oxyfuel became well established. Furthermore, Acetylene was discovered in 1836 by Edmund Davy, however, when the suitable torch was developed, it could not be used practically in welding until about 1900.At first, oxyfuel welding was one of the most popular welding methods due to its portability and relatively low cost. As the 20th century progressed; however, it fell out of favor for industrial applications. It was largely replaced with arc welding, as there was advancement in metal coverings (known as flux).Flux covering the electrode primarily shields the base material from impurities, but also stabilizes the arc and can add alloying components to the weld metal.
World War I caused a major surge in the use of welding processes, with the various military powers attempting to determine which of the several new welding processes would be the best. The British primarily used arc welding and even constructing a ship, the “Fullagar” with an entirely welded hull. Arc welding was first applied to aircraft during the war as well as some German airplane fuselages were constructed using this process. The first welded road bridge in the world, the Maurzyce Bridge was designed by Stefan Bryła of the Lwów University of Technology in 1927, and built across the river Słudwia near Łowicz, Poland in 1928.
During the 1920s, major advances were made in welding technology, including the introduction of automatic welding in 1920, in which electrode wire was fed continuously. Shielding gas became a subject receiving much attention, as scientists attempted to protect welds from the effects of oxygen and nitrogen in the atmosphere. Porosity and brittleness were the primary problems, and the solutions that developed included the use of hydrogen, argon, and helium as welding atmospheres. During the following decade, further advances allowed the welding of reactive metals like aluminum and magnesium. This in conjunction with developments in automatic welding, alternating current, and fluxes fed a major expansion of arc welding during the 1930s and then during World War II. In 1930, the first all-welded merchant vessel, M/S Carolinian, was launched.
Many new welding methods were introduced during the middle of the century. In 1930, Kyle Taylor was responsible for the release of stud welding, which further became popular in shipbuilding and construction. Submerged arc welding was invented in the same year and continued to be popular even today. In 1932 a Russian, Konstantin Khrenov successfully implemented the first underwater electric arc welding. After decades of development, Gas tungsten arc welding was finally perfected in 1941 which allowed fast welding of non-ferrous materials; however, it required expensive shielding gases. Shielded metal arc welding was developed during the 1950s, using a flux-coated consumable electrode, and it quickly became the most popular metal arc welding process. In 1957,plasma arc welding and the flux-cored arc welding process were newly established, in which the self-shielded wire electrode could be used with automatic equipment, resulting in greatly increased welding speeds. Furthermore, Electroslag welding was introduced in 1958and it was followed byelectro gas welding in 1961. In 1953, the Soviet scientist N. F. Kazakov proposed the diffusion bonding method. Another variation was the use of inert gas with small amounts of oxygen that provided the spray-type arc transfer. It became popular in the early 1960s. Quite recently, a variation has been developed for the use of pulsed current. It is switched from a high to a low value at a rate of once or twice the line frequency.
Soon after the introduction of CO2 welding, a variation utilizing a special electrode wire was developed. This wire, described as an inside-outside electrode, was tubular in cross section with the fluxing agents on the inside. The process was called Dual shield, which indicated that external shielding gas was utilized, as well as the gas produced by the flux in the core of the wire for arc shielding. This process, invented by Bernard, was announced in 1954, but when the National Cylinder Company got reintroduced, it was patented in 1957.
In 1959, an inside-outside electrode was produced which did not require external gas shielding. The absence of shielding gas gave the process popularity for noncritical work and this process was named Inner shield. The electroslag welding process was announced by the Soviets at the Brussels World Fair in Belgium in 1958. It had been used in the Soviet Union since 1951, but was based on work done in the United States by R.K. Hopkins, who was granted patents in 1940. The Hopkins process was never used to a very great degree for joining. The process was perfected and equipment was developed at the Paton Institute Laboratory in Kiev, Ukraine, and also at the Welding Research Laboratory in Bratislava, Czechoslovakia. The first production used in the U.S. was at the Electromotive Division of General Motors Corporation in Chicago, where it was called the Electro-molding process. It was announced in December 1959 for the fabrication of welded diesel engine blocks which used a consumable guided tube for welding thicker materials. In 1961 The Arcos Corporation introduced another vertical welding method known as Electrogas which utilized equipment developed for electroslag welding with flux-cored electrodewire and an externally supplied gas shield. It is an open arc process since a slag bath is not involved. A newer development uses self-shielding electrode wires and a variation uses solid wire but with gas shielding. These methods allow the welding of thinner materials than can be welded with the electroslag process. Gage invented plasma arc welding in 1957 which uses a constricted arc or an arc through an orifice which creates higher temperature arc plasma than the tungsten arc, such higher temperature can be easily used for metal spraying and for cutting purposes.
The electron beam welding process, which uses a focused beam of electrons as a heat source in a vacuum chamber, was developed in France. J.A. Stohr of the French Atomic Energy Commission made the first public disclosure of the process on November 23, 1957. In the United States, the automotive and aircraft engine industries are the major users of electron beam welding.
Some other developments in welding included: The 1958 breakthrough of electron beam welding, making deep and narrow welding possible through the concentrated heat source. Following the invention of the laser in 1960, laser beam welding debuted several decades later, which has proved to be especially useful in high-speed, automated welding. Magnetic pulse welding (MPW) is industrially used since 1967. Friction stir welding was invented in 1991 by Wayne Thomas at The Welding Institute (TWI, UK) and found high-quality applications all over the world.
Friction welding was developed in the Soviet Union which requires rotational speed and upset pressure to provide friction heat. It is a specialized process with many applications where a sufficient volume of similar parts are to be welded because of the initial expenses for equipment and tooling.
Lase welding has been one of the newest processes so far which was originally developed at the Bell Telephone Laboratories as a communications device because of the tremendous concentration of energy in a smaller space, it proved to be a powerful source of the heat as it can also be used for cutting metals and nonmetals. Continuous pulse equipment is also available in which the laser is finding welding applications in automotive metalworking operations.
Although robots were firstly introduced into the US industry during 1960s, Robot welding is relatively a new application of robotics. It is the use of mechanized programmable tools (robots) which completely automates the welding process by performing the weld as well as handling it efficiently. The number of robotic usage in industries has been growly tremendously as, in 2005, it had been reported that more than 120,000 robots were used in North American industry for welding purposes.
Quite recently, Robot arc welding has begun growing rapidly and it has been reported that about 20% of industrial robots command applications. The major components of arc welding robots are the manipulator or the mechanical unit and the controller, which acts as the robot’s “brain”. The manipulator is what makes the robot move, and the design of these systems can be categorized into several common types, such as SCARA and cartesian coordinate robot, which uses different coordinate systems to direct the arms of the machine. The robot may weld a pre-programmed position guided by the vision of a machine, or by a combination of the two methods. However, many benefits of robotic welding have proven to make it a technology that helps many original equipment manufacturers increase accuracy, repeat-ability and reach a higher standard of market.