A group of welding processes that produces coalescence of workpieces by heating them with an arc. The processes are used with or without the application of pressure and with or without filler metal. See STANDARD WELDING TERMS.
Arc welding is a nonpressure (fusion) welding process in which the welding heat is obtained from an arc either between the base metal or weld metal and an electrode, or between two electrodes.
Historical Background
1881-1 887- Arc welding had its practical beginning shortly after the introduction of arc lights in 1881. Early experiments in arc welding provided the basic theories for the development of two systems of arc welding five or six years later.
In some respects, arc welding might be considered an outgrowth of the electric furnace. In the electric furnaces of Henry Moissan, a French chemist, and others, the metal to be melted was placed between two carbon electrodes in the path of electric current. While this was considered at that time to be an internal resistance process to melt metal by an electric current, it is now realized that these furnaces represented the earliest examples of metal melting with the electric arc.
Arc welding experiments were first undertaken by DeMeritens in 1881. In his experiments the various parts of a battery plate were joined by lead welding using a carbon arc as the heat source. Guided by these early experiments, N. Von Benardos, a Russian, perfected and patented a carbon arc welding process. The patents were filed on this process in Petrograd on December 3, 1885 and issued May 17, 1887.
In the light of present day welding practice, the Benardos system of arc welding seems difficult and hazardous. It was a direct-current welding process operating on voltages ranging from 100 to 300 volts with a welding current of 600 to 1000 amp. The equipment was operated on straight polarity, which is still the preferred method in carbon arc welding, using carbon electrodes varying in size from 6 to 38 mm (0.25 to 1.5 in.) in diameter. It was common practice to weld with an arc from 50 to 100 mm (2 to 4 in.) long. The equipment was cumbersome and awkward to handle; the electrode holder alone was nearly 50 cm (20 in.) long and very heavy.
1889-1908- A short time later the Slavinoff system of arc welding, in which the carbon electrode of the Benardos system was replaced by a bare metal electrode, came into use. American patents on the metal arc process were issued to Coffin in 1889. In 1908 Kjellberg applied a coating to the bare electrode and began the development of coated metal arc welding. Itarc welding is accomplished using the principles developed by Kjellberg.
As has been the case with many inventions, the industrial world was slow to recognize the inherent possibilities of the process. Many years elapsed before electrical equipment, welding wire, and process control had been sufficiently well developed so that the processes could be economically and safely applied for general manufacturing purposes. Then, too, the engineering community had to be sold on the merits of the welding processes.
1916-1926- Welding was used in a very limited way for manufacturing purposes prior to the World War I period (1914-1918). The war emergency resulted in the use of welding for many applications previously considered inadvisable. During this period, the need for better and less expensive ships allowed persons familiar with ship design and those familiar with the merits of welding to carry out a great deal of design work involving all-welded steel construction. A few small all-welded vessels were produced. If the war had not been terminated by the Armistice (Nov. 11, 1918), all-welded ships would have been produced in quantities within the following few years.
During the war the U.S. Government authorized formation of the U.S. Shipping Board-Emergency Fleet Corporation, which in turn (March 13, 1918) established a sub-committee on welding. At the close of the war this committee had accomplished so much in laying the foundation for welded ship construction that it was considered an economic necessity to continue the work, and to extend the applications in all metal working industries. As a result, the membership f the subcommittee on welding was reorganized in the spring of 1919 under the name “American Welding Society.” The reorganization expanded the scope of activities and offered membership to all interested individuals and industries. From 1919 to 1925, much fundamental research work was carried out by various manufacturers, but the general application of welding in the construction of buildings and bridges did not occur until the latter part of 1925 and early in 1926. This was the beginning of the implementation of welding on a large scale, not only of plain steel but also alloy steels and nonferrous alloys.
1926-1 950- A desire to improve the quality of welds produced by arc welding led to the development of several welding processes which combine gas and arc welding. The first of these is the atomic hydrogen process on which basic patents were obtained in 1924 by Dr. Irving Langmuir. This process employs a pair of tungsten electrodes to maintain an arc which is shielded by a stream of hydrogen. It may be used for either manual or automatic welding.
During this period various carbon steel welding electrodes were manufactured which have produced improved welds in terms of reduced slag inclusions and greater resistance to corrosion. Welds were made with ultimate tensile strengths in the range of 480 MPa (70 000 psi), and ductility such as 28% elongation in 50 mm (2 in.) and 60% reduction of area. Similarly, electrodes were developed for welding various alloy steels such as 12% manganese steel, and stainless steel of the low carbon 18% chromium,8% nickel class. Also, electrodes for welding nonferrous metals, i.e., copper and aluminum, were developed, making it possible to weld practically all commercial metals and alloys in all positions.
During this period, the submerged arc welding (SAW) process was developed for welding carbon steel.
World War II put additional demands on the metal fabricating industry. The search for a method to weld magnesium resulted in the gas tungsten arc welding (GTAW) process. It was originally called HeliarcTM welding because it used helium to shield the arc.
1951-Present- This period saw commercialization of a number of welding processes: gas metal arc, electron beam, laser beam, friction, inertia, electroslag, electrogas, explosion, plasma arc, and hot wire.