Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, but sometimes pressure is used in conjunction with heat, or by itself, to produce the weld. Many different energy sources can be used for welding, including oxy-acetylene gas, an electric arc, a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding can be done in many different environments, including open air, underwater and in space. Until the end of the 19th century, the only welding process was forge welding, which blacksmiths had used for centuries to join metals by heating and pounding them. Arc welding and oxyfuel welding were among the first processes to develop during the 1800s. Welding technology advanced quickly during the early 20th century as World War I and World War II drove the demand for reliable and inexpensive joining methods. Following the wars, several modern welding techniques were developed, including shielded metal arc welding, gas metal arc welding, submerged arc welding and flux-cored arc welding. Today, the science continues to advance, with robot welding becoming more commonplace in industrial settings, and researchers continuing to develop new welding methods.

Read the rest of this article: http://en.wikipedia.org/wiki/Welding

_______________________________ Today's selected anniversaries:

1678: The Godiva procession in Coventry, England, began. (http://en.wikipedia.org/wiki/Godiva)

1889: Johnstown Flood: A flood killed over 2200 people in Johnstown, Pennsylvania, United States. (http://en.wikipedia.org/wiki/Johnstown_Flood)

1916: German and British navies clashed in the Battle of Jutland, the largest naval battle of World War I. (http://en.wikipedia.org/wiki/Battle_of_Jutland)

1974: Syria and Israel signed a disengagement agreement to resolve the Yom Kippur War. (http://en.wikipedia.org/wiki/Yom_Kippur_War)

1977: The Trans-Alaska Pipeline System was completed. (http://en.wikipedia.org/wiki/Trans-Alaska_Pipeline_System)

_____________________ Wikiquote of the day:

"When there are no more memories of heroes and martyrs, And when all life and all the souls of men and women are discharged from any part of the earth, Then only shall liberty or the idea of liberty be discharged from that part of the earth, And the infidel come into full possession." -- Walt Whitman in Leaves of Grass (http://en.wikiquote.org/wiki/Walt_Whitman)