What is the weakest weld?

The Middle Ages saw advances in forge welding. This was accomplished by blacksmiths repeatedly pounding heated metal until bonding occurs. Vannoccio Biringuccio published De la pirotechnia (in 1540), which contains descriptions of the forging operations. It was possible to forge tools by Renaissance craftsmen. This industry grew in the subsequent centuries. Sir Humphry Davy presented his findings in 1801 with the short-pulse electro arc. Vasily Petrov (Russian scientist) created the continuous electric arc in 1802. He then published "News of Galvanic-Voltaic Experiments", in 1803, where he described experiments that he conducted in 1802. It was important to describe a stable arc and indicate its possible uses. Davy, who had not heard of Petrov's work in 1808, discovered the continuous electric ar. Stanislaw Oleszewski (Polish) and Nikolai Benardos(Russian) invented the first electricarc welding method, known as carbon-arc welding. In the late 1800s, a Russian engineer, Nikolai Slavyanov (1888), and a US inventor, C. L. Coffin (1890) made the first metal electrodes for arc welding. A. P. Strohmenger published a coated steel electrode in Britain around 1900. This provided a stronger arc. Vladimir Mitkevich (Russian scientist) proposed using a 3-phase electric arc as a welding method in 1905. C. J. Holslag was the first to invent alternating current welding in 1919. It didn't catch on until a decade later.

The only known welding process up until the end 19th century was forge welding, which blacksmiths had used for millennia in order to join iron or steel by heating and then hammering. Arc welding (and oxy-fuel welding) were two of the first processes that developed late in the century. Electric resistance welding soon followed. As the need for reliable and cheap joining methods increased, welding technology advanced rapidly during the early 20th-century. A variety of modern welding methods were created following World Wars II. In the latter half century, new technologies were introduced such as laser beam welding (electronic beam welding), magnetic pulse welding, friction stirring welding, and laser beam welding. Robot welding is now commonplace in industrial settings. Scientists continue to improve their understanding of welding and develop new welding methods.

Submerged-arc welding (SAW), which is a high productivity welding method, allows the arc to be struck beneath a protective layer of flux. Because contaminants in the air are blocked by the flux, this enhances arc quality. The flux removes the slag on the weld easily. It is also combined with continuous wire feeding to increase the weld ejection rate. As the flux covers the arc, it makes working conditions much easier than other arc welding methods. Also, almost no smoke is created. This process is frequently used in industry, especially when welding large products and pressure vessels. Other arc welding processes include electroslag welding, atomic hydrogen welding, stud arc, and electroslag. ESW can be used to weld thicker materials up to 1 inch (25mm), 12 inches (300mm), in a vertical or near-vertical position.