What is a disadvantage of welding?

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.

Modern welding methods don't involve melting the materials being welded, just as forge weld. Ultrasonic weld is the most widely used method. This involves connecting thin sheets or wires made from metal or thermoplastic. It works by vibrating them at high speed and high pressure. The equipment and procedures are the same as for resistance welding. However, vibration provides energy input instead of using electricity. This method does not require melting of metals. Instead, the weld is created by horizontally applying mechanical vibrations under pressure. Plastics need to have similar melting temperatures. The vibrations are applied vertically. Ultrasonic welding is commonly used to make copper and aluminum electrical connections.

Other solid-state weld processes include friction welding (including magnetic pulse welding and friction stir spot welding), co-extrusion, cold welding or diffusion bonding. You can prepare your welds in many ways. The five most common types of weld joints include the butt joint (or lap joint), corner joint, edge and edge joint, as well as T-joint (a variation of the last, the cruciform joint). There are many other variations. Double V preparation joints have two pieces that each taper to one-half their height at the center. They are also quite common. Single-U or double-U preparation joint are not as straight as double-V or single-V preparation joint edges. Instead, they have curved edges that form the shape a U. Sometimes, lap joints can have more than two pieces. This is due to the fact that depending on the processing and the material thickness, many pieces can still be welded together.