What is weld size?

In high-volume production environments, electron beam welding and laser beam welding are both relatively new methods of energy beam welding. Although the two processes are similar, they differ greatly in their power sources. Laser beam welding uses a laser beam that is extremely focused, while electron beam welds in a vacuum using an electron beam. Both have extremely high energy density which makes deep weld penetration possible. It also minimizes the weld area. Both processes can be easily automated and run very quickly, which makes them highly productive. However, they have a high cost of equipment (which is decreasing), and are vulnerable to thermal cracking. There are many innovations in this area, such as laser-hybrid, which combines principles from laser beam welding and an arc welding process for even better weld results, laser cladding, x-ray welding, and laser-hybrid.

World War I saw a dramatic increase in the use and popularity of welding. Military forces tried to figure out which of the newer welding processes would work best. British were a major user of arc welding and even constructed a ship called "Fullgar" with a fully welded body. Arc welding was also first used to build aircraft fuselages in wartime. The Maurzyce Bridge (1928), in Poland, was also the first welded roadway bridge in the entire world. Welding technology saw major advances during the 1920s. For example, automatic welding was invented in 1920. Shielding gases became a popular topic as scientists tried to shield welds from the damaging effects of oxygen and nitrogen. It was brittleness and porosity that were the major problems. Solutions included hydrogen and argon as welding atmospheres. More advances in welding allowed the welding of metals reactive like aluminum and magnesia over the next decade. This along with advancements in automatic welding (alternating current) and fluxes led to a massive expansion of arc welding during the 1930s as well as during World War II. M/S Carolinian became the first all-welded vessel merchant vessel.

Resistance welding is the creation of heat through passing current through resistance that results from contact between two or multiple metal surfaces. High currents (1000-100,000.00 A) are used to create small pools in the weld area. Though they are effective and don't pollute, the applications of resistance welding are limited and expensive. Spot welding is a common method for joining metal sheets that overlap up to 3mm thick. Two electrodes simultaneously are used to clamp metal sheets together and pass current through the sheets. The advantages include low energy usage, reduced workpiece distortion, high production rate, easy automation and no need for filler material. It has lower welding strength than other methods. This makes it more suitable for some applications. This process is often used in the automotive industry. In fact, ordinary cars can have several hundred spot welds done by industrial robots. Shot welding, a highly skilled process that spots welds stainless steel, is possible.

World War I brought about a huge increase in welding. Many military powers sought to find the best welding process. British used arc welds extensively. They even built a ship, "Fullagar", that had a completely welded structure. It was also used for the first time in aircraft construction during WWII. Some German fuselages were built with arc welding. Notable also is the Maurzyce Bridge in Poland (1928), the first welded road crossing in the world. There were significant technological advancements made in welding technology during the 1920s. The first automatic welding system was introduced in 1920. Shielding gas received much attention because scientists wanted to protect welds and prevent them from being affected by oxygen and nitrogen in their environment. The primary problems were porosity, brittleness, and the solutions found included hydrogen, oxygen, and helium being used as welding atmospheres. The welding of reactive metals, such as magnesium and aluminum, was possible in the decade that followed. This was combined with the development of automatic welding, current alternating, and fluxes that led to an explosion in arc welding during World War II. M/S Carolinian launched the first all-welded commercial vessel in 1930.

The Middle Ages witnessed advances in forge welding. Forgewelders would repeatedly press heated metal against each other until the bonding process occurred. Vannoccio Biringuccio published De la pirotechnia. This book includes detailed descriptions about the forging operation. Renaissance craftsmen were skilled at the task, and the industry grew during the following centuries. Sir Humphry Davy developed the short pulse electrical arc in 1800 and published his results in 1801. Vasily Petrov, a Russian scientist, invented the continuous electric arc in 1802. He later published "News of Galvanic-Voltaic Experiments", 1803, in which he detailed experiments that were carried out in 1802. A stable arc discharge was described and indicated that it could be used in many applications. This was of vital importance. Davy, who didn't know about Petrovs work, discovered the continuous-electric arc in 1808. Stanislaw and Nikolai Olszewski from Poland, who were both Russian inventors, invented the first method for electric arc welding. They used carbon electrodes. In the late 1800s, a Russian named Nikolai Slavyanov (1888), along with an American named C. L. Coffin (1890) introduced metal electrodes to arc welding. A. P. Strohmenger developed a coated metal electrode in Britain around 1900. This allowed for a more stable arc. Vladimir Mitkevich from Russia suggested that a three-phase, electric arc be used for welding. C. J. Holslag created alternating current welding in 1919. But it was not popularized for another ten years.

An increase in fracture toughness could also be due to the embrittlement effects of impurities and, for body-centred cubular metals, to a drop in temperature. Metals and steels have a temperature range that allows for acceptable notch-ductility. Below this range, the material will become brittle. Materials behavior can be unpredictable within the range. Reduced fracture toughness leads to a change in the appearance of fractures. If the fracture appears fibrous above the transition point, it is most likely due to micro-void coescence. If the temperature drops, the fracture may show signs of cleavage. These two appearances can be clearly seen with the naked eye. Under the microscope, chevron markings may appear in steel plates due to brittle fracture. These arrow-like ridges are indicative of the origin of the fracture.