The difference between general welding and brazing (brazing) and soft brazing (soldering) is that the soldering is formed by melting the solder with a lower melting point (lower than the melting point of the workpiece itself), without heating the workpiece itself. There are many sources of energy for welding, including gas flame, arc, laser, electron beam, friction and ultrasonic. In addition to being used in factories, welding can be carried out in a variety of environments, such as outdoors, underwater, and space. Wherever possible, welding can pose a risk to the operator, so proper precautions must be taken when soldering. Welding to the human body may cause damage including burns, electric shock, visual impairment, inhalation of toxic gases, excessive ultraviolet radiation and so on.
Until the end of 19th century, the only welding process was the blacksmith's hundreds of-year-old metal Forge. The earliest modern welding technology appeared at the end of 19th century, first arc welding and oxygen gas welding, and later appeared resistance welding. In the early 20th century, the demand for military equipment in the First World War and the Second World War was high, and the corresponding cheap and reliable metal connection process was valued, which promoted the development of welding technology. After the war, several modern welding techniques have appeared, including the most popular manual arc welding, and automatic or semi-automatic welding technology such as arc welding, submerged arc welding, flux cored wire arc welding and electroslag welding. In the latter half of the 20th century, welding technology was developing rapidly, and laser welding and electron beam welding were developed. Today, welding robots have been widely used in industrial production.
The researchers are still deeply investigating the nature of welding, continue to develop new welding methods, and further improve the quality of welding.