Welding is a kind of manufacturing process and technology of joining metal or other thermoplastic materials such as plastics by heating, high temperature or high pressure. The history of metal joining can be traced back thousands of years ago. The early welding technology was found in Europe and the Middle East in bronze age and iron age. Thousands of years ago, the Babylonian civilization began to use soldering technology.
There are many kinds of energy sources in modern welding, including gas flame, arc, laser, electron beam, friction and ultrasonic. In addition to being used in factories, welding can also be carried out in a variety of environments, such as the field, underwater and space. No matter where, welding may bring danger to the operator, so appropriate protective measures must be taken during welding. The possible injuries to human body caused by welding include burn, electric shock, vision damage, inhalation of toxic gas, excessive ultraviolet radiation, etc.