Welding, is a manufacturing process or technology which joins metals or other thermoplastic materials like plastics by heating, high temperature, or high pressure.

Welding is a process in which two or more materials the same or dissimilar, joined together through the bonding and diffusion of atoms or molecules.

The method which promote bonding and diffusion between atoms and molecules is heating or pressing, or heating and pressing at the same time.

Welding method

Welding technology is mainly applied to metal base materials. The most commonly used welding technologies are arc welding, argon arc welding, CO2 shielded welding, oxygen-acetylene welding, laser welding, electroslag pressure welding, etc. And non-metallic materials such as plastics can also be welded. There are more than 40 metal welding methods, which are mainly divided into three categories: fusion welding, pressure welding and brazing.

1. Fusion welding——Heating the workpiece till partially melting and forming a molten pool. The workpiece will be joined after the molten pool cooled and solidified. If necessary, a filler can be added to assist the welding. It is suitable to weld various metals and alloys, no requirement for pressure.

2. Pressure welding ——The welding process must put pressure to the weldment, which available for various metal materials and some non-metal materials.

3. Brazing——Adapting a metal material which melting point is lower than the base material as the brazing filler metal, then wet the base metal by the liquid brazing filler metal, and fill the joint gap, at last mutually diffuse with the base metal to realize the connection of the weldment. Brazing is suitable for various materials, as well as different metals or dissimilar materials.

The joint, which connects the two connected bodies formed during welding, is called a weld. Both sides of the weld will be subjected to welding heat during welding, and the structure and performance will be changed. This area is called the heat-affected zone. Due to the difference of the workpiece material, welding material, welding current during welding, some bad effect may occur in the weld and heat-affected zone after welding. Such as overheating, embrittling, hardening or softening, which will also reduce the performance of the weldment and deteriorates the weldability. In this situation the welding condition need be adjusted. For example, preheating the joints of the weldment before welding, preserving heat during welding and heat treatment after welding, all those actions can improve the welding quality of the weldment.

Welding Symbols