Under the conditions of certain welding methods, welding materials, welding specification parameters and welding structure, the difficulty of obtaining high-quality welded joints is called steel weldability. Therefore, the weldability should be evaluated from two aspects of manufacturing and application. The weldability of process mainly refers to the possibility of various cracks in welded joints, which reflects the difficulty of manufacturing. Weldability of using mainly refers to the mechanical properties and special properties of heat resistance, corrosion resistance, low temperature resistance and fatigue resistance of welded joints, which reflects the reliability of use.