The welded joint consists of weld metal and heat affected zone

In the welding of large structural parts, there will always be welded joints, and the quality of welded joints has a very important impact on the quality of the whole product. What are the components of welded joints?
(1) Weld metal: during welding heating, the temperature at the weld is above the liquidus, the base metal and filler metal form a common molten pool, which becomes as cast structure after condensation. During the cooling process, the liquid metal crystallizes from the fusion zone to the center of the weld to form a columnar crystal structure. Due to the alloying effect of electrode core and coating in the welding process, the chemical composition of weld metal is often better than that of base metal. As long as the selection of electrode and welding process parameters is reasonable, the strength of weld metal is generally not lower than that of base metal.
(2) Heat affected zone: the area where the microstructure and properties of the metal on both sides of the weld are changed due to the welding heat during the welding process.