Automatic submerged arc welding, submerged arc welding for short, is under the flux layer burning arc, using mechanical automatic arc ignition and control, automatic arc welding wire sent to and moving a arc welding method is used to welding seam: the adoption of granular flux, submerged arc welding are generally only applicable to welding position, other position welding is the use of special measures, to ensure that the flux can overlay welding area, automatic submerged arc welding is mainly suitable for welding of low carbon steel and alloy steel plate, is commonly used in the production of large welding structure of a welding technology.Principle: the burning arc between the welding wire and the welding piece causes the arc heat buried under the granular flux to melt the end of the welding wire and the base material and flux directly affected by the arc and partially vaporize. The gas vaporized by the metal and flux forms a closed cavity around the arc, in which the arc is burned.The cavity is surrounded by a slag film composed of slag, which not only keeps out the contact between air and arc, but also prevents arc light from radiating out.The wire melted by an arc falls in droplet form and mixes with the molten base metal to form a molten pool.The less dense slag floats on the molten pool. In addition to the mechanical protection of molten pool metal, slag also reacts with molten pool metal in the welding process, which affects the chemical composition of weld metal.The arc moves forward and the pool metal cools and crystallizes to form a weld.After the slag floating on the pool is cooled, the slag shell can continue to protect the welding seam at high temperature and avoid oxidation.