Disclosed is a
welding technology for longitudinal joints of a
pipe-plug type channel of a composite-plate type air cooler. An outer layer of the channel is a base layer, an inner layer of the channel is a
coating, each of longitudinal channel joints is formed between each two adjacent perpendicular composite plates, a base layer groove is formed between the base
layers, on the outer layer of each longitudinal channel joint, of each two corresponding composite plates, and a
coating groove is formed between the coatings, on the inner layer of each longitudinal channel joint, of each two corresponding composite plates. The
welding technology includes
welding the base layer grooves and the
coating grooves sequentially, wherein the base layer grooves are bottomed by
argon arc welding and filled with two
layers by
shielded metal arc welding, the rest parts of the base layer grooves are covered by
submerged arc welding, and then the inner coating grooves of the channel are welded on an inner-angle
submerged arc welding machine. The welding technology has the advantages that welded joints are high in heat
conductivity and small in
linear expansion coefficient, channel welding shrinkage
distortion amount is small, and welding material cost is reduced substantially; since the base layer grooves and the coating grooves are welded sequentially, the welded joints in the coating grooves can be protected from secondary heating, and
corrosion resistance of the welded joints of the coating grooves is improved; production cost is reduced and production efficiency is improved.