Small gooseneck type combined welded aluminum alloy longitudinal beam for semitrailer

The invention discloses a small gooseneck type combined welded aluminum alloy longitudinal beam for a semitrailer. The small gooseneck type combined welded aluminum alloy longitudinal beam comprises a front upper beam, a middle neck beam and a rear lower beam, wherein the front upper beam is arranged as a double-web I-shaped beam and comprises a front upper wing plate, a front double-web plate and a front lower wing plate; the middle neck beam comprises at least two parallel like-right triangular web plates; the rear lower beam is arranged as an I-shaped beam and comprises a rear upper wing plate, a rear web plate and a rear lower wing plate; the right-angle sides I and II of the middle neck beam are respectively welded and fixed with the front end faces of the front lower wing plate and the rear lower beam; a gap matched with the front end of the rear lower beam is arranged at the tail end of the front upper beam; the front upper beam and the rear lower beam are welded and fixed through the matched gap. The aluminum alloy longitudinal beam for the semitrailer provided by the invention adopts a three-section type structure, so that the structural strength is enhanced, the manufacturing cost of the products is lowered and the driving safety is increased.