Process for welding steel pipes of pipelines

The invention discloses a process for welding steel pipes of pipelines. The process includes steps that double-edge X-shaped grooves with internal and external groove angles of 45 degrees are formed in steel plates of pipeline steel, and rust on base metal within 50 mm ranges of two sides of each edge of each steel plate of the pipelines is removed; Ar+CO2 mixed gas shielded welding is carried out by the aid of pulse welding power sources matched with solid-core welding wires, and the strength of the solid-core welding wires is not lower than the strength of the base metal; multi-wire submerged-arc welding is carried out, welding sequences include carrying out internal welding at first and then carrying out external welding, the diameters of welding wires are unequal to one another, internal welding is carried out on small welding specifications, external welding is carried out on large welding specifications, submerged-arc welding is matched with the solid-core welding wires and sintered flux, and the streng