METHOD FOR MAKING ELECTRICALLY WELDED METALLIC TUBES AND APPARATUS FOR PERFORMING THE SAME Russian patent published in 2000 - IPC

FIELD: metallurgical production, namely, manufacture of electrically welded metallic tubes for main large-length water ducts with high demands to their surface quality, roughness degree, structure and properties of microlayer. SUBSTANCE: method is realized with use of apparatus including initial coiled band, first vacuum chamber with fluid-tight inlet, electronic-plasma modules, fluid-tight outlet and first cooler. Apparatus also includes reduction stand with cylindrical rolls, shaping mill, welding unit, cutting unit for removing outer burr, first, second and third gas nozzles, electric arc burner with supply of shield gas, device for applying protective coat onto inner surface of ready tube, second vacuum chamber with fluid-tight inlet and with electronic-plasma modules, system of concentric extruders also serving as fluid-tight outlet, second cooler and ready tube. Surface of band is cleaned in first vacuum chamber by means of electric arc discharges in zone of raising portion of volt-ampere characteristics with use of graphite anode. Outer surface of band is cleaned similarly in second vacuum chamber. Process of welding tube edges and applying corrosion resistant coating is normalized. EFFECT: enhanced quality of welded tubes due to preliminary vacuum-electric arc cleaning of surface of initial band, high quality of welded seam, lowered size of inner burr, enhanced cleaning degree of outer surface of ready tube and conditions for applying corrosion resistant coating onto it in vacuum. 2 cl, 1 dwg