Análise de procedimentos de soldagem por arco submerso na recuperação em rolo de laminação

Abstract

The submerged arc, also known as SAW, is a welding process in which an electric arc is established between a continuous consumable electrode and the workpiece. The process is called "submerged" because the arc, the molten zone, and the electrode are covered by a granular flux that melts and forms a protective layer over the weld. During the recovery process of a roll, after its delivery to the customer, indications were observed on the surface of the table, such as weld bead marks. As a result, the roll was returned to the factory for repair, where various tests and non-destructive examinations were conducted. This included metallographic analyses (performed after sending chips to the SENAI laboratory), analyses of the chemical composition of the wire used, liquid penetrant tests, among others. Upon completion of the tests, the need for a change in the welding procedure for the recovery of rolls intended for lamination was identified. The indications appeared at the customer’s site after 36 hours of roll operation, causing marks on the strip and necessitating the roll to be disassembled for intervention by the repair company. The SAW welding process was used in the first procedure with oscillation, and in the second procedure, it was changed to welding without oscillation. The analysis was necessary when the upper roll started operating (this roll is positioned at the end of the Hot Strip Mill), but after 36 hours, these indications appeared along the body of the roll. At the end of the tests, the procedure was altered to non-oscillation welding. This change met the client's expectations when the rolls went back into operation.