Electrodes for manual arc welding in oil and gas complex

Electrodes were designed for pipe welding including the formation of a back bead in welding a joint root, providing high mechanical properties of a welded joint. For manual arc welding of constructions made from carbon and low-alloy steels, as well as for structures operating at low temperatures the electrodes with the main types of coverage such as SSSI are widely used. The mechanical properties of welded joints formed by these electrodes provide high strength, ductility and toughness even at low temperatures. However, these electrodes having standard composition are worse in weldability than the electrodes of foreign manufacturers. This fact limits their usage in pipe welding. However, the analogous foreign electrodes are about 2.5 times more expensive than the SSSI-13/55 electrodes. If we find a replacement for imported electrodes, it will allow gas and petrochemical industries to depend less on the import, while maintaining domestic production of welding electrodes. The task is to get improved welding characteristics, while maintaining the mechanical properties of welded joints. It will allow welding pipe constructions, including pipe joints with a back bead while welding root passes. For this purpose, the electrodes LB 52MK were developed and the guidance to their use in pipe welding was worked out. Positive feedback from many customers was received. A range of tests on the chemical composition and mechanical properties of the weld metal was conducted In St. Petersburg State Polytechnic University. The amount of diffusible hydrogen in the weld metal vacuum method in accordance with GOST 23338-91 on the electrodes with a diameter of 3.2 mm was determined. As a result, the mechanical properties of weld metal of LB-52MK electrodes correspond to the type E50A GOST 9467-75. According to the classification AWS A5.1 they relate to the type of 7015-1. When welding the root passes on the back side of the pipe the back bead of regular shape without undercut on the base metal is formed. For the convenience of consumers who currently use the electrodes of foreign manufacturers it is planned to produce electrodes with a diameter of 4.0 mm; 3.2 mm; and in the future - with a diameter of 2.6 mm.