Abstract
This work consists in the study and development of the Controlled Current Short-circuiting MIG/MAG Welding Process (CCC) and Procedure dedicated to the root pass of pipes butt weld, for the construction of offshore oil pipelines. Currently, this operation is performed with the Coated Electrode Process, of inherent lower productivity. The semi-mechanized, slag free process herein developed (CCC) yields satisfactory properties root welds with higher productivity. Given the significant influence of the welding process over the chronogram, and then over the elevated construction costs, R&D on this technology is highly justifiable, since the aim is make it available to national companies at low cost, increasing their competitiveness in a globalized marketplace as the oil sector.The CCC obtains the advantages of short-circuiting metal transfer and avoids its inconveniences, enabling its use in pipelines root welds, by means of a specific current waveform control, providing stability to the process and weld pool, with low welder training time. The developed procedure permits the making of a continuous root pass, whereas good results were accomplished in the flat position. This was made possible by the stability analysis tools developed. As expected, it was noticed that further work is needed for downwards and overhead positions. The future goal is as on line regulated system, where the welder is able to adequate the process to the current welding position, along the weld girth. As a result, software and hardware, as well as powerful stability analysis tools, suited to the CCC, were generated. By applying them, a waveform was defined, whose phases’ times and relative current levels are adequate to the mentioned weld pass, producing standards meeting root welds with higher productivity than the Coated Electrode. Information concerning the process behavior, when subjected to out of position welding, was generated.
Keywords: metal transfer, oil and gas transport, productivity
Referência:
SILVA, R. H. G. ; Gohr ; OLIVEIRA, M. A. . Controlled Short-Circuiting MIG/MAG Welding Applied to the Root Pass in the Construction of Offshore Pipelines - Process Analyisis Tools. In: COBEM 2005, 2005, Ouro Preto. Proceedings of COBEM 2005, 2005.