Estudo das técnicas de remoção de material empregadas em soldagens de fabricação ou de manutenção de estruturas de aços

Abstract

Industries in general, often have problems with their equipment the occurrence of defects such as cracks that arise often in the heat affected zone (HAZ) of welding, localized corrosion in pre-arranged regions to this phenomenon, and pores that are usually observed in weld beads poorly executed. Thus, it is necessary to carry out repairs on these structures by specific techniques for this purpose, such as; Grinding is the most used, and the processes arc, plasma arc gouging and gouging graphite electrode. In this paper, we carried out a scoping study of removal processes the arc, getting information on operating parameters that provide stability conditions in the process, and can control the volume of material removed. Then a maintenance simulation was performed on a structure built with ASTM 4140 steel joint of 12 mm in length and profile K on a side of the 2/3 thickness, and the other 1/3 of the thickness dimensions of these suggestions made by Petrobras technicians. Of the five joints analyzed at this stage, one has been removed by grinding two goivadas the plasma arc and two goivadas 5 mm graphite electrode diameter and 8 mm, respectively. Through the analysis of hardness and microstructure it was possible to answer the main questions and suspicions inherent in each process, such as carbon based metal contamination in the gouging process with graphite electrode, extension of the heat affected zone (HAZ), a possible hardening of region near the polished surface. Thus it was possible to verify that there was an extension of the HAZ of the arc processed samples, however the gouging process using the electrode of 8 mm diameter critical features presented the processed together. The samples processed at the end of the plasma arc maintaining microstructural changes had fewer steps when compared to the sample processed by grinding.