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Failures in welded joints constitute a challenge that requires a scientific approach due to its phenomenological essence. This work determines the causes of failure in welded joints of a piping system, which were carried out with the SMAW process. Visual inspection, tension tests of the base material, chemical analysis by optical emission spectrometry as well as macrograph and metallography of the welded joint were carried out to a sample extracted from the damaged area using a cooled disc. In conclusion, we can say that the cause of failure has its origin in the poor procedure applied when welding, although other factors such as mechanical fatigue or an inappropriate design could also have been present. [ABSTRACT FROM AUTHOR]

Introduction: The AWS E FeCr-A1 electrode does not guarantee deposits in a single layer that can counteract the wear of the shredder hammers. Microstructure in the first layer is primary austenite (ɣ- Fe) and an interdendritic eutectic network (austenite and carbide). The hardness is 50 HRC. Objective: To evaluate the preheat effect on the hardness and microstructure of deposits obtained with the AWS E FeCr-A1 electrode. Materials and Methods: The deposits were obtained on S275JR steel plates, using single and double layer of recharge at room temperature and at 200°C, with shielded metal arc welding (SMAW). The samples were trimmed, polished and etched with Murakami reagent. The microestructure was observed by optical microscope (OM). The Vickers microhardness was determined using a Shimatsu microdurometer. Results and Discussion: Microstructure of deposits obtained at room temperature using simple and double layer consist of primary grain of austenite (ɣ- Fe) and eutectic (ɣ- Fe and M7C3). The highest hardness was obtained in the sample with double layer (723 HV). Microstructure of deposit performed at 200°C is composed by large amount of austenite (ɣ- Fe) and lower fraction of eutectic (ɣ- Fe and M7C3). Conclusions: With a temperature increase (200°C), predominant microstructure is austenite (ɣ- Fe), and deposit reaches only a hardness of 572 HV, below that indicated for the consumable AWS EFeCr-A1 which is 650 HV. [ABSTRACT FROM AUTHOR]

The effect of welding current on the chemical composition and microstructure of Fe-Cr-C deposits obtained by SMAW and used for working under abrasive and erosive wear conditions was evaluated. Chemical composition of the deposit without dilution was determined and microstructure of the deposits was obtained with and without dissolution. The dilution coefficient was determined based on the geometry of the deposits and the chemical composition of the deposits for different welding currents based on it. It is concluded that all the deposits respond to the AWS EFeCr-A4 designation, characterized by a high predominance of eutectic, being suitable for working in conditions of abrasive and erosive wear. As the current increases, the content of alloying elements decreases due to dilution. The deposit obtained with a 110 A current is considered more appropriate, because 90 A current has very little penetration, which makes adherence difficult. [ABSTRACT FROM AUTHOR]

A plate of carbon steel was cladding with stainless steel by means of a shielded metal arc welding process. The alloys are considered dissimilar materials. At a welding process, is not possible to predict the final metallographic characteristics of the zones at relation with the welding process. The stainless alloy was applied at melted state therefore the high temperature affected the microstructure of carbon steel, which is called heat-affected zone. Rapid solidification of the filler metal and the rapid cooling of the heat-affected zone leaded to meta-stable microstructures formation. The changes of the microstructure at the heat-affected zone were studied by scanning electron microscopy technique. At the heat affected zone of no-aging material samples, multiple carbides of no-globular morphology were recorded, which were transformed to globular morphology after of an aging process of 3 600 hours at room temperature. Passed 10 000 hours of aging, whiskers were developed from the globular carbides. Due to non-stoichiometric chemical composition, the multiple carbides are considered as intermetallic compounds. [ABSTRACT FROM AUTHOR]

This investigation presents the evaluation of AWS E 7018 coated electrodes based on the content of the peripheral coating components in order to improve their performance. Proportions for the coatings were estimated based on an McLean Anderson experimental design where the input variables are: X1- pyrolusite, X2- limestone+fluorite (for limestone: fluorite=1) and X3- FeCrMn. The homogenized blends were agglomerated with sodium silicate and water to form the pastes that were applied by immersion on the basic coating of the 3,2 mm diameter electrodes of the metal core. The isolines of the melting and deposition rates as well as the deposition efficiency and the bead geometry were generated for the evaluation of the electrodes. The results indicate that the composition of the coating with a better performance contributes to favorable changes compared to the electrode without peripheral coating as this increases the depth of the bead penetration, thus providing a narrower profile. [ABSTRACT FROM AUTHOR]

The present work is a study for the conversion from oxiacetylene filler metal R-FeCr to electric arc process with filler metal E-FeCr for surface coating of erosive wear parts, particularly clay extruder screws, due to the need to increase productivity hardfacing processes and reduce deformation without reducing the properties of the deposits. The study was based on a formulation of a low hydrogen coating tested in previous works, which was applied by immersion. Deposits were made using a simulator which allows carrying out handing welding without the welder's direct interference, varying the welding current. In this way, were determined the technical-operative characteristics of the consumable in study (fusion rate, deposition rate, real efficiency, operating stability, metallography and hardness of the deposit). The analysis of these characteristics, allowed to demonstrate the technical feasibility of this conversion [ABSTRACT FROM AUTHOR]

The ability of Monte Carlo simulation and Latin Hypercube Sampling methods in estimating the productivity of the Shielded Metal Arc Welding (SMAW) applied in works of industrial piping assembly based on small samples is evaluated. The study was conducted by analyzing a sample collected from assembly operations done at refinery Duque de Caxias, Rio de Janeiro in Brazil. The ControlTub 5.3 software was used for data acquisition and MathWorks in the simulation step. For data analysis the results were compared using the proposed simulation methods. Then the similarities and differences between the methods to estimate the process productivity in analysis were evaluated. The results demonstrated the feasibility of applying the methods of Monte Carlo Simulation and Latin Hypercube Sampling in estimating productivity considering a welding process of industrial pipes. [ABSTRACT FROM AUTHOR]