Prediction of Mechanical Properties as a Function of Welding Variables in Robotic Gas Metal Arc Welding of Duplex Stainless Steels SAF 2205 Welds Through Artificial Neural Networks

Dual-phase duplex stainless steel (DSS) has shown outstanding strength. Joining DSS alloy is challenging due to the formation of embrittling precipitates and metallurgical changes during the welding process. Generally, the quality of a weld joint is strongly influenced by the welding conditions. Mathematical models were developed to achieve high-quality welds and predict the ideal bead geometry to achieve optimal mechanical properties. Artificial neural networks are computational models used to address complex nonlinear relationships between input and output variables. It is one of the powerful modeling techniques, based on a statistical approach, presently practiced in engineering for complex relationships that are difficult to explain with physical models. For this study robotic GMAW welding process manufactured the duplex stainless steel welds at different welding conditions. Two tensile specimens were manufactured from each welded plate, resulting in 14 tensile specimens. This research focuses on predicting the yield strength, tensile stress, elongation, and fracture location of duplex stainless steel SAF 2205 welds using back-propagation neural networks. The predicted values of tensile strength were later on compared with experimental values obtained through the tensile test. The results indicate <2% of error between observed and predicted values of mechanical properties when using the neural network model. In addition, it was observed that the tensile strength values of the welds were higher than the base metal and that this increased when increasing the arc current. The welds’ yield strength and elongation values are lower than the base metal by 6%, ~ 9.75%, respectively. The yield strength and elongation decrease might be due to microstructural changes when arc energy increases during the welding.

Characterization of Mechanical Properties and Corrosion Resistance of SAF 2205 Duplex tainless Steel Groove Joints Welded using Friction Stir Welding Process.

The aim of this work is to characterize the effect of groove joint designs on mechanical and corrosion resistance properties of friction stir welded SAF 2205 duplex stainless steel (DSS) 6.5-mm-thick plate. Nondestructive tests (NDT), such as Radiographic Test (RT), and Visual Test (VT), show that, high-quality welds were produced for V grooved joints with, 60 ̊groove angle, and 2 mm root face, without root gap, with these joints were welded at constant rotating speed of 300 rpm, 25 mm/min traverse welding velocity, and 20 KN down load, using tungsten carbide (WC) base metal conical tool. Evaluating the mechanical properties using destructive tests (DT) such as tensile test, bending test, impact test, Vickers hardness test, showing that, Vickers hardness was increased at the stir zone, the failure was occurred at the base metal, the bending behavior and the impact energy are acceptable, the evaluation of corrosion resistance rate shows that, the corrosion resistance of this joint is higher than that of the base metal. In addition, it was significantly noted that, mechanical properties and corrosion resistance of these joints welded using FSW process are better than that of those joints welded using fusion welding (FW) possesses, shielded metal arc welding (SMAW), and gas tungsten arc welding (GTAW).

Duplex Stainless Steel Subjected to Normalized Thermal Treatment

In the research, the mechanical behavior of duplex stainless steels SAF 2205 and 2507 subjected to Normalized thermal treatments at temperatures at temperatures of 900, 950 and 1000oC for a time of 7 minutes for SAF 2205 and 15 minutes for SAF 2507 were evaluated. It was determined that the mechanical strength increased considerably the higher value was found at 900 °C. It was determined that the KIC values for the normalized conditions of 900 oC and 950oC, reduce strongly in both steels with respect to the original condition. However, it is clearly reflected that for the normalized condition at 1000 °C the KIC is fully recovered, and for the temperature range of 700 °C to 900 °C, the values of impact toughness suffer a drastic decrease, caused by the appearance of intermetallic phases.

The effect of plasma nitriding on the synergism between wear and corrosion of SAF 2205 duplex stainless steel

Purpose This study aims to assess the performance of SAF 2205 duplex stainless steel against pure wear, tribo-corrosion, corrosion and the synergism between wear and corrosion. The effect of plasma nitriding conducted at low temperature (380°C) on SAF 2205 steel was analyzed. Design/methodology/approach Three systems were used for assessing the synergism between wear and corrosion: tribo-corrosion – wear tests conducted using the micro-scale abrasion test, performed under a slurry of alumina particles containing 3.5% NaCl; pure wear – tests conducted using the previous system but isolated in a glovebox with a 99% N2 atmosphere; and cyclic polarization under 3.5% NaCl solution. A hard nitrided layer of 3 µm thickness was characterized using X-ray diffraction, presenting expanded austenite. Findings The wear mode after micro-scale abrasion tests changed in the absence of an oxygen atmosphere. During pure wear, a mixed mode was identified (rolling + grooving), with the grooving mode more intense for the untreated steel. For tribo-corrosion tests, only rolling wear was identified. For all cases, the nitrided samples presented less wear. The corrosion results indicated a higher repassivation potential for the nitrided condition. Practical implications The synergism was more positive for the nitrided sample than for the untreated one, which can be considered for surface treatments of duplex stainless steels in practical applications. Originality/value A detailed description of wear mechanisms showed a significant change in the presence of oxygen atmosphere, a new approach for isolating pure wear.