Relationship Analysis between Multi-Parameters and Ferrite Number in GTAW Based on ANN Model

Ferrite number (FN) is a crucial parameter for austenite steel-welding products, since it has a specific relationship with crack sensitivity and other important properties. In this paper, artificial neural network (ANN) models were built to predict FN, based on the GTAW tests of 304L plates produced by two different steelworks, Dongfang Special Steel hot-rolled sheet (DFSS) and Anshan Iron and Steel cold-rolled sheet (ASIS). The results show that a high performance, of more than 98% accuracy, can be achieved when the models of DFSS and ASIS are modeled separately, and that accuracy is also above 96% when an integrated model is built. The influences of nitrogen content and multiwelding parameters, such as travel speed, wire-feed rate, welding current and arc length, on FN are also analyzed through the FN-prediction model for DFSS. The results show that FN increases monotonously with the increase of nitrogen content, but the influences of either of the other two parameters on FN are nonlinear.

Experimental investigation of GTA Welded SS316L plates using shape memory alloy as a filler material

Parameter optimization is the active subject of research, and in this current work the ferrite number and gas tungsten arc (GTA) welding SS. Filler material. Models have been developed by welding SD316L slab with NiTinol wire (shape memory alloy) as a filler material by conducting experiments using three-factor, three level factorial designs. Tests have been conducted for various models at UTM and the results are scheduled. The final models were upgraded using the design expert method. It can be seen from the investigation that the interactive effect of the process parameters has a significant effect on the tensile strength and the ferrite number.

Effect of weld metal composition on impact toughness properties of shielded metal arc welded ultra-high hard armor steel joints

Nowadays, ultra-high hard armor (UHA) steels are employed in armor tracked vehicle (ATV) construction because of their high hardness, high strength to weight ratio, and excellent toughness. UHA steels are usually welded using austenitic stainless steel (ASS) welding consumables, to avoid hydrogen-induced cracking (HIC). The use of ASS consumables to weld the above steel was the only available remedy because of higher solubility of hydrogen in the austenitic phase. In this investigation, an attempt was made to investigate the effect of ASS consumables (with different Creq/Nieq ratio) on solidification mode, impact toughness and microstructural characteristics of shielded metal arc (SMA) welded UHA steel joints. The welded joints were characterised based on impact toughness properties, hardness, and microstructural features. As the ferrite number increases with an increase in Creq/Nieq ratio result in different solidification mode (A, FA, F). It is also found that ferrite number of weld metal has appreciable influence on impact toughness and has inversely proportional relationship with impact toughness of the welded joints.

Influence of microstructural evolution and localized delta ferrite number on high-cycle fatigue crack opening and propagation rate

In this research, percentages of nickel as austenizer and chromium as ferritizer, in the molten metal pool of SS304L weldments are varied to analyze the effect on the produced delta ferrites morphology and volume. The resulting localized precipitation of delta ferrite and its effect on the fatigue crack propagation rate of the material are examined in this work. The estimation of localized delta ferrite number for a particular weld zone is assessed through the development of a MATLAB code for image processing. It is observed that a reduction in the percentage of nickel in filler alloy yields randomly scattered granular ferrites in the fusion zone and equiaxed grain growing in the heat-affected zone with the development of blocky ferrites on the grain boundaries, whereas increased percentage of chromium in the filler causes the precipitation of dendritic clusters and vermicular ferrites in fusion zone and heat-affected zone of weldments, respectively. The effect of ferrite numbers and their morphology on the crack opening displacements and the corresponding fatigue crack propagation rate in different weld zones are analyzed. It is observed that the ferrite number ranging between 15 and 19 provides optimum fatigue strength for SS 304L. Paris curves are plotted from the test data, which shows that the weldment attained with filler alloy having Cr 26.60% and Ni 10.92% depicts the highest fatigue life compared to other studied weldments.

Failure analysis of fillet welds with premature corrosion in 316L stainless steel slide gates using constitution diagrams

The service environment of the slide gates may cause localized corrosion at welds. In this work, a failure analysis was conducted to determine the causes of the prematurecorrosion of the fillet welds before the commissioning. According to the contractor, the slide gates were manufactured in ASTM A240 Type 316L stainless steel and welded with GMAW using an ER316LSi filler metal. Test samples of the fillet weld metals were extracted from gates after a preliminary visual inspection. The samples were analyzed using ferrite number measurements, Optical Emission Spectrometry, chemical analysis, metallographic examination and Scanning Electron Microscopy with microanalysis. The analysis of results using the Schaeffler and WRC-92 constitution diagrams showed that the estimatedchemical composition of the filler metal differs with the filler metal specified in the WPS suggesting that an incorrect carbon steel filler metal was used during the construction of the gates