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API pipeline steels are designed to withstand elevated temperatures and pressures in a variety of environmental conditions. The microstructure of API X70 pipeline steel is characterised by a very fine grain, which contributes to its exceptional strength and ductility. This paper investigates the corrosion behavior of API X70 steel when subjected to appropriate heat treatment processes. The study involves a comprehensive weight loss analysis over 50 days to evaluate the susceptibility of the material to corrosion in various corrosive environments. The specimens were exposed to three different corrosive environments (fresh water pH 7, seawater pH 8 and sodium thiosulfate solution pH 5) for 50 days. Macroscopic analysis was carried out at 4 day intervals. The microstructure of the heat treated samples shows the existence of different phases formed during the heat treatment process. A corrosion rate of 9.056 mils per year (mpy, 1 mil equals 0.001 inch) in the base metal as against 8.131 mpy in the heat treated specimen was observed for the specimen immersed in fresh water medium. In seawater medium, the corrosion rate of 11.685 mpy was observed for the base metal while 10.580 mpy was observed for the heat treated specimen.

The pitting corrosion resistance of dissimilar pipeline steel API X70 and Super Duplex 2507 Stainless Steel gas tungsten arc (GTA) welds was studied. The GTA welds were fabricated using Super Duplex 2594 Filler Metal or austenitic 309L Filler Metal. The specimens extracted from the base metal, weld fusion zone, fusion boundary, and heat-affected zones (HAZs) were subjected to a potentiodynamic corrosion test in a 3.5% NaCl water solution. The weld made using the 309L Filler Metal was found to have a smaller pitting resistance equivalent number (PREN) difference between ferrite and austenite, making it more corrosion resistant than the weld fabricated using the 2594 Filler Metal. The HAZ on the X70 side was the most susceptible to pitting and galvanic corrosion for both filler metals. [ABSTRACT FROM AUTHOR]

This study investigates the influence of shielded metal arc welding electrode coating flux on microhardness, microstructure and element transfer. A series of multi-pass bead-on-plate studies were conducted using laboratory-developed electrodes. The flux composition has shown a significant effect on all the responses. An increase in Al2O3and BaOhas shown a positive influence on nickel transfer, whereas an increase in CaOreduces nickel transfer. The slag detachability was found good for ratio CaF2:CaO:Al2O3:: 1.76:0.73:0.51. Energy dispersive spectroscopy has shown inclusions rich in aluminum and oxygen with trace amounts of Ca, Mn, Ti and Si. Artificial neural network models have been developed and then compared to conventional regression predictions.

Bimetallic welds (BMWs) play a critical and indispensable role in the primary heat transport piping system of nuclear reactors. The primary heat transport system itself is the critical part of a nuclear reactor. Any failure of this system can lead to very grave consequences, not only speaking of huge monetary losses resulting from non-utilization of the reactor setup, but also immensely valuable and irreparable loss of human life. This paper describes the experimental efforts towards estimation of Gurson material parameters of base metal and weld metal regions of a BMW so as to use the micromechanical modelling approach for addressing the structural integrity issues in BMWs.

From Fourier optics it follows that it is possible to obtain a Fourier transform of an amplitude distribution in a transparency readily. In intermediate planes an interpolation between the signal and its Fourier spectrum is available. Some pattern recognition schemes may work better in one of these intermediate domains than in the time or the frequency domain.