scholarly journals Corrosion Behaviors of Super Austenitic Stainless Steel Weld Joints in the As-Welded and Post Weld Heat Treated States

2021 ◽  
Vol 59 (6) ◽  
pp. 374-383
Author(s):  
Dong min Cho ◽  
Jin-seong Park ◽  
Won Ki Jeong ◽  
Seung Gab Hong ◽  
Sung Jin Kim
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Pitting Corrosion ◽  
Arc Welding ◽  
Sigma Phase ◽  
Inconel 625 ◽  
Gas Tungsten Arc ◽  
Corrosion Behaviors ◽  
Super Austenitic Stainless Steel

The corrosion behaviors of a combined weld (plasma, gas tungsten arc) joint in a super austenitic stainless steel pipe were investigated using a range of experimental and analytical methods. To ensure superior corrosion resistance, a Ni-based super alloy (Inconel 625) was employed as the welding material only in the gas tungsten arc welding (GTAW). Nevertheless, pitting corrosion occurred preferentially around the sigma phase which had been precipitated in the interdendritic region of the GTAW. This indicated that the Inconel 625, which has a higher pitting resistance equivalent number (PREN), became even more susceptible to pitting corrosion than the base metal (BM). The higher Fe content in the Inconel 625 due to the dilution of Fe, supplied by the leading plasma arc welding, may increase the driving force for the precipitation of sigma phase. It was also revealed that the post weld heat treatment conducted at 1050~1150 oC effectively reduced the fraction of sigma phase precipitated in the weld. Even after such heat treatment, however, pitting corrosion occurred unexpectedly in the center region of the BM. This may be due to additional precipitation of the sigma phase in the BM, caused by inadequate control of the cooling rate during heat treatment at the industrial site.

Heat Treatment Effect on Pitting Corrosion of Super Duplex Stainless Steel UNS S32750 GTA Welds

2013 ◽  
Vol 746 ◽  
pp. 467-472 ◽  
Author(s):  
In June Moon ◽  
Bok Su Jang ◽  
Jin Hyun Koh
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Pitting Corrosion ◽  
Super Duplex Stainless Steel ◽  
Σ Phase ◽  
Gas Tungsten Arc ◽  
Weld Metals ◽  
Pitting Corrosion Resistance ◽  
Heat Treated

The purpose of this study was to investigate the effect of heat treatment (930°C, 1080°C, 1230°C) followed by quenching on the pitting corrosion resistance, sigma phase precipitation, and microstructural change of a super duplex stainless steel (UNS S32750) welds made by gas tungsten arc (GTA). Based on the microstructural examination, the σ phase was formed in welds heat treated at 930°C while there were little σ phases formed in welds experienced the relatively fast cooling from 1080°C and 1230°C. Accordingly, the most weight loss due to pitting corrosion occurred in the as received base and weld metals heat treated at 930°C. It was confirmed that the pitting corrosion occurred in the phase boundaries of ferrite/sigma and austenite/sigma.

scholarly journals Effects of Electromagnetic Stirring on the Cast Austenitic Stainless Steel Weldments by Gas Tungsten Arc Welding

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 630 ◽  
Author(s):  
Sheng-Long Jeng ◽  
Dai-Ping Su ◽  
Jing-Ting Lee ◽  
Jiunn-Yuan Huang
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Grain Boundaries ◽  
Arc Welding ◽  
Gas Tungsten Arc Welding ◽  
Electromagnetic Stirring ◽  
Gas Tungsten Arc ◽  
Welding Defects ◽  
Gas Tungsten ◽  
Notched Tensile Strength

Cast austenitic stainless steel (CASS) often contains high contents of silicon, phosphorus, and sulfur to prompt low melting phases to form in the welds. As a result, welding defects can be induced to degrade the welds. This study’s purpose was to investigate the effects of electromagnetic stirring (EMS) on the CASS weldments. The results showed that the ferrites in the heat affected zone (HAZ) had tortuous grain boundaries, while those that were close to the fusion lines had transformed austenites. EMS could reduce the influence of the welding heat to make the grain boundaries less tortuous and the transformed austenites smaller. Although their temperature profiles were almost the same, the gas-tungsten-arc-welding (GTAW) weld had smaller grains with massive ferrite colonies and more precipitates, while the GTAW+EMS weld had denser ferrite colonies with multi-orientations, but fewer precipitates. The hardness of the base metals and HAZs were typically higher than that of the welds. For both of the welds, the root was the region with the highest hardness. The hardness decreased from the root to the cap regions along the thickness direction. The GTAW weld had a higher hardness than the GTAW+EMS weld. At room temperature, the GTAW+EMS weld had a higher notched tensile strength and elongation than the GTAW weld. This could be attributed to the observation that the GTAW+EMS weld had dense and intersecting dendrites and that more austenites were deformed during tensile testing.

Identification of Optimized Welding Conditions for Pulsed Current Gas Metal Arc Welding of AISI 904 Super Austenitic Stainless Steel

2015 ◽  
Vol 787 ◽  
pp. 500-504
Author(s):  
P. Manavalan ◽  
S. Ravi ◽  
R. Kesavan
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Optimization Techniques ◽  
Pulsed Current ◽  
Metal Arc Welding ◽  
Pulse On Time ◽  
Super Austenitic Stainless Steel

The present investigation is aimed to study the effect of pulsed current gas metal arc welding on the tensile strength of AISI 904L super austenitic stainless steel joint 1.2 mm diameter solid wire of same composition. The joints were fabricated using pulsed current gas metal arc welding and by varying five factors such as peak current, pulse on time, pulse on frequency, background current and welding speed at five different levels. Design matrix based on central composite rotatable design was selected to conduct the experiment and an attempt is made to maximize the tensile strength by optimizing the factors using graphical and numerical optimization techniques. Results were correlated with weld metal microstructures.

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