Development of Pulsed Cold Metal Transfer and Gas Metal Arc Welding Techniques on High-Strength Aerospace-Grade AA7475-T761

2020 ◽  
Vol 29 (11) ◽  
pp. 7270-7290
Author(s):  
T. A. Vigneshwara Kumaran ◽  
S. A. Nithin Joseph Reddy ◽  
S. Jerome ◽  
N. Anbarasan ◽  
N. Arivazhagan ◽  
...  
Keyword(s):  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
High Strength ◽  
Metal Transfer ◽  
Cold Metal Transfer ◽  
Metal Arc Welding ◽  
Cold Metal

A52M/SA52 Dissimilar Metal RPV Repair Weld: Experimental Evaluation and Post-Weld Characterizations

2020 ◽  
Author(s):  
Iikka Virkkunen ◽  
Mikko Peltonen ◽  
Henrik Sirén ◽  
Pekka Nevasmaa ◽  
Caitlin Huotilainen ◽  
...  
Keyword(s):  
Pressure Vessel ◽  
Arc Welding ◽  
Nuclear Power ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Reactor Pressure Vessel ◽  
Cold Metal Transfer ◽  
Metal Arc Welding ◽  
Cold Metal ◽  
Reactor Pressure

Abstract Aging management of the existing fleet of nuclear power plants is becoming an increasingly important topic, especially as many units are approaching their design lifetimes or are entering long-term operation. As these plants continue to age, there is an increased probability for the need of repairs due to extended exposure to a harsh environment. It is paramount that qualified and validated solutions are readily available. A repair method for a postulated through cladding crack into the low alloy steel of a nuclear power plant’s reactor pressure vessel has been investigated in this study. This paper is part of larger study that evaluates the current possibilities of such repair welds. The present paper documents the weld-trials and method selection. A parallel paper describes numerical simulations and optimization of weld parameters. The presented weld-trial represents a case where a postulated crack has been excavated and repaired using a nickel base Alloy 52M filler metal by gas metal arc welding-cold metal transfer with a robotic arm. A SA235 structural steel has been used as a base material in this weld-trial. No pre-heating or post-weld heat treatment will be applied, as it would be nearly impossible to apply these treatments in a reactor pressure vessel repair situation. While Alloy 52M presents good material properties, in terms of resistance to environmentally assisted degradation mechanisms, such as primary water stress corrosion cracking, it is notoriously difficult to weld. Some difficulties and challenges during welding include a sluggish weld puddle, formation of titanium and/or aluminium oxides and its susceptibility to lack of fusion defects and weld metal cracking, such as ductility dip cracking and solidification cracking. Moreover, gas metal arc welding-cold metal transfer is not traditionally used in the nuclear industry. Nonetheless, it presents some interesting advantages, specifically concerning heat input requirements and automation possibilities, as compared to traditional welding methods. The mechanical properties, in terms of indentation hardness, and microstructure of a weld-trial sample have been evaluated in this study. The fusion boundary and heat affected zone were the main areas of focus when evaluating the mechanical and microstructural properties. Detailed microstructural characterization using electron backscatter diffraction and nanoindentation were performed across the weld interface. Based on these results, the gas metal arc welding cold metal transfer is seen as a potential high-quality weld method for reactor pressure vessel repair cases.

Erratum to: Mechanisms of weld pool flow and slag formation location in cold metal transfer (CMT) gas metal arc welding (GMAW)

2017 ◽  
Vol 61 (6) ◽  
pp. 1287-1287 ◽  
Author(s):  
Md. R. U. Ahsan ◽  
Muralimohan Cheepu ◽  
Rouholah Ashiri ◽  
Tae-Hoon Kim ◽  
Chanyoung Jeong ◽  
...  
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Slag Formation ◽  
Cold Metal Transfer ◽  
Metal Arc Welding ◽  
Cold Metal

Mechanisms of weld pool flow and slag formation location in cold metal transfer (CMT) gas metal arc welding (GMAW)

2017 ◽  
Vol 61 (6) ◽  
pp. 1275-1285 ◽  
Author(s):  
Md. R . U. Ahsan ◽  
Muralimohan Cheepu ◽  
Rouholah Ashiri ◽  
Tae-Hoon Kim ◽  
Chanyoung Jeong ◽  
...  
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Slag Formation ◽  
Cold Metal Transfer ◽  
Metal Arc Welding ◽  
Cold Metal

Evaluation of an Alloy 52 / Cladded Carbon Steel Repair Weld by Cold Metal Transfer

2021 ◽  
Author(s):  
Caitlin Huotilainen ◽  
Heikki Keinänen ◽  
Juha Kuutti ◽  
Pekka Nevasmaa ◽  
Henrik Sirén ◽  
...  
Keyword(s):  
Arc Welding ◽  
Nuclear Power ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Lessons Learned ◽  
Cold Metal Transfer ◽  
Repair Welding ◽  
Metal Arc Welding ◽  
Cold Metal ◽  
Reactor Pressure

Abstract Extending the lifetime of existing nuclear power reactors is an increasingly important topic. As the existing fleet of nuclear power reactors ages and approaches the end of their design lifetimes or enters periods of lifetime extension, there is an increased probability for defect repairs due to extended exposure to the operating environment (e.g. high temperature, high pressure, corrosion environment, neutron irradiation, etc.). Concerning repair welding, should a critical need for repair arise, qualified and validated solutions must be readily available for rapid deployment. A proposed method using robotized gas metal arc welding-cold metal transfer to repair a “worst-case” scenario, linear crack like defect beneath the cladding, which extended into the reactor pressure vessel steel, was evaluated on laboratory scale in previous works (PVP2020-21233, PVP2020-21236). These previous studies demonstrated that cold metal transfer has the potential to produce high quality welds in the case of a reactor pressure repair. In the current study, the lessons learned from the previous work were applied to repair a postulated surface crack on a thermally embrittled and cladded low alloy steel plate using a nickel base Alloy 52 filler metal. Two excavations were filled using different weld bead arrangements — a traditional pattern (92 weld beads, Q = 0.6 kJ/min) and a 45°-hatch pattern (184 weld beads, Q = 0.9 kJ/min) — by gas metal arc welding-cold metal transfer. No pre-heating or post-weld heat treatment were applied, to remain in line with what can be expected in a real pressure vessel repair situation. The 0° angle pattern acts as a reference for previous studies, while the 45°-hatch pattern, aims to minimize the residual stresses caused by repair welding. Finite element modeling was used to predict the initial (cladded, embrittled and excavated) condition of the steel plate, followed by simulating the welding using the actual welding conditions and material constants for both bead patterns as input parameters. The resulting deformation, strains and stresses created in the material due to repair welding were predicted and the welding’s effectiveness was estimated. In addition, the post-repair weld mechanical properties and microstructure, specifically focusing on the fusion boundary and heat-affected zone, were evaluated using various microscopy techniques and hardness measurements. The outcomes of the performed simulations, corresponding characterizations and lessons learned are presented in this study.

Welding Investigation on GMAW−Cold Metal Transfer of AISI 201LN for Superior Weld Quality

2020 ◽  
Vol 10 (4) ◽  
pp. 1-12
Author(s):  
Vivek Singh ◽  
M. Chandrasekaran ◽  
Sutanu Samanta ◽  
Kayaroganam Palanikumar
Keyword(s):  
Welding Speed ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Weld Quality ◽  
Cold Metal Transfer ◽  
Gas Tungsten Arc ◽  
Metal Arc Welding ◽  
Electron Microscope Analysis ◽  
Cold Metal

Austenitic stainless steel of AISI 201LN grade has found applications in liquefied natural gas tanks and cryogenic components. They are fabricated using gas tungsten arc welding (GTAW), but weld speed is low due to manual operation. This work aims welding investigation on AISI 201LN Gr. steel with a new hybrid welding approach (i.e., gas metal arc welding [GMAW] combined cold metal transfer [CMT]) for obtaining superior weld quality. Weld experiments were carried out at different welding speed, for example, 300, 400, 600, and 900 mm/min, to study weld quality and its mechanical properties. The microstructural examination of test coupons at higher welding speed shows finer structure in heat-affected zone as well as on weld metal. It was observed that the weld coupon having low heat input (at high weld speed) has maximum tensile strength. Scanning electron microscope analysis shows finer dimples at higher welding speed confirming ductile mode of fracture.

scholarly journals Gas Metal Arc Welding Modes in Wire Arc Additive Manufacturing of Ti-6Al-4V

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2457
Author(s):  
Oleg Panchenko ◽  
Dmitry Kurushkin ◽  
Fedor Isupov ◽  
Anton Naumov ◽  
Ivan Kladov ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Arc Welding ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Metal Transfer ◽  
Process Data ◽  
Cold Metal Transfer ◽  
Wall Width ◽  
Metal Arc Welding ◽  
Wire Arc Additive Manufacturing

In wire arc additive manufacturing of Ti-alloy parts (Ti-WAAM) gas metal arc welding (GMAW) can be applied for complex parts printing. However, due to the specific properties of Ti, GMAW of Ti-alloys is complicated. In this work, three different types of metal transfer modes during Ti-WAAM were investigated: Cold Metal Transfer, controlled short circuiting metal transfer, and self-regulated metal transfer at a direct current with a negative electrode. Metal transfer modes were studied using captured waveform and high-speed video analysis. Using these modes, three walls were manufactured; the geometry preservation stability was estimated and compared using effective wall width calculation, the microstructure was analyzed using optical microscopy. Transfer process data showed that arc wandering depends not only on cathode spot instabilities, but also on anode processing properties. Microstructure analysis showed that each produced wall consists of phases and structures inherent for Ti-WAAM. α-basketweave in the center of and α-colony on the grain boundary of epitaxially grown β-grains were found with heat affected zone bands along the height of the walls, so that the microstructure did not depend on metal transfer dramatically. However, the geometry preservation stability was higher in the wall, produced with controlled short circuiting metal transfer.

scholarly journals Influence of post weld heat treatment on tensile properties of cold metal transfer (CMT) arc welded AA6061-T6 aluminium alloy joints

2019 ◽  
Vol 28 (1) ◽  
pp. 135-145 ◽  
Author(s):  
Addanki Ramaswamy ◽  
Sudersanan Malarvizhi ◽  
Visvalingam Balasubramanian
Keyword(s):  
Heat Treatment ◽  
Tensile Properties ◽  
Gas Metal Arc Welding ◽  
Weight Ratio ◽  
Welding Process ◽  
Metal Transfer ◽  
Post Weld Heat Treatment ◽  
Cold Metal Transfer ◽  
Cold Metal ◽  
Weld Heat

AbstractAluminium alloys of 6xxx series are widely used in the fabrication of light weight structures especially, where high strength to weight ratio and excellent weld-ability characteristics are desirable. Gas metal arc welding (GMAW) is the most predominantly used welding process in many industries due to the ease of automation. In this investigation, an attempt has been made to identify the best variant of GMAW process to overcome the problems like alloy segregation, precipitate dissolution and heat affected zone (HAZ) softening. Thin sheets of AA6061-T6 alloy were welded by cold metal transfer (CMT) and Pulsed CMT (PCMT). Among the two joints, the joint made by PCMT technique exhibited superior tensile properties due to the mechanical stirring action in the weld pool caused by forward and rearward movement of the wire along with the controllable diffusion rate at the interface caused by shorter solidification time. However, softening still exists in the welded joints. Further to increase the joint efficiency and to minimize HAZ softening, the joints were subjected to post weld heat treatment (PWHT). Approximately 10% improvement in the tensile properties had been observed in the PWHT joints due to the nucleation of strengthening precipitates in the weld metal and HAZ.

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