Shielded metal arc welding

About: Shielded metal arc welding is a research topic. Over the lifetime, 4462 publications have been published within this topic receiving 40560 citations. The topic is also known as: manual metal arc welding & flux shielded arc welding.

Characterization of defects in alloy 152, 52 and 52m welds

Abstract: Defect distributions have been documented by optical metallography, scanning electron microscopy and electron backscatter diffraction in alloy 152 and 52 mockups welds, alloy 52 and 52M overlay mockups and an alloy 52M inlay. Primary defects were small cracks at grain boundaries except for more extensive cracking in the dilution zone of an alloy 52 overlay on 304SS. Detailed characterizations of the dilution zone cracks were performed by analytical transmission electron microscopy identifying grain boundary titanium-nitride precipitation associated with the intergranular separations. I. INTRODUCTION Weldments continue to be a primary location of stress-corrosion cracking (SCC) in light-water reactor systems. While problems related to heat-affected-zone (HAZ) sensitization and intergranular (IG) SCC of austenitic stainless alloys in boiling-water reactors (BWRs) have been significantly reduced, SCC has now been observed in HAZs of non-sensitized materials and in dissimilar metal welds where Ni-base alloy weld metals are used. IGSCC in weld metals has been observed in both BWRs and pressurized water reactors (PWRs) with recent examples for PWR pressure vessel penetrations producing the most concern. This has led to the replacement of alloy 600/182/82 welds with higher Cr, more corrosion-resistant replacement materials (alloy 690/152/52/52M). Complicating this issue has been a known susceptibility to cracking duringmore » welding [1-7] of these weld metals. There is a critical need for an improved understanding of the weld metal metallurgy and defect formation in Ni-base alloy welds to effectively assess long-term performance. A series of macroscopic to microscopic examinations were performed on available mockup welds made with alloy 52 or alloy 152 plus selected overlay and inlay mockups. The intent was to expand our understanding of weld metal structures in simulated LWR service components with a focus on as-welded defects. Microstructural features, defect distributions, defect characteristics and weld residual strains were examined by optical metallography, scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. Industry-supplied mock-up welds were characterized including alloy 52 and 152 weldments, alloy 52M overlay and inlay welds, and an alloy 52 overlay. II. WELDMENTS II.A. Alloy 52 and 152 Weld Mockups The alloy 52 and 152 weld mockups were fabricated by MHI for the Kewaunee reactor and were obtained from the EPRI NDE Center. The mockups were U-groove welds joining two plates of 304SS as shown in Figure 1. Alloy 152 butter (heat 307380) was placed on the U-groove surface for both mockups by shielded metal arc welding (SMAW). For the alloy 152 weld mockup, the alloy 152 fill (heat 307380) was also applied using SMAW while for the alloy 52 weld mockup, the alloy 52 fill (heat NX2686JK) was applied using gas tungsten arc welding (GTAW). Welding parameters for the fill materials were substantially different with the alloy 152 SMAW having a deposition speed of 4-25 cm/min with a current of 95-145 A and the alloy 52 GTAW having a deposition speed of 4-10 cm/min with a current of 150-300 A. One prominent feature in these mockup welds is the presence of a crack starting at the 304SS butt joint at the bottom of the U-groove and extending up into the weld. It appears that the 304SS plate on either side of the butt joint acted as an anchor for the weld resulting in a stress rise across the slit that drove crack formation and extension up into the fill weld. As will be shown in the next section, the extent of the cracking around this stress riser was much greater in the MHI 52 weld mockup.« less

Investigation on various welding consumables on properties of carbon steel material in gas metal arc welding under constant voltage mode

Abstract: In this present work, the influence of different consumables on weld properties of carbon steel plate was studied by automatic gas metal arc welding under constant voltage mode. For all experiments, the process parameters such as welding current of 200 A, voltage of 28 V and welding speed of 200 mm/min were kept constant. The results indicate that the angular distortion remained higher for solid wire, whereas it was minimum for flux-cored wire and the lowest in metal-cored wire. Mechanical properties such as yield strength, tensile strength, elongation and joint efficiency remained high for solid wire relative to cored wire. Excellent impact toughness of the weld metal and heat-affected zone was reported for the flux-cored welds compared with solid wire and metal-cored welds.

Effects of Gas Metal Arc Welding Techniques on the Mechanical Properties of Duplex Stainless Steel

Abstract: The study has compared the effect of gas metal arc welding techniques on some mechanical properties of duplex stainless steel. The samples after welded were given post weld heat treatment (quenching in engine and neem oil). After the analyses, it was established that duplex stainless steel can be weld successfully using gas metal arc welding process (GMAW). Both Lubricating oil and neem oil can serve as quenching medium for post welding heat treatment of duplex stainless steel. The results of the studies also show that welding and heat treatment really affect the mechanical properties of the alloy; the control strength was 811.47 MN/m2 while that of the welded samples ranged from 177.07 to 257.32 MN/m2. The control impact energy was 162.70 J, while that of the welded samples ranged from 38.64 J to 56.20 J. The research also shows that the stress relief heat treatment gives better strength (A3 = 331 MN/m2) compared to those that were quenched in lubricating oil (A2 = 329 MN/m2) and neem oil (A1 = 222 MN/m2), but the reverse is the case in terms of toughness.