In this article, I will explain the evolution of gas metal arc welding such as MIG welding and MAG welding, which are widely used in various manufacturing fields as high efficiency welding methods, ...based on the latest trends in arc welding.
Numerical simulation based on an incompressible smoothed particle hydrodynamics method was performed to clarify dominant factors of slag transfer and deposition processes in a metal active gas ...welding with a computational model which considered the effects of a shielding gas flow on a slag floating on a weld pool surface. As a result, the slags generated on the weld pool surface near the center of a heat source were transferred to the edge of the pool, which was similar to an experiment result. The slags stayed at the trailing region of the pool and then deposited on a weld bead. These simulated behaviors supported the validity of the present computational result. In order to identify the dominant factors of the slag behavior on the weld pool, numerical experiments were conducted with individually acting the forces due to the Marangoni effect, the shearing force, the Lorentz force, and the drag by the shielding gas flow. From the computational results, it was suggested that the shearing force and the drag due to the shielding gas were dominant near the center of the heat source, and the slag was transferred from the vicinity of the heat source to the end of the weld pool. On the other hand, it was clarified that the force due to the Marangoni effect was dominant in the trailing region of the weld pool, and consequently the slag was transferred from there to the front region in the welding direction.
•Four types of stainless steel with different chemical composition were MAG butt welded.•Solidification modes, microstructure and mechanical properties of the four welded joints were ...studied.•Fracture mechanisms of the four welded joints were analyzed from the perspective of crystallography.•FQZ generated from FA solidification mode is the main reason for the 304 and 316L welded joints fracturing at HAZ.•Improved understanding of the fracture mechanisms of the four welded joints provides technical guidance for application of different stainless steels.
In this study, four types of austenitic stainless steels (SUS 301L, SUS 304, SUS 316L and SUS 321) with different chemical compositions were butt welded by using MAG (metal active gas) welding. Unique information was gained by studying the solidification mode, microstructure and mechanical properties of the four welded joints under the same welding process, and their fracture mechanisms were analyzed from the perspective of crystallography. The results indicate that the microstructure of the four austenitic stainless steel base metals is uniformly sized equiaxed austenite with δ-ferrite distributed inside or at the boundary of austenite grains in 301L and 304 base metals. The welds of the four kinds of stainless steels are solidified in Austenitic-Ferrite (AF) solidification mode, and the final microstructures of the 301L, 304 and 316L weld are equiaxed grains while the 321 stainless steel weld grows into a dendritic structure due to its low temperature gradient. The microstructures of the fusion zone (FZ)/fine equiaxed zone (FQZ) and heat affected zone (HAZ) of the four types of stainless steels are closely related with the solidification mode of FZ, i.e. small FZ and HAZ regions result from Ferrite (F) solidification mode present in the 301L and 321 welded joints. However, larger FQZ regions generate in the 304 and 316L welded joints due to the Ferrite-Austenitic (FA) solidification mode. The 304 and 316L stainless steel tend to fracture at the HAZ positions due to the formation of FQZ; large angle grain boundary formed at the weld of 301L stainless steel is the reason for its fracture, and the good anisotropy of the weld and heat affected zone of 321 stainless steel also makes it easier to fracture in the base metal (BM). The section hardness distribution characteristics of the four stainless steels welded joints also verify their fracture tendency.
Carbon dioxide gas-shielded arc welding, which is widely used in industry, generates a large amount of spatter in the medium and high current range. To solve this problem, we developed a new welding ...process with low spatter and low gas cost that we call “Pulsed Gas MAG” (PGMAG) welding. In PGMAG welding, the metal transfer is controlled by the suitable addition of Ar gas, but the effect of the welding current has not been clarified. Therefore, we investigated metal transfer in the 235- to 325-A range and found that the pulse frequency of Ar gas must be adjusted between 35 and 65 Hz to match the welding current (i.e., wire feed rate) to control metal transfer. A wide area where metal transfer is controllable is obtained by adjusting the Ar addition frequency for a current of 235-325 A. It was considered that there is a suitable volume for the droplet to be released and that the growth speed depends on the wire feed rate.
Metal Active Gas Welding is a technique for efficiently combining many materials. Al-5052 was chosen for its non-corrosive, wear-resistant, anti-static, light weight, and formability qualities. ...Aluminium alloys are important in engineering and metallurgy because of their superior corrosion characteristics, ease of manufacturing, and high specific strength paired with the ideal balance of toughness and formability. The shape of the weld bead, mechanical properties, and distortion can all be utilised to assess the quality of a weld connection. Through solutioning and ageing, post-weld heat treatment improves weld quality, resulting in grain size refinement and better mechanical characteristics. MAG process utilized in ship, aerospace & marine construction. Determine the gas flow rate influence on impact strength of 5052 AL-Alloy joints size as 45x10x4 in mm. In this, 17.3 Joule impact strength obtained maximum at shielding gas flow of 7 Lt/min with constant current 235 amp.
The article presents an analysis of the Cold Metal Transfer (CMT) method, including the process, advantages and application of the method. The joints made with low energy CMT method and classic MAG ...method were also compared. The paper presents the results of non-destructive penetrant tests of welded joints made of steel in the S235JR grade. Microscopic observations were made using optical microscopy and the hardness was measured in accordance with PN-EN ISO 6507-1:2007. The test results confirmed that the CMT process allows for the production of high-quality joints and a narrow heat-affected zone compared to the classic MAG welding method, and also provides good mechanical properties and elimination of spatter.
In this paperwork is presented a study of dissimilar welding with FCAW welding process, between duplex stainless steel S31803 (1.4462) and naval carbon steel EH36 (1.0546), being analyzed all the ...considerations related to their weldability, resulted mechanical properties, microstructure and evaluation of the toughness and hardness of the weld seam and HAZ area.
Throughout the history of modernization of welding processes, in many cases the research has focused on optimizing the location of energy in the welding area, with the continuous improvement of the ...quality of welded joints. The welding processes in shielding gas environment with fusible electrode (MIG-MAG) have achieved superior performances regarding the increase of the current density around of the welded joint, simultaneously with the increase of the universality degree of their application. This paper is based on researching the possibilities of concentrating energy in the welding area, seeking to obtain both more favorable energy yields and an increased quality of welded joints. In the paper are shown a some results obtained following a comparative study on 2 welding processes in MIG-MAG protective gas medium, differentiated mainly by the metal drop transfer mode: by spraying (Spray arc), respectively by synergistic transfer (Arc pulsed), applied for corner welding of alloy steel sheets.
Workpiece vibration has been applied during arc welding to make weld metal microstructure fine and reduce weld defects such as the blow holes. It was unexpectedly found that the continuous workpiece ...vibration utilizing a sine component with a specific frequency parallel to welding direction changed the penetration shape from finger-shape to pan-bottom shape in the pulsed metal active gas welding via 18% of CO2 shielding gas. A coupled Eulerian Lagrangian finite element model was employed especially for adding workspace vibration to the fluid flow of molten materials. The velocity ofmolten materials through the designated zone of the weld pool was investigated with and without the workpiece vibration. The simulation suggests that increase in the fluid flow velocity along the welding direction at a specific frequency of workpiece vibration led to bringing the high-temperature material to the position where the final penetration shape was determined. Consequently, the penetration bottom would be widened and the middle of fusion line would be deepened, leading to penetration shape change to relatively pan-bottom shape.
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