Abstract:The process of laser welding of sheets of HSLA (high-strength low-alloy steel), DP600 (dual-phase steel) and TRIP steels was investigated. A weld was successfully made in a double-sided hot-dip galvanized sheet with a thickness of 0.78–0.81 mm using a laser power of 2 kW per pass without any pretreatment of the weld zone. Microstructure studies revealed the presence of martensitic and ferritic phases in the weld zone, which could be associated with a high rate of its cooling. This made it possible to obtain go… Show more
“…The reason for this increase is that the solidification rate of the zone in contact with COL was faster during overhead welding, resulting in finer grains and hence higher hardness. The relevant literature shows that the greater the solidification rate, the higher the hardness [21,22]. Figure 4 Hardness distribution of weld cross-section (a)NOL-140A, (b) CEL-140A, (c) COL-140A, (d) COL-150A, (e) COL-160A, (f) COL-170A.…”
During overhead welding, gravity inevitably drives the molten pool downward, resulting in poor adaptability and concave defect. To address this issue, this paper proposed a novel laser-MAG hybrid overhead welding technique utilising a copper liner (COL). Compared to single-arc welding, laser-MAG hybrid welding can reduce the volume of the molten pool, while the laser increases its support force. The COL can accelerate the molten pool's solidification rate. Additionally, the adhesion force between the molten pool and the COL can partially counterbalance gravity. As a result, good weld formation still was achieved even when the misalignment was 0-1 mm and the butt gap was 0-2 mm. Moreover, the back reinforcement height and width were not less than 0.71 and 3.66 mm, respectively.
“…The reason for this increase is that the solidification rate of the zone in contact with COL was faster during overhead welding, resulting in finer grains and hence higher hardness. The relevant literature shows that the greater the solidification rate, the higher the hardness [21,22]. Figure 4 Hardness distribution of weld cross-section (a)NOL-140A, (b) CEL-140A, (c) COL-140A, (d) COL-150A, (e) COL-160A, (f) COL-170A.…”
During overhead welding, gravity inevitably drives the molten pool downward, resulting in poor adaptability and concave defect. To address this issue, this paper proposed a novel laser-MAG hybrid overhead welding technique utilising a copper liner (COL). Compared to single-arc welding, laser-MAG hybrid welding can reduce the volume of the molten pool, while the laser increases its support force. The COL can accelerate the molten pool's solidification rate. Additionally, the adhesion force between the molten pool and the COL can partially counterbalance gravity. As a result, good weld formation still was achieved even when the misalignment was 0-1 mm and the butt gap was 0-2 mm. Moreover, the back reinforcement height and width were not less than 0.71 and 3.66 mm, respectively.
“…Due to the small grain size in weld zone, an improved and higher micro hardness can be obtained. Due to recrystallization and grain growth, a coarser grain size is found at HAZ, but in spite of that, measured hardness is higher than in the base zone for some weld samples as a result of the carbide precipitates by the side of grain boundaries of the HAZ zone as well as of the weld zone [ 32 ].…”
This paper investigates an experimental design of laser butt welding of S32520 duplex stainless steel, which has been passed out with the help of a pulsed Nd: YAG laser supply. The intention of the present research is to learn the impact of beam diameter, welding speed, and laser power on the superiority of the butt weld. The individuality of butt joints has been characterized in terms of tensile properties, fractography, and hardness. It was noticed that unbalanced particle orientations indirectly produce a comparatively fragile quality in the laser welded joint. The outcome of varying process parameters and interaction effect of process parameters on ultimate tensile strength and micro hardness were studied through analysis of experimental data. With different process parameters, the heat energy delivered to the material was changed, which was reflected in tensile strength measurement for different welded samples. From this present research, it was shown that, up to a certain level, an increase in process parameters amplified the tensile strength, but after that, certain level tensile strength decreased with the increase in process parameters. When process parameters exceeded that certain level, the required amount of heat energy was not delivered to the material, resulting in low bead width and less penetration, thus producing less strength in the welded joint. Less strength leads to more ductile weld joints. Microhardness was higher in the weld zone than in the base region of welded samples. However, the heat affected zone had a high microhardness range.
“…During static tensile testing of the welded joints, the strength of the weaker region of the welded joints was determined [34]. Ultimate strength was calculated based on a deformation diagram of the procedure envisaged in the ISO 6892-1:2016 standard [35].…”
Section: Influence Of the Conditions Of The Technology And Process Of...mentioning
The objective of this study is to investigate the formation of the structure and stress–strain state in the joints of AISI 304 stainless steel with a thickness of 2 mm and produced by welding with laser and plasma energy sources. It is established that the microhardness and parameters of the grain and subgrain structures of the welded joint material differ with respect to the dimensions of crystallites, grains, and subgrains according to the welding process. It is shown that, in terms of structure formation, including substructural features, the most favorable structures of 2 mm AISI 304 welded joints are formed by laser–plasma welding. It is predicted that the residual stressed state is less localized with the application of laser–plasma welding than laser welding, and it is characterized by a lower level of residual stresses compared to plasma welding. In all the cases, the maximal stress values are concentrated in the HAZ, and the value obtained using laser–plasma welding is in an intermediate position (431.7 MPa) between those of the laser (443 MPa) and plasma (413.7 MPa) processes. With laser–plasma and laser welding, displacements (deformations) are minimal and close to 0.2 mm. The method of electron speckle interferometry was used, and the results reveal that the error between the calculated and experimental values of equivalent stresses is no more than 6%, which is acceptable. The results of mechanical testing show that, under uniaxial tension, the strength of the welded joints made of AISI 304 steel using laser–plasma and laser welding is the highest and equal to 97% of that of the base metal.
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