Dual phase duplex stainless steel comprised with ferrite and austenite shows its strength and corrosion resistance in many aggressive environments based on outstanding performance over the last 20 ...years establishment is a great attention for researchers, manufacturers and end users. The current worldwide rapid growth, demand, and consumption of duplex- stainless steels, particularly in petrochemical, marine, power plant and other engineering applications, where the multiphase steels are being utilized that require welding for fabrication of components. On the other hand, largest production and applications sectors are captured by austenitic stainless steels globally, but the Ni price volatility breaching the backbone of producers and end users. In such conditions for the cost flexibility, joining of dissimilar metals also reflects the overall industrial need. Joining of duplex alloys is a challenging, due to number of embrittling precipitates and metallurgical changes. On the other hand inappropriate welding conditions, imbalance phase ratio of austenite/ferrite leads to solidification cracking, corrosion susceptibility, and lower ductility. As the demand for higher productivity is increasing worldwide in many domains like oil pipeline, shipbuilding sectors etc., where the thick sections are used, which endorses the requirement of higher heat input, optimization of interpass temperature, cooling rate, proper selection of consumables, defect free joints for fast and rapid productivity. However, many advanced techniques like plasma, laser, PCGTAW, A-TIG and hybrid welding processes are developing to fulfill the requirements for higher productivity without distortion. But high ferritization is another issue with those processes. Moreover, suitability and standardization of duplex alloys for high current and large heat input are still in doubt. Even, no comprehensive accounts of the dissimilar welding operation on the effect of processes and welding conditions are found in the literature. This review paper systematically highlights the effect of welding processes and conditions on microstructure, mechanical properties and corrosion resistance of duplex stainless steels and its various combinations on the basis of structure–property co-relationship.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The thermal shrinkage technique, which uses shrinkage strain to determine weld distortion, shows promise as a simple simulation for predicting the weld distortion of large welded structures. To date, ...there has not been adequate research on how to set input data based on welding conditions. In this work, we perform a parametric study using thermal shrinkage technique in which we vary the input data to investigate the optimum setting method. To compare angular distortion obtained by the thermal shrinkage technique, Metal active gas welding was conducted under five welding conditions and thermal elastic-plastic analysis was conducted under the same welding condition. Under all five conditions, the angular distortion obtained by the thermal shrinkage technique accurately reproduced that obtained by experiments and by thermal elastic-plastic analysis. We found that the optimum input data settings were the shrinkage strain of −0.012 and a shrinkage zone in which the maximum temperature reached 500°C or more. From the results, the similarity and the difference between the characteristics of angular distortion in the thermal shrinkage technique and that in the thermal elastic-plastic analysis was discussed based on the inherent strain and the moment. Moreover, the way in which inherent strain based on the both-ends-fixed-bar analogy occurred can explain the agreement in angular distortion in the case of the optimum input data settings. Our results demonstrate that a suitable setting method of input data has been established.
This novel research aims to examine the macro and microstructural bonding region development during magnetic pulse welding (MPW) of dissimilar additive manufactured (AM) laser powder-bed fusion ...(L-PBF) AlSi10Mg rod and AA6060-T6 wrought tube, using both optimal- and high-energy welding conditions. For that purpose, various joint characterisation methods were applied. It is demonstrated that high-quality hermetic welds are achievable with adjusted MPW process parameters. The macroscale analysis has shown that the joint interfaces are deformed to a waveform shape; the interface is starting relatively planar, with waves forming and growing in the welding direction. The observed thickening of the flyer’s wall after welding is the result of its diametral inward deformation, taking place during the process. A slight increase in microhardness was adjacent to the faying interfaces; a higher increase was measured on the AlSi10Mg material side, while a smaller one was observed on the AA6060 side. Along the wavy interfaces, resolidified “pockets” of material or occasionally discontinuous short layers exhibiting different morphologies, were detected. The jet residues are typically located towards the end of the weld, confirming a temperature rise that exceeds the melting temperature of both alloys. Far from the weld zone, extremely thin-film deposits were clearly observed on the inner flyer surfaces. The formation of isolated Si particles and thin-film deposits may point out that the local increase in temperatures leads to melting or even evaporation vaporisation of superficial layers from the colliding parts. It is worth noting that this type of jet residue was discovered for the first time in the present research. The current research work is expected to provide an understanding of weld formation mechanisms of additively manufactured parts to conventional wrought parts conforming to existing wrought/wrought weld knowledge.
Extrusion welding of AlZnMg alloys encounters great technological difficulties in practice associated with high shaping forces and the low quality of longitudinal welds. Three different chemical ...compositions of 7021 aluminum alloy, differing in terms of Zn and Mg contents, were used in the first stage of the research. The laboratory device modelling the behavior of metal in welding chambers of the porthole die was applied to examine the ability of 7021 alloys to produce high-quality joints. The weldability tests were carried out for different welding temperatures—400, 450 and 500 °C—and for a fixed welding pressure of 300 MPa. The microstructural effects in pressure-welds were evaluated with the use of OM and SEM/EDS. The temperature–pressure parameters in the welding chambers were analyzed by using the FEM method for original porthole dies while extruding tubes with dimensions of Ø50 × 2 mm. Finally, the industrial extrusion trials were performed with examination of the structure and strength of the seam welds. It was found that it is possible to produce high-quality high-strength welds in tubes extruded from AlZnMg alloys in industrial conditions (the strength of welds in the range of 96–101% of the strength of the basic non-welded material) through properly matched alloy chemical composition of the alloy, construction of the porthole dies and temperature–speed conditions of deformation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this study, linear friction welding (LFW) is used to join high carbon steel such as S55C (JIS G 4051) because it controls the maximum temperature during the joining process. The effect of LFW ...conditions on Charpy absorbed energy is studied. The thickness of a rectangular parallelepiped shape is 14 mm, the width is 20 mm, and the length is 64 mm. The applied pressure (P) controls the maximum temperature. Under high-temperature conditions, P is 100 MPa. Under middle-temperatures conditions, P is between 250 and 350 MPa. Under low-temperature conditions, P is between 400 and 450 MPa. Under all condi-tions, joints are cooled to room temperature.The microstructure and hardness of LFW joints are examined. The toughness is determined using a 300 J instrumented Charpy tester. The absorbed energy is estimated using two methods. The first method uses the potential energy difference, and the second involves calculating the area surrounded by the stroke–load relationship. With an increase in P, the microstructure changes from martensite to ferrite and microcementite. In addition, the maximum hardness at the interface decreases from 500 HV–700 HV to 400 HV. The maximum absorbed energy is confirmed at 400 MPa using the potential energy method and at P of 450 MPa using the area method. Energies absorbed before and after the maximum load are assumed to be crack initiation and propagation (Ep) energies, respectively. The maximum ener-gy is due to an increase in Ep, which is enhanced when the microstructure changes from martensite to ferrite and microcementite.
This study examines the effect of welding conditions on the applicability of X-ray stress measurement at weld metal with coarsened grains. Testing material was low carbon austenitic stainless steel ...and 15 welded specimens were prepared through tungsten inert gas (TIG) welding under various welding conditions, in which five kinds of welding currents and three kinds of welding speeds were assigned in all combinations. In the X-ray stress measurement, 2θ-sin2ψ method was applied and then the effectiveness of enlarging a diameter of collimator and applying additional planer oscillation for weld metal with coarsened grains was evaluated. Meanwhile, the effect of welding conditions on crystal grain coarsening at weld metal was examined based on welding thermal conduction theory with a moving point heat source. The results showed that the mean crystal grain size at weld metal correlated linearly with the parameter derived from the welding thermal conduction theory. Based on relation between X-ray irradiation area and the mean crystal grain size, the effect of the welding conditions on the applicability of X-ray stress measurement with or without enlarging a diameter of collimator and applying additional planer oscillation was systematically evaluated.
Friction stir welding of steel is in the early stages of development. The aim to commercialise this process creates a trade-off between welding time, cost and quality of the joint produced. ...Therefore, it becomes critical to analyse the lower quality bound of steel friction stir welds in conventional square edge butt welding configuration. Work has been undertaken to evaluate the microstructure and fatigue performance of 6mm thick DH36 steel plates friction stir welded with sub-optimal process conditions, resulting in the development of embedded and surface breaking flaws. The defective weldments were characterised to understand the nature of the flaws and a programme of mechanical testing was undertaken (including fatigue assessment) to determine the relationship between the flaw geometry, location and weld quality. A number of characteristic flaws were identified and seen to interact with the samples' fatigue fracture mechanisms. Samples with wormholes at the weld root produced the lowest fatigue performance. Fracture from incomplete fusion paths at the retreating side of the welds' top surface was seen to correspond to the highest recorded fatigue lives. The work provides an insight into the complex nature of characteristic flaws in steel friction stir welds and their interaction with fatigue behaviour.
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•Ductile failure in PM during tensile testing did not indicate inherent flaws.•Fatigue performance of FSW of DH36 was influenced by characteristic flaws.•The highest fatigue results corresponded to fracture at incomplete fusion paths.•Longitudinal fatigue tests fractured from top surface incomplete fusion paths•Tensile residual stresses reduced longitudinal fatigue lives.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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