Steel Dissimilar Joints Research Articles

Predicting the quantity and type of intermetallic phases in aluminum–steel dissimilar joints produced by zinc interlayer

Predicting the quantity and type of intermetallic phases in aluminum–steel dissimilar joints produced by zinc interlayer

Interface Characteristics and Mechanical Properties of 2024 Aluminum Alloy and 304 Stainless Steel Dissimilar Alloys FSLW Joint with Ni Interlayer

The composite structure of aluminum and steel (Al/steel) dissimilar metals has been applied in manufacturing industries for lightweight products, and friction stir lap welding (FSLW) has advantages for the welding of these two metals. To further enhance the strength of the Al/steel FSLW joint, a 0.02 mm thick nickel (Ni) foil was chosen as the interlayer, and slight plunging depth of a tool pin into the lower steel sheet was designed, which can respectively change the intermetallic compounds (IMCs) type and produce small welding heat. Choosing dissimilar 2024 aluminum alloy and 304 stainless steel materials as the research subject, the characteristics of the lap interface and the mechanical properties of the joint were mainly discussed. The results showed that the lap interface between the upper aluminum and lower steel sheets was made up of an AlNi3 IMCs layer, hook structure and mechanical occlusion. The AlNi3 IMCs layer with 2 μm thickness was in a reasonable range positive to the joint strength. When the rotating speed of the stirring tool increased from 800 to 1200 rpm and the welding speed of 75 mm/min was constant, the hook structure and the mechanical occlusion were both enhanced, and the tensile shear strength of the joint was decreased. A maximum joint tensile shear strength of 217 MPa was obtained at 800 rpm, and the strength value was 47.2 percent of that of the 2024 aluminum alloy base material. The Al/steel joint with shear fracture mode presented a brittle–ductile mixed fracture.

Mechanical Performance and Corrosion Behaviour of Diffusion-Bonded A5083 Aluminium and A36 Mild Steel with Gallium Interlayer.

This article investigated the mechanical performance and corrosion behaviour of a diffusion-bonded A5083 aluminium/A36 mild steel dissimilar joint with a Gallium (Ga) interlayer. The bonding parameters were the bonding temperature (525 and 550 °C), holding time (60 and 120 min) and surface roughness (800 and 1200 grit). Property characterisation was achieved using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Vickers microhardness tester, Izod impact tester and potentiodynamic polarisation testing. The results revealed that the significance of the bonding parameters was in the order bonding temperature > surface roughness > holding time. Increasing the bonding temperature resulted in an increase in the impact strength and a corresponding reduction in the corrosion rate and microhardness. However, increasing the grit size decreased the microhardness and a corresponding increase in the impact strength and corrosion rate. The impact strength and corrosion rate decreased with the increasing holding time while the microhardness followed a reverse trend. It was also discovered that incorporating the Ga interlayer resulted in a 67.9% improvement in the degradation rate.

Residual stress analysis, microstructural characterization, and mechanical properties of tungsten inert gas-welded P92/AISI 304L dissimilar steel joints

In the present work, the creep strength-enhanced ferritic martensitic P92 steel was welded with 304L austenitic stainless steel. The dissimilar joining of these two different grades of material was performed by using tungsten inert gas welding process. The nickel-based ERNiCr-3 welding consumable was used. The influence of post-weld heat treatment (760 °C, 2h), called as tempering, was also investigated. The secondary electron and optical image confirmed that ERNiCr-3 weld metal is accompanied by an equiaxed austenitic microstructure with Ni weight percentage of 68.29%. The energy-dispersive X-ray spectroscopy and electron probe microanalyzer results of the weld fusion zone revealed the Nb, Cr, and Ti segregation in the inter-dendritic region. The elemental mapping of the carbon-depleted zone, and the interface was performed using an electron probe microanalyzer, which revealed the diffusion of Ni, Cr, and Fe across the interface of P92 steel and ERNiCr-3 filler weld. The tensile test result indicated that part of the dissimilar weld joints (DWJs) with relatively weak ultimate tensile strength was ERNiCr-3 weld metal. The ultimate tensile strength value of the DWJs was observed as 610 MPa and 580 MPa in the as-weld and post-weld heat treatment situations, respectively. The Charpy V-notch impact energy of the ERNiCr-3 weld fusion zone was achieved as 135 ± 2 J and 140 ± 2 J in as-weld and post-weld heat treatment situations, respectively. The low impact toughness of the ERNiCr-3 weld metal was attributed to the presence of niobium carbide (NbC) and titanium carbide (TiC) particles. The peak longitudinal residual stress of 490 MPa and transverse residual stress of 442 MPa were noted in the ERNiCr-3 weld fusion zone at a depth of 3 mm from the top surface. The tempering heat treatment exhibited a significant drop in the residual stresses value for the weld fusion zone and heat affected zone (HAZ).

Characteristics of the Dissimilar AA7075 and Q235 Steel Joints Fabricated by Friction Stir Welding

In this study, dissimilar AA7075/Q235 steel joints were successfully fabricated by friction stir welding (FSW), and the grains of AA7075 in the nugget zone (NZ) were refined and mixed with the broken Q235 fragments (i.e., the steel particles, strips, and blocks). Meanwhile, intermetallic compound (IMC) layers were generated along the aluminum/steel (Al/steel) interface due to the occurrence of Al/steel diffusion. The results also revealed that the macro- and microstructures of the FSW joints varied depending on the welding heat input; under the cold FSW condition, micro-defects formed because of the weak and chaotic material flow in the NZ, reducing the welding heat input gave rise to inhomogeneous grain refinement; and the dynamic recrystallization of Al only occurred in the regions that lacked large steel blocks. In contrast, elevating the welding heat input led to the homogenization of the grain refinement and increased the thickness of the IMC layers. The FSW quality was controlled by both the thickness of the IMC layers and the size of the steel fragments simultaneously. Both the optimal-thickness IMC layers (about 2 μm) and fine steel particles were required to strengthen the joints, and a more than 30 MPa increment in the tensile strength could be obtained by manufacturing the above microstructures. Unfortunately, all the FSW joints failed in a brittle manner and the elongation was lower than 5%. Two kinds of fracture surfaces were observed inside the NZ: one was flat along the Al/steel interface, and the other was uneven due to the pulling out of the large steel strips and blocks.

Improvement of microstructure and mechanical properties for underwater wet 16Mn/304L dissimilar steel welded joints assisted by presetting butter layer

Underwater wet flux-cored arc welding (FCAW) is a simple and economic method to join dissimilar steel structures widely used in offshore applications. The available research on underwater wet welding of dissimilar steel joints is inadequate. In this paper, a butter layer was applied to eliminate the formation of hardened martensite at heat affected zone of 16Mn side and to reduce the stress concentration at the fusion boundary. The influence of ERNiCrMo-3 butter layer on the microstructure, elemental distribution, and mechanical performance of underwater wet 16Mn/304 L dissimilar steel welded joints was investigated. The grain boundary type and grain growth orientation across the fusion boundary were particularly investigated. The use of the ERNiCrMo-3 butter layer helped to eliminate the formation of hardened martensite resulting from the rapid cooling rate. Type I boundary and type II grain boundary were high angle grain boundaries, which was found at the Ni-based weld metal/ferritic steel (butter layer/ferritic steel) interfaces. The impact toughness of HAZ at 16Mn side was improved by the use of butter layer because of the absence of martensite. The butter layer was accompanied by an increase in ultimate tensile strength in the orders of ~80 MPa. The expected research results can enrich the underwater welding/repair technology of dissimilar steel structures and guide the future design of dissimilar steel welded joints.

Study on the Weldability of Copper-304L Stainless Steel Dissimilar Joint Performed by Robotic Gas Tungsten Arc Welding.

The welding process of dissimilar metals, with distinct chemical, physical, thermal, and structural properties, needs to be studied and treated with special attention. The main objectives of this research were to investigate the weldability of the dissimilar joint made between the 99.95% Cu pipe and the 304L stainless steel plate by robotic Gas Tungsten Arc Welding (GTAW), without filler metal and without preheating of materials, and to find the optimum welding regime. Based on repeated adjustments of the main process parameters—welding speed, oscillation frequency, pulse frequency, main welding current, pulse current, and decrease time of welding current at the process end—it was determined the optimum process and, further, it was possible to carry out joints free of cracks and porosity, with full penetration, proper compactness, and sealing properties, that ensure safety in operating conditions. The microstructure analysis revealed the fusion zone as a multi-element alloy with preponderant participation of Cu that has resulted from mixing the non-ferrous elements and iron. Globular Cu- or Fe-rich compounds were developed during welding, being detected by Scanning Electron Microscope (SEM). Moreover, the Energy Dispersive X-ray Analysis (EDAX) recorded the existence of a narrow double mixing zone formed at the interface between the fusion zone and the 304L stainless steel that contains about 66 wt.% Fe, 18 wt.% Cr, 8 wt.% Cu, and 4 wt.% Ni. Due to the formation of Fe-, Cr-, and Ni-rich compounds, a hardness increase up to 127 HV0.2 was noticed in the fusion zone, in comparison with the copper material, where the average measured microhardness was 82 HV0.2. The optimization of the robotic welding regime was carried out sequentially, by adjusting the parameters values, and, further, by analyzing the effects of welding on the geometry and on the appearance of the weld bead. Finally, employing the optimum welding regime—14 cm/min welding speed, 125 A main current, 100 A pulse current, 2.84 Hz oscillation frequency, and 5 Hz pulse frequency—appropriate dissimilar joints, without imperfections, were achieved.

Effects of laser-arc hybrid welding on microstructure and mechanical properties of dissimilar steel joint

Laser-arc hybrid welding can improve production efficiency, and thus, it is being used in an increasing number of industries. Herein, the effects of laser-arc hybrid welding process parameters on the microstructure and mechanical properties of welded joint of low- and medium-carbon steels were investigated. Welding seam with best quality and no defects was obtained at welding current, arc voltage, laser power, and welding speed of 260 A, 24.8 V, 3300 W, and 0.8 m/min, respectively. Moreover, the enrichment of Mn in the weld zone promoted bainite formation. Rapid cooling led to the pseudo-eutectic phenomenon in the heat-affected zone (HAZ) on both sides of the weld; therefore, when an HAZ was closer to the weld on both sides, the pearlite content was higher. For low-carbon steel, the microstructure of the HAZ comprised ferrite, pearlite, and ferrite widmanstatten. For medium-carbon steel, the microstructure of the HAZ comprised a large amount of pearlite and a small amount of ferrite. In welded joint of both types of steels, differences in microstructure and internal stress altered the nanostructure morphology and distribution characteristics of cementite. The welded joint also had considerably better tensile strength due to a large number of dislocations and better grain refinement, which led to tensile fractures in the base metal zone of low-carbon steel. For a prefabricated weld notch, the tensile fracture mode was a ductile fracture with massive dimples.

Influence of hook geometry on failure mechanism of Al6061-galvanized steel dissimilar FSW lap joint

Influence of hook geometry on failure mechanism of Al6061-galvanized steel dissimilar FSW lap joint

Assessment of Rotational Speed and Plunge Rate on Lap Shear Strength of FSSW Joints of AA7075/Mild Steel

Friction stir spot welding (FSSW) is an upgraded version of the friction stir welding process. This welding process can be used to replace permanent and temporary fastens such as bolts and nuts, screws, rivets, and welds. FSSW can be utilized to replace steel rivets in aircraft structure fabrication due to the elimination of time required to complete the joints and special tools. Moreover, the joining of dissimilar joints is very difficult due to the formation of different proportions of intermetallic compounds in the weld region. A lot of process parameters may influence the quality of the joints. This investigation analyzes the effect of speed of tool rotation and plunge rate of tensile shear fracture load of AA7075 mild steel dissimilar metal joints. From the observation, the joint fabricated with a speed of tool rotation of 1000 rpm and a plunge rate of 6 mm/min yielded a maximum shear fracture load of 9.86 kN. This weld strength enhancement may be linked to the formation of dynamic recrystallization and density distribution of strengthening precipitates.

Influence of heat input on weld integrity of weldments of two dissimilar steels

ABSTRACT The present study investigates the influence of heat input on microstructure evolution and mechanical properties of nitronic steel and super duplex stainless steel dissimilar welded joints. For this experimental purpose, carbon steel filler (ER70S–2) was employed using gas tungsten arc welding (GTAW) with two heat input conditions: lower (0.624 kJ/mm) and higher (1.01 kJ/mm). The welded joint was subjected to the microstructure of different zones, including weld metal, base metals, and heat-affected zones/interfaces were accomplished by optical microscopy, scanning electron microscope. Tensile test, Impact test, and Vickers microhardness were conducted to study the mechanical properties. Microstructural evolution in the weld metal and heat-affected zone reported the presence of Type II boundary and macrosegregation. Hardness test investigation reveals that the weld metal’s hardness rises compared to the base metals. Moreover, the weldment hardness decreases at higher heat input than lower heat input. The tensile test study reveals that the lower heat input weldment exhibits more elongation and tensile strength than the higher heat input weldment. The Charpy impact tests show that the average toughness value increases with heat input. The results also indicate that the lower and higher heat input specimen exhibited brittle fracture.

INFLUENCE OF GEOMETRY OF FUSION LINE ON DECARBONIZATION IN DISSIMILAR WELD JOINTS AFTER HEAT TREATMENT

Welded joints of dissimilar steels are widely used in various components of the steam-water circuit at thermal and nuclear power plants. In such welded joints after tempering and during high-temperature operations, carbon migrates through the fusion surface from less alloyed steel to more alloyed steel due to the difference in the chemical potential of carbon in these steels. Decarburization in the weld-adjacent area of ​​the heat affected zone of less alloyed steel, which occurs due to carbon migration, can lead to the formation of defects and subsequent failures in service. It was noticed that the thickness of the decarburized layer varies depending on the geometry of the fusion line: after heat treatment in places of convexity of the more alloyed weld in the base metal the thickness of the decarburized layer in the heat affected zone is less than in places of concavity of the weld. To numerically estimate the influence of the shape of the fusion line on the intensity of decarburization in the weld-adjacent zone, it is proposed to use a geometric factor. The aim of the work was to find such a function for use as the geometric factor, which would allow to estimate locally the variable concavity of a complex curve (in our case - the fusion line) from a point outside the curve and express it through a scalar parameter. An integral function ФL(t) is proposed, which "scans" the fusion line L from the point t in the heat affected zone; the obtained numerical value of this function for each point t can be interpreted as the order of decarburization of this point during tempering or high-temperature operation at a given geometry of the fusion line L, and can be used to construct a scalar field of the decarburization order in the heat affected zone of less alloyed steel by implementation of ФL(t) using computer vision software.

Formation of the anomalous microstructure in the weld metal of Co-based alloy/AISI 410 stainless steel dissimilar welded joint

Formation of the anomalous microstructure in the weld metal of Co-based alloy/AISI 410 stainless steel dissimilar welded joint

Effect of failure modes on ballistic performance of Gas Metal Arc welded dissimilar armour steel joints

In this study, Ultra-high Hard Armor (UHA) steel is welded with Rolled Homogenous Armor (RHA) steels using Gas Metal Arc Welding (GMAW) process with Austenitic Stainless Steel (ASS), Duplex Stainless Steel (DSS), and Low Hydrogen Ferritic (LHF) fillers. Ballistic resistance against Weld Metal (WM) is determined using 7.62 × 39 mm BALL projectile. Three new modes of failure were identified from the ballistic testing (i) Finer Wear Debris with Cleavage (FWDC) (ii) Coarser Wear Debris with Cleavage (CWDC) (iii) Cleavage failure (C), based on the fractured surface. All joints stopped the ball projectile at the weld metal region without perforation. However, the joint fabricated using ASS electrodes shows superior ballistic performance than other joints with Cleavage mode of failure (C) mainly due to the absence of wear debris. ASS weldment (5% Delta ferrite and 95% austenite) performs better in ballistic resistance because of the plastic deformation along with energy absorption properties of the austenite phase than DSS (69 Delta ferrite and 31% austenite) and LHF (100% ferrite). Migration of Chromium (Cr) from the weld metal to base metal results in an unmixed zone and martensitic band in the HAZ of ASS joint.

Influence of welding modes on decarburization in the heat-affected zone of r91 steel in welded joints of dissimilar steels after high-temperature tempering

The Paton Welding Journal, 2022, №03. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Corrosion resistance and metallurgical behaviour of CMT welded Al-LCS dissimilar butt joint exposed in simulated industrial environment

Cold Metal Transfer welding is a predominant process for joining the Aluminium and Low Carbon Steel (LCS) dissimilar joints with enhanced properties. In addition, these joints have vast application in various simulated industrial environmental conditions. However, the formation of thick intermetallic layers during welding over these joints leads to invoking the corrosion attack and causing a catastrophic failure that is the primary concern in life prediction of the joint. Hence, the corrosion behaviour of AL-LCS dissimilar butt joint exposed in the simulated industrial environment has been studied experimentally and it has been compared with the Cold Metal Transfer (CMT) welded aluminium and LCS similar joints. The potentiodynamic polarization and the electrochemical impedance spectroscopy were carried out in 3.5% aggressive sodium chloride medium with varying benzotriazole corrosion inhibitor with varying the concentrations like 10 ppm, 15 ppm and 20 ppm. The results showed that the corrosion resistance behaviour of CMT welded dissimilar joints are increased with increasing inhibitor concentration. The inhibitor showed effective performance, and the efficiency is also found to be 78–80% at 20ppm, which revealed the enhanced corrosion resistance of dissimilar metal joints in simulated industrial conditions. Finally, the dissimilar joints are characterized by sophisticated analytical techniques.

Dissimilar Dual Phase-Low Carbon Steel Joints by the GMAW Process Subjected to Impact Load

Dissimilar welding used in the automotive area are possible joints with the GMAW process; however, its structural performance must be evaluated. The focus of this work is to study the microstructural–mechanical properties of dissimilar welding DPC340Y590T dual phase–JSC270C low carbon steels. Microhardness profile, tensile, and impact tests were used to evaluate the mechanical behavior, while optical and scanning electron microscopy were employed to evaluate the microstructural changes. The tensile strength was 540 and 275 MPa in dual phase and low carbon, respectively. Weld thermal cycles were obtained by means of K type thermocouples. The welding heat input generated martensite and grain growth in the dual phase heat affect zone, while grain growth and perlite phase increased in the low carbon heat affected zone. The variation in microhardness profile was produced by the presence of different phases, and the temperature at the end of dual phase heat affect zone was approximately 242 °C. During impact tests, the absorbed energies were 19.3, 50.7, and 50.2 J for low carbon, dual phase steel, and the welded dissimilar joint respectively. Finally, dissimilar welding subjected to tensile test failed in the low carbon steel (270 MPa), out of the heat affect zone, thus a good dissimilar joint between both steels was obtained.

Influence of Heat Input on Cold Metal Transfer Welded Joints

ABSTRACT During welding, the heat input is a critical parameter in determining the quality of the joints welded by any welding process. In the case of dissimilar welding, as dissimilar metals have significant differences in melting point, it is challenging to achieve an adequate joint. The emerging cold metal transfer welding process can resolve it effectively by controlling the heat while joining dissimilar metals. Therefore, in this research work, Aluminum-galvanized steel dissimilar joints were fabricated using varying heat inputs and their mechanical, metallurgical, and corrosion properties were evaluated. Furthermore, the second-phase formation at the weld interface has been investigated, and corrosion behavior is analyzed using electrochemical techniques in a 0.1% sodium chloride environment. The Tafel polarization and electrochemical impedance spectroscopy studies reveal it improved corrosion resistance due to an increase in heat input. The reduced solidification defects and the establishment of an appropriate intermetallic layer thickness with a suitable microstructure at the interface are the reasons for the improved corrosion resistance and strength of the dissimilar joints.

Numerical Simulation and Experimental Verification of Residual Stress in the Welded Joints of Weldolet-Branch Pipe Dissimilar Steels.

It is well known that welding dissimilar metals can play the advantages and characteristics of those different metals, but it is easy to encounter some problems. In this paper, the thermomechanical behavior of the weldolet–branch dissimilar steel joints in different welding cases is analyzed by establishing a three-dimensional finite element model, and the predicted thermal cycling and residual stresses are verified using experimental tools. The results show that the high temperature area and the heat affected zone on the side of the branch pipe are larger, and there is a large stress gradient at the fusion line on both sides of the weld. Too high or too low temperature between welding layers will cause large residual stress, thus, 200 °C is more suitable for the welding of weldolet–branch joints. The residual stresses of path-1, path-2 and path-3 have similar distributions at 0° and 180° sections, and the circumferential and axial residual stresses on the inner surface are larger than those on the outer surface. The residual stress on the inner and outer surfaces of path-3 is smaller than that of path-1 and path-2 at the 90° and 270° sections as a whole, and the residual stress at the 90° section reaches the minimum.

Investigation of weld defects, microstructural, and mechanical features of TWIP and austenitic stainless steel dissimilar joints by pulsed GTAW process

Investigation of weld defects, microstructural, and mechanical features of TWIP and austenitic stainless steel dissimilar joints by pulsed GTAW process