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In this research, fillet welding was conducted on 8-mm thick Miilux OY Protection 600 (MIL-A-46100) armor steel using AWS A5.9 GeKa ER307 austenitic filler wire. The welding process involved robotic MIG/MAG with five different heat inputs ranging from 0.3 to 1.2 kJ/mm. The study focused on examining the influence of heat input on the microstructure, elemental changes, microhardness, and dimensions of the weld metal and the heat-affected zone (HAZ). These investigations were conducted to determine the welding parameters that they satisfy the quality requirements of the MIL-STD-1185 standard for this steel grade and weld consumable. Through analysis of macrostructure, microstructure, and microhardness, it was observed that increasing the heat input led to a decrease in hardness for both the weld metal and the HAZ, while expanding the HAZ width. The weld metal exhibited a homogenous hardness distribution at lower and higher heat inputs, but hardness increased from the root to the face for both heat inputs of 0.5 and 0.7 kJ/mm welds. Notably, a significant decrease in hardness occurred in the transition of partial transformation region (intercritical HAZ) and tempering region (subcritical HAZ) for heat inputs above 0.7 kJ/mm, indicating softening. Moreover, the width of the subcritical heat-affected zone substantially increased. Evaluation of the distance required to reach base metal hardness from the welding toe revealed that a heat input of 1.2 kJ/mm exceeded the maximum requirement of 15.9 mm according to the MIL-STD-1185 standard. However, the requirements of the military standard were satisfied for other heat input values. These findings were associated with microstructural changes in grain size, martensite, bainite, martensite/austenite morphology and their fractions, as well as delta ferrite morphology. The results successfully demonstrated that robotic GMAW welding can be applied using lower strength (undermatched) filler metal to satisfy the requirements of the respective standard of MIL-STD-1185. [ABSTRACT FROM AUTHOR]

In order to obtain results from simulations that are close to reality, it is necessary to correctly set the parameters of the welding process. One of them is the efficiency of the welding process. Currently, new modifications of MIG/MAG methods are being created, which are characterized by lower heat introduced into the material (smaller efficiency coefficient). The efficiency coefficient determined by the European standard EN 1011–1 is no longer accurate enough for simulations. Therefore, it is necessary to accurately determine the efficiency coefficient of the method even for the mentioned modified welding processes. An experiment of calorimetric measurement of the efficiency of the CMT process (cold metal transfer—modification of the MIG/MAG method) was proposed. The specific heat capacity of the base material was accurately measured. Furthermore, a calorimetric measurement of the efficiency of the welding process was carried out on a flat sample (bead-on-plate method) and on a sample with a V-groove to simulate the treatment of welding surfaces. Accurate method efficiency values were determined for different welding current settings and different V-groove depths. The geometric characteristics of the fusion faces in butt welds have a greater influence on the efficiency coefficient than the size of the welding current. [ABSTRACT FROM AUTHOR]

This study investigates the effect of welding parameters on the microstructural evolution and mechanical properties, such as tensile strength and hardness, in mild steel plates welded using gas metal arc welding (GMAW). The welding parameters examined include welding current, arc voltage, and gas flow rate, with ER K-71 T filler wire as the consumable material. Results indicate that a higher welding current and reduced gas flow rate result in a maximum tensile strength of approximately 533 MPa. However, discrepancies were noted in the microhardness data across different zones, with the heat-affected zone (HAZ) exhibiting a hardness of 115.8 HV, while the weld zone and base metal showed values of 76.7 HV and 112.9 HV, respectively. Microstructural analysis revealed the presence of bainite and ferrite with a tempered martensitic structure in the welded area, demonstrating that the combination of welding parameters plays a critical role in controlling phase transformations and mechanical behavior. It is essential to reconcile the observed hardness values with the conclusions drawn to ensure accurate interpretation of the data. Highlights: The study investigates how different welding process parameters, including current, voltage, and gas flow, affect the internal structure and mechanical characteristics of weld metal. It was found that the highest tensile strength is achieved with a combination of high welding current and low gas flow rate. The welded joint shows greater hardness in the heat-affected zone compared to the original metal, with the fusion zone being less hard. Analysis of the weld area reveals the presence of bainite, ferrite, and tempered martensite, which are responsible for the mechanical properties observed. [ABSTRACT FROM AUTHOR]

In automotive industries, pulsed laser welding has been gaining importance for joining of thin sheet materials for various reasons, e.g., no use of any filler material, precise control over heat input, penetration depth, molten pool shape and short welding cycle. However, improper choice of heat input can lead to the development of weld defects. Hence, the current study is aimed to comprehend the influence of heat input (32.5, 56.25, 72.22 and 92.22 J/mm) on the weld thermal cycle, microstructural evolution and tensile deformation behavior of Nd:YAG pulsed laser-welded dual-phase (DP 780) steel joints in butt configuration. The effect of pulsation on the weld thermal cycles and the corresponding microstructural changes has been studied. It is estimated that the temperatures in the fusion zone (FZ) ranges from 1759 to 1891 K for 32.5 J/mm heat input and 1964 to 2116 K for 72.22 J/mm heat input welds. Depending on heat input microstructures in the FZ containing martensite, bainite and ferrite are changed due to change in the peak temperatures and the cooling rates. Due to softening of FZ and heat-affected zone by tempering of martensite and because of ferrite grain coarsening the yield strength, tensile strength and uniform elongation decreased with an increase of heat input. All welded joints failed in the softened heat-affected zone, and it was found that the amount and distribution of tempered martensite altered the void nucleation mechanism during the tensile deformation. [ABSTRACT FROM AUTHOR]

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Repair welding technology is widely used in the manufacturing and maintenance of rail transit equipment to repair welding defects. However, repair welding induces modifications in joint performance, and it is necessary to study the microstructure evolution behavior to reveal the reasons. In this study, the effects of multiple repair welding on the microstructure, mechanical, and fatigue properties of 06Cr19Ni10 stainless steel samples were studied. The surface texture and fracture morphology analyses of the samples were conducted by optical microscopy (OM), scanning electron microscopy (SEM), and its equipped backscattered electron diffraction (EBSD) technique. The mechanical and fatigue properties of the samples with different repair welding times were further obtained by hardness, tensile, and fatigue tests. The results show an increase in the grain size and the substructure content in the heat-affected zone (HAZ), and the austenite orientation is changed, attributable to multiple repair welding. Multiple heat inputs result in a significant increase in hardness from 165 HV to 185 HV, a noticeable decrease in tensile strength and elongation, and an upward trend in yield strength. Under the constant stress level, the heat input of multiple repair welding causes a decrease in the fatigue life and significantly reduces toughness in the instantaneous fracture zone of the secondary repair sample. [ABSTRACT FROM AUTHOR]

The paper studies the heat treatment effect on the structure and mechanical properties of gas metal arc-welded heat-resistant steel walls obtained by coldArc welding. The specimens are tempered at 600 and 900 °C. It is found that 900 °C tempering leads to a complete recrystallization of the structure, higher ductility, and lower strength. High-temperature tests are carried out at 550 °C. [ABSTRACT FROM AUTHOR]

Analysis of publications has shown that the use of the exothermic addition with a combined oxidizer (xCuO + (x-1)Fe2O3-Al) as components of filler materials will reduce energy consumption and increase the efficiency of the welding/hardfacing process. However, in the literature, there are no studies of exothermic addition with combined oxidizers, which allow to vary the chemical composition of the deposited metal within a wide range. In this paper, the use of exothermic addition with combined oxidizer (xCuO + (x-1)Fe2O3-Al) was considered. To study the characteristics, standard methods were used to determine the arc stability, melting characteristics, weld bead morphology, melting-energy characteristics, and efficiency parameters, and mechanical properties were made. The structural characteristics were analyzed by optical microscope (OM), X-ray diffractometer (XRD). Microhardness values of the hardfaced samples were obtained using a Vickers hardness tester. The greater stability of arc voltage was shown by the processes performed with flux-cored wires in which oxidizing agents of exothermic addition Al-CuO-Fe2O3 in the core filler were taken with an equal content of oxidizing agents or with a slight excess of oxidizing agent CuO/(CuO + Fe2O3) = 0.5–0.6, whereas the greater stability of the welding current was shown by the processes carried out with the use of flux-cored wire with the exothermic addition with an equal or greater proportion of Fe2O3 oxidizer in the combined oxidizer CuO/(CuO + Fe2O3) ≤ 0.5. Further studies of melting characteristics (deposition rate, spattering factor, etc.), melting-energy characteristics (melt-off coefficient CM and deposition rate coefficient Cd), and efficiency showed the efficiency of using exothermic addition with combined oxidizer of Al-CuO-Fe2O3 system. The study showed high arc stability of the hardfacing process, an increase in deposition efficiency (De), and a decrease in spattering loss, which increased deposition rate from 4.73 kg·h−1 to 6.42 kg·h−1 compared to exothermic addition with simple Al-Fe2O3 system. Analysis of weld bead morphology showed improvement in weld bead parameters. The results showed high energy efficiency and productivity of the welding/hardfacing process with the introduction of exothermic addition with combined oxidizer of CuO-Fe2O3-Al system at the following share of copper oxide in combined oxidizer CuO/(CuO + Fe2O3) = 0.5–0.6. [ABSTRACT FROM AUTHOR]

This study investigates the impact of heat input, generated during friction stir welding, on the microstructure, mechanical properties, and corrosion resistance of dissimilar joints between A390-10 wt.% SiC composite and AA2024-T6 aluminum alloy. Welds were created using two rotational speeds: 600 rpm and 1600 rpm, while maintaining a constant traverse speed of 60 mm/min and employing a triangular pin tool. The results reveal that increasing the heat input from 125 to 354 J/mm leads to enhanced mixing in the stir zone, resulting in the formation of a layered structure. The stir zone area increases by 23% with the rise in heat input from 125 to 354 J/mm. Moreover, as the heat input and plastic strain in the stir zone increase, the particle size decreases by 31%, and their distribution becomes more uniform. Furthermore, an increase in heat input leads to the formation of coarser precipitates and particles on both the advancing and retreating sides, regardless of the type of precipitates formed. Conversely, reducing the heat input from 354 to 125 J/mm results in achieving maximum hardness (165.3 ± 2.3 HV0.1), yield strength (410.3 ± 11.3 MPa), ultimate tensile strength (514.5 ± 10.4 MPa), and minimum corrosion rate (0.41 mm/year). [ABSTRACT FROM AUTHOR]

ER2209 type welding consumable was used for welding overlay deposit on 2205 duplex stainless steel plate through gas metal arc welding (GMAW) at different heat inputs. The research focused on analyzing the effect of arc energy on the microstructure of the welded joint, as well as evaluating the corrosion behavior of the weld metal in a 3.5 wt% NaCl solution. The results show that the arc energy has a visible effect on the content of ferrite (δ) and austenite (γ) phases, which distinctly affects the corrosion resistance of the weld metal. It was found that the grain boundary austenite, Widmanstätten austenite, and intergranular austenite were present in all the weld metals, and the weld metal formed with a heat input of 2.206 kJ/mm had a high corrosion performance due to the high austenite content and the presence of a large content of intergranular austenite phases. [ABSTRACT FROM AUTHOR]

The Tungsten Inert Gas-Metal Inert Gas (TIG-MIG) hybrid process has the combined advantages of standalone TIG and MIG welding processes. This study investigates the thermal distribution of the TIG-MIG hybrid welding process compared to the standalone TIG and MIG welding processes. The welds' mechanical properties, microstructural evolution, and phase formation are also discussed. The process parameters for the TIG-MIG, TIG and MIG welding processes used in this study were obtained from prior parametric optimisation for each welding process performed by the Taguchi method with an L-9 orthogonal matrix. The thermal behaviour of TIG, MIG and TIG-MIG welds were investigated by adopting the Gaussian heat source model on the ANSYS workbench. The simulated temperature distributions of the three weld types were validated by the mechanical, microstructural, and phase formation characteristics as obtained experimentally. Similar temperature profiles were observed for all weld types having peak temperatures at the weld seams. The simulated temperature distributions were in good correlation with the experimentally obtained the hardness results, microstructural evolution and phase formation, as revealed from the X-ray diffraction analysis. Hence, the Gaussian heat source model can accurately simulate the properties of a complex heat source interaction, allowing for process optimisation and forecasting. [ABSTRACT FROM AUTHOR]

To reveal the influence mechanism of linear heat input (LHI) on the mechanical properties and corrosion behaviors of SUS304 weldments manufactured by local dry underwater pulsed metal inert-gas welding (LDU-PMIG), phase structure, grain structure, grain preferred orientation, and grain type of weld metal (WM) were investigated in this paper. With LHI increasing, ferrite phase morphology transformed from lath to skeleton, and grain size was enlarged. The content of equiaxed grains was increased, and that of columnar grains was reduced remarkably. The mechanical performance ascended first and then reduced with the increase of LHI. The increase of equiaxed grain content and the diversification of grain preferred orientation were beneficial to the improvement of mechanical performance, then, grain coarsening led to mechanical performance decreasing. Besides, the corrosion potential, corrosion current and pitting potential of WM were detected through electrochemical corrosion tests. The results illustrated that the corrosion resistance of WM was lower than that of base metal (BM), and the corrosion rate was enlarged with LHI enhancing, which meant the corrosion resistance declining. The corrosion resistance was mainly determined by Cr precipitates, ferrite phase and grain size. The microhardness, tensile strength, and elongation reached their maxima in the LHI of 336.7 J/mm. The greatest corrosion resistance of WM was obtained in the LHI of 256.2 J/mm and reached 69.9% of BM. This study is meaningful to promote the further development and application of LDU-PMIG in marine underwater welding field. [ABSTRACT FROM AUTHOR]

Using the example of a welded wire connection made of an alloy Ti–Ni (Ti–55.42% Ni)—nitinol, the shape memory effect is considered. In particular, with the help of nonconsumable electrode welding technology, welded joints of wire with a diameter of 2 mm were produced, the macro- and microstructure of the joints were studied, bending tests were carried out, and the shape memory effect of the obtained welded joints was evaluated. [ABSTRACT FROM AUTHOR]

The present study compares two additive manufacturing methods, wire arc and electron beam ones, by analyzing the structural and mechanical characteristics of 3D printed Ti–Al–Zr–Mo–V alloy components. The macrostructure of the studied Ti–Al–Zr–Mo–V components is represented by columnar primary β grains of the Widmanstatten pattern with lamellar alpha colonies of different sizes and orientation. During the electron beam additive manufacturing (EBAM) process, the concentration of the α-stabilizing Al decreases from 3.81 ± 0.59 to 2.72 ± 0.53 wt.%. However, during the wire arc additive manufacturing (WAAM) process, the Al concentration is kept within the error range. The components printed by the EBAM method show anisotropy of mechanical properties. The ultimate strength is 757–767 MPa for the EBAM-fabricated components and 887– 896 MPa for the WAAM-fabricated components. [ABSTRACT FROM AUTHOR]

Rapidly solidified thin-strip (TS) continuous cast AA5182 Al-Mg alloy was welded for the first time by the friction stir welding (FSW) technique. The response of solute supersaturation that formed during TS casting to thermomechanical processing during FSW was investigated. The analysis demonstrated that the re-precipitation of the intergranular β-Al3Mg2 was strongly affected by weld heat input. Similarly, the microstructural evolution associated with FSW significantly impacted mechanical behavior. It was observed that heat generation results in the formation of a high volume of β-Al3Mg2 intermetallic particles and tunneling defects at the advancing side of the stir zones, as well as grain coarsening. Mitigation of solute supersaturation in the stir zone, linked to excess β-phase evolution and consequently solute depletion in the aluminum matrix, was manifested as the simultaneous work-hardening and ductility decline as well as in the stress drop of inhomogeneous plastic flow observed in the tensile specimens. [ABSTRACT FROM AUTHOR]

In resistance spot welding (RSW), initial resistance between electrodes (RBE) determines heat input (according to Joule's law) and greatly affects the quality of joints. In turn, RBE values are characterized by substantial uncertainty and vary during the RSW processes. To reduce their dispersions, preliminary low-current pulses are applied. In some cases, the quality of the formed RSW joints are controlled using dynamic resistances obtained by feedback from advanced power sources. In these studies, the effect of four preheating current diagrams on the stabilization of the RBE values was investigated for a wide range of parts made of copper, brass, bronze, austenitic stainless steel, as well as aluminum, titanium and zirconium alloys with thicknesses from 0.2 to 1.0 mm in various combinations. Also, the RSW process control capabilities were assessed using feedback from an up-to-date digital synthesizer of unipolar current pulses. As a result, the RBE values were stabilized in all studied cases. Ranges of the variations between the maximum and minimum RBE values decreased from about 5–11 down to 2–5 times. However, the applied algorithms of the preheating current pulses had no effect on the RBE dispersions. It was found that dynamic electrical processes in a welding gun cause distortion of actual RBE curves, which makes it difficult to control heat input and, respectively, the formation of weld nuggets. [ABSTRACT FROM AUTHOR]

This research focuses on the effect of heat input of super duplex stainless steel (sDSS 2507) and nitronic steel (N50) dissimilar welded joints. Two heat input combinations selected as lower heat input (LHI) (0.62 kJ/mm) and higher heat input (HHI) (1.01 kJ/mm) were preferred during the operation of the gas tungsten arc welding process (GTAW) process using ER2594 filler. The macrosegregation like an island, peninsulas are observed in both weldments' HAZ and weld zone. The presence of secondary austenites (γ2) precipitation is observed in HAZ and root region of weldments. As heat input increases, the ferrite content of the weld zone in HHI decreases. Nevertheless, HHI had an advantageous effect on austenite nucleation in the HAZ. To ascertain the mechanical characteristics of the dissimilar metal welds (DMWs), tests such as the Vickers micro-hardness test, Charpy impact test, and tensile test were conducted. The mechanical evaluation reveals that the average hardness of LHI shows more hardness of 280 ± 4 Hv0.5 than HHI weldment of 270 ± 3 Hv0.5. Hence, weld zone, HAZ, and interface hardness do not indicate any significant change with the increment in heat input, which can be credited to the phase balance of ferrite/austenite. The tensile strength of LHI and HHI weldment is 895 ± 4 MPa and 900 ± 5 MPa, respectively, but LHI weldment displays better ductility. The Charpy impact test reveals that the impact toughness value decreases with increased heat input (i.e., 165 ± 5 J and 145 ± 3 J for LHI and HHI weldment, respectively) because of the secondary phase formation and increased grain size. However, the weld metal's Charpy impact toughness was more than the ASME standard value (> 41 J) and the EN 1599:1997 standard value (> 47 J). The microstructural observation and mechanical characterization suggest that lower heat input could be beneficial for weld's structural integrity. [ABSTRACT FROM AUTHOR]

The amount of heat input during surfacing affects the structure and properties of a product. Features of the crystallizing structure depend on the structure of the already deposited layers. The process of structural changes during the interaction of a melt drop with the basis of three grains has been traced by modeling using the molecular dynamics method. The grain parameters in the model are set from the experimental characteristics of the sample obtained by electron-beam surfacing of aluminum bronze. Increasing the temperature of the melt drop improves its spreading and increases the melting depth. The grain growth during crystallization inherits the grain orientation of the basis. During crystallization, stacking faults and twins are formed, oriented similarly to defects in the basis. The grain boundaries change orientation in the direction of the maximum temperature gradient. [ABSTRACT FROM AUTHOR]

The main technologies of semi-automatic gas-shielded root of pipelines that are capable of controlling the transfer of a droplet of molten electrode metal by changing the waveform of the welding current are considered. The process of semi-automatic gas-shielded welding with regulated metal deposition (RMD) is described in detail. The process is used for running root welds of joints of pipelines made of P91 steel and corrosion-resistant austenitic steel without the need to install special internal purge dams to prevent the oxidation of the weld back. The weld back is protected with the gas leaving the welding gun using the Venturi action. [ABSTRACT FROM AUTHOR]

Laser cladding technology is usually employed to produce high-entropy alloy coatings. However, the thickness of coatings is normally up to a millimeter scale, which increased the consumption of laser energy and materials. In this work, a micron-scale coating of CrMnFeCoNi high-entropy alloy on Al alloy by using low-power laser cladding was proposed. The influences of heat input on the geometric parameters and element distribution of coating were studied in detail. The results showed that the effects of heat input on the depth, width and dilution ratio of coating were obvious. The greater the heat input, the greater the uniformity in the element distribution of coating. When the heat input of 2 J/mm was used, the element distribution in the coating was uniform. The above results feasibility confirmed low-power laser cladding of micron-scale coating of high-entropy alloy on aluminum alloy. [ABSTRACT FROM AUTHOR]

In recent decades, laser beam welding of high strength low alloy steel has replaced some other assembly processes used in the automotive, machinery, and agricultural equipment sectors. In this research, the effect of heat input on the microstructure and mechanical properties of the butt joint of high strength low alloy steel S500MC, which had been strengthened by thermomechanically controlled processing, was investigated. The joining process was performed in an autogenous mode at two different heat inputs (140 and 240 J/mm) using the laser beam welding process with a fiber source. Microstructural observations with an optical microscope and scanning electron microscope indicate that the microstructure of the fusion zone consists of acicular ferrite and scattered martensite packets. An increase in heat input reduced the contribution of martensite packets in the fusion zone. The presence of carbides in the coarse-grained heat affected zone created a fine martensitic packet moreover the packet size has increased with the higher heat input and the dissolution of carbides. In addition to the microstructural changes, the grain size in the weld zone and heat affected zone becomes larger than those observed in the base metal consequently, the properties resulting from the controlled thermomechanical treatment have been lost in both zone. This autogenous welding process produced a decrease in hardness in the fusion zone but an increase in local strength in the heat affected zone compared to the unaffected base metal. The tensile test confirmed that the fracture occurred within the mechanically weaker fusion zone. But at a high input of 240 J/mm due to the decrease volume fraction of martensite and coarse grain size, the strength of the fusion zone reaches 581 MPa, which shows a decrease of about 10% compared to the 140 J/mm heat input. [ABSTRACT FROM AUTHOR]

The impact of heat input and scanning strategy during the printing of CuAl9Mn2 bronze by wire-arc additive technology on the structure, geometric parameters, and properties of the resulting products is examined. It is demonstrated that a higher rate of layer deposition results in enhanced mechanical properties of the material and smaller wall width and layer height. This enables the geometric parameters of the formed samples to be adjusted during printing. The deposition strategy also has a significant impact on the geometry of the products with round or rectangular cross-sections. [ABSTRACT FROM AUTHOR]

The demand for additive manufacturing of large-scale complex parts is challenging to obtain high productivity with excellent properties. Wire arc additive manufacturing is one of the best suitable processes using MIG welding to build large-scale parts efficiently. In this study, Inconel 718 was used for deposits by wire arc additive manufacturing. The objective of the present study is to investigate the effect of heat input on microstructural growth in different regions such as bottom, middle and top of the additively manufactured deposits. The penetration is one of the significant distresses to alter the formation of microstructure and resolution. Penetration is directly proportional to heat input, and shallow and consistent penetrations are recommended for additive manufacturing deposits. The accumulation of heat in the deposited parts leads to heat conduction in the building direction and promotes microstructural growth in that direction. In order to identify the heat conduction in wire arc, additive manufacturing and its effect on grain growth were analyzed by numerical analysis of the weld pool, thermal history, solidification rate (R), and temperature gradient (G). The experiment results revealed the development of equiaxed grains for the low heat input and columnar grains for the high heat input deposits. The microstructural growth is faster with the columnar structure of the anisotropic property, as observed in the high heat input deposits. The simulation results confirmed that a low heat input lead to a higher solidification rate resulting in equiaxed grains than the high heat input deposits. [ABSTRACT FROM AUTHOR]

Maraging steels possess ultrahigh strength and excellent fracture toughness which makes it suitable for rocket motor casing and other applications. Though it has good weldability and effectively welded by conventional or cold wire Gas Tungsten Arc Welding (CW-GTAW), defects like entrapped slag, lack of fusion, porosity, etc., are encountered. The weld pool is also sluggish and does not flow freely as with carbon steel or stainless steels and has limitation of low speed and hence lower deposition rates. The hot wire GTAW (HW-GTAW) process is ideally suited for increasing the weld fluidity which helps the slag to afloat easily. It also provides the benefit of elimination of porosity from the weld deposit along with increased weld speed and deposition. In present work, HW-GTAW process was used to weld 8 mm thick maraging steel to reduce slag formation and other types of defects. Welding was done with higher welding speed and higher wire feed rate resulting in higher deposition. Bead on trials with HW-GTAW were conducted to establish the relation between travel speed, wire feed rate and hot wire current. Transverse tensile properties and fracture toughness of weldments were evaluated. Macro and microstructure analysis of weldment was carried out to analyse the various zones. Microhardness across the weld was measured. UTS of 1720–1749 MPa, 0.2% PS of 1687–1713 MPa and FT upto 89 MPa√m was achieved with joint efficiency between 93 and 90% on tensile and fracture toughness, respectively, using HW-GTAW process. Microstructure of weld fusion zone showed dendritic structure having martensite with narrow dark HAZ containing reverted austenite. Reduction in heat input, minimal defects and improved productivity was achieved by using HW-GTAW process. [ABSTRACT FROM AUTHOR]

The extreme heat input in the submerged arc welding (SAW) process can result in significant heat affected zone. This can be controlled by limiting the heat input, say by using a shielding plate. The superior properties of Monel 400 have wide range of applications where corrosion is a concern. In this work, mild steel plates are welded with Monel 400 introduced as an intermediate between the arc and the base plates. This intermediate plate is intended to shield and control the extreme heat input. Also, low thermal diffusivity of this shielding material can promote additional annealing effect which can improve the microstructure and possibly induce ductility in the weld. Infrared imaging-based machine vision system along with image segmentation algorithms is employed to estimate the temperature of the welds. To further support the compatibility and success of this concept, detailed microstructural and chemical composition studies, and some mechanical testing such as residual stress and hardness tests, of different zones of the welds are carried out and compared. Encouraging results have been obtained and successful use of Monel as shield metal to constrict heat transfer has been validated. [ABSTRACT FROM AUTHOR]

The effects of welding heat inputs and reheating processes with various cooling rates were investigated by thermally simulated experiments on the microstructure, tensile strength and impact toughness of high-strength weld metals containing 4% Ni. The microstructure was characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). As a result, an extended continuous cooling transformation (e-CCT) diagram was established. The change in the microstructures is affected from three perspectives. The coarser grains and the generated martensite-austenite (M-A) constituents lead to the deterioration of impact toughness and ultimate tensile strength with the increase in heat inputs. The reheating processes with various cooling rates can change the microstructure, hardness, impact toughness and large angle boundaries. When the heat input increases from 15.8 to 17.9 kJ/cm, the content of block ferrite decreases from the initial 18.9 to 8.5%, and the content of lath bainite increases accordingly. When the heat input is 20.6 kJ/cm, the content of block ferrite increases is 17.3% and the rest is lath bainite. The hardness first decreases in the lower cooling rate range (0.05~1 °C/s) and then increases at higher cooling rates. The minimum hardness at a cooling rate of 1 °C/s may be related to the decrease in the coarse block M-A constituents. The reheating process decreases the impact toughness at room temperature from 83 to 37.45 J for the specimen with a cooling rate of 30 °C/s and increases the impact toughness from 83 to 99.71 J for the specimen with a cooling rate of 0.5 °C/s. The impact toughness at −50 °C after the reheating processes decreases from 74 to 32 J, and the lowest impact toughness after the reheating processes reaches only 32 J. The proportion of high-angle grain boundaries (HAGBs) first increases from 12.13 to 26. 44% and then decreases to 16.34% with increasing cooling rate. [ABSTRACT FROM AUTHOR]

The Wire Arc Additive Manufacturing (WAAM) is a technique for 3D printing of metallic pieces. Aluminum alloys are particularly studied due to their good mechanical properties and low weight. In this investigation, structured layer walls were fabricated by reproducing a WAAM process with a GMAW welding equipment adapted to a robotic arm for welding processes. AlMg5Cr alloy was used as a filler metal to deposit layers on the surface of an Aluminum 6061-T6 plate in metal transfer pulsed mode. After the WAAM process, the presence β-Al3Mg2Si hardening phase was found in the samples. This phase is responsible of high mechanical strength in such Aluminum alloy, and its formation is related to the heat flux from the arc. Moreover, a high heat flux value contributes to a low porosity and good homogeneity of the layered structure, thus promoting the increase of the mechanical resistance. The best results were obtained in samples manufactured at 200 A, with a Qnet = 7.22 kJ/s. Specimens for tensile testing were obtained in a horizontal plane (parallel to the direction of the layers) and vertical (perpendicular to the layers' boundary). The vertical specimens reached up to 267 MPa and they were better than the horizontal specimens because a better distribution of the stress along the layer. In all cases, the predominating failure mechanism was determined as ductile–brittle intergranular. [ABSTRACT FROM AUTHOR]

In welding processes, many factors contribute in achieving a required quality of the welds. Those factors are numerous and they may interact with each other, affecting response parameters such as welding penetration and the heat-affected zone (HAZ) size. Some factors are more important while the influence of others is negligible. To find an optimum factor combination in order to maximize penetration and minimize the HAZ is not an easy task. This contribution is aimed to evaluate the influence of welding energy (E) versus the influence of current (I) and welding speed (Vw) on the penetration and HAZ volume in the autogenous tungsten inert gas welding process. For this purpose, two numerical models are proposed. The first considers an in-house finite volume numerical model, and the second is based on response surface method. A sensitivity analysis of the proposed numerical model using two strategies is also performed. In addition, to determine the best-operating conditions, a multi-objective optimization problem is proposed and solved. The presented numerical models were found to provide good concordance in terms of coefficient of determination and p-value, indicating its significance. Each model (with one or more independent variables) represents detailed information about the physical process and can be used for optimization. The sensitivity analysis demonstrates that the current affects penetration and HAZ volume much stronger than the welding speed does. Physically, this is due to the fact that the current has linear (arc coupling) and non-linear (Joule effect and pressure gradient) influence, and the welding speed contributes linearly, modulating the heat conduction. Finally, it was demonstrated a compromise between the penetration and the HAZ volume by addressing multi-objective optimization. In this context, point C (I = 250 A; Vw = 24.8 cm/min) of the Pareto curve is the optimal option for operation since it provides a lower relative HAZ volume while keeping the same penetration and higher productivity (welding speed). [ABSTRACT FROM AUTHOR]

Microstructure and mechanical characteristics of aluminum bronze fabricated using electron beam additive manufacturing (EBAM) under adjusting the heat input as a function of the sample's height are investigated. It is shown that this adjustment has an effect on the dendrite grain size, morphology and mechanical characteristics. Columnar high aspect ratio grains are formed during deposition at the maximum heat input values. The columnar grain width in the section parallel to the deposition direction is increasing in the EBAM conducted at a lower heat input. The tensile static tests show that the tensile strength values are improving from 435 to 483 MPa. A moderate degree of anisotropy is revealed between the samples oriented by their tensile axes parallel and perpendicular to the deposition direction. The samples with tensile axes parallel to the deposition direction show higher tensile strength and lower plasticity than those of the samples with perpendicular orientations of their tensile axes. Furthermore, the heat input adjustment has no effect on the mean width of the columnar grains measured in a section perpendicular to the deposition direction. [ABSTRACT FROM AUTHOR]

To explore the mechanical behavior of circular steel tube components strengthened with welded casings, two groups of six specimens are designed, and two working conditions of zero-load reinforcement and load reinforcement are defined. Typical failure modes, ultimate bearing capacity, deflection curves, and strain data of measuring points are obtained. The FE modeling method considering the thermal effect of the welding process is proposed and verified. A total of 446 finite element models are established to explore the effects of the initial defects, the slenderness ratio, the boundary conditions, and the area ratio of the welded casing to the circular steel tube on the ultimate bearing capacity of the strengthened components. In addition, the ultimate bearing capacity equations for zero-load strengthened components is proposed using regression fitting and considering the adverse effects of the residual stresses due to the rolling and welding processes. Moreover, equations for calculating the deformation and the ultimate bearing capacity of the load-strengthened components considering the effect of the welding heat are also derived. Finally, the experimental, numerical, and theoretical analyses results were consistent in high calculation validity and efficiency. [ABSTRACT FROM AUTHOR]

This study explores the laser-arc hybrid welding process of high nitrogen steel (HNS) in order to circumvent the problem of welding porosity. The influence of welding heat input on welding porosity has been elucidated by analyzing the changes in the morphological characteristics of the laser keyhole and the molten pool temperature. The results show that the pore ratio increases with a rise in laser power. Meanwhile, the pore ratio first decreases and then increases as the welding current intensifies. Additionally, it decreases as the welding speed and defocus amount increase. The lowest pore ratio of the weld is considered as the desired value, and the response surface method (RSM) is used to optimize the heat input parameters. When the laser power ranges from 2.80 to 2.85 kW, the welding current becomes 260 A, welding speed ranges from 0.73 to 0.80 m/min, defocus amount ranges from 0 to 1 mm, and pore ratio of the weld exhibits its minimum value (4.29 to 4.67%). [ABSTRACT FROM AUTHOR]

In this work, the effect of variation in heat input on friction stir welding of 6 mm thick AA6092/ 17.5 SiCp-T6 aluminum matrix composite joints is analyzed. The effect of heat input on torque and force, time-temperature profile, microstructure and mechanical properties is studied. Heat input to the weld was controlled by varying traverse speed while keeping other process variables constant. The investigation shows that the cooling rate gradually increases from 3.32 to 5.72°C/s when the heat input decreases from 1915.4 to 1004.8 J/mm. Thereafter it increases rapidly to 14.1°C/s when the heat input further decreases to 730.76 J/mm. The particle size in the weld area decreases due to fragmentation as the heat input decreases from high to moderate and then again increases. The overall microhardness of the weld area increases with a decrease in heat input. The joint efficiency of 72, 88 and 84% is found as heat input decrease from high to low heat. The fractography shows a ductile mode of failure at moderate heat input, whereas at higher and lower heat input a mixed-mode of failure is observed. [ABSTRACT FROM AUTHOR]

High-temperature superconducting cables (HTS cables) cooled with liquid nitrogen are an alternative to traditional cables. The amount of heat supplied from the HTS cable to the cryoagent, as well as the choice of the optimal cryoagent circulation scheme and the option of cooling the superconducting line as a whole, depends on the internal structure of the cable. The paper presents a theoretical model describing the transfer of heat flow through the cylindrical layers of the cable. Analytical equations are obtained that determine the specific linear heat flow to cables of various types: with three separate shielded phases contained in separate cryostats with a common return cryogenic pipeline, with three shielded phases in separate cryostats with the organization of a reverse flow of the cryoagent inside the cryostats, and with three shielded phases located in one cryostat, as well as in a triaxial cable with different cryoagent circulation schemes. For all types of cables, the ratios between the total linear heat fluxes through the thermal insulation of the cryostat and the heat fluxes from the cable have been determined depending on the mass flow rate of liquid nitrogen. Also, a comparative analysis of the relationship between specific heat fluxes, temperatures of the cryoagent after cooling, and hydraulic resistances per unit length of cables has been carried out. The proposed technique makes it possible to evaluate the thermal–hydraulic parameters of the considered cable structures and to choose the most appropriate technical solution. [ABSTRACT FROM AUTHOR]

In this study, the heat input from friction stir welding of AA2024 and AA7075 dissimilar alloys was calculated, and the relationship between the heat input and mechanical properties was studied in detail. Additionally, the effect of heat on welding was analyzed. When the welding parameters were 800 rpm-400 mm/min, the Ultimate tensile strength of the joint was at its highest (346 MPa), and the elongation was 3%. A significantly higher or lower temperature led to lower tensile strength and elongation. Too low heat input failed to deform the material completely, and the fluidity of the material formed from the two base metals was poor. Excessive heat input led to the dissolution of precipitates, grain coarsening, reduced grain bonding, and other microstructural changes. When the heat input is higher, the cooling rate is faster, which can easily cause holes at the bonding interface. In the stir zone, owing to the difference in the thermal gradient of the upper and lower parts, the bottom of the material is not softened completely owing to the lack of heat, and stress concentration occurs. [ABSTRACT FROM AUTHOR]

The alloy 2.25Cr-1Mo-0.25V is commonly used for heavy wall pressure vessels in the petrochemical industry, such as hydrogen reactors. As these reactors are operated at elevated temperatures and high pressures, the 2.25Cr-1Mo-0.25V welding consumables require a beneficial combination of strength and toughness as well as enhanced creep properties. The mechanical properties are known to be influenced by several welding parameters. This study deals with the influence of the heat input during submerged-arc welding (SAW) on the solidification structure and mechanical properties of 2.25Cr-1Mo-0.25V multilayer metal. The heat input was found to increase the primary and secondary dendrite spacing as well as the bainitic and prior austenite grain size of the weld metal. Furthermore, it was determined that a higher heat input during SAW causes an increase in the stress rupture time and a decrease in Charpy impact energy. This is assumed to be linked to a lower number of weld layers, and therefore, a decreased amount of fine grained reheated zone if the multilayer weld metal is fabricated with higher heat input. In contrast to the stress rupture time and the toughness, the weld metal's strength, ductility and macro-hardness remain nearly unaffected by changes of the heat input. [ABSTRACT FROM AUTHOR]

A method is described for controlling the heat input in three-dimensional surfacing by means of a numerical algorithm determining the required parameter variation over time in mathematical modeling of the thermal problem. The goal is to ensure stable surfacing, the required geometric characteristics of the multilayer product, and the absence of defects. [ABSTRACT FROM AUTHOR]

The 5A06 aluminum alloy butt joint is fabricated by laser-metal inert gas (MIG) hybrid welding in this investigation. The macro morphology and porosity of welded joints under different heat input are observed by optical microscope. The effect of the laser, MIG, and hybrid heat input on macro morphology and porosity of welded joint is investigated. Furthermore, the force condition inside the laser-MIG hybrid welding pool is analyzed to explain the influence mechanism of heat input on macro morphology and porosity in theory. It is found that the cross-section area of weld seam (WS) is increased with the welding heat input. The porosity of the full-penetration WS is smaller than the partial-penetration WS owing to the different flow characteristic of molten pool. The higher MIG heat input is beneficial to reduce the porosity. It is illustrated that the welded joint with a lower porosity is expected to be obtained under the energy ratio coefficient of 0.5. [ABSTRACT FROM AUTHOR]

The influence of heat input on the microstructural evolution of laser-welded Ti2AlNb joints was investigated in this study. The thermal cycles during welding process were analyzed by numerical simulation. In the heat affected zone (HAZ), the amount of α2 and O phases decreased with laser power increasing. During the heating period, α2 → B2 and O → B2 transformations occurred, but the decomposition of the B2 phase into α2 and O phases was suppressed during the cooling period. The heat transfer in the HAZ generated more equiaxed B2 grains, fewer LAGBs and a weaker {001} < 1 1 ¯ 0 > texture due to recovery, recrystallization and grain growth. The phase composition of the fusion zone remained single with only the B2 phase with the increase in heat input, but the mode of grain growth transformed from cellular growth into cellular dendritic growth. A finite element model was established to simulate the thermal cycles during the welding process. Higher heat input induced higher peak temperature, leading to higher temperatures in the HAZ for longer periods of time, which was beneficial for the α2 → B2 and O → B2 transformations. The calculated cooling rates in both the HAZ and in the fusion zone were faster than the critical cooling rate for B2 → α2 and B2 → O transformations. [ABSTRACT FROM AUTHOR]

Over the past years, the demand for the wire arc additive manufacturing (WAAM) is potentially increased, and it has become a promising alternative to subtractive manufacturing. Research reported that the wire arc additively manufactured (WAAMed) material's mechanical properties are comparable to wrought or cast material. In comparison with other fusion sources, WAAM offers a significant cost saving and a higher deposition rate. However, there are significant challenges associated with WAAM such as undesirable microstructures and mechanical properties, high residual stresses, and distortion. Thus, more research is still needed to handle the above challenges by optimizing the process parameters and post-deposition heat treatment. In line with the above, this paper attempts to fill the gap by presenting a comprehensive review of WAAM literature including stagewise development of WAAM, metals and alloys used, effects of process parameters, methodologies used by various researchers to improve the quality of WAAM component. Besides, this work proposes the areas that could be used as avenues for future research. [ABSTRACT FROM AUTHOR]

The main factors affecting the mechanical properties of the deposited metal in arc hardfacing are primarily the chemical composition and the cooling rate. The latter depends on the filler materials composition, hardfacing condition (mode), and hardfacing technology, determining the geometric parameters and parameters of the welded bead shape, the amount of deposited metal dilution with the base metal, and the amount of the introduced heat. The goal of this work is to analyze the effect of exothermic addition introduction to the core filler and the effect of welding condition on weld bead morphology, thermal indicators, and mechanical properties of the deposited metal. The deposited metal of the Fe-C-Cr-Cu-Ti-V-Al alloying system was used. The Taguchi technique was adopted as the experimental plan design, as follows: the orthogonal array L9 (3 ^ 4) and signal-to-noise ratio (S/N). The analysis of variance (ANOVA) was also applied for determination of the variables contribution to the dependent parameters. Application of the Taguchi method is simpler, more efficient, and quicker. It requires fewer experiments to determine the optimal values of the studied variables. Microstructural studies using an optical microscope were additionally performed for individual samples of the weld metal with the best mechanical properties, for each of the experimental flux-cored wires. We determined that introduction of CuO-Al exothermic addition of to the core filler had a significant effect on such indicators of the weld bead morphology as the weld reinforcement height and the weld reinforcement form factor (WRFF). Introduction of exothermic addition (CuO-Al) to the core filler had a significant effect on the welding current (I), heat input rate (HIR), and microhardness. The arc voltage (Р(Ua)= 45.8 %) had the greatest influence on the microhardness value, while the percentage of exothermic addition in the core filler (P(EM)= 26.9%) and the wire feed rate (P(WFS)= 21.5%) had a smaller effect. It was shown that it is important to take into account complex parameters, such as dilution variation and weld reinforcement form factor (WRFF) for the geometric characteristics of the weld bead and heat input rate (HIR) for heat indicators in order to optimize hardfacing conditions and composition of the core filler (introduction of exothermic addition). According to the results of the article, the value is the most correlated with the average values of microhardness. [ABSTRACT FROM AUTHOR]

Heat input for gas tungsten arc welding process was varied at three different levels to fabricate three AISI 304L stainless steel welds to examine the influence of variable arc energy input on their sensitization and pitting performance. Welds were subjected to post-weld thermal aging treatments comprising of low-temperature sensitization of 500 °C for 1, 5, and 11 days and classical sensitization of 650 °C for 1, 12, and 24 h. Different morphologies of ferrite present in the fusion zone and the degree of the coarsening of grains in the heat-affected zone (HAZ) of the weldments under different aging conditions influenced their tendencies for carbide formation, which consequentially affected their sensitization and pitting corrosion behavior significantly. Lower heat input welds having lathy morphology of δ-ferrite in the fusion zone along with less coarsened HAZ exhibited a lesser degree of carbide precipitation. They hence showed a lower degree of sensitization (DOS), which accounted for higher pitting potential (Epitt). However higher heat input welds having vermicular morphology of δ-ferrite in the fusion zone and relatively higher grain coarsened HAZ promoted a higher degree of carbide precipitation, and thus accounted for the higher value of DOS and lower pitting potential (Epitt). [ABSTRACT FROM AUTHOR]

The welded joints of a nitinol (Ti–55.42% Ni) wire 2 mm in diameter are fabricated using a manual tungsten inert gas welding technology (TIG). The macro- and microstructure of the welded joints are investigated, bending tests are carried out, and the shape memory effect is evaluated. [ABSTRACT FROM AUTHOR]

Gas turbine blades working under extremely harsh operating conditions are made of superalloys. These superalloys are exposed to various damage mechanisms, which wear them out gradually. Welding is often preferred to repair the damaged components for cost minimization. This study aimed to investigate the effects of flexural load, heat input, and welding speed on the weldability and intergranular liquation cracking of high-chromium Ni-based superalloy. For this purpose, a series of Sigmajig tests designed based on the Taguchi method with L4 array, as well as microstructure investigations and residual stress measurements, were performed. The results showed that the microstructures of heat-affected zones (HAZs) were highly susceptible to cracking during the welding process, and all of these cracks appeared in the HAZ and grew perpendicular to the melting zone along grain boundaries. Flexural load contributed the most substantial impact (82%) on crack propagation compared with the 9.7 and 9.2% impacts of welding speed and welding heat input, respectively. We found that the lowest flexural load, welding speed, and heat input are the best welding parameters to reduce the total crack lengths at the welded area of high-chromium Ni-based superalloy. [ABSTRACT FROM AUTHOR]

Heat input has a significant effect on the microstructure and corrosion performance for welded joints. Underwater wet welding (UWW) was applied to high-strength low-alloy steels E40 with different heat inputs. Corrosion performance of the base metal (BM), weld metal (WM), and heat-affected zone (HAZ) was investigated by the electrochemical techniques including electrochemical impedance spectroscopy and potentiodynamic polarization tests emerged in 3.5 wt.% NaCl solution. The results indicated that corrosion resistance of WM decreases with increasing heat input when the welding speed remains constant. Compared with arc voltage and welding current used in UWW, welding speed plays a more important role in the corrosion behavior of WM. The excessive welding speed can cause severe deterioration of corrosion resistance of WM. Meanwhile, the WM indicates the better corrosion resistance than the HAZ and the BM for the sample 2 with a heat input of 2.5 kJ/mm, and the worst corrosion resistance appears in the BM. The critical role of microstructure, grain size, grain boundary and crystal orientation in the corrosion resistance was discussed by optical microscope and electron backscatter diffraction techniques. [ABSTRACT FROM AUTHOR]

An important parameter of non-vacuum electron-beam cladding is the surface density of the input energy that depends on the beam current and the specimen travel speed. The paper presents results of investigation of the effect of the heat input on the structure and properties of composite coatings fabricated by electron beam cladding. The modes of cladding with beam currents of 25 and 40 mA and specimen travel speed varying within 0.5–2.0 cm/s have been studied. It was revealed that the thickness, the dendrite grain size, and the microhardness of the coatings increased, and the volume fraction of the eutectic decreased with increasing specific electron beam power. It is shown that for a low heat input, an austenitic-martensitic structure is formed with carbides in the eutectic and martensite needles. For a large heat input, an austenitic structure with eutectic carbide network is formed. The martensitic structure is formed only along the coating-substrate interface as a result of intense heat removal deep into the substrate material. [ABSTRACT FROM AUTHOR]

The evolution of processing parameters by varying tool eccentricity in AA6061 alloy friction stir welding was examined using a combination of detailed force/torque measurements and thermal history as well as high-speed camera (HSC) observations. Tri-axial forces show larger oscillations during the steady-state phase of welding if the tool eccentricity is increased. However, the tool torque remains similar for up to 0.4 mm eccentricity versus the aligned tool even with varying weld speed. In situ HSC observation indicates that tool eccentricity is reduced during the welding process for larger eccentric setups. Stir zone thermal measurements reveal that the temperature peaks and stabilizes near the solidus temperature of the AA6061 base material. [ABSTRACT FROM AUTHOR]

The austenitic stainless steels used in various industrial fields require low heat input for welding. Laser welding is an excellent welding method in this respect. This study investigates the effect of laser welding speed on the mechanical properties at welding speed of 1.0, 1.5 and 2.0 m/min, using STS304L of austenitic stainless steel. The microstructures of fusion zone (FZ) show a two phase structure consisted of austenite and δ-ferrite, and δ-ferrite in the fusion zone tend to decrease with increase of welding speed. Meanwhile, the mechanical properties were excellent at the welding speed of 1.5 m/min for tensile, bending and impact tests. [ABSTRACT FROM AUTHOR]

The effect of welding thermal cycles on the microstructure and residual stresses was studied in the welding zone of an experimental high strength microalloyed steel with an acicular ferrite and quasi-polygonal ferrite microstructure. Autogenous gas tungsten arc welding was performed on a plate of microalloyed steel to produce a weld bead neglecting the weld joint design and the selection of filler material. To obtain a high welding quality, the welding speed and distance between the electrode and plate was controlled with a small vehicle. To determine the residual stresses, nanoindentation tests were performed in each one of the welding zones and subzones of the heat-affected zone (HAZ). These results showed that all of the nanoindentations presented pile-up and sink-in, and thus, a modification was proposed to calculate the actual contact area and determine the residual stresses. Tensile residual stresses were presented in the coarse-grained HAZ (grain boundary ferrite, acicular ferrite, and bainite); fine-grained HAZ (polygonal ferrite); subcritical HAZ (acicular ferrite and quasi-polygonal ferrite); and base material (acicular ferrite and quasi-polygonal ferrite). The fusion zone (acicular ferrite and bainite) and intercritical HAZ (quasi-polygonal ferrite) had compressive residual stresses. [ABSTRACT FROM AUTHOR]

Influence of varying heat input (0.66-1.43 kJ/mm) and different preheat temperatures (150-350 °C) on microstructure and mechanical properties of the coarse-grained heat-affected zone (CGHAZ) of MAG-welded pearlitic rail steel has been investigated. Results show that at low heat inputs (0.66-1.00 kJ/mm), microstructures are mainly composed of martensite, whereas high heat inputs (1.29-1.43 kJ/mm) have coarsened the grains and formed cracks. 1.16 kJ/mm of heat input is found optimum which has produced a crack-free surface with the least martensite. Afterward, by using the optimum heat input of 1.16 kJ/mm samples are welded at different preheat temperatures ranging from 150 to 350 °C, which has reduced the martensite and increased the pearlite, successively. Preheat temperatures of 250 °C are found optimum, where grain size and t 800 - 300 ∘ C cooling rate are 38.1 ± 9.8 μm and 3.1 °C/s, respectively. Furthermore, hardness is 659 ± 7 HV, tensile strength is 1349 ± 16 MPa, and toughness is 6.4 ± 0.5 J, respectively. Finally, the confocal scanning laser microscopy analysis, at optimum heat input of 1.16 kJ/cm and 250 °C of preheat temperature, is also presented. The entire study concludes that preheating is inevitable in MAG welding of pearlitic rail steel. 1.16 kJ/mm of heat input with 250 °C of preheating temperature is suitable in MAG welding of pearlitic rail steel where microstructure is composed of pearlite, ferrite, and sorbite having no martensite and no cracks. [ABSTRACT FROM AUTHOR]

In the present work, the influence of heat input on phase balance, residual stresses and corrosion resistance of UNS 32101 lean duplex stainless steel welds has been investigated. Three weldment types were obtained with different heat inputs by varying welding current, using gas tungsten arc welding process. The results revealed that increasing heat input caused a significant microstructural evolution with high austenite fraction in weld metals. The residual stresses were measured on the surface and through the sample's thickness by x-ray diffraction technique based on Sin2ψ method. The results showed an inversely proportional relationship between the heat input and the compressive residual stresses on the surface and through the thickness of the weld metal. Potentiodynamic polarization tests of the different welded joints evaluated in 3.5% NaCl solution exhibited high corrosion resistance of the weld metal produced with the low heat input. [ABSTRACT FROM AUTHOR]