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Extrusion welding of AlMgSi(Cu) alloys is carried out by using porthole dies, as a result of which hollow shapes are formed with longitudinal seam welds. In the case of the inappropriate selection of the chemical composition of the aluminium alloy or improper metal welding conditions, the weld may have reduced strength in relation to that of the base material, thus weakening the strength of structures based on aluminium extrudates. The prediction of metal welding conditions, depending on the chemical composition of the alloy, the temperature and the unit welding pressures, effectively supports the design of porthole dies, thus significantly reducing the number of necessary extrusion tests and die geometry corrections needed during its implementation in industrial practice, and consequently significantly reducing production costs. In this work, an original laboratory test device simulating the behaviour of metal in a welding chamber of a porthole die was applied to examine the ability of AlMgSi(Cu) alloys to produce high-quality joints. Two different chemical compositions of AlMgSi(Cu) aluminium alloys differing in Mg, Si and Cu contents were used: alloy no. 1A (0.68% wt. Mg, 1.04% wt. Si, 0.61% wt. Cu) and alloy no. 3A (0.8% wt. Mg, 1.21% wt. Si, 1.22% wt. Cu). The weldability tests were carried out under various welding temperatures of 450, 500 and 550 °C and under various welding pressures of 150 MPa, 250 MPa and 350 MPa. The microstructural changes in the produced welds were evaluated with the use of OM and SEM/EDS with chemical analysis in micro-areas, whereas the mechanical effects were evaluated by using a static tensile test. Samples after static tensile testing were subjected to fractographic tests to determine the nature of the fractures. The highest values of relative weld strength were obtained under the highest welding temperature of 550 °C and the highest unit welding pressure of 350 MPa: 87% for alloy number 1/1A (high-strength weld), and 62% for alloy number 6/3A (medium-strength weld). Finally, the extrusion tests were performed in industrial conditions with an examination of the EBSD structure and strength of the longitudinal welds. High values of relative weld strength for extrudates from alloy no. 1/1A and alloy no. 3A, 96% and 89%, respectively, were found, which confirmed the previous weldability testing results. [ABSTRACT FROM AUTHOR]

Powder metallurgy high chromium cast iron (PM HCCI) and low carbon steels (LCS) were welded by multi-pass manual gas tungsten arc welding (GTAW). The effects of welding current on the microstructure evolution and mechanical properties of the weld joints were systematically investigated, the microstructure evolution model of the weld joints was proposed, and the fracture mechanism of the solders was also discussed. In the results, the tensile strength of the welded joints reaches 538.1 MPa at 140 A welding current, which is 95.3% and 97.4% of the tensile strength for PM HCCI and LCS, respectively. The microhardness of the welded joints decreases from HCCI side to LCS side in the horizontal direction, whereas in the vertical direction, the microhardness distribution is of M-shape due to the secondary tempering and alloying element diffusion/segregation. The fusion zone (FZ) mainly consists of the austenite and tempered martensite at the welding current of 140 A, and there is a single austenite columnar crystals zone between FZ and LCS; while there is a HCCI columnar crystal zone between FZ and the sintered HCCI, in which the coarsen carbides with branches are distributed along the matrix’s grain boundary.

With the development of lightweight aerospace structures, the use of the high-quality and efficient laser welding of near-α titanium alloys has received widespread attention and favor thanks to its superior comprehensive performance. The welding experiment of 3 mm thick TA15 titanium alloy was carried out by YAG laser welding, and the material weldability, microstructure, microhardness, and mechanical properties of welded joints were systematically studied. The results indicated that laser welding of TA15 titanium alloy can produce well-formed welded joints without defects such as cracks and porosity. The welded metal used was a typical basket-weave microstructure composed of a large number of α′ martensitic phases and a small number of high-temperature residual β phases, and the heat-affected zone was a staggered arrangement of undissolved α phase and needle-like α′ martensite. The microhardness of the welded joint showed a hump distribution, and the hardness of WM fluctuated between 410 and 450 HV since the martensitic transformation occurred during the solidification of the weld under thermal cycling, and the β phase changed to the needle-like α′ phase. The tensile test indicated that the fracture position was located in the base metal area, and the fracture morphology showed the equiaxial dimple morphology of different sizes in a ductile fracture mode. The welded metal had the lowest impact performance (average value of 5.3 J) because the weld area was predominantly coarse α′ martensite. This experiment conducted systematic, in-depth, and extensive research on welding processes, hardness, tensile, impact, and fracture mechanisms. Based on the special product applications in the aerospace field, it was more targeted and conducive to promoting the application of the welding process in this material. [ABSTRACT FROM AUTHOR]

The presented work is focused on the influence of imposed strain on the weldability of Dievar alloy. Two mechanisms affecting the microstructure and thus imparting changes in the mechanical properties were applied—heat treatment (hardening and tempering), and rotary swaging. The processed workpieces were further subjected to welding with various welding currents. In order to characterize the effects of welding on the microstructure, especially in the heat-affected zone, and determine material stability under elevated temperatures, samples for uniaxial hot compression testing at temperatures from 600 to 900 °C, optical and scanning electron microscopy, and microhardness testing were taken. The testing revealed that, although the rotary swaged and heat-treated samples featured comparable microhardness, the strength of the swaged material was approximately twice as high as that of the heat-treated one—specifically 1350 MPa. Furthermore, it was found that the rotary swaged sample exhibited favorable welding behavior when compared to the heat-treated one, when the higher welding current was applied. [ABSTRACT FROM AUTHOR]

The weldability of a CoCrFeMnNi high-entropy alloy (HEA) and 304 stainless steel (304 SS) was investigated to determine their potential for application in the nuclear and aerospace fields. Autogenous dissimilar butt welding was performed using gas tungsten arc welding, and the resulting joint was complete with no defects. SEM/XRD analysis showed that the fusion zone microstructure consisted of a single fcc phase without the formation of intermetallic compounds. However, there is an unmixed zone near the 304 SS side, which can be attributed to subcooling of the composition caused by the lower liquidus temperature of the bulk weld metal than that of the base metal. Furthermore, a small increase in the hardness of the fusion zone compared with that of the CoCrFeMnNi HEA was observed. These results can be attributed to the grain refinement of the weld and the strengthening effect owing to the incorporation of carbon. The joints exhibited a tensile strength of ~ 465 MPa and ductility of 38%, where the strength was comparable to that of the CoCrFeMnNi HEA, and a joint fracture was found at the side of the CoCrFeMnNi HEA. This indicates that the weldments are suitable for room temperature structural applications. [ABSTRACT FROM AUTHOR]

Cast Monel alloys are used in many industrial applications that require a combination of good mechanical properties and excellent resistance to corrosion. Despite relative widespread use, there has been limited prior research investigating the fundamental composition–structure–property relationships. In this work, microstructural characterization, thermal analysis, electron probe microanalysis, tensile testing, and Varestraint testing were used to assess the effects of variations in nominal composition on the solidification path, microstructure, mechanical properties, and solidification cracking susceptibility of cast Monel alloys. It was found that Si segregation caused the formation of silicides at the end of solidification in grades containing at least 3 wt pct Si. While increases to Si content led to significant improvements in strengthening due to the precipitation of β1-Ni3Si, the silicide eutectics acted as crack nucleation sites during tensile loading which severely reduced ductility. The solidification cracking susceptibility of low-Si Monel alloys was found to be relatively low. However, increases to Si concentration and the onset of associated eutectic reactions increased the solidification temperature range and drastically reduced cracking resistance. Increases in the Cu and Mn concentrations were found to reduce the solubility limit of Si in austenite which promoted additional eutectic formation and exacerbated the reductions in ductility and/or weldability. [ABSTRACT FROM AUTHOR]

The properties of the intercritically reheated coarse-grained heat affected zone (ICCGHAZ) in X65 pipeline steel with large deformation are studied. The ICCGHAZ is composed of acicular ferrite, granular bainite and lath bainite. With the increasing t 8/5 (the time for specimens to cool from 800 °C to 500 °C), the sulfide stress corrosion cracking (SSCC) resistance with and without pre-strain both increases, and the secondary cracks propagate along the necklace-type martensite-austenite (M-A)/matrix interface or near the M-A constituents, and the fracture toughness decrease. When t 8/5 = 30 s, ICCGHAZ has the most ideal performance on fracture toughness and stress corrosion resistance. • The microstructures of ICCGHAZ with different welding heat input are observed. • The crack propagation path is less affected by the phase interfaces with the increasing t 8/5. • The fracture toughness decreases significantly with the increasing of t 8/5. • When t 8/5 = 30 s, the ICCGHAZ has the best performance on fracture toughness and SSCC resistance. [ABSTRACT FROM AUTHOR]

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This paper investigated evolutions of α-Al sub-grains' morphology and crystalline orientation in the fusion zone during laser welding of 2A12 aluminum alloys. Based on this, a new method for assessing the weldability of materials was proposed. In laser deep-penetration welding, in addition to the conventional columnar and equiaxed dendrites, there also exhibited a corrugated structure with several 'fine-coarse-fine' transformations. In such regions, an abnormal α-Al coarsening phenomenon was encountered, with a more dispersed crystalline orientation arrangement and a decreased maximum pole density value. Particularly, structural alterations appeared more frequently in the weld bottom than the top. The above results indicated that the laser-induced keyhole presented a continually fluctuating state. Under such a condition, the solid–liquid transformation exhibited an unstable solidification front, a fluctuant undercooling, and a variational solidification rate. Meanwhile, the welding quality of this material is in a critical state to generate pores. Therefore, the appearance and relevant number of corrugated regions can be considered as a new way for judging the weldability, which will help to narrow the processing window with better welding stability. [ABSTRACT FROM AUTHOR]

This study presents information on the behavior of paint baking (PB) after resistance spot welding of the 5- and 6xxx series aluminum alloys. The weld parameters are optimized, and the weld specimens are baked three times for 20 min at 180 °C to simulate the heat treatments required for paint baking. The mechanical properties of the samples were characterized by using the lap shear test, micro/nanoindentation hardness, and fatigue test. As the mechanical properties of the weld are affected by the characteristics of the heat-affected zone and those of the fusion zone, the microstructure of the cross-sections was also analyzed through optical and electron microscopy. The investigation of the 6xxx series welds showed that the post-processing heat treatment decreased both the strength and the toughness of the weld, which resulted from the reduced hardness of the microstructure. Additionally, the lap shear test indicated that the failure mode for the 6xxx series changed from nugget failure to partial nugget failure after the paint baking process. However, the mechanical properties of the 5xxx welds were not affected as much as the 6xxx series during baking heat treatment. The fatigue test for the 6xxx series showed a different tendency from the lap shear test. Its fatigue properties improved due to an increased elastic modulus after the heat treatment. [ABSTRACT FROM AUTHOR]

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main objective of this study was to assemble by friction stir welding two dissimilar sheets made with AA5754 Al-Mg alloy and AA 1050 aluminum, which are intensely used in the automotive industry. The applied welding speed was 75 mm/min with different tool rotational speeds (780, 1330 and 2440 rpm). The mechanical properties and the microstructure of the welded joint were investigated by the tensile test, the three-point bending test, the microhardness measurements, the optical microscopy, scanning electron microscopy and energy dispersion spectrometry (EDS). The main zones were observed in the welded joint. Optimum mixing was achieved during the assembly process with a welding tool rotation speed of 2440 rpm. It was determined that the microstructures formed had a significant effect on the hardness and tensile strength of welded dissimilar materials such as the precipitated phases in the nugget zone. The best result in terms of tensile strength was obtained at 780 rpm with 80% performance. [ABSTRACT FROM AUTHOR]

INCOLOY alloy 800 is widely utilized in the outlet manifold bottom header (OMBH) inside a primary reformer at a fertilizer plant. Primary reformers in fertilizer plants usually work at high temperatures and pressures for long periods. In this work, solution annealing and normalization processes were conducted to improve the weldability of INCOLOY alloy 800 after operating for ten years. Characterizations of weldability properties were carried out through dye penetrant, X-ray fluorescence, hardness, X-ray diffraction (XRD), and metallography observations. The annealing and normalization results showed that the weldability of INCOLOY alloy 800 increased, indicating a significant reduction in cracks on the weld zone surface. Microstructure observations revealed that microcracks were not found on the weld joint surface after solution annealing. The maximum hardness value on the fusion zone was obtained at 187 VHN on normalizing, and the minimum hardness was obtained on the nontreatment sample 156.33 VHN. [ABSTRACT FROM AUTHOR]

In this work, the friction stir weldability of Ti6Al4V T-joints has been investigated. Its aims are: (i) to study the influence of tool and welding parameters on weld quality, (ii) to assess the joints' mechanical strength to foresee future applications, and (iii) to characterize Co-based FSW tools' wear by following the wear during the tests. Welds' defectivity is studied by cross-section macrographies analysis. Independently from welding parameters and tools, internal voids are avoided, and a suitable weldability window is identified. Microstructure observations have corroborated temperatures below the β -transus point even in the nugget zone, guaranteeing joints' maximum mechanical strengths at 96% and 87% of the base material for UTS and Y, respectively. Contrarily, elongation at break is very low, without reaching 20% of the base material. The failure is linked to section thinning and kissing bond defects at the joints' corners. Additionally, tool wear proved to be a critical issue while friction stir welding Ti6Al4V. The inner part of the shoulder is the most sensitive to wear. The consequent high wear rate might be a problem for mass production. The work established the pertinence of assembling complex geometries of Ti6Al4V using friction stir welding, considering weld quality and the mechanical strength achieved. However, critical factors such as section thinning, kissing bond, and tool wear must be carefully addressed to avoid joints' low elongation at break and to guarantee their mechanical strength. [ABSTRACT FROM AUTHOR]

The article presents a calculation model of the linear energy of welding P235GH steel tubes with high-frequency currents in order to obtain an optimal microstructure and geometry of the weld of high internal purity. The model was developed based on real data for the standard linear energy used in the steelworks Huta Łabędy and presented as the power factor P/V and P/(V·t), where P is the power [kW], V the production speed [m/min] and t the wall thickness. The model can be used for two ranges of pipe diameters: 114.3–168.3 mm and 219.1–323.9 mm. The data from the model were implemented into the High Frequency Induction (HFI) control panel of Huta Łabędy in order to produce test tubes which were subsequently tested with ultrasounds to verify the quality of the internal weld. In addition, samples were taken for metallographic analysis, which was supposed to check whether the applied linear energy calculation model allows the obtainment of the optimal weld geometry and the optimal angle of the metal flow line allowing for swelling and the extrusion of melted impurities from the inside of the joint by the squeeze rolls. The metallographic analysis also determined the nature of the occurrence of ferrite inside of the center diffusion bond and the zonal microstructure of the joint, the control of which is based on the correlation of the parameters of the mechanical process of forming the tube with the linear energy of welding. Carrying out the technological and technical process based on the applied HFI linear energy calculation model allowed us to obtain a weld of high purity and metallurgical consistency. This model can be used in the future on an industrial scale for the production of pipes using the HFI method. [ABSTRACT FROM AUTHOR]

Utilization of welding technology connecting small precise parts formed by Selective Laser Melting (SLM) and unsophisticated traditional formed parts into significant structural components provides a new way to manufacture large-scale complex 3D-printing parts. It is expected to improve the yield efficiency, save cost, and has a broad development prospect. Existing research results show that SLM forming parts differ quite from traditional casting and forging parts in structure and performance. Whether SLMed parts and rolled ones can be connected by welding and the influence mechanism of the anisotropy on weld performance are unclear. The results show that the joints exhibit good laser weldability without apparent defects. The microstructures of the SLMed base plates and laser-welded joints consist of the cellular dendrite in the austenite matrix within the columnar grains. The tensile strength of the joints is similar to that of rolled ones but lower than that of SLMed base metal; the elongation is about 1.3 times that of the SLMed base metal and 66% of the rolled ones. The corrosion properties of SLM base metal and weld area are superior to rolled plates. The anisotropy of SLM has a noticeable influence on the microstructure and tensile properties of the weld but plays a minor role in determining the element distribution, microhardness, and corrosion resistance. This work provides the theoretical and technical foundation for the innovative manufacture of large-scale, high-quality, and complex-formed metallic parts. [ABSTRACT FROM AUTHOR]

The knowledge and experience gained in the course of research and operation of metal alloys allow us to gradually implement modern metal alloys and methods of their production. Modern metal alloys developed in recent years, compared to traditional alloys used for many years, have higher functional properties, higher durability, higher reliability, lower production cost, lower operating cost, less complicated production technology, easier recycling, and many other properties. The popular metal alloys include both ferrous metal alloys and non-ferrous metal alloys. After the heat treatment, the primary MC carbides were decomposed into M6C carbides, while a needle-like topologically close-packed (TCP) phase was formed in the alloy with high Mo content, in contrast to the other three alloys with low Mo content. [Extracted from the article]

Steel is basically used in construction, automobile, buildings, infrastructure, tools, ships, appliances, machines and weapons due to its good mechanical as well as metallurgical properties. Heat treatment of steels significantly enhance its mechanical and metallurgical properties due to the formation of various phases depending upon the type of steel used for specific application. In present study, blank of EN353 grade steel having different sizes were used to investigate the effect of heat treatment and microstructural changes. JMat-Pro software was used to predict the continuous cooling transformation behaviour of EN353 steel. Different phases such as bainite, perlite and other carbide inclusion can be observed in the microstructural examination. Pearlitic microstructure developed for the specimen of size 40×40×40 mm heated at 870°C for 2 hrs and then isothermal heating was performed for same specimen at 600°C for 73 min followed by air cooling. Relevance Statement: Steel is an important material which is frequently used in almost all areas such as structure building, pressure vessels, transportation and many more other applications. Addition of alloying elements in parent steel significantly improve the metallurgical as well as mechanical properties. Steel properties like tensile strength, toughness, ductility, corrosion resistance, wear resistance, hardness, hot hardness, weldability, fatigue etc. significantly improved with the addition of alloying and heat treatment. Heat treatment processes can be used to improve the properties of steel which are frequently used in many manufacturing industries. Different grades of steels which are heat treated under a set of sequence of heating and cooling to change their physical and mechanical properties so that it can fulfil its function under loading condition. With the help of heat treatment process desired microstructure has been achieved which exhibit good mechanical properties of steels. [ABSTRACT FROM AUTHOR]

This study reports the welded joint of a novel 590 MPa V-N microalloyed wheel steel on microstructure and mechanical properties after flash butt welding. The welding parameters were flash current 48°/582.0 A, upsetting current 44°/516.6 A, and workpiece clearance 1.5 mm. The evolution of microstructure in the welded joint occurred as follows: welding seam (ferrite side plate + acicular ferrite +martensite)→coarse-grained zone (acicular ferrite + granular bainite)→fine-grained zone (fine-grained ferrite + M/A island)→base metal (equiaxed ferrite + pearlite). The standard impact energy value of welding seam, coarse grain zone, fine grain zone, and base metal at −40 °C was 116, 128, 144, and 88 J, respectively. The mechanical property of the joint was excellent. The microstructure, the number of grain boundaries, and the dislocation density directly affected the strength and hardness of the joint. The increase of large angle grain boundaries and the decrease of effective grain size were beneficial to the improvement of toughness. The hot-rolled 590 MPa V-N microalloyed wheel steel had superior weldability. [ABSTRACT FROM AUTHOR]

The influence of heat treatment, simulating thermal cycles and welding in the process of manufacturing joint fittings on microstructure, strengthening phase precipitation, and mechanical properties of base metal and near-weld zone of fittings, made of low-carbon copper-containing steel, is studied. Rolled product specimens are produced under laboratory and industrial conditions. Heat treatment regimes are developed, and mechanical properties of pipeline fittings of strength class K60 (X70) after normalizing with tempering and strength class K65 (X80) after additional quenching before tempering combined with satisfactory impact strength and weldability are provided. [ABSTRACT FROM AUTHOR]

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work control welded joints of plates made of pipeline steel type 07KhG2B of strength class K60 are studied, obtained in a laboratory multi-arc welding stand and samples processed according to welding thermal cycles in a Gleeble 3180 test complex. It is shown that modeling and simulation techniques used make it possible to calculate the thermal cycle and form a structure in a steel sample that is as close as possible to the structure of the HAZ of a real welded joint. Studies carried out show general features of the effect of microstructure on specimen impact strength with a simulated HAZ microstructure and specimens from an actual welded joint in terms of the effect of matrix structure, large particles of titanium and niobium carbonitride phases, and MA-constituents. It is shown that the toughness of specimens with a simulated HAZ overheating area microstructure correspond to the worst test results of a real welded joint in the zone (GOST 6996) and the fusion line (DNV-OS-F101). This result confirms the validity of applying the simulated test technique for evaluating steel weldability. [ABSTRACT FROM AUTHOR]

Resistance spot welding studies at varying current with an 8 mm electrode on steel grades DP980, DP690, TRIP980, and TRIP780, established that peak strength with sound weld could be achieved at a current range of 9 to 10 kA, where the nugget diameter was between 6.9 and 7.5 mm. The joint efficiency, measured as hardening ratio was highest in TRIP690 at 2.22 and for higher strength grade it was between 1.37 and 1.51. The softening ratio in the HAZ associated with tempering of preexisting martensite, was 0.86 to 0.9. Higher fusion strength was associated with alloying content that increased resistance that increased weld pool fusion that further enhanced the nugget diameter and hence the strength. The TRIP steel at high cooling rate showed martensite and retained austenite and the DP steel showed martensite content in higher grade and dispersed ferrite with martensite in the lower DP grade. The Tensile shear strength was lowest (16kN) for DP780, while for other grades it was between 20 and 22 kN. The strength enhancement in TRIP steel was due to higher weld diameter at higher current, where partial pull out failure mode was observed. At lower current, the interfacial pull out failure mode was observed with poor fusion and at high currents partial pull out at HAZ was observed. The Coach peel strength was highest at 3.2 kN for DP780, 2.2 kN for DP980, 2 kN for TRIP 690 and 1.7kN for TRIP 980 which followed the trend in TSS. The observed failure may be attributed to the high fusion strength in TRIP steel due to sound nugget and a microstructure of martensite with retained austenite. The lower strength with DP steels was attributed to low alloyed lath martensite in DP 980 and the lower grade DP780 was softer which was associated with ferrite dispersion in martensite. At very high currents, the fusion was good but there was a pull out at HAZ due to the softening associated with the tempering of preexisting martensite that influenced the failure at HAZ failure mode. [ABSTRACT FROM AUTHOR]

This study investigated the effect of the initial grain size on the laser beam weldability of CoCrFeMnNi high-entropy alloys (HEAs). Cold-rolled, annealed, and cast HEAs with different initial grain sizes exhibited clear differences in weldability. The cold-rolled, annealed, and cast HEAs exhibited grain sizes of 1.5, 8.1, and 1.1 mm, respectively. The grain size of the weld metal (WM) in cold-rolled/annealed HEAs was coarser than that of the base metal (BM), whereas the grain size of the WM in the cast HEA was finer than that of the BM. Shrinkage voids were present in the central region of all laser WMs. The cold-rolled and annealed HEA exhibited a tensile strength greater than 600 MPa owing to the grain size of the coarse WM and the presence of shrinkage voids; however, tensile fracture occurred in the central region of the WM. However, because the grain size of the cast HEA BM was finer than that of the WM, the tensile fracture occurred in the BM, and it had the same tensile properties as the BM. Therefore, the laser weldability of the HEA depended on the initial grain size, and the grain refinement of the WM was essential for improving the weldability. [ABSTRACT FROM AUTHOR]

Fe-based shape memory alloys (Fe-SMAs) have attracted significant interest in various industries due to their outstanding properties, such as superior shape recovery, cost-effectiveness, weldability and vibrational damping capabilities. The ability to achieve shape recovery at room temperature expands their potential for use in a wide range of temperature-sensitive environments, further highlighting their adaptability and applicability in industrial setting. In this study, a series of mechanical processes—such as melting, wire-cutting, machining, grinding, and both hot and cold rolling—were carried out to fabricate the Fe-SMA samples. A specific composition, Fe–29.4Mn–6.2Si–6.2Cr, labeled as the S7-type, was subjected to nanoprecipitation treatment and compared with unprecipitated Fe–Mn–Si-based samples. The results indicated that the nano-precipitated S7-type sample demonstrated an energy absorption effect and damping dissipation ratio of 1649 N m and 21.13%, respectively, in contrast to the unprecipitated St37 samples, which showed values of 429.704 N m and 8.35%. Furthermore, The S7 sample exhibited a damping ratio 2.53 times greater than that of structural steel and 1.34 times higher than that of the S6 sample. This improvement is attributed to nano-sized precipitates that act as sources for the propagation of partial dislocations under applied stress. In conclusion, this research highlights the significant potential and enhanced properties of Fe-SMAs. [ABSTRACT FROM AUTHOR]

Monel 400 with low alloy steel dissimilar joints are widely used in oil industry, petrochemical and nuclear engineering, this kind of applications needs welding joints with good mechanical properties, stable magnetic permeability and good weldability. Difference in mechanical, chemical and physical properties between these unique alloys makes such joint difficult and joints mechanical properties and microstructure will be different from parent metals. In this study, GTAW process has been employed with ERNiCrFe-3 electrode to produce dissimilar welding joints with specifies welding procedure parameters, SEM/EDS microstructure analysis, microstructure optical test, Vickers microhardness and tensile test used to study microstructure details and its impacts on welding joint mechanical properties. Research results according to welding zone microstructure analyses shown formation of Widmanstatten ferrite structures and second phase particles with fine graine structure in low alloy steel side the formation of transion zone (TZ). Moreover, clearly fusion line (FL) clearly marked in Monel 400 side while weld metal solidification microstructure with (MGBs) and (SGBs) respectively and interdendritic microstructure observed in weld zone center. Weldment mechanical and microstructure examination indicated the ability to produce like this dissimilar joint with requirement of design criteria and indicated that the failure in like this joint excepted to be in low alloy steel side. The result and microstructure analyses of this research is very important to understanding the variation in welding zone and HAZ microstructure and its impact in weldment mechanical properties and establish the base to produced best welding procedure according to welding zone microstructure properties. [ABSTRACT FROM AUTHOR]

Results are presented for a study of the weldability of a wide range of pipeline steels by a method of simulating welding thermal cycles. It is shown that the method of simulating the microstructure by exposing base metal to a welding thermal cycle using a Gleeble test complex can be considered as a universal method for assessing steel weldability. The method makes it possible to evaluate steel reaction to thermal action for various welding methods and regimes, and in particular to establish the microstructure and mechanical properties (hardness, toughness, crack resistance). Alongside precise reproduction of the welding thermal cycle for a given range of pipes and welding modes, Gleeble makes it possible to separate the effect of individual thermal cycle parameters on the microstructure and to establish a number of important features. Microstructural mechanisms that determine formation of the heat-affected zone metal properties are discussed. It is shown that during simulation it is important to provide an austenite grain size corresponding to an actual welded joint and the type (section) of the impact specimen, which will allow comparison of material and welding technology. [ABSTRACT FROM AUTHOR]

The present study describes the laser welding of Co-based superalloy L605 (52Co-20Cr-10Ni-15W) equivalent to Haynes-25 or Stellite-25. The influence of laser welding process input parameters such as laser beam power and welding speed on mechanical and metallurgical properties of weld joints were investigated. Epitaxial grain growth and dendritic structures were visible in the weld zone. The phase analysis results indicate the formation of hard phases like CrFeNi, CoC, FeNi, and CFe in the weld zone. These hard phases are responsible for the increase in microhardness up to 321 HV0.1 in the weld zone, which is very close to the microhardness of the parent material. From the tensile strength tests, the ductile failure of welded specimens was confirmed due to the presence of dimples, inter-granular cleavage, and micro voids in the fracture zone. The maximum tensile residual stress along the weld line is 450 MPa, whereas the maximum compressive residual stress across the weld line is 500 MPa. On successful application of Response Surface methodology (RSM), laser power of 1448.5 W and welding speed of 600 mm/min i.e., line energy or heat input equal to 144 J/mm, were found to be optimum values for getting sound weld joint properties. The EBSD analysis reveals the elongated grain growth in the weld pool and very narrow grain growth in the heat-affected zone. [ABSTRACT FROM AUTHOR]

A recently developed solid-state joining technique called "friction stir spot welding" (FSSW) is used to combine metal alloys with low weldability. Significant experimental work for this study is concentrated on the FSSW of AA6063 and AA5083. The study involved fixture setup and welding pattern parameters for the sizes of the material, all of which were done on a milling machine. A cylindrical shoulder with a concave (10°) square pin profile was taken into consideration using various process parameters. The tool material is heat-treated high-carbon steel. The Taguchi L9 orthogonal array is employed for the experimental model. The influence of FSSW factors including spindle speed, time, and depth was studied, along with the relationship between tensile strength, hardness at the contact region, and hook development, which would be a nominal metallurgical pledge established in the welding zone among the interacting sheet plate. The hook structure was found in the area of contact, and thermomechanical effects were seen in the spot-welding area. It has been determined that the influencing variables are spindle speed and plunge depth. As a consequence, it was determined that a tool spindle speed of 1200 rpm, a time of 25 seconds, and a plunge depth of 0.10 mm offer better mechanical properties. The microstructural analysis of welded region was carried out using a scanning electron microscope (SEM). [ABSTRACT FROM AUTHOR]

To clarify the long-term creep rupture strength and microstructure stability of Ni-based alloy HR6W (45Ni-24Fe-23Cr-7W-Ti, ASME Code Case 2684), creep tests were conducted up to about 70,000h and 117,000h for the weldment and parent metal respectively, and the microstructure of crept specimens was experimentally investigated. The weldment showed comparable strength with the parent metal. The metallurgical microstructure characterization and quantitative evaluation on the precipitation behavior indicated the precipitation strengthening of Laves phase, M23C6 carbide and αCr phase in the HAZ (Heat Affected Zone) and parent metal contributing to the long-term creep rupture strength stability of weldment. Satisfactory microstructural stability was proven without distinct degradation during long-term creep at 700°C up to around 117,000h. Furthermore, the internal pressure creep test of circumferential weldment was performed to verify the damage and failure morphology of actual components under the multiaxial loading [ABSTRACT FROM AUTHOR]

The combined effect of the C and Si contents on the microstructure and low-temperature impact toughness of heat-affected zone (HAZ) of the offshore engineering steel. As the C and Si content is decreased from 0.09 to 0.07 wt.% and 0.12 to 0.03 wt.%, the HAZ toughness at −40 °C is increased from 36 to 180 J, and the hardness in the coarse-grained heat-affected zone (CGHAZ) is decreased from 325 to 297 HV0.05. The higher C and Si content promote the precipitation of M23C6 and cementite, but restrain the formation of MC and M2C carbide in the present developed steels. The microstructures in the CGHAZ are comprised of a mixture of martensite and bainite after the welding with the heat input of 50 kJ/cm and are similar with the different C and Si contents. As the C and Si contents are decreased, the density of the geometrically necessary dislocation (GND) is increased. The fracture is changed from brittle to ductile manner, and the cleavage facet size is decreased from 23 to 11 µm. Reducing the C and Si contents significantly decreases the packet size from 25 to 17 µm, thereby leading to the improvement of HAZ toughness. [ABSTRACT FROM AUTHOR]

Purpose: In dental practice, there is necessary to weld gold with titanium under the conditions of a dental technique laboratory, which is difficult. The aim was to assess the weldability of pure gold with the titanium alloy Ti6Al4V using a prosthetic laser welding machine. Design/methodology/approach: Gold wire in a diameter of 0.4 mm made with the use of a jewellery drawbar (GOLDPORT, Szczecin, Poland) was welded to a titanium alloy Ti6Al4V substrate of dental implant abutment screw (MegaGen). Dental laser welding parameters (Bego Laser Star T plus) were 230 V; 6.5 ms; 2.5 Hz; laser spot 0.3 mm, and argon blow. Samples were included in resin, ground (500-4000 SiC), polished (Al2O3 suspension) and etched (Kroll solution) per 20 s before observation under a light microscope. Findings: There were well-welded and poorly joined zones. The discontinuities and voids there were not visible or sparse next to the initial weld point. Dendritic structure at well-welded remelting zones and two-phase microstructure of titanium and Ti3Au phase were found. The heat-affected zone was about of 20 microns. Research limitations/implications: Light microscopy was used, and precise phase identification required further investigations. Weld strength assessment requires further microhardness and load-bearing ability tests. Weldability concerns the model system with pure gold. Practical implications: In the case of elements with dimensions below 0.4 mm, the use of a laser with a smaller spot should be considered for better control of the remelting zone and mechanical positioning of the elements in order to stabilize and avoid discontinuities and voids. Originality/value: Prosthetic laser welding with a laser spot about of 0.3 mm allows to obtain well-welded parts of 0.3 mm in diameter under stable stitching conditions and higher than 0.4 mm in dimensions. [ABSTRACT FROM AUTHOR]

For the production of building reinforcing steel, special charge components were used, consisting of steel waste, cast iron shavings and about 20 % of NVG pellets. Steel was smelted in a 60-ton electric arc furnace. The pouring of liquid steel was carried out on a continuous casting machine. Heat treatment was carried out immediately after the rolling operation to improve the physical and mechanical properties of the construction reinforcing steels melted in the electric arc furnace from the charge material using metal waste. It is recommended that these steels be made of low-carbon (C≤0.25 %) and low-alloy steels in order to have a sufficiently high technology and good weldability. However, in order to meet the requirements of construction standards, these steels must have high structural integrity and physical and mechanical properties. It was found that these requirements can be solved only by heat treatment immediately after the rolling operation of the armature. In this case, the effect can be obtained by reinforcing heat treatment of the fittings by hardening due to the rolling temperature. Therefore, in order to further improve the properties during thermomechanical treatment (TMT), the hardening was carried out directly (immediately) after the deformation in the roll. Immediately after the spread, the physical and mechanical properties, as well as the fluidity and strength properties of the construction low-carbon reinforcement steels met the requirements of the standard by conducting HTMT. Increased strength and technological properties of reinforcing steel are achieved after hardening by dispersion hardening at high-temperature tempering, which is carried out at a temperature of more than 580 °C. [ABSTRACT FROM AUTHOR]

QStE 420 TM quality steel sheet plate materials, which are widely used in sectors such as defense industry and automotive industry, are made of fine-grained and micro-alloyed structure and are joined separately using the shielded metal arc welding method with the help of basic type rod electrodes with 3 different chemical compositions (E11018-G H4, E7018-1 H4R and E7018 H8 AWS coded). Mechanical and metallurgical effects on the welding zone (base material, heat-affected zone and weld metal) formed after the melting of electrodes with different chemical compositions in specified parameters; the samples were examined by applying macrostructure and microstructure examinations, as well as mechanical tests by applying tensile, bending, notch impact and hardness tests. As a result of the tests, the mechanical and metallurgical effects occurring in the weld zone were investigated by performing macro-micro structure examinations and applying tensile, bending, notch impact and hardness tests. In these tests, the fulfillment of the expected mechanical and metallurgical properties of the welded joints obtained from the basic electrodes of different compositions was examined in terms of weldability. Based on the comparative test results, the most appropriate results are; It was obtained from test samples that were combined in 4 passes with the electrode coded E7018 H8, at an average current intensity of 190 A, an arc voltage of 33 V and an average welding speed of 2.93 mm/second. [ABSTRACT FROM AUTHOR]

The research was conducted on a thick-walled welded joint between the HTK 900H wear-resistant steel plates and the A6 cast profile. The aim of the experiment was to produce a joint with the relevant performance requirements, i.e., a good abrasion resistance joint in the weld face area while ensuring its proper plasticity. The welded joint was made using the MAG PULSE and the high-performance MAG TANDEM methods under automated conditions using the linear welding energy ranging from 1.2 to 2.2 kJ/mm for the different joint regions. The scope of the research included both non-destructive and destructive testing. The non-destructive visual (VT), magnetic-particle (MT), and ultrasonic (UT) tests revealed a good quality of the welded joint with no significant welding imperfections. The microstructure of the welded joint in the weld zone was characterized by a dominant volume fraction of martensite/bainite. The measurement of hardness near the face of the weld confirmed obtaining similar values for this parameter. The HTK 900H steel was characterized by hardness at the level of 383 HV10, whereas the A6 cast-328 HV10, and the weld-276 HV10. At the same time, the analyzed joint showed high ductility in the range of 86 to 159 J. The tests carried out showed that the linear energy control allowed a welded joint with the required performance characteristics to be obtained. [ABSTRACT FROM AUTHOR]

Compared to other stainless steels, the supermartensitic stainless steels (SMSS) are a new sub-family with improved weldability and mechanical and corrosion resistance properties. Besides the drastic reduction of carbon content and Ni and Mo addition, these steels may also contain microadditions of Ti, Nb, V and/or N to the improve mechanical resistance. These materials are mainly used as seamless pipes for casings and tubulars for oil and gas off-shore production. After hot rolling (Mannesman process), the tubes are quenched and tempered to achieve the required mechanical properties. Tempering temperature is adjusted as function of the class of mechanical resistance, 95 ksi or 110 ksi. In this work, based on the mechanical properties data, the heat treatment used to produce steels of classes 95 and 100 ksi were determined. The microstructural features of the as tempered steel were investigated and compared to the microstructure of specimens treated for classes 95 ksi and 110 ksi. [ABSTRACT FROM AUTHOR]

The Hastelloy X superalloy is a widely used solid-solution Ni-based sheet alloy for gas turbines, aero-engine combustion chambers, and other hot-end components. To investigate the effect of microstructure, especially grain size, on its weldability, Hastelloy X alloy bars are homogenized, cold-rolled to thin sheets, and recrystallized under different conditions to obtain equiaxed grain microstructures with average grain sizes of ~5 μm, ~12 μm, and ~90 μm. The laser welding process is used for joining the alloy sheets, and then the alloy's weldability is investigated through microstructural and mechanical property characterizations. The microstructures in weld consist of coarse columnar grains with dendrite, and grain sizes of these columnar grains are almost the same when grain size of Hastelloy X base metal increases from ~5 μm to ~90 μm. Moreover, although all welds exhibit lower yield strengths (YS), ultimate tensile strengths (UTS), and elongations to fracture (EF) than the base metal, the degrees of reduction in them become slight when the grain size of base metal increases from ~5 μm to ~90 μm. [ABSTRACT FROM AUTHOR]

The joint conditions of a weldment entirely rely on the set of process parameters applied during the welding operation. In friction stir welding (FSW), proper mechanical mixing of the material signifies the appropriate welding variables. The present work aspires to investigate the influence of tool rotational speed (RS), welding speed (WS) and plunge depth (PD) on external as well as internal defect formation, identify the different types of defect encountered during the FSW process, and evaluate the influence of different parameters on tensile properties and microstructure of the joints. In order to achieve the goal of the present work, a detailed experimental investigation was carried out using AA5086-O as base metal. On account of high strength-to-weight ratio, good weldability and high corrosion resistance, friction stir welded joints of aluminum alloys are widely applications in aerospace, automotive, railway and shipbuilding industry. It has been observed that theultimate tensile strength (UTS) of joint tends to decrease when there is increased in the welding speed at constant PD of 0.2 mm and RS of 1400 rpm. Similarly, with consistent PD of 0.3 mm and rotational speed of 2000 rpm, UTS of joints initially enhanced with an increment in welding speed and then reduced eventually. A joint fabricated with maximum rotation speed, intermediate welding speed and the higher plunge depth produced highest tensile strength of 215 MPa which is 16% higher than the conditions required for aerospace applications of FSW for aluminum alloys, as per the standard of American Welding Society (AWS). Microscopic analysis was conducted to scientifically ascertain the grain size, crystal structure and surface morphology of the FSW joints. [ABSTRACT FROM AUTHOR]

Ultra-high-strength steel significantly contributes to lightweight design. However, it is essential that excellent mechanical properties are maintained after the applied welding process in terms of structural integrity, strength and ductility. This study investigates the microstructural and mechanical properties of metal active gas-welded X-joints of 20-mm-thick S1100 thermomechanically rolled plates with undermatched alform 960 L-MC filler metal. Welding was carried out fully automated in order to obtain uniform properties of the welds for different heat inputs in flat (PA) and vertical up (PF) positions. The mechanical properties of weldments were characterized by hardness, impact and tensile tests and complemented by microstructural analysis using optical and scanning electron microscopy. Different heat inputs due to altered welding positions caused changes in prior austenite grain size and orientation in the weld metal (WM) microstructure which is presented and discussed in detail. The microstructures of the WM consist of ferrite, while the heat-affected zone (HAZ), which was exposed to several thermal cycles, is dominated by bainite and martensite-austenite (M/A) constituents. While in the HAZ the top layer shows fresh martensite of high hardness, the HAZ of filler and root passes was tempered showing lower hardness values. Transverse tensile tests always failed in the weld metal not fulfilling base materials strength requirements. Although the weld metal microstructure consisted of acicular ferrite in PA and PF position, PF weld has lower toughness. [ABSTRACT FROM AUTHOR]

The use of cold metal transfer process (CMT) is an excellent alternative to depositing nickel-based alloys on oil and gas pipelines due to the relatively small dilution. However, sulfide stress corrosion cracking (SSCC) of dissimilar weld joints has proven to be an issue. Therefore, this study investigates the microstructure and SSCC behavior of an Inconel 625/X80 weld overlay fabricated CMT process focusing on the tempering effect. Four-point bending tests show a high SSCC susceptibility of the non-overlap zone due to the formation of coarse structure in the heat affected zone and narrow martensite layer along the fusion boundary. However, microstructural characterization indicates a tempering effect in the overlap zone, producing homogenized microstructure and less residual strain in the heat affected zone. Therefore, the SSCC resistance is greatly improved, especially for the fusion boundary, because reversed austenite in the martensite layer could decrease the accumulation of hydrogen at lath boundaries. [Display omitted] • Martensite layer induces sulfide stress corrosion cracking of the fusion boundary (FB). • Tempering effect produces homogenized microstructure and less residual strain. • Reversed austenite exists in the martensite layer along the FB in the overlap zone. • Sulfide stress corrosion cracking of FB is improved by the reversed austenite. [ABSTRACT FROM AUTHOR]

In order to meet the welding requirements of offshore structures with high load capacity, the microstructure and mechanical properties of CO2 GMAW + SAW joint of high strength marine engineering steel DH36-Z35 with 60mm thickness were investigated. The results showed that no softening occurred in the joints with CHW50C6SM welding wire used for CO2GMAW, and CHW-S3 welding wire and CHF101 flux used for SAW. The mechanical properties of the joints met the requirements of relevant standards. Post-weld heat treatment at 350 °C and below for 1h could refine the microstructure of HAZ, but had little influence on the microstructure of weld, and reduced the strength and low temperature impact toughness of the joint to a certain extent. The bottom layer of CO2GMAW without preheating was a weak layer for the mechanical properties of the joints. [ABSTRACT FROM AUTHOR]

The influence of the pulsed Nd:YAG laser welding process on the microstructure and mechanical characteristics of Inconel 718 alloy weldments of 1 mm thin sheets was investigated. By varying the selected input variables such as laser power, weld speed, and pulse duration, an analysis has been done on the weld characteristics, namely penetration and top and bottom width by Taguchi's approach. The results were presented by focusing on weld bead geometry, grain structure in the Fusion Zone (FZ), Heat Affected Zone (HAZ), and the tensile properties. The FZ and HAZ microstructure consists of equiaxed, columnar grain structures, respectively, and clear ductile failure was observed with weldment. The combination of laser power at 2.5 kW, weld speed at 2.38 mm/min, and pulse duration at 6.6 ms achieves minimum top and bottom width. Similarly, a combination with 3.3 kW laser power, 2.02 mm/min weld speed, and 8.4 ms pulse duration offers maximum possible penetration that results in quality weldments. The influence of process variables was analyzed by ANOVA. A hybrid Grey–ANFIS model is evolved for determining the multiple performance index. From the validation outcomes attained (MAPE – 0.0413, correlation coefficient – 0.9991), it is proved that the evolved model is proficient for precise prediction. [ABSTRACT FROM AUTHOR]

This work presents an analytical methodology for the development of pipeline fitting welding modes, including the calculation of welding cooling rates and the assessment of steel response to the thermal cycle of welding processes. As a result, an optimal range of cooling rates ensuring the formation of a metal structure with the required mechanical properties in the heat-affected zone of the seam was determined. [ABSTRACT FROM AUTHOR]

316L austenitic stainless steels were produced by powder metallurgy method at 600 MPa and 700 MPa pressing pressures in this study. The weldability of these steels was investigated by applying the resistance spot welding method. The microstructure of the welded sample was analyzed in detail with optical microscope. In addition, the hardness values of the base metal, heat-affected zone and weld metal regions formed as a result of resistance spot welding process were measured. Consequently, it was observed that the base metal microstructure was mainly composed of austenite phase. Due to the high heat occurring in resistance spot welding process, weld metal mainly consisted of delta ferrite phase in the austenite matrix. Hardness values increased from base metal to weld metal. Also, the hardness values measured in different welding regions of the sample obtained at 700 MPa pressing pressure were found to be higher than the sample obtained at 600 MPa pressing pressure. [ABSTRACT FROM AUTHOR]

This paper presents a heat treatment process designed to enhance the abrasion resistance of welded joints of Hardox Extreme steel, which is known for its high hardness (>600 HBW) and tensile strength (>2000 MPa). Despite these properties, the steel's weldability, characterized by a Carbon Equivalent Value (CEV) of 0.70, limits its use in applications like mining machinery where welding is essential. The key challenge in welding martensitic boron steels, such as Hardox Extreme, is the reduction in hardness and abrasion resistance in the heat-affected zone, along with cold cracking due to increased hardenability. This study investigates the abrasion resistance and microstructural properties of welded joints made with submerged arc welding (SAW) under different heat treatment conditions. The developed process achieved a uniform tempered martensite microstructure across all welded zones, increased hardness to over 550 HV in the weld material zone and improved the relative abrasion resistance by 25 % compared to the as-welded state. [ABSTRACT FROM AUTHOR]