Welding Machine Research Articles

Experimental Analyses and Predictive Modelling of Ultrasonic Welding Parameters for Enhancing Smart Textile Fabrication.

This study aims to illustrate the design, fabrication, and optimisation of an ultrasonic welding (UW) machine to join copper wires with non-woven PVC textiles as smart textiles. The study explicitly evaluates UW parameters' impact on heat generation, joint strength, and electrical properties, with a comprehensive understanding of the process dynamics and developing a predictive model applicable to smart textiles. The methodological approach involved designing and manufacturing an ultrasonic piezoelectric transducer using ABAQUS finite element analyses (FEA) software and constructing a UW machine for the current purpose. The full factorial design (FFD) approach was employed in experiments to systematically assess the influence of welding time, welding pressure, and copper wire diameter on the produced joints. Experimental data were meticulously collected, and a backpropagation neural network (BPNN) model was constructed based on the analysis of these results. The results of the experimental investigation provided valuable insights into the UW process, elucidating the intricate relationship between welding parameters and heat generation, joint strength, and post-welding electrical properties of the copper wires. This dataset served as the basis for developing a neural network model, showcasing a high level of accuracy in predicting welding outcomes compared to the FFD model. The neural network model provides a valuable tool for controlling and optimising the UW process in the realm of smart textile production.

Analisis Efisiensi dan Efektivitas Sistem Produksi dengan Metode Troubleshooting pada PT Chandra Nugerah Cemerlang

PT Chandra Nugerah Cemerlang is a company that operates in the production of motorcycle and car components. To streamline its production, PT Chandra Nugerah Cemerlang uses production factors including raw materials, labor, capital, and specific technology. The main goal is to maintain and expand market share through good production results. Based on the above background, researchers are interested in knowing the extent of efficiency and effectiveness capacity of the production factors at PT Chandra Nugerah Cemerlang, especially labor and machine factors. CNC Group operates in manufacturing and engineering, producing components and spare parts for two-wheeled and four-wheeled vehicles using pressing and welding processes. PT Chandra Nugrah Cemerlang has customers such as Yamaha, Suzuki, and Kawasaki. One of the production processes to be analyzed is the welding robot line at PT CNC 2, which includes 18 robot welders and 3 Otc Daihen manual welding machines. Manual welding is used to fix suboptimal results from the robot welding. PT CNC Group is also committed to improving culture, human resources, and productivity to face global competition.

Machine learning tool for the prediction of electrode wear effect on the quality of resistance spot welds

The quality of resistance spot welding (RSW) joints is strongly affected by the condition of the electrodes. This work develops a machine learning-based tool to automatically assess the influence of electrode wear on the quality of RSW welds. Two different experimental campaigns were performed to evaluate the effect of electrode wear on the mechanical strength of spot welds. The resulting failure load of the joints has been used to define the weld quality classes of the machine learning tool, while data from electrode displacement and electrode force sensors, embedded in the welding machine, have been processed to identify the predictors of the tool. Some machine learning algorithms have been tested. The most performing algorithm, i.e., the neural network, achieved an accuracy of 90%. This work provides important theoretical and practical contributions. First, the decreasing thermal expansion of the weld nugget as the electrode degradation advances results in a strong correlation between the difference of the maximum displacement value and the last value recorded during the welding and the relative failure load. Then, this work offers a practical decision support tool for manufacturers. In fact, the automatic detection of low-quality welds allows to reduce or eliminate unnecessary redundant welds, which are performed to compensate for the uncertainty of electrode wear. This leads to savings in time, energy, and resources for manufacturers. Finally, general recommendations for the timing of redressing or replacing the electrode are provided in the manuscript based on the company willingness to accept some non-compliant welds or not.

Design and Development of a Portable Resistance Spot Welding Machine for Small-Scale Industries

Resistance spot welding (RSW) is a commonly used process in a variety of fields such as automotive, aerospace, household, furniture, and railway for welding sheet metal parts. These industries further demand a welding machine that is portable and versatile in terms of where it can be utilized, such as, among others, remote locations, and is cost and energy-efficient, reliable, and highly efficient performance-wise. With this aim, the work develops a portable spot-welding machine with specific specifications, of an electrode of 0.394 inches in diameter and 10 inches in length, made of copper, and transformer specifications of 6 V-1500 A with 7 variable current settings. This machine is designed to provide accurate, consistent, and reliable welding readings. Additionally, the machine works on an AC supply of 220 volts, making it easily usable. The machine is found to be cost-effective, with a development cost of only 6100 rupees. It has also been found to be reliable and effective in welding up to two 3 mm mild steel plates under different currents, resistivity, and voltage settings. The machine is simple to operate and user-friendly and with a compact and lightweight design, it is highly versatile and easy to operate for a wide range of welding applications.

Ultrafine industrial aerosol as a risk factor for the health of smelting shop workers at a machine-building enterprise

Aim. To evaluate the amount and physicochemical properties of ultrafine industrial aerosol (UIA) in the work zone air (WZA) of smelting shop workers at a machine-building enterprise during various technological processes (melting, welding, and metal machining). Materials and methods. The physical properties of UIA particles were evaluated with NanoScan 3910 scanning spectrometer: the number of particles (number/cm3), particle surface volume (nm3/cm3), particle surface area (nm2/cm2), and nanoparticle mass concentration (μg/cm3) in the WZA of a furnace operator (n = 416), a welder (n = 315), a cutter (n = 286), a grinder (n = 78), and workers of the control group (n = 315). The chemical composition of the air samples was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using an Optima 2100 DV device. Results. It has been found that the highest concentration of UIA nanoparticles was recorded during metal melting at the workplaces (WP) of furnace operators (4.28 × 104 to 2.41 × 105 particles/cm3) and welders (3.01 × 104 to 3.34 × 105 particles/cm3). During mechanical metal processing, a much smaller number of nanoparticles was produced (for grinders, the number varied from 9.81 × 104 to 1.44 × 105 particles/cm3; for cutters, it varied from 2.71 × 104 to 1.94 × 105 particles/cm3). Indicators of surface area, surface volume and mass concentration at the WPs of furnace operators, welders, grinders and cutters exceeded the corresponding indicators of the control group for almost all sizes of suspended particles with statistically significant differences (p ≤ 0.05). It has been estimated that such metals as Al, Cu, Mg, Mo, Fe, and Ni were present in the workers’ WZA but their content did not exceed the current maximum permissible concentrations. Conclusions. The presence of suspended particles of UIA with a maximum concentration in the range from 20 nm to 70 nm has been confirmed in the WZA during melting, welding of metals and machining. Indicators of concentration, surface area, surface volume, and mass concentration at the workplaces of melting shop workers at the machine-building enterprise significantly exceeded the corresponding indicators in the control group without dust formation processes, showing statistically significant differences (p ≤ 0.05). The evidence of metals in the WZA has suggested their presence in the form of nanoparticles, which are more active and dangerous, thus increasing the risk of their adverse effects on the workers. Ультрадисперсний

Enhancing weld strength in high-strength steels: the role of regional preheating in RSW

Abstract In this study, automotive in sector use STRENX 700 CR and DP 800 steels were joined by resistance spot welding using medium frequency direct current. Some parts were joined under atmospheric conditions, while others were joined by applying regional preheating to their heat-affected zones before welding. The design, manufacturing, and adaptation of the preheating system to the welding machine were carried out as part of this study, considering it as a new system. After the joining process, nondestructive and destructive tests were performed on resistance spot welding connections between STRENX 700 CR and DP 800 steels. Hardness tests revealed that the preheating applied to the heat-affected zones before welding reduced the hardness of the weld metal by approximately 8 %, while the microstructure analysis showed that the regional preheating increased both the weld metal and the heat-affected zones width. The tensile-shear strength increased by about 7 %, and the cross-tension test strength increased by about 5 % with the preheating applied to the heat-affected zones before welding. In both the tensile-shear and cross-tension tests, all failures occurred in the form of button shearing from the heat-affected zones. The regional preheating treated specimens showed the highest fatigue life, with an average of 947,632 cycles.

De-Coupled Control of Energy-Efficient High-Power CC/CV Power Source for Arc Welding

De-Coupled Control of Energy-Efficient High-Power CC/CV Power Source for Arc Welding

Italian School One Piece Implants Stabilized with Electrowelded Titanium Needle for The Rehabilitation in Aesthetic Area of Single Post-Extraction Edentulies with Immediate Loading

The stabilization of an one piece implant with an electrowelded titanium needle is a technique introduced at the end of the seventies of the last century to increase the primary stability, already acquired by means of the wide thread and bicorticalism, of the one-piece implants of the Italian school such as the Tramonte screw, especially in immediate loading rehabilitations of single edentulous upper front teeth and thus make the success of immediate loading predictable. The stabilization of a one piece implant is achieved by inserting a titanium needle (Scialom type) divergent from the axis of the main implant, a needle which must reach and impact the deep cortical bone and be welded with the intraoral welding machine to the one piece basic screw, to form a single prosthetic abutment. In addition to enhancing primary stability and increasing resistance to static and dynamic stress, given that by forming a single body with the implant it extends the support surface over a larger surface, needle stabilization also carries out an anti-rotational action, opposing the "unscrewing" effect that can be caused by the pressure exerted by the tongue during swallowing. Needle stabilization also helps to avoid those micromovements which, when they exceed 150 microns, can prevent the osseointegration process, leading to the failure of the immediate loading implant. Needle stabilization has proven to be particularly effective in the immediate loading of post-extraction single implants in the upper frontal sectors, with reduced bone depth, or with poorly mineralized bone.

Advancements in energy-efficient welding production techniques: Innovative models and methods for combined workpiece fabrication

This article highlights notable advances in energy-efficient welding manufacturing techniques, with particular emphasis on new models and methodologies for combined welding machines. High energy density welding processes such as laser beam and electron beam welding are being investigated for their potential to optimize energy use in various industrial applications. Furthermore, the examination extends to energy- efficient high-density welding procedures, notably encompassing electric arc, gas welding, and autogenous welding, while also taking into account factors tied to corrosion processing. Technological advances in machining, cutting techniques, and specialized connectors are also explored in detail, and their contribution to reducing energy consumption and improving overall equipment efficiency is examined. This thorough investigation would not be complete without considering the implications for the energy sector, where the use of energy-efficient welding techniques is critical in reducing costs and refining manufacturing processes.

Mechanization and import substitution in zimbabwean farmers' equipment: A case study of the revitalization of an abandoned tractor trailer

Abandonment of equipment on Zimbabwean A1 and A2 farms has significant costs for both farmers and the national economy, as farmers often continue using outdated or traditional farming methods. Maintenance practices, innovation, research, design, and modern machinery have evolved considerably over the past hundred years, shifting from old maintenance applications to planned maintenance strategies combined with Import Substitution Industrialization (ISI). For Zimbabwean farmers, adopting this approach is crucial, particularly for revitalizing farm implements and machinery. Currently, it is evident that many farm implements and equipment have been abandoned. These implements and equipment could be assessed and mechanically restored to their operational state. A mechanical assessment of abandoned equipment was conducted, focusing on main components such as the chassis and suspension to facilitate the revitalization process. This was followed by a product development plan outlined in the methodology. The abandoned trailer was dismantled, with selected components purchased locally, and then reassembled using mechanical methods. The mechanical activities involved included cutting with grinders, joining through arc welding, and using bolts and nuts. As a developing country striving to adopt modern technologies, Zimbabwe's application of Import Substitution Industrialization is a crucial strategy for embracing sustainable development. Farmers are advised to integrate basic welding knowledge into their farming activities and acquire essential machinery, such as CO2 welding machines and workbenches, for their mechanical workshops. Large-scale farmers in Zimbabwe typically have workshops equipped with these basic machining tools. The abandoned trailer was reconditioned to a functional state using basic machining methods and tools, as detailed in this paper.

Development and Performance Analysis of a Seam Welding Machine for Thin Plate Applications

Resistance Seam Welding (RSEW) is a welding process that uses rotating wheel-shaped electrodes to produce a continuous weld along the seam of the workpiece. RSEW is used for welding metal sheets and utilizes electrical resistance as its heat source. The welding technique applicable to RSEW is the lap joint configuration. In this study, steel plates with thickness variations of 0.15mm, 0.2mm, and 0.3mm were welded using a current of 20 amperes and a welding speed of 3.125 mm/s. The thickness of the welded plates can affect the welding outcome. For the welding process, a current of 20 amperes was used on specimens with lap joint configurations. The specimens were subjected to tensile testing using a tensile testing machine with a capacity of 30 tons. The test specimens included three types of steel plates with varying thicknesses of 0.15 mm, 0.2 mm, and 0.3 mm. The results of the tensile tests indicated that, with the same welding parameters, the tensile strength decreased as the material thickness increased.

Underwater Friction Welding of Low Carbon Steel

In this study, an attempt was made to obtain a welded joint from the underwater friction welding (UFW) process. The workpiece material used in this experiment was AISI 1018 low carbon steel. The experiment was carried out on a friction welding machine which was designed and manufactured for this purpose. The UFW process was carried out by varying the spindle rotation used to rotate one of the workpieces. The friction force was kept constant. The quality of the welded joints resulting from UFW was determined by measuring the misalignment that occurs in the weld joint, the macro and micro structures formed, as well as the mechanical properties of the welded joint. For comparison, friction welding in air (FW) was also carried out. The results obtained indicate that low spindle rotation results in high misalignment of the welded joint between the two workpieces. During the UFW process, rapid cooling occurs so that the microstructure of the weld metal, TMAZ and HAZ is dominated by a fine pearlite phase so that the hardness and strength of the weld joint are higher than those produced by FW process in air.

Simulation Study of Critical Aspects of MIAB Welding for Analysis of Potential Factors Governing the Performance of Weld Formation

Magnetically Impelled Arc Butt (MIAB) welding, is a solid-state welding technique. The magnetic system of this technique is pivotal for the generation of the Lorentz force, which impels an arc to rotate along the periphery of the weld tubes and thus facilitates the heating of faying surfaces. The magnetic arrangement and the arc dynamics significantly impact the effectiveness of the welding process, eventually dictating the efficiency. This study case investigates the impact of the magnetic arrangement on the arc rotation and possible factors that cause irregularities in the (MIAB) welding through COMSOL simulation. The COMSOL simulation has served as a powerful tool to comprehensively analyse various arc dynamics and magnetic systems and extrapolate the observations to analyse the arc dynamics and magnetic systems involved in MIAB welding. By employing simulation studies, the research aims to unravel critical insights for an efficient design of the MIAB welding system. This work includes a study of the effect of magnetic forces on arc dynamics using various models and attempts to develop an analogy to the MIAB welding process. This is further utilized to explain the process variations in the form of arc displacement, electric potential distribution, and the possibility of self-demagnetization of AlNiCo magnets. Thus, it provides a foundation for advancing the technological aspects of MIAB welding to overcome the limitations and irregularities. This research is instrumental in enhancing the understanding of magnetic interactions involved in the MIAB process, which can further pave the way for improved welding machine designs and consequently, enable research on these lines that can help in establishing an optimized parametric window.

Fusion of dies with economy-layed secondaryhard-ducted steel

Problem. The purpose of the work is to increase the wear resistance and heat resistance of secondary hardening surfacing steels by improving the composition of alloying powder wires due to the optimization of the content of titanium, molybdenum and chromium. It was found that increasing the heat resistance of iron-based Cr-Mn-Ti alloys contributes to an increase in the content of the carbide phase [TiC]; the introduction of [Mo] stabilizes the value of hardness at elevated temperatures, increases heat resistance and hardness during dispersion hardening. High indicators of heat resistance and wear resistance of steel 18X4G10M5T3S are achieved due to additional diffusion formation of the carbide phase during aging, increased contact strength, a significant amount and uniform distribution in the volume of the deposited metal of the carbide phase. Goal. Іncreasing the wear resistance and heat resistance of secondary hardening surfacing steels by improving the composition of alloying powder wires due to the optimization of the content of titanium, molybdenum and chromium. Methodology. For automatic arc surfacing under the flux, attachment devices were designed and manufactured for feeding the de-energized flux-cored wire into the welding bath. The use of these devices on the A-1401 and TS-17M welding machines made it possible to study the influence of the de-sintering additive on the deposition parameters, chemical and phase composition of the deposited metal. The surfacing was carried out on samples made of steel 20 and 50 KhNM according to the "slide" scheme. The powder wire was produced at the laboratory facility of the Department of Welding Production of UIPA. The crack resistance of the alloys was studied at the LTP 1-6 installation. Results. On the basis of experimental studies, it was established that automatic surfacing with a de-energized additive increases the technical and economic indicators of melting - the surfacing coefficient is up to 30 g/Ag, the share of the base metal in the surfacing decreases to 11...14%, reduces the specific fuel costs and energy costs - increases the specific energy for the formation of a seam above the conventional limit of fusion and thermal efficiency. by 60...70% and 40...50%, reduces the coefficients of the relative mass of slag by 24...28%, increases the absorption coefficients of alloying elements by 70...80% in contrast to single-electrode melting. Originality It was found that increasing the heat resistance of iron-based Cr-Mn-Ti alloys contributes to an increase in the content of the carbide phase [TiC]; the introduction of [Mo] stabilizes the value of hardness at elevated temperatures, increases heat resistance and hardness during dispersion hardening. Practical value. On the basis of the conducted research, economically alloyed wear-resistant alloys and the technology of their application were developed to restore the grooves of the matrices of hot metal stamping dies. The use of these alloys and the technology of their application ensures a reduction in energy and resource costs and an increase in the durability of the stamping tool.

Advantages of Friction Welding of Fittings with Small Diameter Conical Contact Form

Introduction. As numerous production tests show, the use of manual arc welding (MAW) of thick-walled fittings of small diameter (up to 80 mm) does not provide a high-quality weld joint that meets the requirements of regulatory and technical documents of nuclear power plants (NPP). The solution to this problem is possible on the basis of research and development of welding technology with optimal heat input instead of MAW. Existing fusion welding technologies do not allow for optimal regulated heat input. However, this can be realized during the development and further use of the friction welding (FW) method. Therefore, this work aimed at developing a technology based on an automated technique of friction welding, which could provide the enhancing of the quality of weld joints of small diameter fittings of power equipment to the level of regulatory requirements.Materials and Methods. Small diameter fittings with a conical contact surface made of low-alloy steel 10GN2MFA were used. The experimental study was performed on a friction welding machine MST–41. Methods of non-destructive and destructive quality control were used in accordance with the regulatory and technical documentation of nuclear power engineering.Results. A methodology was developed, and the optimal dimensions of the conical contacting surface under welding were determined. It was shown that optimal heat input during friction welding was achieved by preparing a conical contacting surface in the angle range α = 30º–40º. The methodology and parameters of the friction welding mode for models of small diameter fittings were experimentally tested. In the course of the research, a cyclogram of the friction welding process was obtained and described, which confirmed the stage-by-stage formation of the weld joint due to the sequential inclusion of annular sections of the conical surface of the connected parts in the heating stage. The results of non-destructive and destructive testing were obtained, confirming the presence of a high-quality weld joint at the level of the requirements of the regulatory and technical documents of the NPP.Discussion and Conclusion. The obtained research results can be used to develop the technology of friction welding of pipes, as well as products made of carbon and low-alloy steels.

High geometric fidelity through closed-loop control of the weld pool size in gas metal arc welding based direct energy deposition

Arc based direct energy deposition combines the flexibility of additive manufacturing with high build rates and low investment costs. However, high geometric fidelity of manufactured components is not possible with state-of-the-art methods. Highly varying and geometry-dependent boundary conditions, e.g. heat dissipation and the interpass temperature, are quasi-random influences with a strong impact on the geometric fidelity and the manufactured microstructure. Without adjusting for these variations, process stability decreases, geometric deviations become more likely and defects accumulate from layer to layer. A high geometric fidelity of the manufactured components can therefore not be guaranteed with the state of the art. Due to the large number of influencing variables in the arc-based manufacturing process, this problem cannot be solved by the definition of simple setpoints. Closed-loop control, however, offers the opportunity to flexibly counteract any deviations that occur by adjusting the process parameters in real time. Since the manufactured part is created by solidification from the weld pool, a closed-loop control of the weld pool size is being developed. The developed controller uses the weld pool properties and the interpass temperature as feedback variables and takes into account the non-linear system behaviour as well as the process noise and the parameter uncertainties. The subordinate control of the welding power source is further used for improved process stability. To the best of our knowledge, this solution provides a level of robustness, steady-state accuracy and geometric fidelity that has not been achieved by previous approaches reported in the literature. To illustrate the performance of this closed-loop control for components with low heat dissipation, we demonstrate the fabrication of thin-walled components with high geometric accuracy for a fast 3D printing process and investigate the influence of the welding process variables on the microstructure, the evaluation of the geometric fidelity is based on EN ISO 1101.

Operational determination of current-voltage characteristics welding power sources in nuclear engineering

Welding equipment is everywhere equipped with modern digital welding arc power systems based on microprocessor and other logical element bases. At the same time, there is a tendency to minimize information not only for Chinese, but also for equipment of well-known brands, so it is important to quickly monitor the accuracy of the accompanying documentation in order to avoid deterioration in the quality of products and waste of time re-equipment. Modern recorders of welding processes allow several times to reduce the time for checking the declared characteristics of all power sources certified for use in the nuclear power industry. Among the characteristics and service functions analyzed by the recorder, it should be noted static current-voltage characteristics, oscillograms of «hot start», «afterburner» and «anti-sticking». The paper presents the data of selective tests for compliance with the declared passport data of inverter power supplies INEM-200T (MMA process), Artsen CM-500 (MAG process) and ION 48-900 (SAW process). Based on the results of the research, conclusions were drawn about the benefits of using the proposed model of the welding process recorder at enterprises of heavy nuclear engineering.

Hot Tool Welding of Pipelines from Polyethylene for Gas Supply with a Diameter of 90-315 mm

Purpose of research. GOST P 55276-2012 applied in the Russian Federation does not regulate concrete data on the choice of this or that procedure under various conditions of welding and standard sizes of the applied pipes, leaving it to the discretion of the consumer. Unlike the procedure of the welding with only low pressure which is well fulfilled and widely applied in domestic practice, the welding according to the procedure with the only high pressure allowing to reduce three times time of a welding cycle is practically not used and specially intended welding machines in Russia are not issued. In this regard this work is devoted to development of the modes of hot tool welding of abutting connections of pipes from polyethylene with a diameter from 90 to 315 mm for SDR 13.6 - SDR 9.0 with the only high pressure, to the choice of possible domestic welding equipment and experimental check of the developed modes.Methods. In this article for butt welding by the heated tool of pipes from polyethylene with a diameter from 90 to 315 mm, using a design technique, main parameters of welding procedure are determined with the only high pressure. When choosing the welding machine necessary for tube welding of the considered range on welding procedure with the only high pressure, by results of the carried-out analysis of technical datas of domestic welding machines and features of their operation capabilities it is preferred as the welding machine with the hydraulic drive "Native of the Volga Region of SSPT-315". For experimental check of the executed payment of parameters of the procedure of welding under the cyclogram with the only high pressure four joints of pipes with a diameter of 110 mm with thickness of a wall of 10 mm from PE-100 (SDR 11.0) have been welded and visual and measuring quality control of the executed connections and short-term tests of technological samples on axial stretching by the R-50 machine is made.Results. Mechanical tests of technological samples of all joints of the pipes from PE-100 with a diameter of 110 mm (SDR 11.0) executed on the SSPT-315 welding machine on welding procedure with the only high pressure have shown 100% - ny result of plastic nature of destruction at the size of lengthening from 500 to 600%.Conclusion. The high quality of experimental joints of pipes from PE-100 assumes a possibility of use of the SSPT- 315 machine for hot tool welding of pipes from polyethylene of everything of the range regulated by technical datas on welding procedure with the only high pressure.

Characterization and Eddy Current Flaw Detection of Dissimilar Aluminium Butt Joint by Friction Stir Welding

Dissimilar aluminum butt joints were successfully joined using a friction stir welding machine, employing four welding speeds (50, 60, 70, 80 mm/min), four rotational speeds (900, 1000, 1100, 1200 rpm), and four different weld tool profiles (T1=12/4, T2=15/5, T3=16/4, T4=20/5 in D/d ratio). The corrosion analysis suggests that specimens 9, 10, 11, and 13 exhibit higher corrosion resistance, with a breaking potential of -0.6 eV, while specimen 8 shows the lowest corrosion resistance with a breaking potential of -2.1 eV. The results from the differential scanning calorimeter illustrate the formation of precipitation dissolution due to high heat generation at the nugget zone. An eddy current defect detector experiment was conducted to detect surface flaws in the welded samples. Few surface cracks were observed in the T2 profile specimens, which have a larger contact region or shoulder diameter, while more surface cracks were observed in the T1 profile samples.

Обзор современных требований к сварке трубных высокопрочных низколегированных сталей

For many years, proven arc welding processes have been used to weld large pipes of oil and gas pipelines, the scope of which extends from manual arc welding with stick electrodes to the use of metal orbital welding machines. Introduction reflects that the creation of new steel compositions for oil and gas pipelines is an urgent task to ensure its high reliability. Research Methods. Low-carbon steels with ferrite-perlite structure are usually used in pipe production, but these steels are unable to meet the increased market demands. New grades of steel with bainitic structure are appearing. Results. The failure of welded joints of pipelines made of high-quality steel is becoming a serious problem for the pipeline industry. Discussion. This paper analyzes the characteristics of weld microstructure and its relationship with impact toughness. The prediction of impact toughness based on the microstructural characteristics of weld-seam metals is complicated due to a large number of parameters involved. The common practice linking this property to the microstructure of the last roll of a multi-pass weld turned out to be unsatisfactory because the amount of needle ferrite, the most desirable component, may not always be the main factor affecting the impact toughness. The present review reports on the most representative study regarding the microstructural factor in the welded seam of pipe steels. It includes a summary of the most important process variables, material properties, normative rule, as well as microstructure characteristics and mechanical properties of the joints. Conclusion. It is intended that this review will help readers with different backgrounds, from non-specialist welders or material scientists to specialists in various industrial applications and researchers.