Manual Metal Arc Research Articles

Implementation of Manual Metal Arc Welding with Pulsed Current on TIG Modern Inverter Welding Equipment

The TIG welding technique in pulsed current using inverter welding equipment allows the realization of welds at a high technological and qualitative level due to the advantages that the process offers, the control of the welding pool, of the energy introduced in the components, the increase of the arc stability when using low welding currents or when welding at high speeds. Some manufacturers of welding equipment [1, 2] propose the option of using pulsed current on manual metal arc welding sources to increase the technological performance, primarily for the control of the welding pool by using low values of the current frequency below 10Hz, but with limited possibilities to modify the other parameters of the welded joint. The paper proposes the use of TIG welding equipment in pulsed current, in manual metal arc welding using the pulsed welding technique, starting from the advantages that this equipment offers in terms of the much greater possibility of adjusting all the parameters of the pulsed current according to the technological needs. This is possible because the two welding processes use welding equipment with identical external static volt-ampere characteristics.

Influence of the Pulse Mode of Manual Metal Arc Welding on Weldment Distortions.

As a result of the thermo-mechanical impact during welding, distortions are generated in welded structures. These distortions significantly influence the geometric and dimensional accuracy of welded structures, in many cases lowering their working characteristics and reliability. An optimal design for welded structures is a prerequisite for increased reliability and reduction in manufacturing cost, and such an optimal design can be achieved knowing the distortions in weldments. Despite the fact that pulsed metal inert gas welding and metal active gas welding have been broadly applied in the last few decades, nowadays, few manufacturers, for instance, Fronius, EWM, Redco, and Perfect Power Welders, offer such an option for manual arc welding. This work aims to determine the influence of the parameters of pulsed welding modes on distortions that are generated during manual arc welding. Two different inverter welding power sources were used, and the welding distortions were measured by 3D scanning. The results showed that the pulsed mode during manual arc welding led to a reduction in distortions compared to the conventional welding mode. The crucial part of the manual welding system proved to be the qualification and performance of the welder.

Nrf-2/HO-1 activation protects against oxidative stress and inflammation induced by metal welding fume UFPs in 16HBE cells

As one of the main occupational hazards, welding fumes can cause oxidative damage and induce series of diseases, such as COPD or asthma. To clarify the effects of the metal fume ultrafine particulates (MF-UFPs) of welding fumes on oxidative damage, UFPs were collected by melt inert gas (MIG) and manual metal arc (MMA) welding, and the composition was confirmed. Human bronchial epithelial 16HBE cells were treated with 0–1000 µg/cm2 MF-UFPs to analyse the cytotoxicity, oxidative stress and cytokines. The protein and mRNA expression of Keap1-Nrf-2/antioxidant response elements (AREs) signalling pathway components were also analysed. After 4 h of treatment, the cell viability decreased 25% after 33.85 and 32.81 µg/cm2 MIG/MMA-UFPs treated. The intracellular ATP concentrations were also decreased significantly, while LDH leakage was increased. The decreased mitochondrial membrane potential and increased ROS suggested the occurrence of oxidative damage, and the results of proteome profiling arrays also showed a significant increase in IL-6 and IL-8. The expression of AREs which related to antioxidant and anti-inflammatory were also increased. These results indicate that the MF-UFPs can cause oxidative stress in 16HBE cells and activate the Nrf-2/ARE signalling pathway to against oxidative damage.

Experimental evaluation of multiple-component residual stress distribution in a dissimilar metal repair joint of ferritic/martensitic steel using the asymmetric-cut and the symmetric-cut contour method

A thick multi-pass butt-welded ferritic/martensitic steel (P91) joint is prepared and the local region of the weld is repaired with an ENiCrFe-3 nickel-based alloy using the manual metal arc welding method. The repair weld including part of the base metal is then subjected to ultrasonic impact treatment (UIT). A three-cut contour method, including two asymmetric cuts and one symmetric cut, is developed in the present study to obtain the two-dimensional residual stress distributions at different locations, and the stress release after multiple cuts is considered to get the original stress distribution before cuts. The measurement procedure is introduced in detail. The longitudinal stresses in the repair weld and the initial weld of the P91 steel joint, as well as the transverse stress at the weld center, are finally obtained. The effects of the dissimilar metal repair weld at the local region on the longitudinal and transverse welding residual stresses are investigated. In addition, the applicability of UIT to mitigate the surface stress in nickel-based alloy repair weld is analyzed. The results show that the transverse and longitudinal stresses in the nickel-based alloy repair weld are both tensile stresses, the maximum longitudinal stress is close to the yield strength of the B91 weld metal and occurs in the heat-affected zone of the repair weld located in the initial weld. Repair welding causes the internal transverse compressive stress region to be narrower than in the original weld. UIT can be used to introduce compressive stress to the surface layer of the nickel-based alloy repair weld.

Mechanical and Metallurgical behavior of Manual Metal Arc Welded P91 Ferritic Martensitic Steel Joints

In the nuclear power plant industry, Cr-Mo ferritic steels are indispensable due to their high-temperature tensile strength, creep strength, and resistance to stress corrosion cracking. This study evaluated and analyzed the mechanical properties and metallurgical behavior of indigenously developed filler (over matched with base metal) manual metal arc welded Cr-Mo ferritic steel (hereafter referred as P91 steel). The analysis revealed that the ultimate tensile properties of the weld joint exceed those of the unwelded metal, being 6% higher than the base metal. Consequently, the joint efficiency for the weld joint is 106%. However, the impact toughness of the weld pad is significantly lower compared to the unwelded metal, nearly 2.5 times less than the base metal. The weld metal region’s microstructure is characterized by untempered lath martensite pinned with dense dislocations, which is attributed to rapid cooling from the liquidus range. Furthermore, a distinct Heat-Affected Zone (HAZ) was identified adjacent to the weld metal region, which results from the elevated temperature experienced in this area.

Effects of metal oxide inhalation on the transcription of some hormone receptors in the brain, examined in an in vivo mouse model

Respirable metal oxide nanoparticles in welding fumes pose significant health risks upon inhalation, potentially leading to neurodegenerative diseases. While the exact mechanisms remain unclear, it is evident that metal oxide nanoparticles can disrupt cellular functions, including metabolism and inflammatory responses after crossing the blood–brain barrier (BBB). Our study investigates the impact of manual metal arc welding fumes on hormone receptor transcription in an in vivo mouse model. After collecting samples from six different brain regions at 24 and 96 h upon exposure, we focused on expression levels of estrogen receptors (ERs), thyroid hormone receptors (TRs), and peroxisome proliferator-activated receptors (PPARs) due to their roles in modulating neuroprotective responses and neuroinflammatory processes. Analysis revealed differential susceptibility of brain regions to hormonal disruption induced by welding fumes, with the hypothalamus (HT) and olfactory bulb (OB) showing prominent changes in receptor expression. Considering ERs, 24 h sampling showed an elevation in OB, with later increases in both ERα and ERβ. HT showed significant ERβ change only by 96 h. TRs mirrored ER patterns, with notable changes in OB and less in HT. PPARγ followed TR trends, with early upregulation in HT and downregulation elsewhere. These findings suggest a compensatory response within the CNS aimed at mitigating neuroinflammatory effects, as evidenced by the upregulation of ERβ, TRα, and PPARγ. The coordinated increase in ERs, TRs, and PPARs in the hypothalamus and olfactory bulb also highlights their potential neuroprotective roles in response to welding fume exposure. Our results also support the theory of metal oxide penetration to the CNS via the lungs-blood-BBB pathway, making HT and OB more vulnerable to welding fume exposure.

Physical survey on the health hazards of welding activities on welding operators in Uyo, Nigeria

Background: Welding operators are subjected to several forms of hazards during welding activities. Aim: The study aimed to identify the common practices in welding operations, assess the potential health hazards associated with these practices, and propose recommendations for improving the well-being of welding operators. Methodology: The survey was conducted at different welding workshops in Uyo, Akwa Ibom State, Nigeria. A total of 100 welding operators were observed and interviewed to gather data on their working practices and the health effects they experienced. Results: The findings revealed that the most common welding practices included manual metal arc welding, gas metal arc welding, and gas tungsten arc welding. These practices involved exposure to various hazards such as fumes, gases, noise, and ultraviolet radiation. The survey also found that a significant number of welding operators reported experiencing health issues such as respiratory problems, skin irritation, eye injuries, and hearing loss. These health effects were attributed to the lack of proper ventilation, inadequate personal protective equipment, and poor ergonomic practices in the welding workshops. Conclusion: The findings of this study highlights the importance of addressing the health hazards associated with welding operations to ensure a safer and healthier work environment for improved work conditions and well-being of welding operators. In light of the findings, several recommendations including the implementation of proper ventilation systems, provision of adequate personal protective equipment, regular health screening for welding operators, and training programs on safe welding practices is proposed in order to improve the well-being of welding operators

A comparison of different experimental approaches in the determination of dynamic fracture toughness (J1d) behavior for RHA steel cost sustainable MMAW weldments

In the present investigation, the low hydrogen ferrite consumable weldment (weldment-1) and austenitic stainless steel consumable weldment (weldment-2) of rolled and homogenous armor steel (RHA) have been prepared with manual metal arc welding (MMAW). Further, the influence of weldments (weldment-1 and weldment-2) microstructure on the dynamic fracture toughness (J1d), strength, ductility and hardness has been evaluated and compared. The three different approaches have been utilized to estimate J1d for RHA weldments. Further, all three approaches’ outcomes have been compared with the elastic-plastic fracture mechanics (EPFM) approach through Jp-R curve. The results revealed that weldment-1 (yield strength 504.24 MPa and ultimate tensile strength 763.03 MPa) exhibited 26.93 and 25.07% more yield and tensile strength respectively than weldment-2 (yield strength 384.55 MPa and ultimate tensile strength 593.05 MPa). Further, the elongation of weldment-2 (elongation 42%) is 26.72% more than weldment-1 (elongation 32.10%). The joint efficiency and fusion zone hardness of weldment-1 are 5.85 and 57.56%, respectively more than weldment-2. The EPFM approach has good agreement with the correction factor approach (approach 2) and the compliance change rate approach (approach 3) with less than 7% difference in the estimation of dynamic fracture toughness of base metal and weldments (weldment-1 and weldment-2). Further, the percentage difference between maximum load point approach (approach 1) and the EPFM approach is more than 15% difference. The fractographic investigation confirms the ductile fracture in all under-investigated materials.

A MICRO-COOLED HIGH-STRENGTH WELD FOR HEAVY TRANSPORT MEANS

This paper focuses on the technical problem of repairing the main operating elements of heavy vehicles (semitrailers, dumps, and drums). If these vehicles are in service, significant changes in work schedules can occur, and costs can be generated immediately. Therefore, using the correct technology for repairs is crucial to minimizing financial and logistic difficulties. The article aims to analyze the mechanical properties of an MMA (Manual Metal Arc) welding (covered electrodes) joint made of Hardox 450 steel. This kind of material has a martensitic microstructure, which is difficult to weld because of changes in the components to the other ones during the joint process. Other inconveniences are related to the different chemical composition of steel and covered electrodes, their mechanical resistance, and thermodynamic conditions (consisting of the pre-heating temperature and the cross-pass temperature). Therefore, the joint quality should be determined using a few methods. In this case, NDT (magnetic and radiographic tests) and DT (microstructural analysis and static as well as fatigue tests) were used. All obtained results have enabled the proposed guides for the MMA welding of the steel grade. This is indicated as follows: (1) the method of bevelling the sheets before welding should be used, (2) pre-heating is necessary at temperature levels of 100 C and 125 C, and (3) the recommended interstitial temperature is between 170 C and 200°C.

Experimental studies on fillet weldment joints by artisans in Ghana’s Western Region

Constant progress, demand in the manufacturing of mechanisms parts, and the ability to join parts together is another critical aspect of manufacturing for assemblers. Joining methods plays a significant role and welding must be constantly improved, experimented with, and upgraded due to its increasing use in all aspects of manufacturing. The quality of a weld joint is highly dependent on the process parameter. Welds are examined to ensure that they meet specifications through various experimental processes ranging from computational networks, evolutionary algorithms, non-destructive testing (NDT) and destructive testing (DE) to ascertain the quality of joints. The main objective of the study was to ascertain the quality of welded joints through non-destructive evaluation (NDE). To achieve this goal, an experimental method of four (4) NDE methods were employed to evaluate the quality of weldment joints on a mild steel material joined using manual metal arc welding (MMAW) process in selected fabrication shops in Takoradi-Kokompe, Ghana. Steel specimens were prepared and taken to the artisans to be created into corner joints using the fillet method. The specimens were tested using non-destructive testing techniques. The results on the welded joints were evaluated using the AWS D1.1 code of acceptance for structural steels. The results revealed that all welded joints from fabricators failed to meet the AWS D1.1:2000 acceptance criteria and, thus, had to be rejected. The results implies that through the artisans have worked for many years in the welding trade, their lack of competence and skills in the selection of right input welding parameters contributed to the results. The results implies that, the finished artefacts may look fine but internal structures may contribute to future failure of the fabricated artefacts.

Analysis of Electric Current on Aluminum Plate Welding Using MMA (Manual Metal Arc) Method

Many industries depend on welding, which joins materials with heat. This research focuses on Manual Metal Arc (MMA) welding aluminum plates due to its adaptability for thin materials and compatibility with aluminum's unique properties. The study investigates how electric current affects aluminum plate MMA welding, improving welding methods. The study examined the effect of electric current on aluminum plates using the MMA method using a qualitative descriptive research design. Sorong Merchant Marine Polytechnic's workshop laboratory conducted the research from February to May 2023 using AWS E 6013 welding electrodes and ASTM A36 plates. Data was collected through observation, documentation, and literature review, then analyzed using data reduction principles. Results show that electric current variation significantly affects welding characteristics. Increased amperage penetrates deeper, but excessive current can melt and weaken joints. Amperage, weld rate, joint quality, and penetration depth must be balanced. The study emphasizes precise welding control, improving welding efficacy. The complex relationship between critical parameters emphasizes the need for careful equilibrium and the importance of following welding guidelines and parameters in the Welding Procedure Specification. As inadequate or excessive current can affect weld quality, this research improves MMA aluminum plate welding results.

Hybrid Optimization of Process Parameters in Manual Metal Arc Welding for Nanostructured Hard facing

AISI 310 stainless steel and EN24 steel were welded together using Manual Metal Arc Welding. Minitab and Design Expert software were applied to predict and optimize the results for bead width (BW) and weld penetration (PE). Total of 30 experiments were conducted according to the Box-Behnken design in RSM. Four different welding parameters current, voltage, welding speed, and root gap were employed to examine their effects on output values. The optimal conditions for BW were determined using the SN ratio, leading to an optimal parameter combination of C1-V4-W4-R4. This combination corresponds to a current of 75A, a voltage of 18V, a welding speed of 50 mm/min, and a root gap of 3 degrees. The optimal parameter value obtained from the Design Expert software were used to find the BW and PE to evaluate the weld quality. Under the optimal conditions, the supreme BW achieved was 13.994 mm, while the extreme PE reached 4.43976 mm, indicating satisfactory weld quality.

Kinetics of Intermetallic Phase Precipitation in Manual Metal Arc Welded Duplex Stainless Steels.

The article presents the influence of heat treatment on the kinetics of transformations in lean duplex LDX2101 steel and a weld made of standard duplex 2209 material, which was welded by manual metal arc welding. Changes in the microstructure, hardness, and magnetic phase content were analyzed after heat treatment was conducted at a temperature of 800 °C for a period ranging from 15 to 1440 min. Light and scanning microscopy, Vickers hardness measurements, and magnetic phase content measurements using a ferritoscope were used for the research. In the LDX2101 steel, the presence of δ-ferrite and γ austenite was identified and additional Cr2N nitrides were observed in the heat-affected zone. After heat treatment, the decomposition of δ ferrite into γ2 austenite and Cr2N nitrides was observed in both areas. In the case of weld made by the coated electrode in 2209 grade, a ferritic-austenitic microstructure with allotriomorphic austenite (γA), Widmanstätten austenite (γW), and idiomorphic austenite (γI) and δ-ferrite area with "bee swarms" of fine precipitations of chromium nitrides Cr2N and non-metallic inclusions (NMIs) of slag, formed during the welding process, are observed in the as-welded state. After heat treatment, the presence of the χ phase (after 15 min of annealing) and the σ phase (after 120 min of annealing) was additionally identified. The kinetics of intermetallic phase evolution in welds made from 2209 material were presented. The obtained results of hardness measurements and metallographic tests were correlated, which allowed for a quick check of the precipitation processes on the used element.

Investigation of mechanical properties and microstructure characterisation of MMA-MIG-TIG-SAW welded EN8 steel joints via shot blasting method

The industries of energy, transportation, and other engineering components all benefit greatly from the use of medium carbon (C) steel EN8. For these applications, welding is typically used to join the material. Conventionally welded joints, however, struggle to meet the exacting standards of industrial applications. In this comprehensive study, the tensile strength, microhardness, and microstructure of joints made of medium C EN8 steel using manual metal arc (MMA), metal inert gas (MIG), tungsten inert gas (TIG), and submerged arc (SAW) welding were investigated. These weld joints were then subjected to the shot blasting method to determine the effect on the mechanical properties of these weldments, Different response characteristics have been studied in relation to the shot blasting with various time periods. A detailed characterisation of the samples has been carried out optical microscopy, surface electron microscopy (SEM), energy dispersive spectroscopy (EDS), optical emission spectroscopy (OES), microhardness, and tensile testing with fractographical analysis. The maximum percentage increase in the microhardness in fusion zone (FZ) occurred in case of TIG welded specimens, i.e. 29.63% after 25 min of abrasive blasting period. However, the maximum change in the tensile strength, i.e. 10.53% has been observed for MMA welded specimens after 15 min of abrasive blasting period. Microstructural analysis revealed TIG has a columnar dendritic structure, MIG and SAW have an equiaxed dendritic structure. MMA has a cellular dendritic structure. The outcomes revealed that abrasive blasting improves the mechanical characteristics of industrial MMA, MIG, TIG, and SAW welded specimens.

Effect of water salinity on properties of multipass underwater wet manual metal arc welded joints

The weldability of steel under the water is limited due to the influence of the environment. Water causes limited visibility, presence of the residual stresses, increasing the cooling rate, and increasing the diffusible hydrogen content in deposited metal, leading to the formation of brittle microstructures in heat-affected zone (HAZ). The paper presents the results of mechanical properties testing of S420G2+M steel welded joints made with covered electrodes in the water with salinity values: 0‰, 7.5‰, and 35‰. The non-destructive tests: ultrasonic (UT) and radiographic (RT), and destructive tests: Vickers HV10 measurements, Charpy impact, and bending and metallographic macro- and microscopic tests were performed. Moreover, the diffusible hydrogen content in deposited metal by the mercury method was measured. It was observed that water salinity has an influence on the stability of the welding arc and the properties of joints. In particular, it was found that increasing the water salinity provides to: decreasing the hardness of HAZ (from 211 HV10 to 193 HV10), increasing the impact strength (from 82.5 to 101.3 J/cm2). Additionally, a slight increase in the diffusible hydrogen content in deposited metal (up to 65 ml/100g) was observed. The number of microcracks in the joints decreased with increasing the water salinity.

Finite element analysis results visualization of manual metal arc welding using an interactive mixed reality-based user interface

Welding is extensively used in manufacturing industries for various applications. However, residual stress is induced due to the non-uniform temperature distribution on the weld plates during the welding process, which significantly affects the fatigue strength. In addition, the non-uniform expansion and contraction of the weld and surrounding base metal cause structural distortion. The distortion affects final product quality and results in lower productivity. Therefore, the structural analysis of the welded component is significantly important. In this work, a mixed reality (MR)-based user interface was developed to overlay the finite element analysis (FEA) results on the real weld plates in real time for manual metal arc welding (MMAW). Since the numerical simulation using FEA requires a large number of computational resources, a gradient boosted regression tree (GBRT) model was trained to predict the residual stress and deformation results. Furthermore, a lookup table and a trilinear interpolation method were used to render the results based on users' input data using Microsoft HoloLens 2 in real time. The developed interactive MR-based user interface can help welders quickly predict and control the residual stress and welding distortion before the real welding process and help novices learn the relationship between the welding parameters and the induced residual stress and deformation.

FTIR spectroscopy as a convenient tool for detection and identification of airborne Cr(VI) compounds arising from arc welding fumes

Given the significant presence of the carcinogenic Cr(VI) in arc welding fumes from stainless steels, it is also important, in addition to estimating the Cr(VI) levels, to identify Cr(VI) compounds, as it throws light on the mechanistic pathways towards fume formation. FTIR data is presented in this paper for arc welding fumes collected from Manual Metal Arc Welding (MMA), Flux Cored Arc Welding (FCAW) and Solid Wire Welding (Metal Inert/ Active Gas Welding [MIG/ MAG]). For MMA and FCAW samples, clear spectra corresponding to Na, K, dichromates was observed at wave number of around 725-740 cm-1 and at 890-900 cm-1. Chromate species were also observed at around 850-855 cm-1, as was evidence of CrO3 (chromium trioxide) too (950-970 cm-1). The identification of these compounds was done by carefully identifying the Cr-O-Cr anti-symmetric vibrations, the symmetric stretching of the CrO4 tetrahedra, and the stretching vibrations of the planar CrO3 structure for the chromium trioxide. All the above compounds were volatile, and present as nanoparticles in welding fumes, thereby potentially causing significant harm to the welders. Additionally, crystalline phases (Fe-Mn spinels) were also observed through powder XRD, and the data was compared with ion chromatography estimates for Cr(VI) and found to be consistent.

Welder's lung and brain MRI findings in manganese-exposed welders.

Biomarkers of manganese (Mn) exposure and manganism are poorly understood. Blood Mn levels are often used to assess exposure, while brain Mn accumulation may be demonstrated by pallidal hyperintensity at magnetic resonance imaging (MRI). Mn-containing electrodes used in manual metal arc welding may be associated with the welder's lungs. A cross-sectional study was set up to compare T1 intensity in basal ganglia at MRI and Mn blood levels in subjects with or without pneumoconiosis. Clinical, radiological, pulmonary function and laboratory parameters were assessed among 154 welders referred to our hospital for suspected pulmonary pathology. The study group included 123 male welders with pneumoconiosis (79.9%) and 31 welders without pulmonary damage (20.1%). The cases without pneumoconiosis were younger (38.5±6.6 vs 42.1±7.1, p=0.012). Cases with pneumoconiosis had blood lower Mn levels [13.5 (10-21)] as compared to those without pneumoconiosis [18.5 (7.8- 34)], p=0.035. In the same groups, the cases with high blood Mn levels were 49 (39.8%) and 18 (58.1%) p= 0.052, respectively. Brain MRI hyperintensity was found in 86 (55.8%) subjects with welder's lung 63 (51.2) but also in 23 (74.2) individuals without welder's lung. MRI hyperintensity in basal ganglia was significantly related to high blood Mn (p<0.005). This is the first study evaluating blood Mn levels of welders and their correlation with pulmonary and neurological effects. Poor working conditions may be associated with exposure to Mn and fibrogenic fumes leading to chronic lung diseases and hyperintensity in brain MRI suggesting Mn accumulation.

Hardness Analysis of Weld Metal Electrode Low Hydrogen Potassium E7016 and E7018

Electrodes for the Manual Metal Arc (MMA) welding process or welding electrodes are classified based on the type of coating which is informed by the last digit code of the electrode. Electrodes E7016 and E7018 are basic types of electrodes with a Low Hydrogen Potassium coating type which are widely used in welding heavy construction equipment and piping. This electrode has a minimum tensile value of 70 ksi (480 MPa) with a carbon content of 0.07% for E7018 and 0.08% for E7016. The difference in carbon content in the composition of the electrode will determine the hardness value of the resulting weld. In use in the field these two electrodes are often recommended and can even be exchanged according to the assumption that the minimum tensile value is relatively the same between the two electrodes. However, due to the difference in carbon content, it will affect the hardness of the weld (weld metal) after welding. Many studies have been carried out to determine the mechanical properties of the welded joints using these electrodes, but research on the specific mechanical properties of the welds of the two electrodes is very rarely carried out. The test method is carried out by making 2 test specimens each for currents of 80A, 100A, and 120A using E7016 and E7018 electrodes with a diameter of 3.2mm. The material used is SA.36. The hardness test was carried out using the Rockwell-C (HRC) method. The test results show that the hardness value of the basic low hydrogen potassium electrode E7018 has a higher hardness value than E7016 for the same current. At currents of 80A, 100A, and 120A, there was an increase in the hardness of the E7018 weld metal against E7016 by 2.0% each; 9.8%; and 6.7%. The highest hardness value is found at 80A of 42.3HRC for the E7018 electrode, and 41.5 HRC for the E7016 electrode. In E7016 the increase in current causes a decrease in hardness level of 8.2% from 80A to 100A; 12.3% from 100A to 120A. In E7018 the increase in current causes a 1.2% decrease in hardness from 80A to 100A; 14.7% from 100A to 120A

Study of corrosion resistance of friction welding joints between tubes and tube plate

The cost of production and reliability of shell-and-tube heat exchangers is mainly determined by the features of the tube bundle and the joint between tube and tube plate (TTP) in particular. This paper provides a comparative analysis of the weld structure and electrode potential distribution of weld joints and base metal seams simulating the joint between heatexchange tube and tube plate (steel 5CrMo16) using the following welding methods: manual metal arc welding, gas tungsten arc welding and rotating friction welding. Comparison between macro- and microstructures of certain zones of tested welded joints, as well as values of electrode potential at specific points of the base metal and welded joints obtained by various methods, made it possible to conclude the effectiveness of application of specific ways of welding by their effect on corrosion resistance of given assembly.