Welded Joint Samples Research Articles

Corrosion mapping of intermetallic in a dissimilar weldment using in-situ alternating current scanning electrochemical microscopy

In the present work, in-situ corrosion activity mapping across explosively welded 304 L SS-Zr-4 dissimilar joint interfaces was performed using intermittent contact alternating current-scanning electrochemical microscopy (IC-AC-SECM). Two weld joint samples, one with a regular interface and another with an irregular interface, were examined for their local surface activities at an open circuit potential in tap water without using a redox mediator. The SEM micrographs showed the formation of intermetallics at localized regions of the irregular interface weld sample but not in the regular interface sample. The 304 L SS regions of the welds were relatively anodic, with current and impedance magnitude values of 270 ± 20 nA and 380 ± 20 kΩ respectively, when compared to the Zr-4 regions with the corresponding values of 160 ± 20 nA and 630 ± 20 kΩ, due to galvanic coupling effect. The IC-AC-SECM technique enabled the in-situ determination of corrosion activity of localized intermetallic region within the weldment. The current and impedance magnitude values of the intermetallic region were ∼ 240 nA and ∼ 450 kΩ, respectively, showing only a slightly lesser anodic activity as compared to the 304 L SS base metal. The results obtained from the IC-AC-SECM mapping showed a good correlation with the EDS elemental mapping of the dissimilar weldment with intermetallic. The findings indicate the effectiveness of the IC-AC-SECM technique for the in-situ localized corrosion mapping of dissimilar weld joints, showcasing its potential for various applications in assessing weld integrity.

Evaluation of Tensile Strength of Dissimilar Metals SS 316-pure Zn Joining by Friction Welding Method

Welding of dissimilar metals has always been a challenge in industrial applications. In this study, the joining of SS 316 and 99.9% pure zinc by continuous drive friction welding has been carried out. The welding process is carried out with parameters such as rotation speed, friction pressure, forging pressure, and burn length being kept constant for all weld joint samples. This friction time is selected through the process parameter approach carried out on aluminium alloy material. The experimental results were analysed by tensile test and microstructure using a scanning electron microscope (SEM) to characterise the microstructure. Tensile test results from friction welding with variations in friction time from 30 to 80 seconds obtained a higher tensile strength of the joint in the 30 to 50 seconds friction time range. In this experiment, the maximum joint tensile strength is obtained at 53.93 MPa, and the maximum modulus elasticity of 128.60 GPa at 35 seconds of friction. Solid-state welding makes it possible to join SS 316 and pure zinc, which is difficult to join in conventional fusion welding methods.

RESEARCH ON THE DESTRUCTION PROCESSES OF WELDED JOINTS UNDER CONDITIONS OF DETACHMENT OF THE VERTICAL STEEL TANK BODY FROM THE BOTTOM DURING A FIRE

The study presents a comprehensive analysis of welded joints by applying advanced mathematical modelling and experimental research methods. The primary objective was to develop and validate a methodology for mathematical modelling of the behaviour of welded joints under mechanical loading, as well as to assess the effectiveness of the proposed approaches in predicting their strength and durability. Based on the research results, we can draw the following conclusions. The authors obtained the results of welded joint samples and analysed the corresponding curves of the dependence of force factors on their deformations. The study showed that the destruction of welded joints occurs mainly along the weld seam, where the strength is lower than in the base material of the rods. It is consistent with the practical data of the experiment, which confirms that the weld is the weakest link in the structure. The article substantiated a set of provisions and assumptions for implementing mathematical modelling of the behaviour of samples of welded joints imitating welded joints in a reservoir for petroleum products under mechanical tensile tests. The test results justified the mathematical models of the steel material of welded joints of petroleum product tanks and obtained numerical parameters of the mechanical properties of steel of welded joints. Yield strength is in the range of 240–300 MPa, the modulus of elasticity is 190–240 GPa, the hardening modulus is 18–20 GPa, and the ultimate plastic deformation is 0.00334. Based on a complex of well-founded mathematical models of welded joints, we carried out calculations regarding the numerical study of the behaviour of welded joints under the conditions of their mechanical tests. We compared the obtained results with the results of experimental tests and, based on this comparative analysis, established that they were adequate since the Fisher criterion did not exceed the tabular value and the relative error did not surpass 12%. The findings of this research offer valuable insights and practical recommendations for improving the design and evaluation of welded structures, enhancing their performance and safety in engineering applications.

Improvement of the high-temperature oxidation resistance of 254SMo using ultrasonic strengthening grinding

This paper used ultrasonic strengthening grinding (USGP) to process 254SMo welded joints. The mechanical properties of processed and unmachined samples of welded joints, including grain size, dislocation, microhardness, residual stress, and high-temperature oxidation resistance at 900 °C, were investigated. The results indicate that the grains of the processed samples exhibit significant refinement and a high dislocation density and that the maximum microhardness and residual compressive stress are 392.5 HV0.3 and −633.44 MPa, respectively. In addition, the processed sample exhibits excellent oxidation at high temperatures. At 900 °C, the mass gain of the USGP-processed sample is reduced by 47.5 % compared to its mass gain prior to processing. These results highlight the potential of this method in improving the high-temperature resistance of various mechanical components, particularly those made from special materials.

The effect of combined laser bionic and ultrasonic impact on the microstructure and fatigue properties of AZ31B magnesium alloy TIG welded joints

The present work investigates the effect of combined laser bionic treatment (LBT) and ultrasonic impact treatment (UIT) on the fatigue properties of AZ31B magnesium alloy TIG welded joints. The fine grains with random orientation were obtained in weld seam after LBT, resulting microhardness increased, and the surface of welded joint formed a “soft-hard” alternating bionic structure. After the composite treatment, the maximum compressive residual stress was induced on the surface of welded joint, which was about −272 ± 30 MPa. In addition, obvious plastic deforming layer and nanocrystalline grains were formed. The grains with preferred orientation were obtained in the plastic deforming layer. The fatigue test showed that the fatigue strength of composite treated welded joint sample increased by 33% and 125% compared with LBT treated welded joint and untreated welded joint samples at 107 cycles, respectively. The composite treatment changed the nucleation position and fracture morphology of the crack, as well as induced a series of strengthening mechanisms.

Mechanical and Micro-Structural Characterisations of Submerged Arc Welded Steel Plates

The goal of the study is to find out how the welding parameters current (I), voltage (V), and speed (S) affect the mechanical characteristics and mechanical characterization of the submerged arc welding (SAW) process. Tensile strength, Microhardness, Impact load was determined using the universal testing machine (UTM), micro Rockwell Hardness machine and Impact load by Charpy and Izod method. With the help of several Submerged Arc Welding (SAW) factors, notably welding voltage (V), welding current (I), and welding speed, this research aims to examine and analyze the mechanical characteristics of welded connections. (S). The investigation involves cutting and machining samples of welded joints, which are then tested for mechanical qualities using tensile, impact toughness, and hardness methods. Analyses were done on how welding parameters affect the mechanical characteristics of welded joints. It has been noted that when heat input increases, the hardness of the weld first increases up to 100 HRC before declining as heat input continues to increase. The ultimate tensile strength and yield strength of the welded joints increases as the heat input increases, but it decline as the heat input increases more. The slower cooling rate has been achieved with high input heat consequent the coarse grains achieved in the weld metal. In contrast the low input heat results in the faster cooling and finer microstructure.

Microstructure and Properties of High Frequency Pulse MAG Butt Welded Joints of S355 Steel with Different Diameters

In this paper, the diameter of 1.2mm and 1.6mm welding wires were used to carry out high-frequency pulse MAG butt welding process test on S355J2W+N weathering steel. The analysis of the microstructure characteristics of the welded joints under the two working conditions shows that there is little difference and both are ideal. There were more acculate ferrite (AF), less pearlite (P) and bainite (BG), and no larger Weisserite structure and less ferrite side-plate (FSP) structure. The weld is well formed, weld defects such as gas pores and cracks are not found. The impact test showed that the impact energy Akv (-40 °C) of the welded joint at -40 °C was higher than the specified minimum impact energy of 27 J. Compared with the 1.2mm welding wire, the impact energy of the 1.6mm welding wire is lower. Tensile test results show that the fracture occurs at the base metal position. and the fracture height is uneven, forming an angle of 45° with the tensile stress direction, which is a ductile fracture. When the bending angle of the butt joint samples reaches 180°, no cracks are both found on the tensile surface, and the plastic index of the welded joint samples is qualified and has good bending performance.

STRENGTH OF BUTT WELDED BUTT JOINT OF REINFORCEMENT OF CLASS A500C

The paper presents the results of experimental studies of the strength of cross-shaped welded joints of types К1-Кт and К3-Рр [1] of thermomechanically hardened reinforcement of class A500C [2] for hardening during welding of the main bar [3].
 Experimental studies included testing three series of samples of welded joints and reinforcement samples in the initial state. The first series included testing welded joints of type К1-Кт to strengthen the main bar during welding. Reinforcement Ø14A500С was accepted as the main (working) bar, and reinforcement Ø12A500С and Ø8A240С were accepted as the transverse bar. For each joints, 6 samples were tested on the lower and upper limits of the carbon equivalent values of the grade steel class Ст3пс, 0.245% and 0.346%, respectively. The second series included testing of welded joints of the K3-Pp type to strengthen the main bar during welding. To directly compare the test results of different types of cross-shaped welded joints, the diameter of the main and transverse rods, the number of samples and the value of equivalent were the same as in the first series. The third series included testing welded joints of type К1-Кт for cutting. Reinforcement Ø14A500С was taken as a longitudinal bar, and reinforcement Ø12A500С and Ø8A500С was taken as a transverse rod. For each joints, 12 samples were tested at the lower and upper limits of the carbon equivalent values.
 As a result of testing samples of welded joints of types К1-Кт and К3-Рр of reinforcement A500C for strengthening during welding, it was established that the destruction occurs along the main bar and in the zone of thermal exposure, the amount of hardening was up to 4% for the К1-Кт compound, and for the К3-Рр type connection - 4... 10%.
 Failure of samples of welded joints of type К1-Кт reinforcement A500C with reinforcement Ø12A500C and Ø8A240C during the cut test usually occurred in the zone of thermal exposure, or in some cases, in the presence of both rods from reinforcement of class A500C - directly at the welding site. The average value of cut strength for a sample of 24 samples of reinforcement connections of class A500C with reinforcement A240C was 356.5 MPa, or 0.89 of the temporary resistance of the reinforcement in the initial state, with a coefficient of variation - 0.08 and a span of 107.4 MPa. The average cut strength for a sample of 24 samples of reinforcement connections of class A500C with reinforcement A500C was 541.1 MPa, or 0.80 of the temporary resistance of the reinforcement in the initial state, with a coefficient of variation – 0.152 and a span of 280.0 MPa.
 The first series included fittings Ø12A500C, Ø14A500C, Ø16A500C from steel of the ST3ps brand and Ø18A500C, Ø20A500C, Ø22A500C from steel of the Ст3пс brand. A total of 278 samples of welded joints were tested. The second series included samples of C1-Co welded joints from the rest of the nomenclature of diameters and grades of steel reinforcement class A500C, namely Ø16A500C from steel grade St3ps, Ø20A500C, Ø22A500C from steel grade St3Gps and Ø25A500C, Ø32A500C, Ø32A500C, Ø32A500C. For each of the diameters, 6 samples were tested in the initial state and 6 samples of C1-Co welded joints.
 It was found that the destruction of the butt contact connection type C1-Co thermomechanically reinforced reinforcement class A500C of all diameters, from 12 to 32 mm, and steel grades, takes place in the zone of thermal impact and is plastic.
 Experimental data on the strength of the butt contact weld type C1-Кo reinforcement class A500C for the entire range of diameters and grades of steel produced in Ukraine. It is established that the greatest degree of hardening within 19-20% takes place at diameters of armature of 12… 16 mm from steel of the Ст3пс brand, at diameters of armature of 18… 22 mm from steel of the Ст3Гпс brand of marking made 15-17%, and at diameters of 25… 32 mm from steel of the 25Г2С brand - 2,5… 8%.

INCREASING CORROSION RESISTANCE OF WELDED JOINTS AS A RESULT OF HEAT TREATMENT

Welded joints with corrosion-resistant steels and heat-resistant alloys, which require different modes of heat treatment to achieve the level of mechanical properties specified in the design documentation, are used for the manufacture parts and assemblies of the rocket engine turbopump unit. Problem statement. In the production of rocket engine parts and components, due to difficulties in supplying materials from EU countries, Ukrainian machine-building enterprises have to substitute semi-finished products. It is necessary to replace sheet metal from high-alloy alloys with one alloy with a high complex of physical and mechanical characteristics. Materials and methodology. Inconel 718 alloy is selected as a substitute for heat-resistant alloys in welded joints with 316L steel. Results. As a result of comparative studies for resistance to intergranular corrosion of welded joints of heat-resistant alloy Inconel 718 with stainless steel after different modes of heat treatment the regime of low-temperature heating during soldering at 950 °С is recommended. Samples of welded joints treated according to the recommended mode showed increased corrosion resistance. Scientific novelty. The sensitivity to intergranular corrosion was found to result from the structural heterogeneity of the grain boundaries and the separation of secondary phases. Practical value. On the basis of experimental researches the mode of heat treatment with heating to 950 ± 10 0С, cooling to 300 0С − with the furnace, further − in air, instead of existing high-temperature heating to 1 200 0С is recommended, that promotes energy saving at welding of alloys.

INCREASING THE CORROSION RESISTANCE OF HEAT-RESISTANT ALLOYS FOR PARTS OF POWER EQUIPMENT

For the manufacture of parts and assemblies of the turbopump unit of details of power equipment, welded joints with corrosion resistant steels and heat-resistant alloys are used, requiring various modes heat treatment to achieve the required level of mechanical properties. In the manufacture of parts and assemblies of details of power equipment at the machine-building enterprises of Ukraine, it became necessary to replace semi-finished products. It is necessary to replace sheet products from high-alloy alloys ХН67МВТЮ and 06Х15Н6МВФБ with one alloy with a high complex of physical and mechanical characteristics. In the work, as a replacement for the applied heat-resistant alloys, Inconel 718 alloy welded to 316L steel. Samples of welded joints, processed according to the recommended mode, showed increased corrosion resistance.

The effect of heat treatment on the corrosion resistance of power equipment parts

For the manufacture of parts and assemblies of the turbopump unit of details of power equipment, welded joints with corrosion resistant steels and heat-resistant alloys are used, requiring various modes heat treatment to achieve the required level of mechanical properties. In the manufacture of parts and assemblies of details of power equipment at the machine-building enterprises of Ukraine, it became necessary to replace semi-finished products. It is necessary to replace sheet products from high-alloy alloys ХН67МВТЮ and 06Х15Н6МВФБ with one alloy with a high complex of physical and mechanical characteristics. In the work, as a replacement for the applied heat-resistant alloys, Inconel 718 alloy welded to 316L steel. Samples of welded joints, processed according to the recommended mode, showed increased corrosion resistance.

Crack Detection for Welded Joint With Surface Coating Using Unsaturated AC Magnetic Flux Leakage

Fatigue cracks occurred in the welds of steel structure are easily propagated. Therefore, it is important to detect the fatigue cracks at an early stage. However, most of the steel structures are protected by surface coating, which requires removing and restoring the coating for the inspection. This makes the inspection time-consuming. Magnetic methods such as eddy current testing (ECT) and magnetic flux leakage (MFL) can be used without removal of surface coating. However, these magnetic methods are difficult to apply to the shape of the welds and affected by nonuniform magnetic permeability. In this study, we developed a sensor probe adapted to the shape of the welded joint using the unsaturated ac MFL (USAC-MFL), which is less affected by the nonuniform magnetic permeability. To evaluate the performance of the developed sensor probe, the welded joint samples with the surface coating and shallow cracks of which depth ranges from 1 to 5 mm were measured. The measurement results showed a strong correlation between the intensity of the MFL and the crack depth. The detection performance was evaluated using the confusion matrix and the receiver-operating characteristic (ROC) curve. The area under curves (AUCs) of the ROC curves were around 0.9. In order to maximize the true positive rate (TPR) and minimize the false negative rate, the threshold of the intensity to identify a crack was obtained using the ROC curve. As the results of evaluating the detection performance using the obtained threshold, the four metrics (accuracy, precision, recall, and specification) were all above 0.8.

STRENGTH OF BUTT WELDED BUTT JOINT OF REINFORCEMENT OF CLASS A500C

The paper presents the results of experimental studies of the strength of the butt welded joint type C1-Кo for thermo-mechanically reinforced reinforcement class A500C.The experimental studies included tensile tests of two series of reinforcement specimens, each of which included reinforcement specimens in the initial state and with a butt contact weld of the C1-Сo type.The first series included fittings Ø12A500C, Ø14A500C, Ø16A500C from steel of the ST3ps brand and Ø18A500C, Ø20A500C, Ø22A500Cfrom steel of the Ст3пс brand. A total of 278 samples of welded joints were tested. The second series included samples of C1-Co welded joints from the rest of the nomenclature of diameters and grades of steel reinforcement class A500C, namely Ø16A500C from steel grade St3ps, Ø20A500C, Ø22A500C from steel grade St3Gps and Ø25A500C, Ø32A500C, Ø32A500C, Ø32A500C.For each of the diameters, 6 samples were tested in the initial state and 6 samples of C1-Co welded joints.It was found that the destruction of the butt contact connection type C1-Co thermomechanically reinforced reinforcement class A500C of all diameters, from 12 to 32 mm, and steel grades, takes placein the zone of thermal impact and is plastic. Experimental data on the strength of the butt contact weld type C1-Кo reinforcement classA500C for the entire range of diameters and grades of steel produced in Ukraine. It is established that the greatest degree of hardening within 19-20% takes place at diameters of armature of 12… 16 mm from steel of the Ст3пс brand, at diameters of armature of 18… 22 mm from steel of the Ст3Гпс brand of marking made 15-17%, and at diameters of 25…32 mm from steel of the 25Г2С brand - 2,

Improving Quality Control Methods to Test Strengthening Technologies: A Multilevel Model of Acoustic Pulse Flow

This article describes an approach that makes it possible to substantiate quality control criteria and methods to improve strengthening technologies. The approach was used to test the quality of products made using these technologies and analyze different strengthening methods applied to structural materials. In the experiment, samples of welded joints subjected to various types of strengthening were used that underwent acoustic emission (AE) testing. The results of quick evaluations produced by the proposed multilevel model of acoustic pulse flow were compared with the results of long-term cyclic tests to make a conclusion about the effectiveness of the approach being discussed. To improve strengthening quality control, a method is proposed that can be applied to complex and large-sized structures in the construction industry.

Investigation of the Nature of Damage to Welded Flexible Compensating Elements Made of Austenitic Stainless Steels

Welded flexible compensating elements made of austenitic stainless steels, such as metal hoses and bellows expansion joints, operate in a complex stress state; therefore, almost all corrosion damage of these products occurs in a stressed state. In addition, in welded joints, defects are possible associated with elastic-plastic deformations and stresses arising in the manufacturing process. Paper considers the defects of welded joints of multilayer bellows expansion joints made of stainless steels AISI 304 and AISI 316 types. The influence of the parameters of the argon tungsten electrode welding mode, with or without filler wire, on the mechanical characteristics of welded joints was studied. Mechanical tests of samples of welded joints were carried out on a tensile testing machine. The optimal range of variation of the parameters of the welding mode has been established, in which the plastic characteristics of the welded joints have maximum values. A metallographic study of the microstructure of welded joints of metal hoses and bellows expansion joints was carried out. The influence of the content of nonmetallic inclusions in the material of products on the conditions of melting and crystallization of the weld pool, contributing to the appearance of pores and hot cracks in the metal of the weld and the heat affected zone, has been established. To reduce the influence of the content of non-metallic inclusions in the weld metal and the heat-affected zone on the conditions of melting and crystallization of the weld pool, it is recommended to carry out preliminary heat treatment of the austenitic steel strip.

EFFECTS OF POST WELD HEAT-TREATMENT ON MICROSTRUCTURE AND MECHANICAL BEHAVIOR OF DIS-SIMILAR MATERIALS PRODUCED BY GTAW PROCESS

Welding is a well-known economic fabrication process in that GTAW is one of the reliable and easy weld techniques compared with other fabrication techniques. The present research focused on the dissimilar metal welds, a weldment between ferrous and non-ferrous alloys taken into consideration. A part of experimental work, AA6061 with Ferrous alloys like EN8, SS302, SS316 welded with TIG welding process known as GTAW. Aluma steel filler rods are used for the weldment in a twostep process; the primary rod is used to fill the ferrous side, and the second filler is used to join them both. The structures for different samples of post welded joints to check the structural variation between all 3-zones, basemetal, Heat affected zone (HAZ), and weld zone using optical microscopy and scanning electron microscopy (SEM). The investigation further continued to check the mechanical properties of weld structures tensile and hardness. Hardness testing has been carried out like structures in 3- zones to check the hardness variation in HAZ and weldment. The results obtained are satisfactory based on weld strength and structures obtained in the sample analysis.

Study of the Structural-Phase State of Pipeline Welded Metal

The issues of research of structural changes as applied to welded joints of steam pipelines are considered. The results of metallographic analysis of structural changes in the metal of steam pipelines are presented. There was carried out the analysis for a number of samples cut from different sections of the steam line at different operating time under creep and low-cycle fatigue conditions. In the analyzing process of the images of micro sections, the relative content of the structural-phase components and their distribution in the metal were revealed. A comparative analysis of the statistical characteristics of the distribution and the relative content of structural components for different sections of the metal of welded joints with different operating time is carried out. A scientifically substantiated description of structural changes in the metal of various sections of samples of welded joints is given, as well as the possibility of extending the service life of elements of steam pipelines with a degraded structure and the presence of damageability. The most promising, in the opinion of the authors, directions of further research of samples to provide conditions for extending the service life of steam pipelines have been formulated and substantiated.

Effect of Laser Peening with a Microchip Laser on Fatigue Life in Butt-Welded High-Strength Steel

Laser peening introduces compressive residual stresses on the surfaces of various materials and is effective in enhancing fatigue strength. Using a small microchip laser, with energies of 5, 10, and 15 mJ, the authors applied laser peening to the base material of an HT780 high-strength steel, and confirmed compressive residual stresses in the near-surface layer. Laser peening with a pulse energy of 15 mJ was then applied to fatigue samples of an HT780 butt-welded joint. It was confirmed that laser peening with the microchip laser prolonged the fatigue life of the welded joint samples to the same level as in previous studies with a conventional laser.

Corrosion and mechanical behavior of 17G1S-U pipeline steel and its weld joint of in the terms simulating operational conditions

Corrosion and mechanical behavior of weld joint samples of the straight-weld pipe of 17G1S-U pipeline steel in the conditions simulating the operating conditions of internal and external corrosion has been studied. It is shown that the initiation of local corrosion of welded joints from the inner surface of the pipeline is due to thin-film corrosion in a two-phase medium (hydrocarbon-water) under deformation conditions. The depth of local damages of the base metal and weld metal can reach 0.337 mm and 0.381 mm. Stress corrosion cracking is a danger for the outer surface which is under cathodic protection. Maintaining the potential at the level of the maximum protective potential -1050 mV increases the stress corrosion cracking inclination of pipeline 17G1S-U steel and its weld joint, due to deterioration of the plastic properties of the metal during longtime exposure at cathodic polarization: decreasing in the relative elongation of the base metal is equal near 11 %, weld joint – by 20%. The KS susceptibility, estimated by the KS coefficient, under these conditions is equal to 1.8 for 17G1S-U steel, 1.5 for weld joint.

Investigation of breaks of the «Sparking» type of brass‑plated wire for metal cord and high‑pressure hoses and the causes of their formation

The article examines the breaks of thin brass‑plated wire for metal cord and high‑pressure hoses of the “sparking” type and the causes of their formation. The wire was manufactured in OJSC “BSW” – he Management Company of the Holding” BMC “ in the conditions of steel‑wire workshops. The appearance and microstructure of breaks of thin brassplated wire of the “sparking” type are investigated. As a result of the analysis of the appearance and microstructure of the breaks, it was assumed that surface defects are formed on the brass‑plated wire – billet during the welding connection in the jaws of the welding machine during annealing. To confi m this, experiments were carried out with the implementation of welded joints of brass – plated wire‑blanks in wet drawing areas, the appearance and microstructure of the obtained samples of welded joints were studied.As a result of experiments and metallographic studies, the assumption was confirmed that local defects such as “cauterization from sparking” on the surface of the workpiece wire are formed during welding during the annealing operation, it was established that the cause is a violation of contact between the wire and the pressure jaws of the welding machine, wear of the pressure jaws. Photos of the defect, a description of its appearance and microstructure are given.Based on the obtained studies, a number of measures were carried out aimed at eliminating the causes of this defect.