Zone Of Welded Joints Research Articles

Cracking Failure Analysis of Pipe to Flange Weld Joint

Cracking failures occurred frequently in blowdown pipe to flange weld joint, and the root crack appeared on the blowdown pipe side of the weld joint and extend into the base metal of pipe. To explore the reason why cracking failures occurred on the blowdown pipe side of the weld joint, the weld joint was analyzed via macroscopic and metallographic structure observation, and blowdown pipe was tested by physical and chemical property testing, and corrosion scale was analyzed by SEM, EDS, and XRD. The dent and thinner wall thickness of pipe are found in the internal pipe to flange weld joint. Widmanstatten metallographic structure is found in heat affected zone (HAZ), fusion zone (FZ) and weld metal zone (WZ) of weld joint. Stress concentration form in the weld joint at blowdown pipe side during welding due to the dent and different wall thickness. Under the action of gas vortex in the dent of weld joint, corrosive droplets aggravate the localized corrosion of the weld joint. Stress corrosion cracking (SCC) were initiated in FZ and WZ from the surface of weld joint and propagated into the base metal of pipe under the combined actions of stress resulting from weld process and during operation, and corrosion.

INFLUENCE OF THE CHEMICAL COMPOSITION AND METHOD OF SMELTING ON THE PROPERTIES OF THE METAL OF WELDED JOINTS OF ECONOMICALLY ALLOYED CHROMIUM-MANGANESE-NICKEL STEELS

The results of studies on the influence of the chemical composition on mechanical properties of the base metal and the metal of the near-seam zone of welded joints of ferrite-austenitic steels are presented. The positive effect of microalloying of steels with calcium and cerium on the resistance to embrittlement of the metal after exposure to the thermal welding cycle is shown. It is established that alloying ferrite-austenitic steels with molybdenum and vanadium reduces the tendency to grain growth during welding heating, and doping with nitrogen leads to the stabilization of the phase composition of steels under the influence of elevated welding and operating temperatures.

Impact of pin tool designs on the mechanical properties and microstructure of aluminum alloys AA7075- AA6061

ABSTRACT In this work, Friction Stir Welding (FSW) is used to study the impact of different pin tool geometries on hardness, microstructure, and tensile strength of welded AA6061 and AA7075 butt joints. H13 steel-tool including three distinct pin geometries, i.e. threaded cylindrical (THC), straight cylindrical (SC), and tapered cylindrical (TAC) are used for welding. The welds were produced using a spindle speed of 1800 rpm and welding speed (traverse speed) of 15 mm/min by a customized clamping system. As shown by the hardness test, the welded sample using the threaded pin tool geometry produces more hardened joints than other geometries of the pin tools. As analyzed by the tensile strength experiment performed on the Universal Testing Machine (UTM), the samples welded by threaded pin give higher ultimate tensile strength, i.e. 282 MPa compared to other tool geometries. A fine grain structure was also observed in the nugget zone of welded joints obtained by threaded pin.

Prediction of distortions and residual stresses in narrow gap weld joints prepared by hot wire GTAW and its validation with experiments

The present paper aims to predict distortions and residual stresses in thick plate weld joints of austenitic stainless steel material prepared by automatic hot wire gas tungsten arc welding (GTAW) process and narrow gap technique using finite element analysis (FEA). The prediction has been validated by carrying out experiments. The variables considered in welding of plate joints are narrow groove configuration, high deposition rate leading to lower heat input (hot wire GTAW), and stress relieving treatment. A suitable stress-relieving treatment has been proposed for relaxing residual stresses and preventing sensitization of the heat-affected zone (HAZ) of the ASS weld joint. Predicted and experimental results of temperature distribution, distortions, and residual stresses were found to be in good agreement. The applicability of prediction of residual stresses for higher weld thicknesses has also been verified. The nature of residual stresses across thickness has also been compared with that given in Structural Integrity Assessment Procedures for European Industry (SINTAP) and BS 7910 standards. Details of the above finding are discussed in this paper.

Properties of amorphous Fe-based alloy

The paper presents the results of tests for multi-cycle fatigue of laboratory samples of welded joints of exploration drill pipes in a combination of steel s 32-2-Mn of strength group L (pipe body) with 40-Cr-Ni (tool joint part) and solid samples of pipe body material. Welding of the joint part with the pipe body was carried out by rotary friction welding. Multi-cycle fatigue tests were carried out according to GOST 25502 on a test machine with a two-support rotating specimen under constant torque. Mathematical processing of the results of fatigue tests was carried out, linear regression equations were obtained, fatigue curves were constructed, the endurance limits σ-1 of samples with a welded joint and solid samples were determined, taking into account the relative error of the regression equations. On the basis of metallographic analysis, vulnerabilities in welded joints were identified, in which the initiation and development of fatigue cracks occurred. Fractograms are presented that illustrate the mechanism of fatigue fracture of solid and welded samples. It is shown that the development of a fatigue crack in specimens of welded joints occurs with a greater proportion of microplastic deformation. It has been established that rotary friction welding of a pipe body made of 32-2-Mn steel of strength group L and a joint made of 40-Cr-Ni steel contributes to an insignificant decrease in the fatigue limit of welded joints relative to the pipe body, providing its value at the level of 43-47 % of the ultimate strength of 32-2-Mn steel. The data obtained assume trouble-free operation of the welded joint zone in the drill pipe string made of steel 32-2-Mn, strength group L with welded joints made of steel 40-Cr-Ni.The reported study was funded by RFBR, project number 19-38-90079.

Endurance limit and mechanism of fracture of friction welded joints of exploration drill pipes in the conditions of multi-cycle fatigue

The paper presents the results of tests for multi-cycle fatigue of laboratory samples of welded joints of exploration drill pipes in a combination of steel s 32-2-Mn of strength group L (pipe body) with 40-Cr-Ni (tool joint part) and solid samples of pipe body material. Welding of the joint part with the pipe body was carried out by rotary friction welding. Multi-cycle fatigue tests were carried out according to GOST 25502 on a test machine with a two-support rotating specimen under constant torque. Mathematical processing of the results of fatigue tests was carried out, linear regression equations were obtained, fatigue curves were constructed, the endurance limits σ-1 of samples with a welded joint and solid samples were determined, taking into account the relative error of the regression equations. On the basis of metallographic analysis, vulnerabilities in welded joints were identified, in which the initiation and development of fatigue cracks occurred. Fractograms are presented that illustrate the mechanism of fatigue fracture of solid and welded samples. It is shown that the development of a fatigue crack in specimens of welded joints occurs with a greater proportion of microplastic deformation. It has been established that rotary friction welding of a pipe body made of 32-2-Mn steel of strength group L and a joint made of 40-Cr-Ni steel contributes to an insignificant decrease in the fatigue limit of welded joints relative to the pipe body, providing its value at the level of 43-47 % of the ultimate strength of 32-2-Mn steel. The data obtained assume trouble-free operation of the welded joint zone in the drill pipe string made of steel 32-2-Mn, strength group L with welded joints made of steel 40-Cr-Ni.The reported study was funded by RFBR, project number 19-38-90079.

Assessment of microstructure and mechanical properties of friction stir welded AA2014-O and AA2014-T6 sheets

In this study, friction stir welding of AA2014-O and AA2014-T6 aluminum alloy was performed at various welding speeds to evaluate the influence of temper conditions of base metal (BM) on the properties of the welded joints. The results showed strong influence of BM temper conditions on the microstructural morphologies and mechanical behavior of the welded joints. In the 2014-O joints, different zones of weld joint were diffused into each other and there was no clear interface between them. In 2014-T6 joints, there was a distinct demarcation between the nugget zone (NZ), thermomechanically affected zone TMAZ, heat-affected zone (HAZ), and BM. The welded joints in 2014-O temper condition showed increase in hardness in the vicinity of weld center due to grain refinement whereas, in 2014-T6, softening occurred in the same region by the dissolution of strengthening precipitates. The mechanical properties of 2014-O joints were equivalent to the base metal showing a 100% weld efficiency with fracture located in the base metal, whereas 2014-T6 welds exhibited about 70% weld efficiency with fracture located at the NZ/TMAZ interface. All the samples in mechanical testing fractured at retreating side (RS) which exhibited heterogeneity in the mechanical properties of the welded joints. Scanning electron microscopy fractographic analysis revealed a ductile fracture mode comprising of dimples in both temper conditions. The size and shape of the dimples were strongly dependent on base metal temper condition.

Анализ параметров донных сигналов в зоне сварных стыков рельсов при высокоскоростном ультразвуковом контроле

The present research is a continuation of works aimed at analyzing the parameters of ultrasonic signals during high-speed inspection of rails. The article analyzes the zones of welded joints of rails in a wide range of inspection speeds. The change in the amplitudes of the bottom signals in the zone of welded joints is analyzed. At certain scanning speeds, many areas of welded joints can be attributed to untested rail sections with significant loss of bottom signals. The research results can be used to improve the designs of search systems for high-speed diagnostic systems, as well as to determine the permissible scanning speeds of the rail track.

Welded joint geometry effect on fatigue crack growth resistance in different metallic materials

Fatigue crack growth through different welded joint regions was investigated, in terms of welded joint geometry and fatigue crack position. In the first phase of investigation, numerical simulation of crack growth in a welded joint made of steel P460NL1 was performed using extended Finite Element Methods (xFEM). Numerical models employed Paris law, using experimentally determined coefficients for each welded joint zone. Weld geometry was varied by using different heat affected zone (HAZ) widths, i.e. fatigue crack lengths. The second stage involved similar numerical models with different material (Protac 500). Fatigue lives for regions in both models were then compared.

MODELING OF TITANIUM ALLOYS PLASTIC FLOW IN LINEAR FRICTION WELDING

The article presents the results of the analysis of the plastic flow of titanium alloys in the process of the Linear Friction Welding (LFW). LFW is a high-tech process for joining critical structural elements of aerospace engineering from light and high-temperature alloys. Experimental studies of LFW modes of such alloys are expensive and technically difficult. Numerical simulation was carried out for understanding the physics of the LFW process and the formation laws of a strong welded joint of titanium alloys. Simulation by the SPH method was performed using the LS DYNA software package (ANSYS WB 15.2) and the developed module for the constitutive equation. The new coupled thermomechanical 3D model of LFW process for joining structural elements from alpha and alpha + beta titanium alloys was proposed. It was shown that the formation of a welded joint occurs in a complex and unsteady stress-strain state. In the near-surface layers of the bodies being welded, titanium alloys can be deformed in the mode of severe plastic deformation. A deviation of the symmetry plane of the plastic deformation zone from the initial position of the contact plane of the bodies being welded occurs during a process of LFW. Extrusion of material from the welded joint zone in the transverse direction with respect to the movement of bodies is caused by a pressure gradient and a decrease in the alloy flow stress due to heating. The hcp-bcc phase transition of titanium alloys upon heating in the LFW process necessitates an increase in the cyclic loading time to obtain a welded joint.

Flat-Top Cylinder Indenter for Mechanical Characterization: A Report of Industrial Applications.

FIMEC (flat-top cylinder indenter for mechanical characterisation) is an instrumented indentation test employing a cylindrical punch. It has been used to determine the mechanical properties of metallic materials in several applications of industrial interest. This work briefly describes the technique and the theory of indentation with a flat-ended punch. The flat indentation of metals has been investigated through experimental tests, and an equation has been derived to calculate the yield stress from the experimental data in deep indentation. The approach is supported by many data on various metals and alloys. Some selected case studies are presented in the paper: (i) crank manufacturing through pin squeeze casting; (ii) the evaluation of the local mechanical properties in a carter of complex geometry; (iii) the qualification of Al billets for extrusion; (iv) stress–relaxation tests on CuCrZr heat sinks; (v) the characterization of thick W coatings on CuCrZr alloy; (vi) the measure of the local mechanical properties of the molten-zone (MZ) and the heat-affected zone (HAZ) in welded joints. The case studies demonstrate the great versatility of the FIMEC test which provides information not available by employing conventional experimental techniques such as tensile, bending, and hardness tests. On the basis of theoretical knowledge and large amount of experimental data, FIMEC has become a mature technique for application on a large scale in industrial practice.

Digital Image Correlation of Tensile Properties for Monel 400/SS 316L Dissimilar Metal Welding Joints.

Dissimilar metal weld joints of Monel 400 and Stainless Steel 316L stainless steel were carried out using Gas Tungsten Arc Welding (GTAW). Conventional annealing and cryogenic treatment were performed on the welded joints. Weld joints of this combination of materials have enormous potential applications in power industry and the available related literature is limited. In the present study, the tensile properties of heat treated (HT), cryotreated (CT), and untreated (UT) specimens were studied. The engineering stress and strain were determined experimentally as per Standard Test Methods for Tension Testing of Metallic Materials (ASTM E8). The strain distribution was evaluated at different zones of weld joint was evaluated using Digital Image Correlation (DIC). Significant difference was noticed between the zones. Weld zone of all samples had less local stress and strain and SS 316L heat affected zone (HAZ) zone had more local stress and strain when compared to other zones. The local strain distribution along distance from weld center line and local stress-strain curves of different zones are also predicted. Scanning Electron Microscopy was used to analyze the fracture behavior of welded samples for HT, CT, and UT specimens.

Corrosion Resistance of Rolled and Welded Tube-to-Tube Sheet Joints Made Using Different Technologies

In the manufacture of heat exchange equipment, which has been widely used in the oil and gas industry, arc welding methods are often used. This can lead, depending on the material performance of the apparatus, to a significant increase in energy and labor costs. The purpose of the studies in this article was to find out whether samples obtained using friction welding technology, which is an alternative to arc welding methods, meet the requirements for corrosion resistance of heat exchange equipment from heat-resistant hardening steels during its operation, and also compare them with samples obtained using arc welding methods. To do this, studies were carried out on the microstructures of welded joints and distributions of electrode potential values in various zones of welded joints and base metal. At the end of the article, conclusions are drawn based on a comparison of the microstructures of the investigated compounds, as well as the distribution of electrode potential values over the base metal and welded joint of samples made using various welding methods.

Effect of grain boundary precipitation on the mechanical integrity of EBW joints of Inconel 625

The precipitation effects on the mechanical behavior of electron beam welded joints of Inconel 625 in the as-welded [AW] and post-weld heat treatment [PWHT] conditions have been investigated in this research study. A PWHT comprising of direct aging [DA] treatment at 700 °C for 100 h in vacuum at a pressure of 10 −5 mbar was performed on the weld joints. The microstructure of the base alloy opined the precipitation of MC system carbides and γ′′ strengthening phase after subjecting to DA. Also, Nb–Mo rich precipitates and the Laves phase was noticed in the inter-dendritic arms of the fusion zone (FZ) of welded joints in the AW conditions. DA treatment has a notable effect on the weld mechanical characteristics of Inconel 625 joints. The precipitation of γ′′ strengthening phase is reasoned for the significant rise in the yield strength [YS] and tensile strength [TS] of the base alloy and EBW joints. • Grain boundary precipitation of MC carbides on EB weld seams of Incoloy 925. • Formation of M 23 C 6 , M 6 C carbides in the grain boundaries of weld microstructures in both the conditions. • Improved yield and tensile strengths after subjecting to PWHT conditions.

Analysis of Methods of Protection of Inner Surface of Welds of Field Pipelines

In order to increase corrosion resistance, different types of insulation of the inner surface of pipes are used, but corrosion in this case often occurs on the inner surface of pipes in the zone of annular welded joints, where there is no insulation. There is no doubt that protection of the internal weld joint is an urgent task, the purpose of which is to increase the reliability of pipeline transport systems. There is a problem of insulation of the area of welded joints of pipes. In areas of welded joints of pipelines, effective corrosion protection shall be provided. A variety of methods have been used to protect internal coated welded joints from corrosion. Protective bushings are the most common method of protection of welded joints of field pipelines with internal coating.

SPECIAL METALS INCONEL C-276

Abstract Special Metals Inconel C-276 is a wrought, Ni-Mo-Cr-Fe-W alloy that has excellent corrosion resistance in a wide range of aggressive media. The high molybdenum content makes the alloy especially resistant to pitting and crevice corrosion. The low carbon content minimizes carbide precipitation during welding to maintain resistance to intergranular attack in heat-affected zones of welded joints. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-768. Producer or source: Special Metals Corporation.

Joining of Steels to Aluminum and its Alloys by Friction Stir Welding

The main mechanisms of structure formation in zones of welded joints of unlike metals (steel – aluminum) obtained by friction stir welding in the mode of structural superplasticity are considered. Sheet billets of different steels (St3ps, 12Kh18N10T) and deformable aluminum alloys (AD1, AMg6) with a thickness of 3 mm are butt- and lap-welded by the friction stir technique. The microstructures, the phase components and the mechanical properties of the welded joints are determined.

Achievements of the department for development of new products, related technologies and materials of JSC RosNITI

The latest achievements of the department for new products, related technologies and materials are presented in the following areas: creation of anti-corrosion and conservation coatings; development of cylinders; development and testing of rolling tools, technological lubricants and coatings. Based on the results of the activities of the department employees, high-tech science-intensive types of new products with high added value, which are in demand in the market, have been developed and implemented, such as heat-insulated lift pipes, oil and gas pipes with a metal coating of the welded joint zone, pipes with threaded casing connections with GW coatings, pipes with deoxidized inner and outer surfaces, cylinders of new designs, original lubricants and deoxidizing materials.

A Comparative Studyon Characteristics of Inconel-625 Joints Developed through Microwave Hybrid Heating and Tungsten Inert Gas Welding

In recent years, microwave welding has received attention for joining of similar and dissimilar metals due to its major advantages like volumetric heating, selective heating of target materials, energy saving and sustainability. In the present work, the microstructural characteristics and mechanical properties of Inconel-625-welded joints developed through microwave hybrid heating and those produced by TIG welding have been compared. Welding through microwave hybrid heating (MHH) was carried out using Inconel-625 interface filler powder of 50 μm size, while TIG welding was carried out using ERNiCrMo-3 filler wire of 2.5 mm diameter which had a composition similar to that of Inconel-625 alloy. The welded samples were characterized in terms of microstructural observations and tensile and microhardness properties. The study reveals that the joining of bulk metals through MHH has potential in manufacturing industries in the near future. TIG-welded joints exhibit superior strength compared to MHH joints because of fine grain structure, lower amount of segregation in the weld zone and also smaller width of the weld zone in joints developed through MHH. The hardness in the weld zone of welded joints in both the cases is observed to be almost the same. Use of a finer interface filler of 20–25 μm particle size may further contribute to improving the mechanical properties of the joints developed through MHH. Furthermore, the use of industrial microwave furnace may improve the strength of MHH-welded joints as the process may be integrated with real-time temperature measurement of the joint zone so as to achieve better control over the process.

Decomposition mechanisms of continuously cooled bainitic rail in the critical heat-affected zone of a flash-butt welded joints

Abstract The joining process of bainitic rails is significant in terms of their industrialization in high-speed and heavy-loaded railways. This paper demonstrates the microstructure changes in the critical zone of the welded joint, which is responsible for the greatest deterioration in mechanical properties. Extensive progress in the decomposition of the retained austenite and bainitic ferrite occurs in the low-temperature heat-affected zone (LTHAZ) of the flash-butt welded joint of low-carbon bainitic rail. The decomposition products of the retained austenite were mainly a mixture of cementite and ferrite. The cementite was mainly precipitated at the boundary of the bainitic ferrite laths, which indicates lower thermal stability of the filmy austenite. Moreover, it was found that a part of the refined blocky retained austenite was decomposed into the ferrite and nanometric cementite, while another remained in the structure. The decomposition mechanisms are rather heterogeneous with varying degrees of decomposition. A relatively high proportion of dislocations and stress fields prove the occurrence of residual stresses formed during the welding process.