Papers by Keyword: Welded Joint

Abstract: This study employs hydrogen permeation tests, slow-strain-rate tensile tests, and Charpy impact tests to investigate how the welding process and PWHT influence hydrogen diffusion behavior and hydrogen embrittlement susceptibility of welded joint. The research results indicate: The microstructure of all regions of the welded joint consist of granular bainite, MA islands, and precipitated carbides, carbides are mainly M₂₃C₆, M₇C₃, M₂C, and M₆C types. These carbides act as irreversible hydrogen traps and are the primary reason for the reduced hydrogen diffusion coefficient in the material. The heterogeneous microstructure of the weld metal causes direction-dependent hydrogen diffusivity. PWHT also influence hydrogen embrittlement susceptibility. The findings of this study can provide theoretical guidance for optimizing welding procedures in the fabrication of hydrogenation reactors.

Abstract: Stress-corrosion cracking (SCC) of buried gas pipelines has remained a global problem for over 50 years. As pipelines age, new SCC cases emerge, including in welded joints. Improving ductility in these joints is one way to enhance SCC resistance. A welded joint of X70 steel was made using single-arc submerged arc welding (OK10.74, Sv-08GNMA wire). SCC behavior was studied under cathodic polarization in NS4 solution using ANSYS modeling, slow strain rate tests, and scanning electron microscopy (SEM). Results showed that SCC in joints without a stress concentrator occurs along the base metal at a polarization potential of -1.050 V (vs. Ag/AgCl), indicating high weld quality and resistance to brittle fracture. Finite element modeling revealed stress concentration in the base metal during rupture. SEM analysis confirmed increased brittle fracture zones in these joints. With a V-shaped stress concentrator, SCC propagated along the weld, avoiding the heat-affected zone and base metal, which highlights the joint’s ductility. Numerical modeling showed maximum deformation beneath the notch, where fracture initiates. These findings demonstrate that ductile welded joints can effectively resist SCC, and stress concentrators significantly influence crack propagation paths. The study emphasizes the importance of weld quality and joint design in maintaining pipeline integrity under corrosive conditions.

Abstract: The creep behaviour of new grades of austenitic creep resistant steels used mainly for USC boiler superheaters reflects the development and degradation of microstructure with respect to changes that occur during long-term creep exposure. This mainly involves the formation of a brittle intermetallic σ-phase, which significantly affects mechanical properties, creep rupture strength and creep plasticity. The paper describes the creep cavitation damage of heterogeneous TIG weld joints of tubes made of HR3C steel and Inconel 617 alloy welded with Inconel 617 alloy-based welding wire, that were tested by internal pressure creep test. The final damage always occurred in HR3C steel beyond the heat-affected zone of the weld joint. Creep cracks propagated along grain boundaries decorated with M₂₃C₆ carbides and also sigma phase. The extent and range of creep cavitation damage was evaluated according to the NORDTEST TR 302 procedure (hereafter referred to as NT TR 302).

Abstract: Taking into account the history of problems concerning high-strength low-alloyed (HSLA) steel used for manufacturing of penstocks (partly presented by authors in previous studies), this paper is oriented toward specifics on structural integrity assessment of construction in question. Experimental testing of parent material, i.e. HSLA steel, such as microstructure analysis, impact toughness testing and hardness measuring provide insight into characteristics of parent material properties. Considering geometry of penstock and specific requirements, finite element method (FEM), i.e. ABAQUS, was used to assess the structural integrity of penstock as a whole, specific the longitudinal welded joint under the different internal (working) pressure. It should be emphasized that a slight undermatching effect was investigated by FEM approach in this case. Focus is being put on plastic deformation investigation on aforementioned welded joint under maximum internal pressure of 120 bar.

Abstract: In this paper, the effect of direct and pulsed current in the arc welding with the use of UONI 13/Moroz coated electrodes on the structure and properties of 10KhSND structural low-alloy steel joints was investigated. Welding was performed in winter at an ambient temperature of-40oС. This work is a continuation of the cycle of research on welding of structural steels, carried out by the authors for several years.

Abstract: The paper deals with research, development and verification of production technology of selected welded joints for pressure vessels located in primary circuit of nuclear power plants type MIR 1200. Effects of various welding technologies on mechanical and fracture properties were studied. Four types of weld joints made of 10GN2MFA steel grade were prepared for experimental programme consisted of testing of conventional mechanical (tensile and impact tests) as well as fracture toughness and low-cycle fatigue tests and also stress corrosion cracking test in water environment. Effect of elevated operating temperature on material properties was evaluated, too.

Abstract: This paper presents studies of welded joints of steels 30KhGSA and 40KhMFA made by rotary friction welding. The influence of the forging force on the microstructure and tensile properties of standard specimens and specimens with a notch in the contact zone is analyzed. The results of measuring the microhardness and fractogram of the fracture surface are presented. It has been established that in the selected range of forging forces, the strength of the contact zone is higher than other sections of the thermomechanical affected zone and the base metal of the materials to be welded. In this case, the maximum strength of the contact zone occurs at lower values ​​of the forging force due to the formation of common grains along the contact line as a result of the process of mutual volumetric recrystallization.

Abstract: The analysis of official data shows that the average service life of a ship in Russia exceeds 25 years, but it is no secret that a significant part of all ships is operated beyond the standard period. The ability of ship structures to withstand fatigue damage (cracks) from variable loads and extreme load damage (cracks, plastic deformations and loss of stability due to violation of their shape) is a complex concept that determines the strength of the entire welded hull. When repairing a ship, hull work accounts for up to 30% of the total repair and is carried out in difficult working conditions. The cost of hulls repairing is high not only because of the basic material costs, but also because the ship is decommissioned for a long time. Additional work on the repair of welds defective sections increases the time and complexity of the construction as well as ships repair. In this regard, the authors of the article consider it necessary to establish dependencies showing the mutual influence of defects in welded steel joints, the parameters of cyclic loading and the duration of the stages of fatigue failure. For this purpose, the authors analyze the cases of destruction of welded structures from welding. The choice of research methodology and materials for the study is justified. To study the effect of internal weld defects on the fatigue strength, the optimal number of test samples is taken. In connection with the specificity of the tasks to be solved, the authors were tasked to develop a scheme and design as well as to manufacture an experimental installation for conducting fatigue tests.

Abstract: The effects of welding wire composition on microstructure and mechanical properties of welded joint in Al-Mg-Si alloy were studied by electrochemical test, X-ray diffraction (XRD) analysis and metallographic analysis. The results show that the weld zone is composed of coarse columnar dendrites and fine equated grains. Recrystallized grains are observed in the fusion zone, and the microstructure in the heat affected zone is coarsened by welding heat. The hardness curve of welded joint is like W-shaped, the highest hardness point appears near the fusion zone, and the lowest hardness point is in the heat affected zone. The main second phases of welded joints are: matrix α-Al, Mg₂Si, AlMnSi, elemental Si and SiO₂. The addition of rare earth in welding wire can refine the grain in weld zone obviously, produce fine grain strengthening effect, and improve the electrochemical performance of weld.

Abstract: The article discusses the types of dangerous defects in welded joints. The main methods of non-destructive testing are described, their advantages and disadvantages are briefly reflected. The comparison of the automated ultrasonic testing methods with radiographic ones is given on the example of testing the welded joints of ASME DN350 Py250 pipe fittings with a thickness of the welded edges of 53.9 ÷ 61.3 mm. The comparison results of the methods by the criterion of the accuracy of determining the coordinates of defects are presented, which show the expediency of replacing the automated ultrasonic method with the radiographic one, provided that the thickness of the welded edges is shallow.