Thick Welded Joints Research Articles

Evaluation of multiple residual stress components in a thick welded joint using extended contour method

Evaluation of multiple residual stress components in a thick welded joint using extended contour method

Characterization of heterogeneous mechanical properties for thick welded joints with flow stress variation in the transverse and thickness directions

Characterization of heterogeneous mechanical properties for thick welded joints with flow stress variation in the transverse and thickness directions

Structure and mechanical properties of a 132 mm thick welded joint of low-carbon Nb and Nb + Ti heavy plate steel after TM+AcC

Structure and mechanical properties of a 132 mm thick welded joint of low-carbon Nb and Nb + Ti heavy plate steel after TM+AcC

Fatigue performance assessment of thick TIG-Dressing cruciform welded joints made by Q355D structural steel

TIG-Dressing treatment is often used for steel welded joints in construction machinery manufacturing as an effective and reliable method for post-weld fatigue strength improvement. This paper investigates the fatigue performance of thick Q355D cruciform joints in heavy load-carrying steel structures under different TIG-Dressing treatments. Two TIG-Dressing treatments for the full-penetration welded joints were used for fatigue tests considering filling metal during this post-welded processing. Experimental tests studied the fatigue strength of TIG-Dressing cruciform welded joints of Q355D structural steel. The geometric parameters and relevant statistical analyses were performed by actual 3D optical measurement. Moreover, the stress concentration factors are calculated according to the actual geometrics of the welded joint. On the other hand, the effective notch stress and hot spot stress methods were employed to evaluate the fatigue data of Load-Carrying Welded joints (LCWJs) under different notch radius. The collected fatigue data from the literature was compared with the tested data by the above methods. The results show that the fatigue strength of LCWJs under TIG-Dressing processing without filler metal is higher than those under the same TIG-Dressing treatment with filler metal. The effective notch stress method with a fictitious notch radius r = rtrue + 1 mm (rtrue is the actual notch radius at weld toe) could obtain smaller scatter bands for the tested fatigue data.

Analysis of Microstructure and Mechanical Properties of AZ31B Thick Plate Magnesium Alloy Stir Friction Welded Joints

Welding of 10 mm thick AZ31B magnesium alloy by stir friction welding technique. The effects of process parameters on the microstructure, tensile strength and impact resistance of the joints were analyzed. The results showed that the joints were formed with good quality and no obvious defects, and the joints were fine-grained and accompanied by grain dislocations. The grain dislocation in the hot machine influence zone is more obvious there is a dense grain dislocation zone, and the distribution is not uniform. When the spindle speed is 800 and 1000 rpm, respectively, the best impact resistance of the welded joint impact work is 8.02 J, which is about 94.2% of the impact resistance of AZ31B magnesium alloy base material. When the spindle speed is 1000r/min and the welding speed is 150 mm/min, the tensile strength of the welded joint is the largest, reaching 85.8% of the base material and the post-break elongation is 1.9 times that of the base material. Thick plate magnesium alloy plate welded joints overall performance is not uniform, welded plate bottom mechanical properties of the worst, weld core area doped magnesium alloy oxide, joint tensile fracture crack source from the bottom of the plate to the weld surface expansion.

Effect of Postweld Heat Treatment on Microstructure and Properties of Thick S11306 Ferritic Stainless Welded Joints

This study investigated the evolution of microstructure and mechanical properties of 25 mm thick S11306 ferritic stainless steel welded joints during Post weld heat treatment (PWHT) by a series of tests, including the optical microscope observation, hardness test, tensile test, bending test, and scanning electron microscope tests. The experimental results show that at as-welded and 870 °C, the toughness of welded joints was poor; and when the heat treatment temperature is between 770 and 820 °C, the content of the composite phase of lower bainite and martensite (LB/M) in the weld zone increased to 43.9~47.6%, and the mean values of tensile strength and yield strength were 476 MPa and 309 MPa, the elongation was close to 40%, and the welded joints show good toughness. The bending test of the welded joints under several groups of PWHT was qualified. Heat preservation of welded joints was conducted at 820 °C for 30 s~1 h and with the increase of holding times, the content of the LB/M in weld zone showed an upward trend, and the recrystallization of base metal zone was basically completed at 15 min. In addition, a recrystallization kinetic model of the base metal zone was also established by measuring the hardness of the base metal zone at 820 °C for different holding times, which provides reference opinions for obtaining the favorable microstructure of steel grades during PWHT in the engineering.

Effect of Welding Sequence and Constraint on the Residual Stress and Deformation of Thick Welded Butt Joint Made of Q345qD Steel

In this paper, the residual stress and deformation of 32 mm thick welded butt joints made of Q345qD steel using gas metal arc welding (GMAW) are studied by using the thermoelastic‐plastic finite element analysis (FEA). Element birth and death technique is used to simulate the deposition of the welding consumables, and the volume heat source in double‐ellipsoidal distribution is used. An in‐house python code is developed to enable the volume heat source movement. After the finite element model was verified against the experimental results, the effects of five welding sequences and two types of boundary constraint conditions on the residual stress and deformation of the thick welded butt joints were investigated. Results of the experimental measurement and the numerical simulation are in good agreement. The transverse residual stress and the vertical deformation can be significantly reduced by increasing the alternating times of the welding beads in two halves of the weld. The transverse residual stress and the vertical deformation can be reduced by 21.4% and 87.4%, respectively. In addition, the residual stress and deformation of the thick welded butt joints are significantly affected by the applied constraints. Increasing the constraint significantly increases the overall level of the transverse residual stress but can decrease the maximum longitudinal residual stress by 51.8% and the vertical deformation by 65.9%.

Effect of residual stress modification technique on CTOD test results in heavy thick welded joints

ABSTRACT In order to investigate the effects of residual stress modification on the results of crack-tip opening displacement (CTOD) tests in heavy thick welded joints, experiments using a submerged-arc welding (SAW) joint of an EH47 steel plate with the thickness of 70 mm and residual stress analyses by the finite element method (FEM) were performed. It was confirmed that appropriate reversed bend conditions improved fatigue precrack front shapes, and the low ratio of the fatigue precrack length to the size of the compressive plastic zone induced by reversed bending contributed to the fatigue crack shape improvement. Although the local compression with a large diameter platen was effective in improving the fatigue precrack front shape, small diameter platens were not effective even if they applied to wide ranges of specimens. In addition, specimens treated by the reversed bending showed higher critical CTOD values than those treated by local compression. According to the FEM analysis, the reversed bending introduced tensile residual stress at the mechanical notch root, although the initial residual stress distribution of the welded joint still remained a little away from the notch root. On the other hand, the initial residual stress was almost removed by the local compression with a large diameter platen. It was presumed that the initial residual stress distribution affected fatigue precrack front shapes and the critical CTOD in welded joints. The reversed bending is very useful if appropriate conditions can be used.

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.

Distortion and residual stresses in thick plate weld joint of austenitic stainless steel: Experiments and analysis

Abstract The present work aims to evaluate distortion and residual stresses in thick plate weld joints of austenitic stainless steel. Quantification of residual stresses in thick austenitic stainless steel weld joint is important because it is not desirable to carry out stress relieving after welding owing to the susceptibility to sensitization in the heat-affected zone. Therefore, systematic studies were carried out to predict and measure distortion and residual stresses in the austenitic stainless steel plate weld joint. Variables influencing the generation of residual stresses such as heat input, welding speed, constraints during welding were considered. 20 mm thick plate weld joint of austenitic stainless steel material was prepared using gas tungsten arc welding (GTAW) in unclamped condition and distortions were measured during welding after each pass. Sub-surface and through-thickness residual stresses were measured using blind hole drilling (BHD) and deep hole drilling (DHD) techniques respectively. Thereafter, the weld joint was modeled using the finite element method and analyzed for residual stresses and distortions. Thermal analysis was carried out using actual welding parameters and temperature-dependent material properties to generate temperature profile and compare it with the measured values. The temperature profile along with necessary boundary conditions was used for structural analysis to obtain distortion and residual stresses. Experimental and finite element analysis results for distortion and residual stresses compare well. Details of the experimental and numerical analysis results of distortion and residual stresses for thick section plate weld joints have been discussed in this paper. Also, the effects of differences in yield strengths of weld and base metals on distortion and residual stress results have been brought out.

Assessment of the Effect of Laser Welding on the Properties and Structure of TMCP Steel Butt Joints.

The research work and related tests aimed to identify the effect of filler metal-free laser beam welding on the structure and properties of butt joints made of steel 700MC subjected to the TMCP (thermo-mechanically controlled processed) process. The tests involved 10-mm thick welded joints and a welding linear energy of 4 kJ/mm and 5 kJ/mm. The inert gas shielded welding process was performed in the flat position (PA) and horizontal position (PC). Non-destructive testing enabled classification of the tested welded joints as representing the quality level B in accordance with the requirements set out in standard 13919-1. Destructive tests revealed that the tensile strength of the joints was 5% lower than S700MC steel. The results of tensile tests and changes in structure were referred to joints made using the MAG (Metal Active Gas) method. The tests of thin films performed using a high-resolution scanning transmission electron microscope revealed that, during laser beam welding, an increase in dilution was accompanied by an increase in the content of alloying microadditions titanium and niobium, particularly in the fusion area. A significant content of hardening phases in the welded joint during cooling led to significant precipitation hardening by fine-dispersive (Ti,Nb)(C,N) type precipitates being of several nanometres in size, which, in turn, resulted in the reduction of plastic properties. An increase in the concentration of elements responsible for steel hardening, i.e., Ti and Nb, also contributed to reducing the weld toughness below the acceptable value, which amounts to 25 J/cm2. In cases of S700MC, the analysis of the phase transformation of austenite exposed to welding thermal cycles and the value of carbon equivalent cannot be the only factors taken into consideration when assessing weldability.

Microstructure and Properties of Welded Joint of 6063 Aluminum Alloy Medium and Thick Plate

In this paper, the welding parts of the 6063 aluminum alloy 15mm and 20mm plate on the solar wing expansion frame of a certain type of satellite are studied. The structure of the welding structure is analyzed and tested. The relationship between the distribution characteristics of the joint and the mechanical properties of the weld and the influence law of the weld are analyzed, and the welding process is rationally formulated in the actual production. Provide theoretical basis and technical support for improving welding quality. The two thickness aluminum plates are formed by MIG welding. The metallographic samples and tensile specimens are intercepted from the welded parts, and the metallographic samples are prepared. The microstructure and tensile strength and hardness of the welded joints are analyzed by metallographic microscope, scanning electron microscope, X ray diffractometer, tensile test machine and microhardness tester. Degree. The results show that there is a softening zone in the welded joint, which mainly exists in the heat affected zone; at the same time, there will be a high hardness point (15mm 84.6HV; 20mm 70HV) in the fusion zone, which is due to the presence of more strengthening phase Mg2Si and a small amount of Al12Mg17. The average tensile strength of the welded joint with two thickness is 166MPa and 218MPa respectively, and the thickness of 15mm is lower than the tensile strength of 6063 aluminum alloy, while the 20mm thickness is higher than the theoretical tensile strength of 6063 aluminum alloy, and the elongation is higher than that of the 6063 aluminum alloy theory, in which the joint of 15mm thick welded joint is pulled from the 15mm at the weld seam. Extension fracture, 20mm thick welded joint tensile fracture at the weld.

Weld joint design and thermal aging influence on the metallurgical, sensitization and pitting corrosion behavior of AISI 304L stainless steel welds

Experimental investigations were carried out to study the influence of weld joint design and post weld thermal aging treatments on the metallurgical, intergranular and pitting corrosion behavior of AISI 304L stainless steel welded joints. 10 mm thick linear weld joints were fabricated using gas metal arc welding process using single-V and double-V joint design with an average heat input of 503.42 J/mm and 562.78 J/mm respectively. Thermal aging of these welds was carried out at 750 °C for 0.5 h and 4 h, and the cooling media used was furnace, air and water quench (used separately for each specimen), so as to induce variable degree of carbide precipitation in different zones of these welds. Microstructural studies revealed that the extent of carbide precipitation was more in case of welds made using double-V joint design as compared to single-V joint welds. Degree of sensitization (DOS) and pitting performance of these welds evaluated using double loop electrochemical potentiokinetic reactivation (DLEPR) technique and potentiodynamic anodic polarization technique respectively, further showed that single-V joint performed better in terms of corrosion properties owing to lesser precipitation as compared to the double-V joint. This study shows that in comparison to double-V joint, single-V joint design can prove to be an important part of fabrication procedures where service conditions demand better corrosion properties of these welds.

Однопроходная электродуговая сварка под тонким слоем шлака толстолистовых конструкций стали 09Г2С

Introduction. The technology of single-pass arc welding under a thin layer of slag (AST) of thick plate welded structures in the thermal and nuclear engineering is considered. The structure material is 09G2S steel. The work objective is the experimental study on the applicability of the AST method instead of the automatic welding under flux (AWF) and electroslag welding (ESW) under manufacturing the package units of the power plants. Materials and Methods. The technology is developed on the basis of the calculation results of the thermal welding mode (thermal cycle parameters and welding mode settings). Test joint weld-samples, 100 mm thick, are made of 09G2S lowcarbon low-alloy steel. Welding is performed on the certified equipment of “EMC-Atommash” JSC. The welded joints quality is assessed on the standard control results by the following techniques: magnetic-particle testing (MPT), ultrasonic control (USC) and radiographic testing (RT). The non-destructive testing results were supplemented with the metallographic study data. To investigate the nature of the weld metal crystallization along the length of the weld, the macrotemplates were cut out mechanically from the middle through-the-thickness and at the distance of 10 mm from the surface. The technique and installation of “TCS-1” for simulating the thermal cycle of the metal welding of the heat affected zone (HAZ) of the welded joints; standard methods for determining mechanical properties; hardness and microhardness indices; and method for determining the grain size in micrographs according to GOST 5639-82 were used in the experiments. The microstructure was studied with MMP-2P and Reichert optical microscopes with increase up to thousandfolds. Besides, the distribution pattern and identification of the second phases of nonmetallics; welded samples and samples modeling the HAZ metal for the notch sensitivity; structure stability and welding cracking resistance were studied through the replica technique using the EMV-100LM electron microscope. Research Results. Based on the thermal calculation results and the HAZ metal modeling, the optimum values of the heat input and welding variables are validated and experimentally verified. The welded joints quality is estimated by the nondestructive and destructive methods. The effect of the welding method on the structure, quality and mechanical properties of the welded joints is established. Discussion and Conclusions. Positive results of the theoretical and experimental studies are obtained. They indicate the technological and economic efficiency of the AST method application (instead of AWF and ESW) under manufacturing the 100 mm thick welded joints of 09G2S low-alloy steel. Moderate heat input in AST allows for the one-pass forming of a welded joint with better fine-grained structure and higher mechanical characteristics as compared to the ESW and AWF. Recommendations on the use of the AST technique in the welding production are given.

Analysis of the thickness effect in thin steel welded structures under uniaxial fatigue loading

This paper investigates the scale effect in relatively thin welded joints subjected to fatigue loading made of steel. In the scientific literature, the fatigue behaviour of arc-welded joints is usually divided into two groups: thick and thin joints. A cut-off thickness, typically in the range of 13–22mm, was introduced; under such cut-off value, the design fatigue strength does not increase when the thickness is decreased. Despite this common approach, in this paper, the concept of cut-off thickness is revised and a numerical procedure is proposed, regardless of the thickness of the joint, by means of the implicit gradient method. Classical non-load-carrying and load-carrying cruciform joints made of steel are considered in the three-dimensional numerical analysis. Finally, the fatigue behaviour of joints two millimetres thick with a longitudinal or transversal stiffener was also analysed by means of the implicit gradient approach. The Woehler curve was evaluated in terms of the nominal stress of such a series and a good correlation was found with experimental data by using the numerical procedure optimised for thick welded joints.

Cyclic Polarization Study of Thick Welded Joints of Lean Duplex Stainless Steel for Application in Biodiesel Industry

Thick welded joints of UNS S32304 lean duplex stainless steel (LDSS) has been studied in acidified glycerin, a byproduct of biodiesel plants, using cyclic polarization technique. LDSS S32304 thick plates were welded by different processes commonly employed in the fabrication process: shielded metal arc welding, gas metal arc welding and flux cored arc welding. The electrochemical behavior of different weldment zones was characterized. Transmission electron microscopy and scanning electron microscopy (SEM) were used for sample characterization. SEM images showed that the heat affected zone was the most critical zone for pitting corrosion for all samples. The results were associated to the microstructural features of the materials. Generally, the breakdown potential of the top regions of welds was higher in acidified glycerin than the weld root for welds fabricated with two different filler metals. Basically, all the welded samples exhibited similar or higher corrosion resistance, compared with the corresponding base metal.

Electrochemical study of passive films formed on welded lean duplex stainless steel

Duplex stainless steel (DSS) has been considered as an excellent material of construction for applications where high corrosion resistance and high mechanical strength are required. The use of this material can minimize costs related to corrosion in different industries, for example, in the biodiesel industry. The objective of this study is to evaluate the electrochemical and electronic properties of passive films of thick welded joints of UNS S32304 lean duplex stainless steel (LDSS) fabricated by different welding processes, in acidified glycerin, a byproduct of the biodiesel industry. The electrochemical and electronic behavior of the passive films formed on UNS S32304 LDSS was evaluated using electrochemical impedance spectroscopy and Mott–Schottky measurements. The capacitance study shows that the passive films formed on welded DSS behave as n‐ and p‐type semiconductors above and below the flat band potential, respectively. Furthermore, the samples welded by the gas metal arc welding process exhibited better corrosion resistance than other welding process using the same filler metal.

Microstructural and mechanical inhomogeneity in the narrow-gap weld seam of thick GMA welded Al–Zn–Mg alloy plates

Abstract

Residual stress variation in a thick welded joint after ultrasonic impact treatment

The effects of ultrasonic impact treatment (UIT) on the residual stress within a 45 mm-thick high-strength steel welded joint were investigated. The internal residual stresses after UIT was measured with contour method and compared with the as-welded stresses simulated by finite element method. The surface stresses were also measured by X-ray diffraction method and hole-drilling method to validate the simulation model. Results show that UIT introduces compressive stress layer in the weld zone and has the same effect on the longitudinal and transverse welding stresses; the interior stresses increase and demonstrate more uniform distribution after UIT; UIT would not affect the initial compressive stress presented far away from the weld zone.

Evaluation of Through-Thickness Residual Stresses by Neutron Diffraction and Finite-Element Method in Thick Weld Plates

Through-thickness distributions of the welding residual stresses were studied in the range of 50–100 mm thick plates by using finite-element modeling (FEM) and neutron diffraction measurements. In order to simulate the residual stresses through the thickness of the thick weld joints, this paper proposes a two-dimensional generalized plane strain (GPS) finite-element model coupled with the mixed work hardening model. The residual stress distributions show mostly asymmetric parabola profiles through the thickness of the welds and it is in good correlation with the neutron diffraction results. Both the heat input and plate thickness have little influence on the residual stress distributions due to the relatively large constraints of the thick specimen applied for each welding pass. A general formula has been suggested to evaluate the distributions of the through-thickness residual stresses in thick welds based on FEM and neutron diffraction experimental results.