Welded Tubes Research Articles

Experimental investigations on penetration failure by tube ejection for an APR1400 ICI nozzle during a severe accident

This paper describes experimental investigations on the penetration failure by tube ejection for an APR1400 in-core instrumentation nozzle during a severe accident. The penetration tube specimens interacted with around 2500 °C ZrO2 and UO2-ZrO2 melts and pressurized up to 1.3–3.2 barg. The ERVC (external reactor vessel cooling) effect on the tube ejection was investigated under the maximum heat removal of 466 kW/m2 by water flow at 2.5 m3/hr. ERVC was found to be an effective means to prevent tube ejection by maintaining the structural integrity of the penetration tube weld. However, contrary to the predictions by existing criteria, no tube ejection occurred in all non-ERVC tests despite the penetration tube weld failure. In order to validate the existing criteria, it is still needed to realize the tube ejection using the penetration tube specimen with a freely expanded RV lower head under higher in-vessel heat flux and pressure conditions.

Optimization of post-weld heat treatment condition of arc-welded T91 steel tubes

Modified 9Cr–1Mo ferritic/martensitic (T91) steel tubes have been welded with gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) processes. The welded tubes have been post-weld heat-treated (PWHT) at selected temperatures (i.e., at 720 °C, 760 °C and 775 °C for different times) below their Ac1 critical temperature (~791 ± 5 °C). The PWHT microstructures, mechanical properties and fracture behavior of welded samples have been investigated. The results suggest that the PWHT temperatures closer to Ac1 critical temperature (i.e., 760 °C and 775 °C) has a strong influence on the properties of the T91 welds. They have shown uniform hardness and enhanced tensile strength and percent elongation as against as-welded and 720 °C – 120 min PWHT condition. Further investigation suggests that the strength and percent elongation for 775 °C – 30 min condition were highest among all the PWHT conditions examined. The observed variation in mechanical properties has been related with the finer microstructural features (mainly grain size and precipitate size). This work further confirms that for PWHT temperatures closer to Ac1, as the holding time increases the failure shifts from base metal (BM) to weld metal (WM) region, predominantly due to de-cohesion at the Mn, Cr, Mo rich coarse precipitate/matrix interface. From this study, a novel PWHT condition at 775 °C – 30 min is being proposed for optimum microstructure and mechanical properties for the T91 steel tube welds.

Magnetic pulse welding of copper to steel tubes–Experimental investigation and process modelling

Abstract Magnetic pulse welding allows joining of metallic tubes by a short electromagnetic pulse and the resulting high strain rate impact and plastic deformation. Since melting of materials is avoided, magnetic pulse welding is an efficient method for joining of dissimilar materials. However, the process occurs very fast with little opportunity for real-time monitoring and control, which is also difficult due to the presence of a high amplitude electromagnetic field. A novel attempt is presented here to examine the underlying phenomena for magnetic pulse welding of copper flyer tubes to steel target tubes by computational process modeling and a focused experimental investigation. A coupled electromagnetic and mechanical finite-element model was created to compute the electromagnetic field and pressure distribution, and the progressive nature of flyer tube impact velocity on the target tube. The consequent progress of the angle of impact and contact length are examined for a range of standoff distances between the flyer and target tubes, the target tube wall thickness. The computed results are validated extensively with corresponding experimentally measured results. Overall, the coupled theoretical and experimental investigation provided a useful quantitative insight of magnetic pulse welding of copper and steel tubes, which is expected to help in the advancement of practical application of the process.

Adhesive-free bonding fiber optic Fabry–Perot pressure sensor based on oxy-hydrogen flame welding and spiral tube

In this paper, a fiber optic Fabry–Perot (F–P) cavity high pressure sensor used in oil wells is presented. An F–P cavity probe encapsulated by silica capillary was fabricated through oxy-hydrogen flame welding, and the F–P cavity was fully sealed with adhesive-free bonding. A spiral tube filled with silicone oil was chosen to prevent the probe from directly contacting with down-hole corrosion fluid and to transfer pressure. A fiber Bragg grating was linked with the F–P cavity probe to measure ambient temperature for the probe’s temperature compensation. The sensing pressure can be as high as 82 MPa with a sensitivity of 241 nm/MPa, a repeatability of 0.05% F.S.(full scale), a resolution of 0.0004 MPa with the temperature ranging from room temperature to 175 °C. Besides, the maximum fluctuation of the F–P cavity length can be as small as about 0.0072 MPa within 40 days at the pressure and temperature of 42 MPa and 130 °C. In addition, this kind of sensor has been used in Shengli Oil Field.

Determination of continuous constitutive relationship of weld zone of high-strength steel rectangular welded tube

For QSTE700 high-strength steel rectangular welded tube, the mechanical properties of the weld zone vary with the distance from the centerline of the weld. Therefore, the accurate description of constitutive relationship of the weld zone is of great significance for the study of formability of QSTE700 rectangular welded tube. Firstly, the mechanical properties of parent and mixed specimens containing weld zone and parent zone were obtained by uniaxial tensile test. And based on the microhardness test, the width and the microhardness distribution of the weld zone were determined. Secondly, by subdividing the weld zone into several small areas, and combining with the rule of mixtures and nanoindentation test, the continuous functional relationships of strength coefficient K, hardening coeffecient n and elastic modulus E were obtained, and then, the continuous constitutive relationship of QSTE700 rectangular welded tube was established. Finally, the validity and reliability of the continuous constitutive relationship of welded tube were verified by nanoindentation test and rotary draw bending of rectangular welded tube. Besides, it was found that the finite element model of rotary draw bending of QSTE700 rectangular welded tube established by using the continuous constitutive relationship can well simulate the cross section deformation and wall thickness variation.

Innovation of quality improvement to reduce weld defect through six sigma methods in the fabrication process of power plant component

This study aims to improve the quality of boiler through six sigma methods. Quality of boiler in the thermal power plant should be maintained with a good performance in order to assure that power plant can operate normally. DMAIC principle, defining, measuring, analyzing, improving, and controlling processes is implemented in this research. The reseach finding that the average rejection rate that exceeds the target rejection rate are Radiography Test (RT) of welding tube- tube, header-header, and header-end caps. Porosity is a type of weld defect that often occurs, around 36%. Project team concluded three critical that influence the output variables the most. These four variables are welder skill, welding fluxes gas, and welding condition. By implemented improvement of six sigma methods, sigma value increased from 4.1 become 5.

Analysis on Coupled Forming-Welding Process Using FEM Simulation and Experimental Verification

In this paper, a coupled forming-welding process is to be analyzed. Therefore, the process chain of a tube u-/o-bending process was combined with the longitudinal welding of slotted tubes. Both processes were conducted and evaluated experimentally as well as numerically. To verify the process in a wide range of experimental technologies, different analyzing methods were used, which include geometric measurements, microsections (microstructure), X-ray-diffraction and material phase analyses. A good agreement was found for the numerical simulation of the welded tube in accordance with the experimental processes, based on the different evaluation methods. For this reason, it can be concluded that the developed setup can be used as a good forecast for metal inert gas welding processes of tubular products.

Cross-sectional deformation of high strength steel rectangular welded tube in rotary draw bending with different constitutive relationships

An accurate constitutive relationship of rectangular welded tube is important to improve prediction accuracy of cross-section deformation in rotary draw bending by simulation. So five constitutive relationships of QSTE700 high strength steel rectangular welded tube were selected and determined. And five FE models of rotary draw bending process of rectangular welded tube by using these five constitutive relationships were built. Based on the above FE models, the effect of different constitutive relationships of rectangular welded tube on cross-sectional deformation in rotary draw bending process was studied. The results showed that height deformation ratio and width deformation ratio obtained by simulations were gradually increased to approach experimental results when using mixture-model, homogeneity model, W1H model, W2H model and W4H model, successively, and the simulation results obtained by W4H model were closest to experimental results, so the “weld and four heat affected subzones” model was suitable for describing the constitutive relationship of rectangular welded tube, which further meant that when the heat-affected zone was subdivided into more subzones, the constitutive relationship of QSTE700 rectangular welded tube became more accurate.

Effect of bulge ratio on the deformation behaviour and fracture location during welded steel tube hydroforming process

A drawing quality welded steel tube with outer diameter of 57.15 ​mm and thickness of 1.6 ​mm was used in this study. These tubes were hydroformed at bulge ratio (or L/D ratio) of 1, 2 and 3 to achieve different strain paths. It was observed that the tubes after hydroforming fractures in the base metal near the weld for L/D ​= ​1 whereas for L/D ​= ​2, 3 the fracture occurs in the base metal opposite to the weld which was a novel observation. The experimental and simulated strain paths for two extreme L/D ratios of 1, 3 were analysed. It was found that the maximum value of major strain was found at the base metal for all L/D ratios, however, its location and subsequent fracture depends upon L/D ratio. Therefore, to investigate this anomaly, the detailed FE analysis was carried out by varying the ratio of strain hardening exponent between base and weld metal and by introducing the thickness imperfection in the tube. The FE analysis predicts the trade-off between the material inhomogeneity and thickness imperfection leading to fracture at specific location for both L/D. The present study concludes that the relative sensitivity of thickness imperfection versus material inhomogeneity is dictated by the tube bulge ratio.

Qualifying the TIG orbital welding technology of titanium pipes with a perforated bottom

The article presents the method of qualifying orbital welding technology using the TIG (142) method of the perforated bottom heat exchanger made of steel A516M (Grade 485) explosively clad with titanium B265 (Grade 1) with titanium pipes B338 (Grade 2) with a diameter of 34.93 mm and thickness 0.7 mm. Based on preliminary tests, welding technologies have been developed that meet the acceptance criteria for acceptance requirements. Qualification of the developed technology and welding parameters that were used during welding was carried out in accordance with PN-EN ISO 15614 Specification and qualification of metal welding technology, welding technology testing, Part 8: Welding of tubes with perforated bottom. This standard specifies the requirements for the qualification of automatic arc welding technology, metal pipe joints with perforated bottom by means of technology testing.

An experimental study of effects on tube to tube sheet expansion joint grip strength due to seal welding or blanking of adjacent bank tubes of bi-drum boiler

Industrial boilers used in processing industry and auxiliary units for start up steam supply of super critical boilers generate steam with the help of bi-drum arrangement. The tube connecting upper and lower drums are called bank tubes and situated in the flue gas path. Bank tubes are fitted in both the drum with the help of tube to tube sheet expansion joint. During prolonged operation this tubes got punctured due to flue gas erosion or becomes loose at its expansion joints due to improper operation, during drum repair and started leaking. Leaking tubes were repaired either by blanking the tubes or seal welding depends on the nature of failure. As drum is of higher thickness and tubes are of lower thickness, as a procedural drum surface required to be pre-heated before seal welding. This pre-heating and welding affects the joint strength of surrounding tubes. This study focuses on lose of grip strength of surrounding tubes due to pre-heating and welding of central tube during repair, by comparing its micro structure, hardness and pull out load strength. During micro structure analysis polygonal grains of ferrite and pearlite were observed. No significant change in microstructure dimensions between each expansion trail was observed visually. Hardness value falls around 20 Hv near 0° angle of HAZ and falls around 10 Hv at 180° angle of HAZ for 12% expansion. For wall thinning above 10% and ligament efficiency less than 0.4 grip strength falls drastically, and requires complete re expansion of surrounding tubes.

Push-out resistance of concrete-filled spiral-welded mild-steel and stainless-steel tubes

Spiral welded tubes (SWTs) are fabricated by helically bending a steel plate and welding the resulting abutting edges. The cost-effectiveness of concrete-filled steel tube (CFST) columns can be enhanced by utilising such SWTs rather than the more conventional longitudinal seam welded tubes. Even though the steel-concrete interface bond strength of such concrete-filled spiralwelded steel tubes (CF-SWSTs) is an important consideration in relation to ensuring composite behaviour of such elements, especially at connections, it has not been investigated in detail to date. CF-SWSTs warrant separate consideration of their bond behaviour to CFSTs of other tube types due to the distinct weld seam geometry and fabrication induced surface imperfection patterns of SWTs. To address this research gap, axial push-out tests on forty CF-SWSTs were carried out where the effects of tube material, outside diameter (D), outside diameter to wall thickness (D/t), length of the steel-concrete interface (L) and concrete strength grade (f'c) were investigated. D, D/t and L/D values in the range 102-305 mm, 51-152.5 and 1.8-5.9 were considered while two nominal concrete grades, 20 MPa and 50 MPa, were used for the tests. The test results showed that the push-out bond strengths of CF-SWSTs of both mild-steel and stainless-steel were either similar to or greater than those of comparable CFSTs of other tube types. The bond strengths obtained experimentally for the tested CF-SWSTs, irrespective of the tube material type, were found to be well predicted by the guidelines contained in AISC-360.

Studies on the role of total welding rotation in friction welding of tube-to-tube plate using an external tool

Friction welding of tube-to-tube plate using external tool (FWTPET)11FWTPET-Friction Welding of Tube to Tube Plate using External Tool is an innovative friction welding process wherein a friction stir welding tool is used to join tube and tube plate. This work investigates the combined effects of tool rotation speed and plunge duration in terms of a parameter named Total Welding Rotation (TWR)22TWR-Total Welding Rotation, on the quality of FWTPET joints. A mathematical model is proposed to understand the upper and lower limits of TWR, beyond which the process is inclined to give defective joints. This model is verified using experimental studies on joints between AA6061 plate and AA1060 tube. The welded specimens are non-destructively evaluated using Digital Radiography (DR)33DR-Digital Radiography and Phased Array Ultrasonic Testing (PAUT)44Phased Array Ultrasonic Testing, which show that above and below certain TWR values the process leads to defective joints.

Realizing a Novel Friction Stir Processing-Enabled FWTPET Process for Strength Enhancement Using Firefly and PSO Methods.

The friction welding of tube to tube plate using an external tool (FWTPET) is widely deployed in several industrial applications, such as aerospace, automotive, and power plants. Moreover, for achieving a better tensile strength and hardness in the weld zone, the friction stir processing (FSP) technique was incorporated into the FWTPET process for joining aluminum alloys (AA6063 tube, AA6061 tube plate). Furthermore, it has to be noted that FWTPET was applied for joining the AA6063 tube to the AA6061 tube plate, and FSP was deployed for reinforcing the weld zone with carbon nanotube (CNT) and silicon nitride (Si3N4) particles, thereby attaining the desirable mechanical properties. Subsequently, the Taguchi L25 orthogonal array was used for identifying the most influential input and output FWTPET + FSP process parameters. Furthermore, particle swarm optimization (PSO) and the firefly algorithm (FFA) were deployed for determining the optimized input and output FWTPET + FSP process parameters. The input process parameters include CNT, Si3N4, rotational tool speed, and depth. Furthermore, the tensile strength of the welded joint was considered as the output process parameter. The process parameters predicted by PSO and FFA were compared with the experimental values. It was witnessed that deviation between the predicted and experimental values was minimal. Moreover, it was found that FFA provided a superior tensile strength prediction than PSO.

Three-dimensional numerical study of heat-affected zone in induction welding of tubes

Purpose Quality of the weld joint produced by high-frequency induction (HFI) welding of steel tubes is attributed to a number of process parameters. There are several important process parameters such as the speed of the welding line, the angle of the approaching strip edges, the physical configuration of the induction coil, impeder, formed steel strip and weld rolls with respect to each other, the pressure of the weld rolls and frequency of the high-frequency current in the induction coil. The purpose of this paper is to develop a 3D model of tube welding process that incorporates realistic material properties and movement of the strip. Design/methodology/approach 3D numerical simulation by the finite element method (FEM) can be used to understand the influence of these process parameters. In this study, the authors have developed a quasi-steady model along with the coupling of electromagnetic and thermal model and incorporation of non-linear electromagnetic and thermal material properties. Findings In this study, 3D FEM model has been established which gives results in accordance with previously published work on induction tube welding. The effect of the Vee-angle and frequency on the temperature profile created in the strip edge during the electromagnetic heating is studied. Practical implications The authors are now able to simulate the induction tube welding process at a more reasonable computational cost enabling an analysis of the process. Originality/value A 3D model has been developed for induction tube welding. A non-linearly coupled system of Maxwell’s electromagnetic equation and the heat equation is implemented using the fixed point iteration method. The model also takes into account non-linear magnetic and thermal material properties. Adaptive remeshing is implemented to optimise mesh size for the electrical skin depth of induced current in the strip. The model also accounts for the high welding-line speeds which influence the mode of heat transfer in the strip.

Innovation Method of Production of Extremely-Thin-walled Welded Tubes on the Tube-electric Welding Machine TESA 10-20

Innovation Method of Production of Extremely-Thin-walled Welded Tubes on the Tube-electric Welding Machine TESA 10-20

Optimization of Process Parameters in Electro-Magnetic Welding of D9 Tube to SS316 L (N) Plug

In electro-magnetic welding (EMW) process, optimization of process parameters is very important aspect. Optimization process leads to generation of mechanically and metallurgically sound interface weld without overstressing tool coil and electromagnetic welding equipment. This work investigates the effect of four important process parameters (Magnetic field in coil ID, Frequency of current pulse, Taper angle of SS316 L (N) plug and Stand-off distance between D9 tube and SS316 L (N) plug) on weld quality and their optimization. Multiple experiments were conducted to arrive at optimized value of above mentioned process parameters which generated heat effected zone free, mechanically and metallurgically qualified interface weld of reasonable length. The welded interface revealed a wavy morphology of 35 - 40 μm as maximum crest height and lowest helium leak rate of 4 × 10?10 m?bar?L/s. Experimental results have proved that 27 T magnetic field is needed in coil ID to produce optimum weld quality at interface. Experimental data has proved that at higher frequency, similar quality of electro-magnetic welding can be obtained at lower bank energy. Experimental results have also proved that taper angle of 8? produces weld interface at lowest possible magnetic field in coil ID. It is also proved experimentally that 0.5 mm stand-off distance produces better weld length as compared to no stand-off distance and 1.0 mm stand-off distance.

An investigation on friction welding of tube to tube plate by using friction stir processing with CNT and Si3N4 composites

Abstract The advanced metal joining process have been witnessed tremendous improvement in various field of engineering. Particularly, friction welding of tube to tube plate using an external tool (FWTPET) is one the welding technique and it has been extensively applied in power plant industry. This research work will be carried out with various conditions and joining of tube to tube plate takes place with different types of methodology. The combined effect of friction stirs processing and FWTPET technique are used to weld AA6063 tube to AA6061 tube plate reinforced with CNT and Si3N4 particles. This is incorporated into the weld zone, to obtain desirable properties. In the proposed work, CNT and Si3N4 reinforced particles will be introduced into the alloy matrix through Ex-situ approaches. The FSP joints are the most prevalent in the fabrication and construction of thermal power equipment. The systematic characterized tests are used to find mechanical properties and detailed micro structures by using vicker micro hardness and macroscope.

Formation of low angle boundaries and stray grains in welds of single-crystal Mo-3Nb alloys

ABSTRACTMo-3Nb single-crystal alloy is an ideal material for emitters of thermionic fuel elements. In this experiment, heat-affected zone of electron beam welding of Mo-3Nb single-crystal tubes was investigated, and it was discovered that heat-affected zone basically inherited the orientation of parent metal while there were still plenty of low angle boundaries and a few stray grains (SGs). Those low angle boundaries (LABs) stemmed from the fusion line and converged toward the centreline. Besides, the distribution of LABs was asymmetrical about the centreline of welding pool, and Laue diffraction pattern showed that the side with more LABs had higher dislocation density than the other. Furthermore, SGs existed merely at the bottom of welding pool and were discontinuously distributed along the circumferential direction of single-crystal tube.

Improving induction tube welding system performance using soft magnetic composites

Purpose This paper aims to demonstrate the benefits of using different impeder materials for induction tube welding systems. Design/methodology/approach To show the difference in using various impeder materials, a new approach was taken to model tube welding systems in two and three dimensions. Three-dimensional (3-D) electromagnetic models were used to determine the current distribution along the weld vee as well as the permeability of the tube along the length of the welding system. Two-dimensional (2-D) coupled electromagnetic plus thermal models with rotational movement were used to determine the temperature distribution in the heat-affected zone. Findings Simulation results suggest upwards of 25 per cent system power savings when using a soft magnetic composite (SMC) impeder rather than the traditional ferrites. Research limitations/implications There is currently a lack of experimental data to validate the models, but future work will include comparison of models to real-world trials. Practical implications When dealing with tube welding systems, there are possibilities to improve process efficiency or increase production quality and output by improving the impeder material. Originality/value While simulations of tube welding systems have been done previously, studies on improving impeder materials are rarely carried out. This paper brings to light possible improvements to be made to induction tube welding systems.