Longitudinal Submerged Arc Welding Research Articles

Waste Reduction in Pipe Industry Through Lean Six Sigma Implementation

This research investigates to manage waste in longitudinal submerged arc welded (LSAW) steel pipes by the utilization of Lean Six Sigma (LSS) tools, with an emphasis on promoting sustainability through waste reduction. The DMAIC approach was implemented to ascertain underlying causes, enact modifications, and oversee practices. Reusing, recycling, and repurposing of materials was employed to minimize production waste. The findings demonstrate a noteworthy decrease in waste with regards to the overall weight of raw material, from 5.3% to 3.4%, and a reduction in monetary losses by 58.07%. The implementation of the LSS methodology has been shown to augment customer satisfaction, minimize waste and variation, and improve sustainability in numerous industries. The effectiveness of the LSS approach in managing waste and promoting sustainability in the LSAW sector was validated by consistent results, as evidenced by the control plan. Given the crucial significance of efficient waste management for sustainable production and consumption, this research underscores the potential of LSS as a resilient methodological approach to reduce waste and advance sustainability in the industry.

The JCOE/JCOC manufacturing process and collapse resistance of submarine pipeline

Submarine pipeline is an important part of deep-sea and ultra-deep-sea oil and gas development. In the cold forming process of longitudinal submerged arc welded (LSAW) pipe, the JCO manufacturing process is one of the key forming technologies for manufacturing submarine pipeline. The main problem encountered by submarine pipelines in offshore oil and gas transportation is insufficient pipeline collapse pressure, which leads to pipeline collapse and shortens the service life of the pipeline. Therefore, the analysis of the JCO manufacturing process is of great significance to improve the collapse resistance of pipelines. In this paper, the development and research status of the JCOE/JCOC manufacturing process are reviewed. The stress, contact, and deformation of the plate are symmetrical in the JCOE/JCOC manufacturing process. The effects of expanding and compression on pipe collapse performance in the JCO manufacturing process are summarized. The asymmetric factors can reduce the collapse performance of the pipeline. Compared with expanding, compression can effectively reduce the ovality of pipe and strengthen the compression performance of pipe, to improve the collapse performance of pipe; finally, the JCOE/JCOC manufacturing process and collapse resistance of submarine pipeline is summarized and prospected.

Research on the welding performance of X70 longitudinal submerged arc welding ultra-abyssal pipeline steel

In this paper, Gleeble 3800 was used to simulate the changes in microstructure and properties of X70 ultra-abyssal pipeline steel at room temperature under different welding line energies. The industrial welding test of X70 pipeline steel was also conducted by adopting the 4-wire Longitudinal Submerged Arc Welded process. By optimizing welding process parameters, a reasonable welding specification process was developed. The results show that at different welding line energies, when the cooling time t8/5 is 12 ~50s, the microstructure of the welding coarse crystal zone is mainly lambellar bainite and granular bainite, and the uniform distribution of granular bainite exists in the austenite, obtaining better impact toughness. Ultra-abyssal longitudinal submerged arc welding steel producing by the optimized 4 - wire energy welding process has excellent mechanical properties and crack propagation resistance.

Mechanical properties and microstructure of longitudinal submerged arc welded joint of a new C–Mn steel sheet cladding fine grained ferrite in surface layer for a long distance transport pipeline

A new type of C–Mn pipeline steel plates with the ult5ra-fine grained ferrite in surface layer and the fine-grained ferrite in the central layer has been developed successfully. In order to manufacture the long distance oil pipelines using this new ultra-fine grain pipeline steel sheet, the microstructure and mechanical properties of the welded joints by the Longitudinal Submerged Arc Welding (LSAW), especially the impact toughness, need to be evaluated. Tensile tests, impact tests, are used to study the mechanical properties in this paper according the Chinese National standards. The metallographic technique and SEM are adapted to analyze the microstructure and impact fracture morphology of the LSAW joint. The research results show that the HAZ near the fusion line is a weak part of impact toughness of LSAW joint. However, the base metal is of the fine-grained and ultra-fine grained microstructure itself, and the heat treatment effects between the post-process welding seam and pre-process welding seam on the multi-layer and multi-pass submerged arc welding process, the impact toughness of the HAZ is greatly improved. The whole welded joint is better than the performance of ordinary pipeline steel, which is satisfied with the welding performance requirements of steel sheet engineering application, and can be used in long distance pipeline manufacturing projects.

Research on Four-Point Air Bending Process and Contour Detection Method for JCO Forming Process of LSAW Pipes

Aiming at the forming efficiency and roundness of the longitudinal submerged arc welded (LSAW) pipes in JCO (J-shape to C-shape to O-shape) forming process, this paper proposes a four-point air bending process. Compared with the traditional three-point air bending process, The new process can provide a more uniform bending moment, does not need to crimp the edges of steel sheet, shorten the residual straight segment length, and lengthen the forming length in single pass. The mechanical model is established to analyze the static equilibrium conditions and elastic–plastic deformation. The process is simulated by using the software package ABAQUS, to find the maximum punch spacing, and further determine the formulation principles of other process parameters. In addition, a contour detection method for the LSAW pipes in forming process is proposed based on machine vision (planar-array CCD camera produced by Gray Point Corporation, Vancouver, Canada). This method can not only quickly detect the contour of each pass, but also splice the detected contours together to obtain the overall contour with the given splicing algorithm. According to the measured contour, the bending angle, radius, and roundness can be calculated, to correct the punch reduction in the next pass and improve the forming accuracy of the pipes. Finally, an experimental system is designed to verify the proposed four-point bending JCO forming process and contour detection method. The result shows that the error between the contour detection method and CMM (coordinate measuring machine) is less than 0.5% for the overall contour, the two experimental pipes require 13 and 15 passes respectively, the roundness of pipes are less than 1.1%, which is much better than that of traditional three-point bending JCO forming process.

Fracture Control of the 2nd West to East Gas Pipeline in China

The 2nd West to East Gas Pipeline ( WEGP) is the first major pipeline project in China importing abroad natural gas and also the longest and largest gas transmission pipeline in the world with gas supply of Middle Asian natural gas and adjusting gas supply of domestic gas from Tarim Basin and Ordos Basin. Its total length is 9 000 kilometers, in which the total length of artery from Khorgos to Guangzhou is 4 900 kilometers. Its design throughput is 30 billion cubic meters per year. Designed maximum operation pressure is 12 MPa, largest diameter of pipe is 1219mm and highest steel grade is X80. To ensure the long-term safety and reliability in operation, fracture control program has been proposed through systematic research, including crack initiation control, brittle fracture control and ductile long-running fracture control. The requirement of arrest toughness of the 2nd WEGP had been studied on the basis of pipe full-scale burst test data base in the world, Battelle Two Curve (BTC) method and GasDecom software. Full-scale burst tests of X80 high-pressure gas pipeline had been successfully performed based on previous research results. The fracture control program was set up based on different fracture criteria and the principle of both safety and economy. The crack arrest ability of X80 spiral submerged arc welded (SSAW) steel pipe was firstly verified and a new correct factor of arrest toughness prediction was obtained. Results presented that the crack arrest ability of SSAW pipe is better than longitudinal submerged arc welded (LSAW) pipe. It lays a solid foundation for the safe operation of the X80 pipeline after construction and completion.

Induction Preheating for the Submerged Arc Welded Steel Tube Production

Tenaris is a leading supplier of tubes and related services for the world’s energy industry that manufactures a complete range of seamless and welded steel tubular products. The welding facilities are located in North and South America, and perform three types of welding processes, namely Electric Resistance Welding (ERW), Spiral Submerged Arc Welding, and Longitudinal Submerged Arc Welding (LSAW). Regarding the ERW process, in recent years we studied both the welding using Comsol [1,2], and the ulterior seam heat treatment using an in-house developed FEM model [3,4]. During the LSAW process, after the plate is conformed through the UOE forming process, the butt joint of the pipe is welded in three phases, first of which aims at presenting the edges and joining them but without filling in the bevels, the second one is to fill in the seam region at the inside of the pipe and the third one to do this operation on the outside. The welds are made by melting with an electric arc the bare metal electrodes. Pressure is not applied on the pipe during welding. Depending on the final product properties sought, a preheating near the edges with a relatively narrow temperature range is required for these three welding stages. In this article we focus on the inductive preheating for the tack welding stage of a continuous production line; it involves an open tubular geometry whose edges are facing and separated approximately 10 mm. There is no need to reheat the full tube, but only a region of ±75 mm from the edges approximately. Given the geometry and the required localized preheating, usual solution would be bar type inductors as those used typically for seam annealing. Alternatively, cylindrical coils can be used instead of inductive bars. 2D and 3D numerical models of different inductor bars and cylindrical coils are used in order to assess both kinds of preheaters and to understand the advantages and disadvantages of each one.

Research of Jet Coupling Method of AUT for Weld Seam of SAWL

The actuality analysis and systematic research of jet coupling method Automated Ultrasonic Testing(AUT) for the weld seam of Longitudinal Submerged Arc Welding (SAWL) pipe have been done. It’s certain that jet coupling method AUT for the weld seam of SAWL pipe can be fully achieved by means of Partition testing. Research mainly includes the following aspects, such as probe arrangement and distribution, detection threshold setting, reference block design, artificial defect selection, testing result display and record, etc. The research results provide a reference for the method research of AUT jet coupling method for the weld seam of SAWL pipe, and also give some basis for formulating the standard of jet coupling method AUT for the weld seam of SAWL pipe.

Influence of Non-Metallic Inclusions on the Fracture-Toughness Properties on the Longitudinal Welding of an API 5L Steel Pipeline

Abstract In previous works, it was demonstrated that the average fracture-toughness values were higher in the circumferential-longitudinal direction (CL) than in the circumferential-radial direction (CR) on the longitudinal submerged arc welding (SAW) in API 5L pipeline steel. Nevertheless, such differences in fracture-toughness values were attributed to the density distribution of microstructural phases and porosity, but the effect of non-metallic inclusions on this fracture property was not considered; therefore, the present work analyzed the effect of non-metallic inclusions on the fracture-toughness values by fractographic and electron diffraction scattered analyses. The results showed the presence of titanium (Ti), calcium (Ca), and aluminum (Al) constituents in the non-metallic inclusions for the CR direction of the pipeline. These elements tended to form compounds that promoted brittle-fracture by cleavage, decreasing the toughness properties of the weld. For the CL direction analysis, the elements presented on the non-metallic inclusions were manganese (Mn), silicon (Si), and sulfur (S), which promoted the nucleation and coalescence of cavities, all of which were typical for ductile fracture. Calculations on the KIC showed that the non-metallic inclusions with elements of Ti, Ca, and Al contributed to lower KIC values on the CR direction under analysis.

Calculation tool and closed loop control for the JCO ® pipe forming process

Abstract In this paper, a new solution for the process planning and closed loop control of the JCO ® pipe forming process is presented. JCO ® pipe forming enables the production of open seam pipes out of steel plates by progressive bending (usually between 15 and 23 subsequent circumferential bending steps). Typical JCO ® pipes can be found in a diameter range from 457 to 1422 mm (18 to 56 inch) with wall thicknesses of up to 45 mm. These longitudinal-submerged arc-welded (LSAW) pipes are usually 12.2 or 18.3 m long. One crucial process parameter is the stroke for each single bending step depending on the required open seam pipe shape: With regard to subsequent process steps a perfect round shape is not always beneficial. Thus, the calculation software ShapeBase has been implemented into practice recently, taking into account the most important steps in the pipe production process chain. This fast software tool allows the process planning and optimisation of JCO ® plate forming to pipe. But due to variations in raw material (e.g. chemistry, yield point, wall thickness) even reliable theoretical calculations of process parameters can only be taken as initial machine values. To decrease further optimisation effort and increase the quality not only of the whole pipe lot but also of each single pipe, the above mentioned tool has been extended by an in-line measuring unit ShapeView and a real-time process control module ShapeControl.

Numerical Analysis of Microstructure and Residual Stress in the Weld Zone of Multiwire Submerged Arc Welding

As oil and gas pipelines develop toward large throughput and high pressure, more and more attention has been paid to welding quality of oil pipelines. Submerged arc welding is widely applied in manufacturing of large-diameter welded pipes, and the welding quality has an impact on pipeline safety. With a multiwire submerged arc welding test platform and real-time temperature measurement system, temperature measurement has been done for multiwire submerged arc welding process with and without flux coverage, respectively. As a result, thermal cycling curves in both cases have been obtained, and convection and radiation coefficients of flux-covered X80 pipeline steel in air-cooled environment have been corrected. By using sysweld software, a finite-element computational model was set up for microstructure and residual stress in the weld zone of multiwire longitudinal submerged arc welding. Comparative experiment has been done to obtain welding temperature field with relatively high accuracy. Calculation and analysis of residual stress versus preheat residual stress decreased with increasing preheat temperature up to 100 °C, meanwhile content of bainite in microstructure fell, facilitating reduction in residual stress to some extent. This study provides quantitative reference for further optimization of welding parameters and improvement in weld mechanical properties.

A comparison between fracture toughness at different locations of longitudinal submerged arc welded and spiral submerged arc welded joints of API X80 pipeline steels

In this paper, extensively experimental testing of fracture toughness for two different welded joints of API X80 pipeline steels after service were carried out. The microstructures and CTOD resistance curves of longitudinal submerged arc welded (LSAW) and spiral submerged arc welded (SSAW) joints were investigated at different locations of the base metal (BM), weld metal (WM) and heat affected zone (HAZ). The critical fracture toughness values were compared with each other. The optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were used to analyze the fracture mechanism and precipitates composition. This investigation will provide an important reference to engineering practice and evaluation of pipeline structures.

Pure Bending Equivalent Principle for Over-bend Straightening and Its Experimental Verification

Straightening is the key technology to deal with the curving pipe in the manufacturing processes of large diameter longitudinal submerged arc welded(LSAW) pipes production.The research of forming rules is the theoretical foundation for reasonably determining the process parameter.According to the small deformation feature in the straightening process,the concept of equivalent initial strain is firstly proposed,and based on this concept the relationship is built between initial curvature and strain distribution of the curved beam.Under the basic hypothesis of pure bending engineering theory for elastic-plastic small deformation,the geometrical equation and the springback equation for planar curved beam is deduced.Further the equivalent relation is demonstrated between over-bend straighting of curved beam and pure bending of straight beam,and then the equivalent principle for over-bend straighting is put forward,which is equivalent relation between the bending moment in straight beam bending and curved beam being straightened.The validity of the equivalent principle is verified by three point bending,four point bending and their reverse bending.All these works establish the theoretical and experimental base for over-bend straighting technology and its control strategy.

Springback Analysis of Expanding and Setting Round for Large Diameter Pipe

Expanding and setting round is one of the most important processes for large diameter longitudinal submerged arc welded(LSAW) pipes production.The research of springback rules for pipe's expanding and setting round is the theoretical foundation for reasonably determining the process parameters.Expanding and setting round process is divided into three steps,namely,setting round,expanding and unloading in sequence.Based on the process characteristics,the step of setting round is considered as elastic pure bending.The step of expanding is divided into three conditions due to the strain of pipe by elastic critical expanding rate and plastic critical expanding rate,which are pure elastic deformation,partial plastic deformation and pure plastic deformation.The curvature radius of any point on cross-section's center line is given by geometric constraint equations and springback equation.Excellent agreement is found between theoretical and experimental results,which are obtained by physical simulation experiments and large diameter LSAW pipes.The results indicate the process principles of pipe's expanding and setting round,as well as the effect law of main influencing factors on the roundness after springback,and which has important practical application value.

Crack Analysis of Induction Heating Bent Pipe

There were 20 of 103 length of pipe found cracks on the extrados surface of the bent pipe made of Φ406.4×10mm L360 Longitudinal Submerged Arc Welding (LSAW) pipe, the cracks were mostly distributed in the extrados surface and the arc initial point of the bent pipe, the cracks were spindle-shaped and narrow at both ends with the longitudinal direction vertical to the axis of bent pipe. The mechanism and the causes of the cracks were studied by macro inspection, mechanical property test, microscope, scanning electron microscopy and energy spectrum analysis, which shown that the cracks were result from the contamination of copper or its alloy during or before the bent pipe production. The contaminated material like copper infiltrated and diffused into the base metal at high temperature, and could hardly stead to and transfer the normal stress from the base metal where the inertial crack was shaped. Meanwhile, the new crack was formed at the tip of inertial crack after the new infiltration and diffusion under the condition of both high temperature and tensile stress, so that the crack progressed and extended in this way.

Investigation on the Key Technologies of Mechanical Expanding of Large Diameter LSAW Pipe

Long distance transmission pipeline is one of promising transportation methods developed in recent years. It is safe, economical, convenient and prompt. It is mainly used in transmitting gas, liquid, and other dispersed material. Oil and natural gas is especially suitable to be transmitted by high pressure large diameter longitudinal submerged arc welded (LSAW) pipelines. Mechanical expanding is one of the most important processes in the production of large diameter LSAW steel pipe for long distance transmission pipeline. Firstly, the LSAW steel pipe mechanical expanding is modeled. Two FEM models are established to simulate the mechanical expanding process at the cross section and longitudinal section of the LSAW steel pipe respectively. Secondly, the deformation characteristics of the LSAW steel pipe are simulated while mechanical expanding processes. Finally, main mechanical expanding process parameters and their influence on the quality of finished LSAW pipe are analyzed in detail according to the FEM simulation. The results presented by the analyses are very consistent with the experiment, and can be used to direct the production of LSAW steel pipe.

Influence of Softened Heat-affected Zone on Stress Oriented Hydrogen Induced Cracking of a High Strength Line Pipe Steel.

The susceptibility to hydrogen induced cracking under applied stress was examined for a large diameter high strength sour service line pipe steel produced by employing the thermo-mechanical control process, i.e. controlled rolling followed by accelerated cooling. The low carbon content aimed at high toughness and weldability resulted in softening in the grain-refined and inter-critical heat-affected zone by thermal cycles of longitudinal sub-merged arc welding. The cracking susceptibility of weldment was transversely evaluated by TM0177-90 method A and compared with the parent metal.The parent metal indicated high resistance to cracking. Nonethelss, the weldment indicated the decrease in threshold stress, since the weldment ruptured preferably along the softened heat-affected zone. The cracking morphology in the softened heat-affected zone was recognized as stress oriented hydrogen induced cracking. Also performed was a large scale test to reveal the internal incipient cracks in the softened heat-affected zone. The observation confirmed that the initiation site was a small cluster of non-metallic inclusions which had probably no adverse effect on the resistance of the parent metal. He stress analysis of the weldment proved that the tension through thickness was generated at mid-thickness under the deformation constraint from surrounding harder parts. The enhanced tri-axiality of stress in company with the through thickness tension facilitates the onset of cracking caused by the hydrogen pressure mechanism. The crack morphology was consistently associated with the stress distribution.