Welded Steel Pipe Research Articles

Atypical Cases of Welded Structure Failures

First case describes hot temperature corrosion of 1.4841 heat resisting steel, which was caused by formation of the low melting nickel sulphide (LME effect).In the second case centrifugally cast tubes of Ø52.6 x 5.8 mm size made of 25/35 CrNi steel, which are exposed to high temperature and to severe reducing environment (carbon activity ac >> 1), are concerned. In such condition a graphitization may start, that results in the disintegration of its structure, which is called ,,metal dusting”.The third case is dealing with an attack of the 1.4301 steel pipe welds by microbiologically influenced corrosion. After short service time several leakages of water were revealed. It was proved, that failure was caused by microbiologically influenced corrosion of sulphate-reducing bacteria (SRB) and not by an improper welding technology.

Numerical analysis on dynamic stress and vibration for tubular joints of welded steel pipes under axial loads

Reported researches rarely focus on dynamic stress concentration factors (SCF) of tubular joints between the chord and brace, where the chord is a square pipe, and the brace is a circular pipe. Tubular joints between a square pipe and circular pipe are widely applied in spatial structures as a support structure. Therefore, tubular joints of welded steel pipes under axial loads were studied numerically for determination of dynamic stress concentration factors (SCF). Finite element models were setup for a total of 165 tubular joints with various configurations, obtaining dynamic stress distributions of each model along the joint. Dynamic stress concentration factors on the brace and the chord were extracted respectively. Relations between sizes of dynamic stress concentration factors between the joint and structural parameters were discussed. The computational model was finally validated by the experimental test. The experimental curve was basically consistent with the finite element at the elastic stage of loading, indicating that the computational model at the elastic stage was very accurate. The paper mainly studied dynamic stress distribution of the tubular joint of welded steel pipes under an excitation load at the elastic stage, so the finite element model could be used to replace experimental test. SCF was 180° symmetric under different parameters. This angle was located at the crown point of tubular joints, while the welded steel pipe structure was a symmetric structure relative to the longitudinal plane. In addition, the chord and brace had SCF peaks at the angles of 90° and 270° because the two points were located at the saddle point of the tubular joints. Under angles of 0° and 180°, the SCF had obvious valley values because the two points were located at crown points of tubular joints. Finally, the vibration performance of the tubular joint was also analyzed. Vibration displacement could be reduced obviously through reinforcement of tubular joints with the collar plates. Axial pre-tensile forces would increase vibration displacement on top and bottom positions of the chord pipe. This paper can provide an important reference for the improvement of the dynamic stress concentration of joints of welded steel pipes.

Effect of Cooling Lubricants on Welded Steel Pipe Quality

The main properties of domestic (Karbon-2) and three overseas (HAKUFORM 50-65-2, Multan 7040, ToolWay ST) cooling lubricants (coolant) are studied, making it possible to evaluate quantitatively their efficiency in welded pipe manufacture. The effect of different coolant grades on depth of score marks and surface roughness of welded steel pipes at the Filit Moscow Pipe Plant is studied. An integral method is proposed for evaluating coolant quality under plant conditions.

Experimental validation of a model for seismic simulation and interaction analysis of buried pipe networks

A finite-element model is established to evaluate the seismic responses of buried pipe networks. In the model, pipes are simulated as beams on elastic foundation, the joints of the segmented pipes are modeled by axial and rotational springs, and the pipe–soil interactions are simulated by springs. The seismic wave acts on one end of the soil springs to induce the seismic responses of the pipe networks. The test results of a buried pipe network subjected to an artificial earthquake is adopted as benchmark to validate the model. The tested pipe network has a size of 24m×24m and consists of ductile cast iron and welded steel pipes. The artificial earthquake is produced by 30kg of TNT explosives. Two important responses are compared, i.e., the joint deformations of the ductile cast iron pipes and the strains of the welded steel pipes. Results indicate that the model can evaluate the seismic responses of the buried pipe networks well. The pipe interactions are analyzed using the model by comparing the seismic responses of the single pipe and its counterpart in the pipe network.

Fatigue life analysis of steel tube member with T-shaped welded joint by FEM

T-shaped welded steel pipe members are one of the pipe members which are widely used for civil and architecture structures. T-shaped tube member is connected by welding. These pipe members are known that fatigue crack in welding joint is frequently occurred due to fatigue loading. In this paper, the 3D FEM fatigue analysis method was proposed. In order to simulate a fatigue phenomenon that can predict fatigue life, 3D FEM analysis method considered the following theories: cyclic hysteresis constitutive equation, isotropic hardening rule, kinematic hardening rule, ratcheting effect, strain range effect, mean stress relaxation effect and cyclic elastic-plastic-damage constitutive equation etc. In order to simulate welded pipe member, threedimensional non-steady heat conduction analysis and thermal elastic-plastic analysis were also carried out. The overall fatigue behavior of steel pipe member was clarified under high cycle loading. From the result of this study, it was analyzed the fatigue life of the T-type pipe welding member under high cycle loading by FEM. And, it was clarified that the proposed 3D Fatigue FEM analysis method is useful as a numerical tool for calculating the remaining fatigue life accompanied with crack.

A Gaussian surrogate model for residual stresses induced by orbital multi-pass TIG welding

A surrogate model is developed for the mechanical analysis of welded steel pipes. The objective is to build a simple and fast model for calculating residual stresses as a function of the dimensions and the welding parameters. This model is based on numerical experiments which are made of multi-physical finite element simulations. First, the analysis of variance is used to attest the great influence of the input parameters. Then, the polynomial approach and the Gaussian process are compared for calculating the residual hoop stresses. Experience shows that the Gaussian process can be very successful for non-linear multi-physical welding applications.

Numerical Investigation of Heat Transfer Behaviour During TIG Welding of Stainless Steel Pipes for Various Welding Heat Input Conditions

In the present work, tungsten inert gas (TIG) welding was carried out on stainless steel pipe joints and the heat transfer behaviour for various welding heat input was analysed. In this work austenitic stainless steel of grade 304L was used and the experiment was carried out on bead on plate and weld profile was analysed. The bead profile was obtained from the experiment and microstructure was characterized. The bead profile dimensions from the experiment were used in the calibration of heat source model during finite element heat transfer analysis. Based on the calibrated heat source model, TIG welding of stainless steel pipes was analysed. Numerical simulation was considered as conduction heat transfer analysis and weld pool convection was neglected in the model. The non-linear transient heat transfer analysis was carried out on pipes and thermal cycles at various locations were analysed.

電縫溶接部の低温靱性に優れる極寒冷地用電縫鋼管の開発

電縫溶接部の低温靱性に優れる極寒冷地用電縫鋼管の開発

Investigation properties of high frequency welded steel pipes for natural gas transportation made of X60 steel

Basic idea in this research work is to check prescribed quality requirement of steel pipes welded by implementation of high frequency contact welding process (HFCW). These pipes are intended for natural gas transportation. As a raw material for pipes production was used X60M steel coils with thickness of 6.5 mm. Outer diameter of pipe is Φ508 and length 12000 mm. Preliminary welding procedure is given based on personal experience and technical knowledge. Special attention was paid to the most important welding parameters: current frequency, voltage and welding speed. After performing of welding additional heat treatment (normalization) of the welded pipes (joints) was performed at the temperature of 900ºC. In order to confirm proposed welding technology, complex investigations were performed. As first chemical analysis of base metal was performed. Nondestructive testing encompass visual inspection, and ultrasound testing of pipes, while destructive testing consists of tensile testing, bend testing and hardness measurement. Besides, for analysis of micro and macro structure of welded joint metallographic investigation was made. Hydrostatic test and flattening test as technological investigations were performed too. Carried investigations confirmed that produced pipes with predicted welding parameters completely fulfilled standard requirement, and serial production of ordered pipes for natural gas transportation was realized.

Failure analysis of a welded steel pipe at Kullar fault crossing

Abstract The seismic response of a 2200-mm-diameter welded steel pipe at strike slip Kullar fault crossing in Izmit, Kocaeli during 1999 Kocaeli earthquake is investigated. The pipe was crossing the fault-line with an angle of 55° and suffered leaks due to 3.0 m of right lateral movement of fault, which imposed compressive axial strain in the pipe. The backfill material of the trench was native soil which was non-homogenous (soft and stiff clay) with respect to fault line-soft material on the North side, stiff material on the South side. Field observations revealed two major wrinkles with finger width cracks and a minor wrinkle on the soft soil side of the fault. Large plastic strains and local folding were observed at wrinkles due to compressive strains. The case is known as one of the best documented fault crossing examples. The failure behavior of the Thames water pipe during 1999 Kocaeli earthquake is simulated by utilizing a 3D nonlinear continuum FE model. The numerical model considers contact surface at soil pipe interface and performs large deformation analyses of the pipe. The locations of wrinkles as well as axial displacements/rotations demands due to fault rupture are predicted. It is observed that once wrinkle initiates, strain in the pipe away from the wrinkle reduces after initial local buckling and additional shortening of the pipeline tends to accumulate at the wrinkle causing large plastic strains and rotation demands associated with fault rupture, an observation consistent with field observations and 2005 ALA guidelines.

Artificial earthquake test of gas supply networks

In this paper, seismic behavior of gas supply networks is investigated by constructing a 24m×24m buried network and conducting an artificial earthquake test by detonating TNT explosives. The pipe network consists of typical welded steel pipes used in gas supply networks. Ground motion is produced by detonating 30kg of TNT explosives buried 5m below ground surface and 15m away from the network. The test preparations are presented, including site selection, network layout, ground motion generation, and arrangements of different sensors. The measured ground acceleration, strain, and acceleration of welded steel pipes, and pipe–soil relative slippage are discussed. The deformation patterns of welded steel pipes are also analyzed and explained, including axial and bending deformations, systematic network characteristics, deformation relationship between ground and pipes, and dynamic response of buried pipes.

Fatigue crack propagation analysis for multiple weld toe cracks in cut-out fatigue test specimens from a girth welded pipe

Multiple fatigue cracks are prevalent in welded structures. Current fatigue assessment code procedures employ various simplifications in the treatment of multiple cracks that result in over-conservative life predictions. In this work, crack coalescence and fatigue crack closure are incorporated into established models of crack propagation analysis. The model is verified by fatigue tests of cut-out welded steel pipes (butt weld) subject to four-point bending fatigue. A large number of starting weld toe cracks are determined from the experiments, with 12–22 cracks used in the fatigue life prediction of the fatigue tested pipes. The fatigue crack growth approach proposed is taken into account to predict remaining life more accurately compared to the threshold stress intensity factor approach used in the BS 7910 standard.

Numerical Study on Weld Joints of Steel Longitudinal Welded Piles during Pile Driving Process

Longitudinally welded steel pipe piles are not as commonly used as seamless steel pipe piles in offshore platform. Although longitudinally welded steel pipe piles are considerably cheaper than seamless steel pipe piles, yet many feared that longitudinally welded steel pipe piles are prone to fail because of non-uniformity in the heat affected zone (HAZ), especially when receiving impact loads during the installation process. In this paper, a finite element model is developed to study the deformation and failure of the longitudinal welded piles. Two modelling cases are performed: single and double piles, with two different failure parameters: maximum stress and maximum plastic displacement.

Effect of Groove Design and Post-Weld Heat Treatment on Microstructure and Mechanical Properties of P91 Steel Weld

The martensitic creep-resistant steel designated as ASTM A335 for plate and as P91 for pipe is primarily used for high-temperature and high-pressure applications in steam power plants due to its excellent high-temperature properties such as high creep strength, high thermal conductivity, low thermal expansion, and so on. However, in the case of welded joints of such steels, the presence of an inter-critical heat-affected zone (IC-HAZ) can cause the joint to have lower creep strength than the base metal. In the present study, the effect of post-welding heat treatment (PWHT) and weld groove designs on the overall microstructure and mechanical properties of P91 steel pipe welds produced by the gas tungsten arc welding process was studied. Various regions of welded joints were characterized in detail for hardness and metallographic and tensile properties. Sub-size tensile samples were also tested to evaluate the mechanical properties of the weld metal and heat-affected zone (HAZ) with respect to PWHT. After PWHT, a homogenous microstructure was observed in the HAZ and tensile test fracture samples revealed shifting of the fracture location from the IC-HAZ to the fine-grained heat-affected zone. Before PWHT, the conventional V-grooved welded joints exhibited higher tensile strength compared to the narrow-grooved joints. However, after PWHT, both narrow- and V-grooved joints exhibited similar strength. Fractography of the samples indicates the presence of carbide precipitates such as Cr23C6, VC, and NbC on the fracture surface.

Assessing carbon dioxide emission reduction potentials of improved manufacturing processes using multiregional input output frameworks

Evaluating innovative process technologies has become highly important within the last decades. As standard tools different Life Cycle Assessment methods have been established, which are continuously improved. While those are designed for evaluating single processes they run into difficulties when it comes to assessing environmental impacts of process innovations at macroeconomic level. In this paper we develop a multi-step evaluation framework building on multi regional input–output data that allows estimating macroeconomic impacts of new process technologies, considering the network characteristics of the global economy.Our procedure is as follows: i) we measure differences in material usage of process alternatives, ii) we identify where the standard processes are located within economic networks and virtually replace those by innovative process technologies, iii) we account for changes within economic systems and evaluate impacts on emissions.Within this paper we exemplarily apply the methodology to two recently developed innovative technologies: longitudinal large diameter steel pipe welding and turning of high-temperature resistant materials. While we find the macroeconomic impacts of very specific process innovations to be small, its conclusions can significantly differ from traditional process based approaches. Furthermore, information gained from the methodology provides relevant additional insights for decision makers extending the picture gained from traditional process life cycle assessment.

Investigation of surface residual stress profile on martensitic stainless steel weldment with X-ray diffraction

The development of residual stresses during fabrication is inevitable and often neglected with dire consequences during the service life of the fabricated components. In this work, the surface residual stress profile following the martensitic stainless steel (MSS) pipe welding was investigated with X-ray diffraction technique. The results revealed the presence of residual stresses equilibrated across the weldment zones. Tensile residual stress observed in weld metal was balanced by compressive residual stresses in the parent material on the opposing sides of weld metal.

3D Simulation of Residual Stress Developed During TIG Welding of Stainless Steel Pipes

This paper deals with the effects of weld parameters on residual stress developed during TIG welding of pipes. Circumferential TIG welding is widely used in industries such as piping, oil refineries, power stations, etc. The 3D numerical simulation ANSYS code is used to predict the residual stress distribution developed during circumferential TIG welding. Due to non-uniform distribution of plastic and thermal strains in and around the weld pool, large amounts of residual stresses and deformations are present in all welded structures. The simulated results are validated using experimental results available in the literature. The effects of welding current and pipe thickness on residual stress and temperature fields at different locations were assessed.

Study on effectiveness of education and training for ultrasonic examiner in austenitic stainless steel piping welds

Study on effectiveness of education and training for ultrasonic examiner in austenitic stainless steel piping welds

Review on Effect of Repetitive Rework on Dissimilar Austenistic Stainless Steel Pipes by Using GMAW Orbital Welding

Dissimilar metal welding is widely applied to meet the rquirement of transition in mechanical properties and/or difference in working conditions. For instance, even though AISI 304 and AISI 316L are both belong to austenitic stainless steels, but they are applied in different working environment. AISI 304 is used at high temperature applications, whereas AISI 316L is used at low temperature. Repair welding is able to return a part back to its normal service life if weld failure happened due to service deterioration or defects during fabrication stage. However, repetitive heat input due to repair welding will cause changes in welded structure and properties. In this article, the effect of repetitive repair welding of dissimilar austenitic stainless steel pipes to the microhardness, tensile strength, microstructure and quality of the weldment has been reviewed.

The Effect of Ultrasonic Peening on Service Life of the Butt-Welded High-Temperature Steel Pipes

Residual stresses introduced by manufacturing processes such as casting, forming, machining, and welding have harmful effects on the mechanical behavior of the structures. In addition to the residual stresses, weld toe stress concentration can play a determining effect. There are several methods to improve the mechanical properties such as fatigue behavior of the welded structures. In this paper, the effects of ultrasonic peening on the fatigue life of the high-temperature seamless steel pipes, used in the petrochemical environment, have been investigated. These welded pipes are fatigued due to thermal and mechanical loads caused by the cycle of cooling, heating, and internal pressure fluctuations. Residual stress measurements, weld geometry estimation, electrochemical evaluations, and metallography investigations were done as supplementary examinations. Results showed that application of ultrasonic impact treatment has led to increased fatigue life, fatigue strength, and corrosion resistance of A106-B welded steel pipes in petrochemical corrosive environment.