Groove Weld Research Articles

Ultra-narrow gap welding of thick section of austenitic stainless steel to HSLA steel

A substantially narrow GMAW torch nozzle head has been designed that enables narrowing down of weld groove up to a limit of just accommodating the nozzle in it where the groove wall of thick section virtually acts as a side wall of the nozzle head to produce a narrowest possible butt welding. A model of shielding gas flow dynamics and its flow rate in case of employing newly developed GMAW nozzle head has been studied at different projection angle of torch nozzle inside the narrow groove of butt joint by using ANSYS-CFX(14.5) software. The utility aspect of such a narrow nozzle head from the view point of smooth flow of shielding gas inside a close fitted ultra-narrow weld groove has also been studied. The outcome of the analytical studies has been used to produce a defect free ultra-narrow multi-pass weld by employing P-GMAW process with vertically placed electrode depositing single bead per layer in weld groove.

A framework for fracture assessments of dissimilar girth welds in offshore pipelines under bending

This work describes the development of a framework for structural integrity assessments of dissimilar girth welds in clad and lined pipes subjected to high levels of bending load for a wide range of pipe geometries, crack configurations, weld grooves and weld strength mismatch levels based upon an EPRI estimation scheme for crack driving forces coupled with a weld groove simplification procedure and the equivalent stress–strain relationship. Systematic validation of the method is provided and the crack driving force estimation accuracy is demonstrated through comparisons with numerical tools and 3-D finite element analyses for reeled pipelines.

Experimental study on steel built‐up column moment connections with top and bottom trapezoidal side plates

SummaryBuilt‐up and box columns are used extensively in steel structures. A kind of built‐up column is composed of two I rolled shapes separated by calculated interval and welded between two cover plates. The uncertainties due to these columns are the flexibility of the column cover plates under the transferred beam flange plate forces and the brittle behavior of the groove weld between the beam flange plate and the column cover plate. The top and bottom trapezoidal side plates are proposed to improve the behavior of these column moment connections. Using this approach, the total beam flange forces transfer to the lateral sides of the column, parallel to the beam web, by means of top and bottom side plates. An experimental test is developed to study the behavior of the proposed connection under cyclic loading. The results indicate that the proposed connection has sufficient strength and ductility to apply in special moment frames. Also, the rehabilitated connection eliminates the vulnerabilities of deformation of the column cover plate and brittle fracture of groove welds in conventional connections. Copyright © 2016 John Wiley & Sons, Ltd.

Analysis of process parameter effects during narrow-gap triple-wire gas indirect arc welding

Narrow-gap triple-wire gas indirect arc (TW-GIA) welding is a novel process. Previous studies have reported the process and explained how the wire arrangement affects the arc behavior and the metal transfer which correspondingly affect the sidewall fusion. In this paper, effects of process parameters on sidewall fusion, weld bead formation, microstructure, and hardness are studied, to reveal more characteristics of the narrow-gap TW-GIA. Results show that welding currents affect the sidewall penetration more significantly than groove gap and welding speed. In addition, sidewall penetration increases with larger welding currents. The heat affected zone (HAZ) width decreases with lower welding current, wider groove gap, or higher welding speed. With all the parameters, weld beads produced by narrow-gap TW-GIA present convex surfaces, which can lead to serious incomplete fusion at the weld root for the next weld layer. To solve this problem, addition of a gas tungsten arc (GTA) behind the TW-GIA is proposed. An additional benefit is that the arc pressure and extra heat input of the GTA obtain weld beads with concave surfaces.

Comparison the capacity of box steel columns, fabricated with groove and fillet welds

Currently, box columns are fabricated by welding plates using fillet or groove welds. According to probable seismic failure mechanism of these columns, their nonlinear behavior in terms of ductility and strength is necessary. In this research, a variety of columns with different welding patterns including groove and fillet welding with various overlap values and weld legs are numerically modeled and their nonlinear behavior is studied in finite element domain by using ABAQUS software. Suitable welding pattern is proposed by evaluation the energy absorption as well as stress distribution and concentration in box section. Results indicate that the section fabricated through groove welding has the best nonlinear performance and in the next priority, the sections with overlap size and weld leg equal to 20 and 80, or 50 and 50 percent of plate thickness, respectively, lead to suitable performance.

Plasma beam radius compensation-integrated torch path planning for CNC pipe hole cutting with welding groove

In order to achieve accurate pipe hole cutting applied to joint preparations for joining pipe with set-in branch, this paper presents a novel method of torch path planning which integrates the plasma beam radius compensation. The geometrical models of intersecting pipes and sing-V welding groove cover the most complex intersecting mode and provide adjustable groove angle configuration. They construct the foundation of the path planning method and generate the theoretical cutting line. Based on the principle of three-dimensional tool radius compensation, a plasma beam radius compensation interface is designed for dynamic compensation value, which can cope with variable plasma kerf width caused by large fluctuant bevel angle. The correlative algorithm modules are connected by homogeneous matrices, with which the torch’s position and orientation are described as well. The experiment validates the feasibility of the torch path planning method and demonstrates the corresponding accuracy improvement.

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.

Effects of panel zone yielding on seismic behavior of welded-flange-plate connections

In this study, effects of panel zone yielding on the seismic performance of welded-flange-plate (WFP) connections are investigated. In this work, four full-scale beam-to-column connections were used to run the experiments under cyclic loading. The obtained results can potentially lead to a better understanding of the influence of the panel zone inelastic shear deformation on the cyclic behavior of WFP connections for external joints in steel moment resisting frames (SMRFs). The main parameter in the testing program was the panel zone strength having a wide variation to gain the different levels of panel zone yielding. Results showed that all specimens had a high connection rotation capacity to satisfy the requirements of special moment frame connections. However, specimens with different panel zone strengths could provide the different amount of energy dissipation. Severe beam buckling was followed by tearing along the k-line region of the beam in the plastic hinge location, as well as tearing of the beam at the nose of the bottom flange plates which were both observed as a predominant failure mode in the specimens with a stronger panel zone. However, specimens with weak panel zone could develop a significant plastic rotation without causing any major problem to the beam-to-column connection groove welds. Based on mentioned observations and considering the effect of panel zone yielding because of different panel zone strengths on the hysteresis behavior of specimens, failure modes, plastic rotation capacity, and energy dissipation, some modifications were proposed for design requirements of the panel zone strength.

Effect of Heat Treatment on Microstructure and Hot Impact Toughness of Various Zones of P91 Welded Pipes

The new generation super critical thermal power plants are required to operate at enhanced thermal efficiency of over 50% to reduce the fuel consumption and environmental pollution. Creep strength-enhanced ferritic steels, commonly known as Cr-Mo alloys such as P91 (X10CrMoVNb 9-1) are such material of choice for the next generation power plants. The operating requirement of these next generation power plants is that steam temperature of around 650 °C is maintained. For such high-temperature application, creep strength of material is the primary consideration together with adequate weld heat-affected zone (HAZ) toughness. Present work deals with the effect of high service temperature on impact toughness of P91 (X10CrMoVNb 9-1) base material, weld fusion zone, and HAZ. The impact toughness of HAZ for conventional weld groove design and narrow weld groove design has been evaluated experimentally in as-welded and at different post-weld heat treatment conditions. Fractography of the impact toughness specimens of base metal, weld fusion zone, and HAZ was carried out using scanning electron microscope. The effects of heat treatment schemes on the percentage of element present at the fracture surface were also studied.

Prediction of brittle fracture from defects at groove face of complete joint penetration welded joints

This paper concerns the applicability of the Weibull stress approach, instead of toughness scaling model approach, for prediction of brittle fracture initiated at defects existing at the weld terminations. Beam-to-diaphragm joint models, which were designed to represent a connection of an I-section beam to RHS column member with through diaphragms, were tested under cyclic loads. Complete joint penetration groove welds were used for the connection between the beam flange and the diaphragm. Specimens had those discontinuities at the roots of welds to the beam bottom flanges, which were created by inserting copper plates into the grooves before welding or by using wire electrical discharge machining. The prediction of brittle fracture with a variety of defect sizes by using the FE analysis was conducted. The fracture moment predicted by using the critical Weibull stress accorded with the test results of specimen with defects such as the blowhole.

Optimal Pass Planning for Robotic Welding of Large-dimension Joints with Deep Grooves

Large-dimension welding joints are widely used in shipyards and oilfields. These joints need multi-pass welding processes and tens of hours to complete. Although the development of robotic welding techniques shortens the welding time, it is important to have a detailed plan of the entire process before welding starts. During detailed planning, pass planning is crucial for the trajectory generation of the robot, since pass planning provides the welding sequence in a deep groove and the welding parameters of every pass. A knowledge database is used in this research to obtain the relationship between the bead geometry and welding parameters. For the pass planning of deep groove welding, this paper proposes an optimization method with the objective to maximize the section area of the weld bead, so that the number of passes can be minimized. The welding passes of a deep groove are planned using the proposed method. The planning results show that the optimization method is able to provide feasible passes and welding parameters for every pass.

The Mathematical Model Research on MIG Groove Welding Process

Through analysis the MIG groove welding process and the welding experimental result, a complete two-dimensional mathematical model of weld section molten pool characteristics was established. Use Gaussian heat source distribution to describe the weld heat source, introduced the welding speed to establish transient heat source model on the cross section. By introducing scalar of liquid fraction, mushy region dynamic character which was described using “Darcy” model proposed for porous media, and phase change which was taken into account using source-based method, establish a unified liquid and solid control equation, CFD model was established to simulate transient heat and mass transfer phenomena in welding process. The effect of surface tension was considered in the molten pool free surface stress model. The reliability of the model was verified by experiments. The effect of groove angle, groove depth and the welding speed on the molten pool were discussed in this paper.

ЛАЗЕРНАЯ И ГИБРИДНАЯ ЛАЗЕРНО-ДУГОВАЯ СВАРКА ХЛАДОСТОЙКИХ СТАЛЕЙ С СОДЕРЖАНИЕМ НИКЕЛЯ ДО 9%

Heat treated 9%Ni steel is considered the most suitable and economic material for construction of large-size liquefied natural gas (LNG) storage tanks which operate at cryogenic temperatures (-196°C). Strength above 700 MPa as well as a minimum impact value of 60 J are required to ensure reliable operation of the LNG tanks at operating temperature. Conventional arc welding processes, including shielded metal arc welding, gas metal arc welding, gas tungsten arc welding and submerged arc welding, are currently used in construction of LNG tanks. Ni based filler wire is the preferred filler metal of choice in LNG tank construction. The main problem with this choice is the lower mechanical properties, particularly tensile strength of the weld metal. To compensate, the wall thickness needs to be excessively thick to ensure the strength of the welded structures. Ni based filler material is expensive and a large quantity is needed to fill the multi-pass weld grooves. These factors significantly add to the cost in the fabrication of LNG storage tanks. For these reasons, exploration of new welding technologies is a priority. A big potential can be seen in laser based welding techniques. Laser beam welding results in much smaller fusion Zone with chemical composition and mechanical properties similar to that of the base material. Laser welding is a much faster process and allows for a joint geometry which requires less filler material and fewer welding passes. The advantages of laser welding can help to overcome the Problems pointed out above. Trials of autogenous laser welding, laser cold-wire welding and hybrid laser-arc welding conducted on the 9%Ni steel are presented in this paper. Chemical composition of the weld metal as well as effects of welding parameters on the weld formation, microstructure and tensile strength is discussed. Filler wire penetration depth as well as character of its distribution in the narrow laser welds was examined using EPMA - electron probe microanalysis.

선체구조용 EH36 TMCP 후판의 FCAW 및 EGW 조합 용접부 기계적 성질에 미치는 개선조건의 영향

Characterization of microstructures and mechanical properties of 83mm thickness EH36-TM welds produced by the combined flux cored arc (FCA) and electro gas (EG) welding processes has been studied with the two different groove conditions, single-V (SV) and double-V (DV) bevels. The welding consumables used for FCA and EG welding processes were ASME/AWS A5.29 (E81T1-K2) and A5.26 (EG72T), respectively. Experimental results showed that all the mechanical properties of welds such as tensile property, CVN toughness and Vickers hardness met IACS requirements. The tensile strength of EG welded plates were reduced by approximately 4% (DV: 3.8%, SV: 4.2%) compared to the base metal. The hardness value of SV-beveled weld metal was slightly lower than that of DV-beveled one. There were no significant differences as per welding groove conditions except for the weld metal. In addition, at the fusion line, the toughness of SV condition was 20J lower and the weld metal was 40J lower than DV condition, respectively. On the basis of microstructural analysis, grain boundary ferrite (GBF) structures for SV condition were 2 times higher volume fraction than for DV condition and their packet sizes were coarsened to almost double. It was thus suggested that the GBF volume fractions and packet sizes in the weld metal of EH36-TM steel plates are the most important factors affecting the mechanical properties of the combined FCA and EG welded joint. Nevertheless, all the results of welds with both DV and SV conditions were found to be excellent.

Measured Biaxial Residual Stress Maps in a Stainless Steel Weld

This paper describes a sequence of residual stress measurements made to determine a two-dimensional map of biaxial residual stress in a stainless steel weld. A long stainless steel (316L) plate with an eight-pass groove weld (308L filler) was used. The biaxial stress measurements follow a recently developed approach, comprising a combination of contour method and slitting measurements, with a computation to determine the effects of out-of-plane stress on a thin slice. The measured longitudinal stress is highly tensile in the weld- and heat-affected zone, with a maximum around 450 MPa, and compressive stress toward the transverse edges around −250 MPa. The total transverse stress has a banded profile in the weld with highly tensile stress at the bottom of the plate (y = 0) of 400 MPa, rapidly changing to compressive stress (at y = 5 mm) of −200 MPa, then tensile stress at the weld root (y = 17 mm) and in the weld around 200 MPa, followed by compressive stress at the top of the weld at around −150 MPa. The results of the biaxial map compare well with the results of neutron diffraction measurements and output from a computational weld simulation.

Laser welding to expand the allowable gap in bore welding for ITER blanket hydraulic connection

For application to bore welding of hydraulic connection in the ITER blanket module, laser welding presents the following benefits: low weld heat input is preferred for re-welding of the irradiated material. Its contactless process can intrinsically avoid a failure mode of the tool sticking on the weld. The exact requirements for pipe alignment were assessed in comparison with the assembly tolerance. The groove geometry was modified to expand the allowable initial gap. The groove was machined to be partially thick to obviate the filler wire. First, plates with partially thick grooves were welded to elucidate the preferred groove geometry and welding conditions. With the modified groove, the plates were welded for the initial gap of 1.0mm. Then the groove geometry and welding conditions were adjusted based on results of pipe welding tests. By application of the additional 0.5-mm-thick and 2.5-mm-wide metal in the groove, pipes with an initial gap of 0.7mm were welded successfully.

Stress corrosion cracking of austenitic weld deposits in a salt spray environment

ER 308L and 309LMo were utilized as the filler metals for the groove and overlay welds of a 304L stainless steel substrate, which was prepared via a gas tungsten arc-welding process in multiple passes. U-bend and weight-loss tests were conducted by testing the welds in a salt spray containing 10 wt% NaCl at 120 °C. The dissolution of the skeletal structure in the fusion zone (FZ) caused the stress corrosion cracking (SCC) of the weld. The FZ in the cold-rolled condition showed the longest single crack length in the U-bend tests. Moreover, sensitization treatment at 650 °C for 10 h promoted the formation of numerous fine cracks, which resulted in a high SCC susceptibility. The weight loss of the deposits was consistent with the SCC susceptibility of the welds in a salt spray. The 309LMo deposit was superior to the 308L deposit in the salt spray.

Design by Qualification Testing of Reduced Beam Section Welded Connections

Steel moment frames are common systems in multi-storey buildings. Even the relatively low stiffness of the system limits the applicability, they remain popular in seismic applications due to the good dissipation capacity. Considered deemed-to-comply in seismic applications, welded beam to column connections experienced serious damages and even failures during strong seismic earthquakes. These failures included fractures of the beam flange-to-column flange groove welds, cracks in beam flanges, and cracks through the column section. To reduce the risk of brittle failure of welded connections, beam weakening near the ends became popular. To assure the desired behavior, i.e. the development of plastic deformations in the reduced beam section zones rather than at the face of the column, proper detailing and sizing is necessary. Today design provisions are limited to long beams, where the effect of shear stresses may be neglected. The application of the same rules for short beams might be non-conservative, and therefore qualification testing is necessary. The study presents the qualification testing of reduced beam sections welded connections of short beams. Both monotonic and cyclic tests were performed and numerical models were validated based on the test data.

Seismic Response of Partial-Joint-Penetration Welded Column Splices in Moment-Resisting Frames

Current standards require that welded column splice connections in special or intermediate moment resisting frames (SMRFs or IMRFs) feature complete-joint-penetration (CJP) groove welds to develop the full flexural strength of the column. CJP welds are often costly, requiring additional material, inspection and labor. Compared to beam-to-column connections, column splices have modest deformation demands. This suggests that perhaps with modern, toughness-rated weld filler materials and welding practices, PJP welded splices may offer acceptable performance under seismic loads. A study featuring five full-scale tests on PJP-welded column splices is presented. The test matrix investigates a range of parameters including column sizes as well as variations in connection details. Specimens were loaded cyclically in a three-point bend configuration subjecting the splice to demands consistent with those in severe earthquakes; a loading protocol was developed specifically for this purpose based on nonlinear time history simulations. All the full-scale specimens exhibited excellent performance. A series of finite element fracture mechanics simulations is also presented to assist with the generalization of test results. The test and simulation data are encouraging from the perspective of adoption of PJP welded splices in IMRFs and SMRFs in seismic regions. Limitations of the research are outlined, along with discussion of future work to develop the concept further.

Optimum drilled flange moment resisting connections for seismic regions

Extensive damage in welded unreinforced flange (WUF) connections in previous earthquakes has led to the idea of using reduced beam section (RBS) connections to prevent brittle failure modes in welded joints. Using a similar concept, drilled flange (DF) moment resisting connections are established by a series of holes drilling on the top and the bottom flanges of the beam to create an intentional weak area to shift nonlinear deformations. DF connections are very easy-to-construct and they can also prevent the premature local buckling modes in the reduced section of RBS connections. This study aims to improve the performance of DF connections to make them viable alternatives to RBS connections for ductile steel frames in seismic regions. A wide range of experimentally validated non-linear FE models are used to investigate the effects of different design parameters such as drilled flange hole locations, hole configurations, panel zone shear strength ratio and doubler plate thickness. The results indicate that there is an optimum location and configuration for the drilled flange holes, which can reduce by up to 40% the maximum Equivalent Plastic Strain and Rupture Index of DF connections. It is shown that using strong panel zones can also improve the seismic performance of DF connections by reducing stress concentrations at the CJP groove weld lines. The results of this study are used to develop optimum design solutions for DF connections, which should prove useful in practical applications.