Showing papers on "Butt welding published in 2008"

Three-dimensional finite element simulation of residual stresses in circumferential welds of steel pipe including pipe diameter effects

Abstract: In circumferential welding of a pipe component, it is often considered that axisymmetric model can provide a reasonable prediction of the residual stress distributions However, in general, the axisymmetric model cannot reproduce the traveling arc along circumferential welds and rapid change of residual stresses that can be observed in the overlapping region Moreover, it tends to overestimate the hoop residual stresses in circumferential welds Therefore, three-dimensional finite element (FE) model is essential for the accurate simulation of circumferential welding which can incorporate the three-dimensional effects This paper presents the three-dimensional FE simulation of circumferential butt welding of a steel pipe The thermo-mechanical model used as well as the simulation methodology is detailed, and the results are discussed In addition, parametric studies with inside radius to wall thickness ratio ranging from 100 to 1000 have been presented to investigate the effects of pipe diameter on residual stresses Axial and hoop residual stresses are plotted for the considered range of pipe diameters, and the differences are discussed

Effect of initial butt surface on tensile properties and fracture behavior of friction stir welded Al-Zn-Mg-Cu alloy

Abstract: A new experimental procedure—stir-in-plate welding was adopted to eliminate the initial butt surface of two plates to be joined and examine the effect of the initial butt surface on the formation of the zigzag line and the tensile properties of the welds. The comparison between the butt and stir-in-plate welds indicated that under as-welded condition the zigzag line did not show up in the welds, and two welds exhibited similar tensile properties and fracture characteristics. After post-weld T6-treatment, the zigzag line appeared on the butt weld as zigzag micro-crack at the root tip and discontinuously-distributed cavities of 50–200 μm throughout the weld, which were verified to be associated with the oxide particles. This resulted in the reduced tensile strength and significantly deteriorated ductility with the fracture initiating and propagating along the zigzag line. No zigzag line was discernible on the T6-treated stir-in-plate weld.

Automatic gap detection in friction stir butt welding operations

Abstract: Friction stir welding (FSW) is a new solid-state welding technology that has been used successfully in many joining applications. A common problem that arises when welding two sheets is the presence of a gap between the sheets. Gaps may be due to improper fixturing, imprecision in the processes used to manufacture the sheets, etc. When the FSW tool encounters a gap, material can possibly escape from the processing zone and the welded part's effective cross-sectional area around the gap will decrease. Both of these effects can possibly cause an unsuitable weld. This paper develops a monitoring algorithm to detect gaps in friction stir butt welding operations in real time (i.e., during the operation). Experimental studies are conducted to determine how the process parameters (e.g., tool rotation rate and tool traverse speed) and the gap width affect the welding process; particularly, the plunge force (i.e., the force acting vertically down on the part). The proposed monitoring algorithm examines the filtered plunge force in the frequency domain to determine the presence of a gap. Several experimental studies are conducted for 2024 aluminum with a variety of process parameters and the monitoring algorithm is shown to be able to reliably detect the presence of gaps in friction stir butt welding operations for tool traverse speeds below 4.233 mm/s and gap sizes above 0.3048 mm.

Microstructure and properties of friction stir butt-welded AE42 magnesium alloy

Abstract: The aim of the present work was to develop a friction stir joint and to investigate the microstructural and mechanical properties of magnesium (AE42 Mg alloy) sheets joined by friction stir welding (FSW). The two sheets, aligned perpendicular to the welding directions, have been successfully welded. Light optical microscopy was used to observe and study the weld zone characteristics. Dynamic recrystallisation was observed in the weld region as well as in the thermo-mechanical heat-affected zone (TMAZ). There was a clear decrease in the precipitate size from the base material through the TMAZ and into the weld zone. The precipitates observed were β-Mg17Al12, Al11Ce3 and Al2Ce. The welds were free of porosities. XRD, SEM and TEM characterization performed on the weld region showed the presence of intermetallic phases. Vickers micro-hardness testing was done along the thickness (transverse direction) of the plate in the weld region to study and understand the variation of hardness with thickness. A good correlation between the precipitate size and micro-hardness was observed.

Residual strains and microstructure development in single and sequential double sided friction stir welds in RQT-701 steel

Abstract: Single and double sided partial penetration friction stir butt welds, in a rolled, quenched and tempered steel (RQT-701), were produced at The Welding Institute (TWI) under controlled process conditions. The residual strain distributions in the longitudinal and transverse directions have been measured using energy dispersive synchrotron X-ray diffraction. The measured strains were indicative of longitudinal tensile residual stresses at levels greater than the 0.2% yield stress of the parent metal in both the single and double pass welds. In both cases, the maximum tensile strain was found in the parent metal at the boundary of the heat affected zone (HAZ). Microstructural analysis of the welds was carried out using optical microscopy and hardness variations were also mapped across the weld-plate cross-section. The maximum hardness was observed in the mixed bainite/martensite structure of the weld nugget on the advancing side of the stir zone. The minimum hardness was observed in the HAZ.

High‐Strength Steels in Welded State for Light‐Weight Constructions under High and Variable Stress Peaks

Abstract: In design codes (Eurocode, British Standard and others) for the dimensioning of welded joints, no distinction is made between low-, mediumand high-strength steels. Because of a lack of general knowledge about the benefits of high-strength steels and also because of missing information in design codes, in many cases design engineers still use lowor medium-strength steels (Rp0.2 < 400 MPa) and compensate for high loads under constant or variable amplitude loading or overloads by increasing dimensions. Given this situation, it was deemed necessary to establish criteria for the design of light-weight welded constructions under high and variable stress peaks using new classes of high-strength steels, such as S355N (normalized), S355M (thermomechanically treated), S690Q (water quenched) and S960Q (water quenched), and to perform more reliable evaluations of the fatigue performance of high-strength steel structures subjected to complex loading with regard to light-weight design and economics. For the comparison of the fatigue strengths of the investigated steels the notch factors present were taken into account. Additionally, the real damage sums were determined in order to give recommendations for the fatigue life estimation, i.e. Dal = 0.5. Under constant amplitude loading, no significant difference in the bearable local stress amplitudes for the butt welds can be detected for the four investigated steels. Under variable amplitude loading, the butt welded (lower notch factor) high strength steel S960Q has advantages in the case of the normal Gaussian spectrum and in the case of overloads, especially under pulsating loading. For the transverse stiffeners (high notch factor), slight advantages for the high strength steel S960Q exist, only in the case of pulsating overloads. However, the advantages of high strength steels in case of static loading are indisputable. In most of the investigated cases, overloads lead to a benefit in fatigue life.

Welding simulation program, welding simulation device, and welding simulation method

Abstract: PROBLEM TO BE SOLVED: To provide a program, a device and a method which can swiftly and easily perform the simulation of a welding operation. SOLUTION: The program 41 includes: a first step where data 5 at least including the two-dimensional coordinates of welding spots e are inputted; a second step where, using the data 5 or the data 5 and the welding face f of each respective welding spot e, the welding spot e and a weld axis J are created; a third step where a welding gun G is virtually arranged at the welding spot e in accordance with the welding axis J; a fourth step where at least any of a treatment in which a welding group name is changed or a treatment in which the welding gun G is changed or any of the welding spots e is deleted or the approach angle of the welding gun G is changed or the arrangement of the upper/lower-normal/reverse rotation of the welding gun G is changed is performed; and a fifth step where the information of the first to fourth steps is stored. COPYRIGHT: (C)2009,JPO&INPIT

Residual stress in a thick section high strength T-butt weld

Abstract: Residual stresses in a structure are generated as a result of the various fabrication and welding processes used to make the component. Being able to quantify these residual stresses is a key step in determining the continuing integrity of a structure in service. In this work, the residual stresses around a high strength, quenched and tempered steel T-butt web to curved plate weld have been measured using neutron strain scanning. The results show that the residual stresses near the weld were dominated by the welding residual stresses, while the stresses further from the weld were dominated by the bending residual stresses. The results suggest that the combination of welding-induced residual stress and significant pre-welding residual stress, as in the case of a thick bent section of plate can significantly alter the residual stress profile from that in a flat plate.

Joining technologies for automotive steel sheets

Abstract: The reasons for the high international competitivity of the Japanese automotive industry are quality, performance and high productivity. Welding is an important production technology and welding te...

Arc welding robot control system and method thereof

Abstract: An arc welding robot control system of the present invention includes memory devices, controlling devices, a welding condition changing position calculating device, a weaving operation controlling device that outputs a signal of completion of one weaving cycle every time when a welding torch completes to perform one weaving cycle of a predetermined movement pattern, a welding condition calculating device for calculating to-be-changed welding conditions, and a welding condition changing device that changes welding conditions of an arc welding robot, based on to-be-changed welding conditions, every time when a signal of completion of one weaving cycle is input. With this configuration, it enables a continuous change of welding conditions and a copying arc welding with high accuracy even in the case in which the arc welding robot performs a weaving operation.

Effects of welding procedures on mechanical and morphological properties of hot gas butt welded PE, PP, and PVC sheets

Abstract: Mechanical and morphological properties of hot gas butt welds on polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) sheets for four different procedures, which are single and double V-welds with and without a welding shoe, were investigated. Besides, weldabilities of base materials were evaluated by rheological measurements. These revealed that weldabilities of PE and PP sheets were better than that of PVC. Welding energy (Ew), which is transferred onto weld surfaces, was calculated to evaluate weld quality. The results of tensile, impact, and bending tests indicated that the weld strengths of PVC sheets were lower than those of PE and PP sheets. When the welding shoe was used, weld strength increased significantly for each material because of the presence of sufficient welding pressure and the effective heating on surfaces. The best results were attained for the double V-welds with the welding shoe. Morphology of welded regions was evaluated by polarized light, stereo, and scanning electron microscopy. Polarized light microscopy studies indicated that the heat-affected zone (HAZ) consisted of welding rod core, molten zone, and deformed spherulitic zone, and the welding interface was indistinguishable from the base material when the welding pressure was enough. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Hybrid Laser-GMA Welding for Improved Affordability

Abstract: Maturing high power solid-state laser technology is fueling an interest in hybrid laser-GMA welding for shipyard fabrication activities. Hybrid laser-GMA welding has demonstrated an ability to both reduce the distortion of thin steel butt welds and increase the production rate of pipe welds relative to conventional joining techniques, both leading to improved affordability. The paper discusses the potential benefits of hybrid laser-GMA welding, results of experiments to address both distortion and production rate, and provides an overview of a hybrid pipe welding system recently installed in a shipyard.

Effects of Preheating and Interpass Temperature on Stresses in S 1100 QL Multi-Pass Butt-Welds

Abstract: Most of the research on Hydrogen Assisted Cold Cracking (HACC) in high strength steel welds conducted over the last several decades has focused on single-pass welds, especially considering materials with yield strengths about 700 MPa. The guidelines for avoiding cracking that have been developed from such work are therefore useful only where a root pass is the critical event. The well-known guideline is using preheating temperature. Such guideline is very limited when applied to multi-pass welds. In order to support this need, this paper presents the influence of inhomogeneous Hydrogen Removal Heat Treatment (HRHT) procedures, i.e. sole preheating, controlled interpass temperature and combined preheating and controlled interpass temperature, on the residual stresses in multi-pass welds of S 1100 QL. Thereafter, these results are used to identify HACC problems in S 1100 QL and are not reported here. The results were achieved by decent thermal and structural finite element simulations of a five-layer welded 12 mm thick plate at a realistic restraint provided by respective Instrumented Restraint Cracking (IRC) test. The simulations show that the inhomogeneous heat treatment procedures significantly increase the residual stresses as compared to welding without any heat treatment. In contrast to more general anticipations, an increasing controlled interpass temperature does not necessarily lead to a stress reduction, but can even increase the stresses dependent on the location in the multi-pass welds. Maximum residual stresses generally appear in the upper third part of the weld and are not located beneath the top surface where is a typical location used to detect residual stresses in real welded components. If the restraint intensity given to the welded component is not proper, such heat treatment procedures with various temperatures seem to be useful to reduce residual stresses in multi-pass welds.

Hybrid welding method

Abstract: A welding method is disclosed. The welding method includes making a weld via laser-arc hybrid welding. The welding method also includes using a fiber laser source in the laser-arc hybrid welding.

Comparative Study of Welding Residual Stresses in Carbon and Stainless Steel Butt Welds

Abstract: With the increased use of stainless steels in construction, it has become of critical importance to estimate the magnitude and distribution of welding residual stresses in a welded structure made of stainless steels. Simulation tools based on the finite element (FE) method are very useful to predict welding-induced residual stresses. Welding residual stresses in carbon steel welds have been thoroughly investigated through numerous FE models. In the case of stainless steel welds, a large number of FE simulations focusing on welding residual stresses have been performed; however, most of them have been confined to circumferential welding with the emphasis on pressurized pipe components, whereas few analyses have been carried out on a conventional structural member such as a butt-welded plate. Stainless steel has material stress-strain characteristics and thermal properties that differ from those of carbon steel; both properties influence the formation of welding residual stresses. This suggests that established FE models for predicting welding residual stresses in carbon steel welds may not be appropriate for stainless steel welds. Three-dimensional FE simulation of welding residual stresses in stainless steel butt welds has therefore been carried out. The thermomechanical FE model and the simulation methodology used are detailed and the results are discussed. In addition, welding residual stresses in carbon steel butt welds are examined for comparison.

Numerical investigation of the residual stresses in strength‐mismatched dissimilar steel butt welds:

Abstract: The presence of residual stresses in and around the welds can be detrimental to the performance of the welded part. Therefore, a good estimation of residual stresses in welds is needed. Simulation tools based on the finite element (FE) method are very useful to predict welding residual stresses. However, the numerical simulation of residual stresses in dissimilar steel welds is generally more challenging than that of residual stresses in similar steel welds because of the difference in the mechanical properties of the base metals to be joined and the weld metal strength mismatch which lies between two different base metals resulting from the use of weld metal fitted to either one. This paper presents the characteristics of residual stresses in strength‐mismatched dissimilar steel butt welds by carrying out three‐dimensional thermal elastic—plastic FE analysis, and the effects of weld metal strength on residual stress distributions are further investigated on the basis of the FE analysis results. Moreover,...

Large straight-line joint submerged arc welding tube fast production process

Abstract: The invention provides a big vertical masonry joint hidden arc welding tube fast production method belonging to the processing and forming fields of metal plate and relating to the bending processing and forming technology of metal plate which is mainly used for the fast production of the big vertical masonry joint hidden arc welding tube. The invention adopts continuous array rollers of a coil stock to form, high frequency prewelding on line, then utilizing a off-line automatic submerged arc welding to carry out the inner welding and outer welding of the welded pipe as well as expanding, water pressure and nondestructive examinations; thereby realizing the high efficiency production of the big vertical masonry joint hidden arc welding tube products. The invention adopts a plate-coiling mode to supply materials, cutting materials, shearing and butt welding, utilizes milling edge to finish the online-processing of a divided edge beside the plate, primary roller forming, fine roller forming, high frequency prewelding after a rough material is continuously formed by the array rollers and sawing as well as baiting and the steel tube rough material needed by a hidden arc welding working procedure can be acquired through online dimension fixing and cutting off; hidden arc inner welding and hidden arc outer welding, inner control examination, expending, water pressure test, repairing ends by machinery are carried out on the steel rough material to exam to acquire a finished product. The technique has a reasonable design and has the advantages of good steel tube forming quality and high production efficiency as adopting the array rollers to form and high frequency prewelding; thereby ensuring the overall production efficiency of the technique and the welding line quality can also be ensured reliably.

Magnetic flux distribution modelling of magnetically-impelled arc butt-welding of steel tubes using finite-element analysis

Abstract: Magnetically-impelled arc butt-welding (MIAB) is a pressure-welding process. In this process, heat is generated prior to forging by an arc created between two clamped and aligned tubes. This arc rapidly rotates along the peripheral edges of the tubes to be welded due to the electromagnetic force resulting from the interaction of the arc current and the magnetic field in the gap. To be precise, the magnetic flux density is the significant parameter that governs the arc rotation and the weld quality. This paper presents a three-dimensional finite-element model to determine the magnetic flux density distribution in the MIAB welding process. The objective of this study is to perform a non-linear electromagnetic analysis using the finite-element package ANSYS, and to explore the interdependence of MIAB welding parameters such as gap size, exciting current in the coil, and coil position from the weld centre, which influence the electromagnetic force generated in the welding process and weld quality. The results...