Showing papers on "Butt welding published in 2016"

Parameters optimization of hybrid fiber laser-arc butt welding on 316L stainless steel using Kriging model and GA

Abstract: It is of great significance to select appropriate welding process parameters for obtaining optimal weld geometry in hybrid laser-arc welding. An integrated optimization approach by combining Kriging model and GA is proposed to optimize process parameters. A four-factor, five-level experiment using Taguchi L 25 is conducted considering laser power (P), welding current (A), distance between laser and arc (D) and traveling speed (V). Kriging model is adopted to approximate the relationship between process parameters and weld geometry, namely depth of penetration (DP), bead width (BW) and bead reinforcement (BR). The constructed Kriging model was used for parameters optimization by GA to maximize DP, minimize BW and ensure BR at a desired value. The effects of process parameters on weld geometry are analyzed. Microstructure and micro-hardness are also discussed. Verification experiments demonstrate that the obtained optimum values are in good agreement with experimental results.

Temperature measurement and control of bobbin tool friction stir welding

Abstract: Bobbin tool friction stir welding (BTFSW) is a relatively new, solid-state welding technology, but its control is not the same as the conventional friction stir welding (FSW) due to the unique welding tool structure. In this paper, closed-loop control system was developed and the Smith predictive proportional-integral-derivative (PID) control method was presented to assist the welding system in producing an appropriate interface temperature response. As it is difficult to accurately detect the temperature in full range of the welding zone, the tool-workpiece interface temperature is detected by thermocouple and wireless transmission technology. Initial experiments were conducted to derive a qualitative understanding of bobbin tool friction stir welding processes. Ziegler-Nichols setting method was adopted to determine parameters of the PID controller. While examining the capabilities of Smith predictive PID control in BTFSW, this paper focuses on the control effect of hysteretic characteristics of welding temperature during butt welding. A compensation strategy was setting gaps along the welding path, and the gap could affect the distribution of temperature. Through our experiments, we demonstrate that temperature control strategy is feasible, and the tensile properties of the weld are uniform along the welding direction.

Temperature Field Evolution during Flash Butt Welding of Railway Rails

Abstract: Flash butt welding (FBW) of railway rails was investigated in this work. For this purpose samples of R260 rail steel and 60E1 profile were instrumented and subsequently welded on a Schlatter GAA 100 welding machine under industrial conditions. The intention is to gain in depth process knowledge by more accurately depicting thermal cycles for an entire welding sequence in the immediate proximity of the weld as well as in the heat affected zone (HAZ). A detailed characterization of the single stages of the heat up phase of the process is important. Additionally, the secondary welding voltage was measured simultaneously during the experiments to characterize the transient heat input. Moreover, these data were used in the analysis of the temperature signals to better cope with electrical interferences. Additionally, a finite element (FE) model of this FBW process was developed in the present work. Its implementation and solution is realized with the help of ESI’s FE-software SYSWELD. A strong coupled thermo-electrokinetical and metallurgical calculation routine was used. The model comprises the transition resistance at the welding surfaces as the main heat source to the process. Temperature dependent material properties and a corresponding metallurgical model based on an experimental CCT diagram of the rail steel R350HT are implemented in the simulation as well.

Optimization of MIG Welding Parameters to Control the Angular Distortion in Fe410WA Steel

Abstract: In the fabrication industry, metal inert gas (MIG) welding is a very important process and Fe410WA is the most commonly used material for the manufacturing of fabricated structures. During the preparation of butt welded joints, angular distortion is a major concern. Angular distortion can be minimized by optimizing the input parameters. In this paper, a study of the optimization of controllable input parameters such as current, voltage and gas flow rate by using the Taguchi method is performed. Butt welding samples were prepared by using three levels and three factors. An orthogonal array of nine trials is considered for the design of the experiment. After measuring the distortion angle, observed readings were verified by using analysis of variance (ANOVA) technique and it was found that the p-values were less than 0.05. Theoretical calculations were performed to optimize the process parameters to achieve the minimum distortion angle. A confirmation test was taken for validation purposes and to confirm th...

Effects of Microstructural Heterogeneity on Very-High-Cycle Fatigue Properties of 7050-T7451 Aluminum Alloy Friction Stir Butt Welds

Abstract: High strength aluminum alloy is widely used in aerospace and the railway traffic engineering. These components are subjected to 10 10 and more loading cycles during their time in service. Therefore the very-high-cycle fatigue behavior and the corresponding failure mechanisms of the base material and the welded joints have to be understood. However, conventional fusion welding methods for aluminum alloys often produce some porosity and hot crack in the weld metal. The problems are well solved by the development of friction stir welding (FSW) technology. In this study, the very-high-cycle fatigue properties of 7050-T7451 aluminum alloy and its friction stir welding butt welds have been investigated. Both electron backscatter diffraction (EBSD) analysis and scanning electron microscopy (SEM) analysis are performed to study the correlation of microscopic structure characteristics and the failure behavior. The results show that the failure of the FSW joints still occurs at 7.0×10 8 cycles. The fatigue properties of the FSW joint are superior to those of the base material, especially in the super long life regime. Most fatigue cracks initiate at the thermo-mechanically affected zone and heat affected zone on the advancing side of the FSW joints, and the susceptibility of these zones to fatigue is attributed to the metallurgical heterogeneity. The fatigue crack sources of the base material are all on the surface, while surface cracking, subsurface inclusion cracking are mostly observed on butt welds specimens, with the minority cracking from defect of incomplete penetration. The incomplete penetration defect caused by FSW reduces the fatigue life of welds specimens significantly.

A Numerical Simulation for Dissimilar Aluminum Alloys Joined by Friction Stir Welding

Abstract: Dissimilar aluminum alloy sheets of 2017A-T451 and 7075-T651 (6 mm thickness) were friction stir welded in a butt weld configuration. A numerical simulation of the joining process was developed to visualize the material flow patterns and temperature distribution and to correlate the microstructure to the hardness behavior. Due to the complementary downward flow of surface material into the workpiece thickness and upward flow of mid-plane and bottom-plane material, the weld nugget is composed of alternating layers of 7075 and 2017A. These layers have unique temperature histories depending on the material’s initial location within the cross section; therefore, they also have distinctive precipitate distributions. Supersaturated surface material flows into the process zone and forms a core in which GP zones reprecipitate upon cooling. Mid-plane and bottom-plane material flow toward the workpiece surface and encompass the surface material core. Within this region, the weld temperatures overage the equilibrium θ phase in 2017A, decreasing the hardness, and at the same time, dissolve the equilibrium η/T phase in the 7075, leading to reprecipitation of GP zones upon cooling and a hardness recovery.

Fatigue behaviour of G20Mn5QT cast steel and butt welds with Q345B steel

Abstract: A total number of 44 fatigue tests were conducted under total stain control, 26 for G20Mn5QT cast steel and 18 for butt welds between G20Mn5QT cast steel and Q345B steel. Based on the test results, cyclic stress response, plastic strain energy, strainlife curves and Coffin-Manson equations were presented. Comparing with hot rolled steels widely used in steel construction, the fatigue behaviour of G20Mn5QT cast steel is poor, the reason for which was imputed to the defects caused by the casting process. The welds between G20Mn5QT cast steel and Q345B steel exhibited similar fatigue performance as G20Mn5QT cast steel. Fatigue crack tends to initiate in the heat affected zone (HAZ) at the cast steel. Microstructure observations using optical and scanning electron microscope showed that casting defects are the common fatigue source for both G20Mn5QT cast steel and the butt welds between G20Mn5QT cast steel and Q345B steel.

Microstructure and mechanical properties of aluminium alloy 7A52 thick plates welded by robotic double-sided coaxial GTAW process

Abstract: The high strength aluminium alloy 7A52 thick plate is commonly welded by double-V butt welding. The general one sided arc welding requires indispensable root cleaning before the rear side root weld, which consumes excessive time and cost. Thus the robotic welding is always difficult to be carried on. In this paper, a novel robotic double-sided coaxial GTAW process has been applied to the welding of Al7A52. The microstructure and mechanical properties of the thick weld joints both welded by robotic self-fluxing double sided coaxial GTAW (RSF-DSC-GTAW) and robotic wire-feed double sided coaxial GTAW (RWF-DSC-GTAW) has been investigated. It was found that the microstructures of weld zones of both processes typically consist of α (Al) and β (MgZn 2 ) phases. Moreover, the weld zone of the RWF-DSC-GTAW joint exhibits Interval layers distribution because of the less proportion of β phase. The average micro hardness in the weld zone of RSF-DSC-GTAW joints and RWF-DSC-GTAW joints are 91.9 HV and 80.1 HV, respectively. With a better elongation property, the average ultimate tensile strength of RSF-DSC-GTAW joint is 344 Mpa. While it is 244 Mpa for the RWF-DSC-GTAW joint. It is considered that the mechanical properties of the RSF-DSC-GTAW joint are more superior to the RWF-DS-GTAW joint.

Importance of Fundamental Manufacturing Technology in the Automotive Industry and the State of the Art Welding and Joining Technology

Abstract: The automotive vehicle is made through the following processes such as press shop, welding shop, paint shop, and general assembly. Among them, the most important process to determine the quality of the car body is the welding process. Generally, more than 400 pressed panels are welded to make BIW (Body In White) by using the RSW (Resistance Spot Welding) and GMAW (Gas Metal Arc Welding). Recently, as the needs of light-weight material due to the CO2 emission issue and fuel efficiency, new joining technologies for aluminum, CFRP (Carbon Fiber Reinforced Plastic) and etc. are needed. Aluminum parts are assembled by the spot welding, clinching, and SPR (Self Piercing Rivet) and friction stir welding process. Structural adhesive boning is another main joining method for light-weight materials. For example, one piece aluminum shock absorber housing part is made by die casting process and is assembled with conventional steel part by SPR and adhesive bond. Another way to reduce the amount of the car body weight is to use AHSS (Advanced High Strength Steel) panel including hot stamping boron alloyed steel. As the new materials are introduced to car body joining, productivity and quality have become more critical. Productivity improvement technology and adaptive welding control are essential technology for the future manufacturing environment.

Full-automatic protective tube double-wire butt welding terminal press

Abstract: The invention discloses a full-automatic protective tube double-wire butt welding terminal press, comprising a cuboid mobile base, wherein a workbench I and a workbench II which are opposite are respectively arranged at the left and right ends of the upper surface of the mobile base, a vibrating disk feeding mechanism is arranged on the back of the upper surface of the mobile base, a protective tube welder is arranged between the workbench I and the workbench II, and a host control is arranged in the mobile base. The terminal press has the advantages of simple structure and strong practicability.

A comparison of as-welded and simulated heat affected zone (HAZ) microstructures

Abstract: The high-strength steel grade S690QL and a filler welding wire Mn3Ni1CrMo were the materials chosen for welding a V-shaped butt weld. In order to prevent the weld’s cold cracking, a multi-pass welding technique was applied. A metallographic investigation revealed microstructure variations in different areas of the weld’s heat-affected zone. A reverse-engineering approach was used to test a dilatometer’s capabilities to simulate different HAZ microstructures. Hollow steel-cylinder specimens were subjected to several weld thermal cycles in order to generate similar microstructures as in the real weld’s HAZ. The microstructures of the as-welded and simulated heat-affected zone specimens were investigated. Good agreement was found between the dilatometer-simulated HAZ microstructures and those in a real HAZ weld.

Multi-objective optimization of weld geometry in hybrid fiber laser-arc butt welding using Kriging model and NSGA-II

Abstract: An integrated multi-objective optimization approach combining Kriging model and non-dominated sorting genetic algorithm-II (NSGA-II) is proposed to predict and optimize weld geometry in hybrid fiber laser-arc welding on 316L stainless steel in this paper A four-factor, five-level experiment using Taguchi L25 orthogonal array is conducted considering laser power (P), welding current (I), distance between laser and arc (D) and traveling speed (V) Kriging models are adopted to approximate the relationship between process parameters and weld geometry, namely depth of penetration (DP), bead width (BW) and bead reinforcement (BR) NSGA-II is used for multi-objective optimization taking the constructed Kriging models as objective functions and generates a set of optimal solutions with pareto-optimal front for outputs Meanwhile, the main effects and the first-order interactions between process parameters are analyzed Microstructure is also discussed Verification experiments demonstrate that the optimum values obtained by the proposed integrated Kriging model and NSGA-II approach are in good agreement with experimental results

Influence of PC-GTAW Parameters on the Microstructural and Mechanical Properties of Thin AISI 1008 Steel Joints

Abstract: Butt weld joints are prepared using pulse current gas tungsten arc welding out of thin sheets of AISI 1008 steel using various combinations of pulse parameters. During welding, the welding speed was kept high, but with the increase of welding speed the mean current was also increased to get the required weld joint at the constant heat input. The use of pulse current has led to improvement in mechanical and metallurgical properties of weld joints. It has resulted in less development of humping which is a common problem with high-speed welding. The undercut or dipped weld face is not observed severe. The tensile strength and hardness are enhanced by 12.5 and 12%. The increase of tensile strength and hardness is justified through TEM micrograph showing the presence of dislocation.

Single pass fiber laser butt welding of explosively welded 2205/X65 bimetallic sheets and study on the properties of the welded joint

Abstract: In this study, the explosively welded 2205 duplex stainless steel/X65 pipe steel bimetallic sheets were butt welded by a fiber laser in single pass. The microstructure, mechanical, and corrosion properties of the laser butt welded (LBW) joint were investigated. The results show that the upper fusion zone (FZ) is composed of the martensite and bainite phases, while the lower FZ is composed of austenite (A) and ferrite (F). Energy dispersive spectroscopy (EDS) test results indicate that only a small amount of Cr, Ni, and Mo migrated from the lower FZ to the upper FZ, whereas a small amount of Fe has been moved from the upper FZ to the lower FZ. During the tensile test process, The digital specklegram processing technology test results demonstrated that the fracturing of the specimens started at the lower FZ, and then the fracture grew towards the parent plates near the upper FZ. The face and root bend tests were carried out, and no separation, tearing, or fracture was observed around the joint. Accelerated corrosion test results show that the LBW joint has the superior corrosion resistance, but it has poor pitting corrosion resistance.

Simulation of the Thermal Process of Butt Welding of Polyethylene Pipes at Low Temperatures

Abstract: A theoretical study has been made of the thermal process of welding polyethylene pipes for gas pipelines at low ambient air temperatures. The mathematical model used takes into account the heat of the phase transition in the temperature range, as well as the thermal effect of the fin formed by the slip. Computing experiments have shown that it is possible to control the temperature regime in welding at low ambient air temperatures and provide, in the thermal influence zone, the same change in the temperature field as at permissible air temperatures.

Smart ultrasonic welding of thermoplastic composites

Abstract: This paper presents an overview of the latest research on ultrasonic welding of composites performed at the Delft University of Technology. Firstly, we showed that for thermoplastic composites, a simple flat energy director shape, made of a loose film of neat resin, can be used to produce welds of high quality. Furthermore, for single lap shear coupons, it was shown that the use of a microprocessor-controlled welder allows for in-situ monitoring through power and sonotrode displacement data. As a result, a smart ultrasonic welding procedure was designed in which the feedback from the ultrasonic welder was used to define the processing parameters that yield optimum weld quality, significantly decreasing development times. Based on the knowledge developed at a lab-scale level, a welding strategy was developed to demonstrate the assembly of small and medium-sized components. Experimental comparison between ultrasonically spot-welded and mechanically fastened joints into double-lap shear and pull-through configurations further outlined the potential application of this technology, as well as its limitations. While ultrasonic welding is an efficient technique to join thermoplastic composites components, another potential application was shown to be the welding of thermoplastic and thermoset composites, enabled through the very short heating times in the ultrasonic welding process. This opens up new possibilities for ultrasonic welding where optimum design and manufacturing of aircraft parts call for the assembly of dissimilar materials, and could lead to significant costs and weight reduction as compared to mechanical fastening.

Welding structure for inner container longitudinal seam of stainless steel gas cylinder and welding method

Abstract: The invention discloses a welding structure for an inner container longitudinal seam of a stainless steel gas cylinder and a welding method. The welding structure comprises a strip-shaped auxiliary board, wherein a main gas guide hole and a gas guide groove are formed in the strip-shaped auxiliary boar in the length direction; the main gas guide hole and the gas guide groove are arranged in parallel; a plurality of gas guide small holes are formed between the main gas guide hole and the gas guide groove; the two ends of the gas guide small holes are respectively communicated with the main gas guide hole and the gas guide groove; and the cross section of the gas guide groove and the cross section of the longitudinal seam to be welded are positioned in the same plane. The welding method comprises the following steps: rolling round; carrying out butt welding and spot welding; carrying out spot welding on run-on plates and run-off plates; clamping; and welding. According to the invention, an MIG automatic welding process is adopted, so that the primary input-cost of welding equipment is low; in a later using process, the input using and maintenance costs are relatively low and the working efficiency is improved greatly. By adopting the process in the invention, the qualification rate of nondestructive testing reaches 99.4% or above in an actual longitudinal seam welding process of an insulated gas cylinder and a cylinder for an LNG vehicle; and physical and chemical test projects completely meet standard requirements.

In-situ load analysis in multi-run welding using LTT filler materials

Abstract: Modifying the level of mostly detrimental welding residual stresses already during the welding process would be highly attractive as time- and cost-consuming post processing may be prevented. The nature of stress buildup during welding-associated cooling is highly affected by phase transformations. Up to now, it is not clear in which way this is applicable to real component welding exhibiting high shrinkage restraint and complex heat input. In this study, two different low transformation temperature (LTT) alloys have been investigated concerning the stress development in restrained multi-run butt welding in order to evaluate the potential of stress reduction. Pulsed gas metal arc welding (P-GMAW) welding was executed on a testing facility designed to simulate real lifelike restraint conditions of component weldments. The effect of reduced MS-temperatures and the heat control on the globally acting stresses was monitored by in-situ measurement of the reaction forces during welding fabrication. Additional local residual stress measurements allowed analyzing global as well as local loading of the welded construction. Although phase transformation has a significant influence on unloading the joint during each weld pass, the reaction stress upon cooling to room temperature seems to be determined mainly by the heat input. On the surface, low longitudinal residual stresses were observed in case of LTT whereas transverse residual stresses are less affected.

Fine tuning of dwelling time in friction stir welding for preventing material overheating, weld tensile strength increase and weld nugget size decrease

Abstract: After successful welding, destructive testing into test samples from Al 2024-T351 friction stir butt welds showed that tensile strength of the weld improve along the joint line, while dimensions of the weld nugget decrease. For those welds, both the base material and the welding tool constantly cool down during the welding phase. Obviously, the base material became overheated during the long dwelling phase what made conditions for creation of joints with the reduced mechanical properties. Preserving all process parameters but varying the dwelling time from 5-27 seconds a new set of welding is done to reach maximal achievable tensile strength. An analytical-numerical-experimental model is used for optimising the duration of the dwelling time while searching for the maximal tensile strength of the welds